WO2000072851A1 - Method of sterilizing - Google Patents

Abstract

A method of sterilizing objects as well as the sterilized objects obtained from the method are disclosed. The method involves contacting an object such as a medical device to be reused with polycationic dendrimer under conditions which result in rendering a conformationally altered protein (e.g. a prion) non-infectious. A disinfecting agent or surgical scrub composition which comprises the dendrimers is also disclosed as are gelatin capsules treated with polycationic dendrimers.

Description

METHOD OF STERILIZING

GOVERNMENT SUPPORT

This work was supported, in part, by grants from the National Institutes of Health NS 14069, AG08967, AG02132, AG10770 and K08 NS02048-02. The government may have certain rights in this work.

FIELD OF THE INVENTION

The present invention relates generally to methods of sterilizing materials and particularly to a method of inactivating infectious prions .

BACKGROUND OF THE INVENTION

There are large numbers of known methods of sterilizing materials. Many methods involve heating a material to a temperature at which pathogens are killed or inactivated. Other methods involve exposing the material to compounds which kill or inactivate pathogens which are contacted by the compounds. Still other methods involve irradiating a material with a sufficient amount of a particular type of radiation for a period of time sufficient to inactivate, disrupt or kill pathogens in the material. These methods are generally directed toward killing bacteria and inactivating viruses present in or on the material. Although sterilization methods may be quite affective in killing bacteria or inactivating viruses, they do not generally inactivate pathogenic proteins such as prions which can be responsible for a number of fatal diseases.

There are a considerable number of diseases associated with a conformationaUy altered protein. For example, Alzheimer's disease is associated with APP, Aβ peptide, αl-antichymotrypin, tau and non-Aβ component. Many of these diseases are neurological diseases. However, type II Diabetes is associated with Amylin and Multiple myeloma-plasma cell dyscrasias is associated with IgGL-chain. The relationship between the disease onset and the transition from the normal protein to the conformationaUy altered protein has been examined very closely in some instances such as with the association between prion diseases and PrP^S . Pπon diseases are a group of fatal neurodegenerative disorders that can occur in hereditary, sporadic, and infectious forms (Prusiner, S B Scrapie pπons Annu Rev Microbwl 43, 345-374 (1989)) These illnesses occur m humans and a variety of other animals (Prusiner, S B Pπons Proc Natl Acad Sci USA 95, 13363-13383 (1998)) Pπons are infectious protems The normal, cellular form of the pπon protein (PrP) designated PrP^c contains three α- helices and has little β- sheet, m contrast, the protein of the pπons denoted PrP^Sc is rich m β-sheet structure The accumulation of PrP^Sc m the central nervous system (CNS) precedes neurologic dysfunction accompanied by neuronal vacuolation and astrocytic ghosis

The spectrum of human pπon diseases mcludes kuru (Gajdusek, D C , Gibbs, C J , Jr & Alpers, M Experimental transmission of a kuru-like syndrome to chimpanzees Nature 209, 794- 796 (1966)), Creutzfeldt- Jakob disease (CJD) (Gibbs, C J , Jr , et al Creutzfeldt- Jakob disease (spongiform encephalopathy) transmission to the chimpanzee Science 161, 388-389 (1968)), Gerstmann-Straussler-Schemker disease (GSS) and fatal familial msomma (FFI) (Goldfarb, L G , et al Fatal familial msomma and familial Creutzfeldt- Jakob disease disease phenotype determmed by a DNA polymorphism Science 258, 806-808 (1992), Medon, R , et al Fatal familial msomma a second kindred with mutation of pπon protem gene at codon 178 Neurology 42, 669-670 (1992)) , and a new form of human pnon disease, new vaπant CJD (nvCJD), which has emerged m Great Bntain and France (Will, G , et al A new vaπant of Creutzfeldt- Jakob disease m the UK Lancet 347, 921-925 (1996), Cousens, S N , Vynnycky, E , Zeidler, M , Will, R G & Smith, P G Predicting the CJD epidemic m humans Nature 385, 197-198 (1997), Will, R G , et al Deaths from vaπant Creutzfeldt- Jakob disease Lancet 353, 979 (1999)) Several lmes of evidence have suggested a link between the nvCJD outbreak and a preceding epidemic of bovine spongiform encephalopathy (BSE) (Will, G , et al A new vanant of Creutzfeldt- Jakob disease m the UK Lancet 347, 921-925 (1996), Brace, M E , et al Transmissions to mice indicate that 'new vaπant' CJD is caused by the BSE agent Nature 389, 498-501 (1997), Hill, A F , et al The same pπon strain causes vCJD and BSE Nature 389, 448-450 (1997), Lasmezas, C I , et al BSE transmission to macaques Nature 381, 743-744 (1996)) Although it is too early to predict the number of nvCJD cases that might eventually aπse m Great Bntain and elsewhere (Cousens, S N , Vynnycky, E , Zeidler, M , Will, R G & Smith, P G Predicting the CJD epidemic m humans Nature 385, 197-198 (1997)), it is clear that effective therapeutics for pπon diseases are urgently needed Unfortunately, although a number of compounds including amphotencins, sulfated polyanions, Congo red dye, and anthracycline antibiotics have been reported as prospective therapeutic agents (Ingrosso, L , Ladogana, A & Pocchian, M Congo red prolongs the mcubation penod in scrapie-infected hamsters J Virol 69, 506-508 (1995). Taghavim, Ε , et al Effectiveness of anthracycline against experimental prion disease in Syrian hamsters. Science 276, 1119-1122 (1997); Masullo, C, Macchi, G., Xi, Y.G. & Pocchiari, M. Failure to ameliorate Creutzfeldt-Jakob disease with amphotericin B therapy. J. Infect. Dis. 165, 784-785 (1992); Ladogana, A., et al. Sulphate polyanions prolong the incubation period of scrapie-infected hamsters. J. Gen. Virol. 73, 661-665 (1992)), all have demonstrated only modest potential to impede prion propagation, and none have been shown to effect the removal of pre-existing prions from an infected host.

The PrP gene of mammals expresses a protein which can be the soluble, non-disease form PrP^c or be converted to the insoluble, disease form PrP^Sc. PrP^c is encoded by a single-copy host gene [Basler, Oesch et al. (1986) Cell 46:417-428] and when PrP^c is expressed it is generally found on the outer surface of neurons. Many lines of evidence indicate that prion diseases result from the transformation of the normal form of prion protein (PrP^c) into the abnormal form (PrP^Sc). There is no detectable difference in the amino acid sequence of the two forms. However, PrP^Sc when compared with PrP^c has a conformation with higher β-sheet and lower α-helix content (Pan, Baldwin et al. (1993) Proc Natl Acad Sci USA 90: 10962-10966; Safar, Roller et al. (1993) JBiol Chem

268:20276-20284). The presence of the abnormal PrP^Sc form in the brains of infected humans or animals is the only disease-specific diagnostic marker of prion diseases.

PrP^Sc plays a key role in both transmission and pathogenesis of prion diseases (spongiform encephalopathies) and it is a critical factor in neuronal degeneration (Prusiner (1997) The Molecular and Genetic Basis of Neurological Disease, 2nd Edition : 103-143). The most common prion diseases in animals are scrapie of sheep and goats and bovine spongiform encephalopathy (BSE) of cattle (Wilesmith and Wells (1991) Curr Top Microbiol Immunol 172:21-38). Four prion diseases of humans have been identified: (1) kuru, (2) Creutzfeldt-Jakob Disease (CJD), (3) Gerstmann-Straussler-Scheinker Disease (GSS), and (4) fatal familial insomnia (FFI) [Gajdusek (1977) Science 197:943-960; Medori, Tritschler et al. (1992) NEngl JMed 326:444-449]. Initially, the presentation of the inherited human prion diseases posed a conundrum which has since been explained by the cellular genetic origin of PrP.

The assembly and misassembly of normally soluble proteins into conformationaUy altered proteins is thought to be a causative process in a variety of other diseases. Structural conformational changes are required for the conversion of a normally soluble and functional protein into a defined, insoluble state. Examples of such insoluble protein include: Aβ peptide in amyloid plaques of Alzheimer's disease and cerebral amyloid angiopathy (CAA); α-synuclein deposits in Lewy bodies of Parkinson's disease, tau in neurofibrillary tangles in frontal temporal dementia and Pick's disease; superoxide dismutase in amyotrophic lateral sclerosis; huntingtin in Huntington's disease; and prions m Creutzfeldt-Jakob disease (CJD) (for reviews, see Glenner et al. (1989) J Neurol. Sci. 94 1- 28; Haan et al (1990) dm. Neurol. Neurosurg 92(4) 305-310).

Often these highly insoluble proteins form aggregates composed of nonbranching fibnls with the common characteristic of a β-pleated sheet conformation In the CNS, amyloid can be present in cerebral and memngeal blood vessels (cerebrovascular deposits) and m brain parenchyma (plaques)

Neuropathological studies m human and animal models mdicate that cells proximal to amyloid deposits are disturbed in their normal functions (Mandybur (1989) Ada Neuropathol 78 329-331, Kawai et al (1993) Brain Res 623 142-6, Martin et al (1994) Am J Pathol 145 1348-1381, Kalana et al (1995) Neuroreport 6 477-80, Mashah et al (1996) J Neurosct 16 5795-5811) Other studies additionally mdicate that amyloid fibnls may actually initiate neurodegeneration

(Lendon et al (1997) J Am Med Assoc 277 825-31, Yankner (1996) Nat Med 2 850-2, Selkoe (1996) 7. Biol. Chem. 271.18295-8; Hardy (1997) Trends Neurosci. 20: 154-9).

In both AD and CAA, the mam amyloid component is the amyloid β protein (Aβ). The Aβ peptide, which is generated from the amyloid β precursor protein (APP) by two putative secretases, is present at low levels in the normal CNS and blood. Two major variants, Aβ _l^₀ and Aβi.₄₂, are produced by alternative carboxy-terminal truncation of APP (Selkoe et al.(1988) Proc. Natl. Acad. Sci. USA 85:7341-7345; Selkoe, (1993) Trends Neurosci 16:403-409). Aβ_W2 is the more fibrillogenic and more abundant of the two peptides in amyloid deposits of both AD and CAA. In addition to the amyloid deposits in AD cases described above, most AD cases are also associated with amyloid deposition in the vascular walls (Hardy (1997), supra; Haan et al. (1990), supra; Terry et al., supra; Vinters (1987), supra; Itoh et al. (1993), supra; Yamada et al. (1993), supra; Greenberg et al. (1993), supra; Levy et al. (1990), supra). These vascular lesions are the hallmark of CAA, which can exist in the absence of AD.

Human transthyretin (TTR) is a normal plasma protem composed of four identical, predominantly β-sheet structured units, and serves as a transporter of hormone thyroxin Abnormal self assembly of TTR mto amyloid fibnls causes two forms of human diseases, namely semle systemic amyloidosis (SSA) and familial amyloid polyneuropathy (FAP) (Kelly (1996) Curr Opin Strut Biol 6(1) 11-7) The cause of amyloid formation in FAP are pomt mutations m the TTR gene, the cause of SSA is unknown The clinical diagnosis is established histologically by detecting deposits of amyloid m situ m bioptic matenal

To date, little is known about the mechamsm of TTR conversion mto amyloid in vivo However, several laboratones have demonstrated that amyloid conversion may be simulated in vitro by partial denaturation of normal human TTR [McCutchen, Colon et al (1993) Biochemistry 32(45) 12119-27; McCutchen and Kelly (1993) Biochem Biophys Res Commun 197(2) 415-21] The mechamsm of conformational transition mvolves monomeπc conformational mtermediate which polymerizes into linear β-sheet structured amyloid fibrils [Lai, Colon et al. (1996) Biochemistry 35(20):6470-82]. The process can be mitigated by binding with stabilizing molecules such as thyroxin or triiodophenol (Miroy, Lai et al. (1996) Proc NatlAcad Sci USA 93(26): 15051-6).

The precise mechanisms by which neuritic plaques are formed and the relationship of plaque formation to the disease-associated neurodegenerative processes are not well-defined. The amyloid fibrils in the brains of Alzheimer's and prion disease patients are known to result in the inflammatory activation of certain cells. For example, primary microglial cultures and the THP-1 monocytic cell line are stimulated by fibrillar β -amyloid and prion peptides to activate identical tyrosine kinase-dependent inflammatory signal transduction cascades. The signaling response elicited by β-amyloid and prion fibrils leads to the production of neurotoxic products, which are in part responsible for the neurodegenerative . C.K. Combs et al, J Neurosci 19:928-39 (1999).

Although research efforts relating to conformationaUy altered proteins are advancing efforts to sterilize materials to avoid infections with such proteins are not keeping pace. The present invention offers a means of sterilizing materials which contain conformationaUy altered proteins such as prions.

BRIEF DESCRIPTION OF THE DRAWING

Figure 1 is a schematic drawing of a dendrimer molecule showing the defined "generations" of homodisperse structure created using a repetitive divergent growth technique. The specific diagram is of PAMAM, generation 2.0 (ethylene diamine core).

SUMMARY OF THE INVENTION A method is disclosed whereby any type of object can be sterilized by combining normal sterilization procedures with the use of a polycationic dendrimer which is capable of rendering a conformationaUy altered protein such as a prion non-infectious. The method is particularly useful in sterilizing medical devices such as surgical instruments and catheters which have been used and brought into contact with blood or brain tissue. Objects sterilized via the method are also part of the invention and include capsules which are made from geletin extracted from cattle which cattle may be infected with prions, i.e. have undiagnosed BSE known as "mad cow disease." The polycationic dendrimers can be combined with conventional antibacterial and antiviral agents in aqueous or alcohol solutions to produce disinfecting agents or surgical scrubs. Branched polycations for use in the invention include, but are not limited to, polypropylene imine, polyethyleneimine (PEI) poly(4'-aza-4'-methylheptamethylene D-glucaramide), polyamidoamines and suitable fragments and/or variants of these compounds. An aspect of the invention is a method of treating objects with a composition characterized by its ability to render proteins associated with diseases non-infectious.

An advantage of the invention is that proteins such as prions can be rendered non-infectious without the need for extreme conditions such as exposure to heat over long periods of time, e.g. 1-10 hours at 100°-200°C.

A feature of the invention is that compositions can be useful while containing only very low concentrations of polycationic dendrimers, e.g. 1% to 0.001%.

Another aspect of the invention is that capsules made with bovine gelatin can be certified prion free. Another aspect of the invention is that drugs produced from cell cultures treated with polycationic dendrimers can be certified prion free.

Still another aspect of the invention is that medical devices being reused after exposure to blood or brain tissue can be certified prion free.

Still another aspect of the invention is that hospitals, operating rooms and the devices and equipment within them can be certified prion free by contacting them with polycationic dendrimers at standard temperatures and pressures. A pharmaceutical composition for the treatment of insoluble protein deposit formation in an animal, said composition comprising a therapeutically effective amount of a branched polycation; and a pharmaceutically acceptable excipient. In one embodiment, the branched polycation is a branched polymer, and wherein at least one branch is positively charged, and the branched polymer may have multiple charged branches. The branches may have the same chemical structure, or the branches may vary in structure within a single molecule. Examples of polymers that may be used in such a pharmaceutical composition include polypropylene imine, polyethyleneimine (PEI) poly(4'-aza-4'-methylheptamethylene D-glucaramide), polyamidoamines and pharmaceutically effective variants or fragments thereof. In one embodiment of the pharmaceutical composition, the composition also contains a second therapeutic agent, such as an analgesic agent, an antimicrobial agent, anti-inflammatory agent, an antioncogenic agent, an antiviral agent, and the like.

The present invention also provides a method of enhancing clearance of a disease related conformation of a protein from cells by contacting cells with a branched polycation for a time sufficient to enhance the rate of clearance of a disease related conformation of a protein from the cells. This branched polycation can be administered in vivo or ex vivo to a subject including a human, cow, sheep, deer, dog, cat, goat, chicken and turkey. Examples of such disease related proteins include PrP^Sc, APP, Aβ peptide, α-1-antichymotrypsin. The method is thus useful for subjects suffering from disorders such as bovine spongiform encephalopathy, Creutzfeldt- Jacob Disease, fatal familial msomma, GSS for Gerstmann-Straussler-Schemker Disease, kuru, scrapie, Alzheimer's Disease, Frontal temporal dementia, Huntington's disease, ALS, Pick's disease, Parkinson's disease, Diabetes Type II, multiple myeloma, familial amyloidotic polyneuropathy, medullary carcinoma of thyroid, chrome renal failure, congestive heart failure, semle cardiac and systemic amyloidosis, chrome inflammation, atherosclerosis, and familial amyloidosis The branched polycation can be administered to a subject in an amount non-toxic to the subject, for example a dosage of 0 001 mg to 1 mg/kg body weight per day The polycation may be administered m a smgle dosage form, or it may be repeatedly administered to the subject The branched polycation may also be administered prophylactically to prevent the formation of the disease conformation of these protems

The invention also provides a food composition for the preventing insoluble protem deposit formation m an animal, where the food contains a therapeutically effective amount of a branched cation which enhances clearance of conformationaUy altered protem The food can be any food product, mcludmg solid foods such as meat (e g , beef or lamb) and liquid foods such as vmegar, oil, and condiments such as steak sauce and ketchup The branched polycation is allowed to contact the food pnor to ingestion for a time sufficient to allow clearance of the conformationaUy altered protems

The present mvention also provides a method of preventing a farm animal from acquiring a disease associated with a conformationaUy altered protem by feeding the animals animal feed containing a branched polycation The feed containing the branched polycation may be synthetically produced, and fed directly to the animals, or the branched polycation may be mtroduced to a natural food source, e g , the animal feed is grass and the branched polycation is sprayed on the grass or mtroduced to the grass through a plant fertilizer One aspect of this embodiment of the mvention is a method of preventing disease caused by mgestion of contaminated food products by feeding animals foods containing branched polycations

The present mvention also provides a method of enhancing clearance of a disease related conformation of a protem from a meat food product by contacting the meat with a compound which enhances clearance of a conformationaUy altered protem at a pH of 5 or less for a time sufficient to allow for destruction of conformationaUy altered protem An advantage of the mvention is that conformationaUy altered protem such as pnons can be rendered non-infectious with a method which need only consist of applying a polycationic dendrimer preferably held at a pH of 5 0 or less

Another aspect of the mvention is soaps, surgical scrubs, detergents and the like with polycationic dendrimers therein <■

-1- An advantage of the mvention is that compositions containing polycationic dendrimers can be used to mactivate pπons which might be present on surgical instruments, k ves and/or other tools or equipment used by butchers, particularly those used m the butchering of cows or other animals which might be infected with pπons A feature of the mvention is that compositions of the mvention can be effective m activating prions when the polycationic dendrimers are present m very low concentrations, e g 1% to 0 001% or less

These and other aspects, advantages, and features of the mvention will become apparent to those persons skilled m the art upon reading the details of the compounds, and assay method more fully descnbed below

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Before the present methods, objects and compositions are descnbed, it is to be understood that this mvention is not limited to the particular steps, devices or components descnbed and, as such, may of course vary It is also to be understood that the terminology used herem is for the purpose of descnbmg particular embodiments only, and is not mtended to be limiting, smce the scope of the present mvention will be limited only by the appended claims

Unless defined otherwise, all technical and scientific terms used herem have the same meaning as commonly understood by one of ordinary skill m the art to which this mvention belongs Although any methods and mateπals similar or equivalent to those descnbed herem can be used m the practice or testing of the present mvention, the prefened methods and mateπals are now descnbed AU publications mentioned herem are incorporated herem by reference to disclose and descnbe the methods and/or mateπals m connection with which the publications are cited

The publications discussed herem are provided solely for their disclosure pπor to the filing date of the present application Nothing herem is to be construed as an admission that the present mvention is not entitled to antedate such publication by virtue of pnor mvention Further, the dates of publication provided may be different from the actual publication dates which may need to be independently confirmed

DEFINITIONS

The term "detergent" is used to mean any substance that reduces the surface tension of water The detergent may be a surface active agent which concentrates at oil-water mterfaces, exerts emulsifying action and thereby aids m removing soils e g common sodium soaps of fatty acids A detergent may be anionic, catiomc, or momomc depending on their mode of chemical action Detergents include linear alkyl sulfonates (LAS) often aided by "builders " A LAS is preferably an alkyl benzene sulfonate ABS which is readily decomposed by microorganisms (biodegradable). The LAS is generally a straight chain alkyl comprising 10 to 30 carbon atoms. The detergent may be in a liquid or a solid form.

The term "conformationaUy altered protein" is used here to describe any protein which has a three dimensional conformation associated with a disease. The conformationaUy altered protein may cause the disease, be a factor in a symptom of the disease or appear as a result of other factors. The conformationaUy altered protein appears in another conformation which has the same amino acid sequence. In general, the conformationaUy altered protein formed is "constricted" in conformation as compared to the other "relaxed" conformation which is not associated with disease. The following is a non-limiting list of diseases with associated proteins which assemble two or more different conformations wherein at least one conformation is an example of a conformationaUy altered protein.

Disease Insoluble Proteins Alzheimer's Disease APP, Aβ peptide, α 1 -antichymotrypsin, tau, non-Aβ component, presenillin 1, presenillin 2 apoE

Prion diseases, Creutzfeldt Jakob disease, scrapie and bovine spongiform encephalopathy p_rpSc

ALS SOD and neurofilament

Pick's disease Pick body

Parkinson's disease α-synuclein in Lewy bodies

Frontotemporal dementia tau in fibrils

Diabetes Type II Amylin

Multiple myeloma- plasma cell dyscrasias IgGL-chain

Familial amyloidotic polyneuropathy Transthyretin

Medullary carcinoma of thyroid Procalcitonin

Chronic renal failure β₂— microglobulin

Congestive heart failure Atrial natriuretic factor

Senile cardiac and systemic amyloidosis Transthyretin

Chronic inflammation Serum amyloid A Atherosclerosis ApoAl

Familial amyloidosis Gelsolin

Huntingdon's disease Huntingtin

The term" acid" is used to describe any compound or group of compounds which has one or more characteristics of (a) sour taste; (b) turns litmus dye red; (c) reacts with certain metals to form a salt; (d) reacts with certain bases or alkalines to form a salt. An acid comprises hydrogen and in water undergoes ionization so that H₃0⁺ ions are formed - also written as HT and refeπed to as hydronium ions or simply hydrogen ions. Weak acids such as acetic acid or carbonic acid may be used as may strong acids such as hydrochloric acid, nitric acid and sulfuric acid. In compositions of the invention the acid is preferably present in a concentration so as to obtain a pH of 5 or less, more preferably 4 or less and still more preferably 3.5 ± 1.

The terms "sterilizing", "making sterile" and the like are used here to mean rendering something non-infectious or rendering something incapable of causing a disease. Specifically, it refers to rendering a protein non-infectious or incapable of causing a disease or the symptoms of a disease. Still more specifically, it refers to rendering a conformationaUy altered protein (e.g. PrP^Sc known as prions) incapable of causing a disease or the symptoms of a disease.

By "effective dose" or "amount effective" is meant an amount of a compound sufficient to provide the desired sterilizing result. This will vary depending on factors such as the type of object or material being sterilized and the amount or concentration of infectious proteins which might be present. Polycations of the invention or more specifically polycationic dendrimer compounds of the invention could be mixed with a material in an amount in a range 1 to 500 μg of dendrimer per ml or mg of material being sterilized. The concentration is sufficient if the resulting composition is effective in decreasing the infectivity of conformationaUy altered proteins such that the treated material over time would not result in infection. Because (1) some materials will have higher concentrations of altered protein than others (2) some materials are contacted more frequently than others and (3) individual proteins have different degrees of infectivity the effective dose or concentration range needed to sterilize can vary considerably. It is also pointed out that the dose needed to treat an amount of material may vary somewhat based on the pH the treatment is carried out at and the amount of time the compound is maintained in contact with the material at the desired low pH (e.g., 5.0 or less) level.

The term "LD₅₀" as used herein is the dose of an active substance that will result in 50 percent lethality in all treated experimental animals. Although this usually refers to invasive administration, such as oral, parenteral, and the like, it may also apply to toxicity using less invasive methods of administration, such as topical applications of the active substance. The term "amine-terminated" includes primary, secondary and tertiary amines. The terms "PrP protein", "PrP" and like are used interchangeably herein and shall mean both the infectious particle form PrP^Sc known to cause diseases (spongiform encephalopathies) in humans and animals and the noninfectious form PrP^c which, under appropriate conditions is converted to the infectious PrP^Sc form.

The terms "prion", "prion protein", "PrP^Sc protein" and the like are used interchangeably herein to refer to the infectious PrP^Scform of a PrP protein, and is a contraction of the words "protein" and "infection." Particles are comprised largely, if not exclusively, of PrP^Sc molecules encoded by a PrP gene. Prions are distinct from bacteria, viruses and viroids. Known prions infect animals to cause scrapie, a transmissible, degenerative disease of the nervous system of sheep and goats, as well as bovine spongiform encephalopathy (BSE), or "mad cow disease", and feline spongiform encephalopathy of cats. Four prion diseases known to affect humans are (1) kuru, (2) Creutzfeldt-Jakob Disease (CJD), (3) Gerstmann-Straussler-Scheinker Disease (GSS), and (4) fatal familial insomnia (FFI). As used herein "prion" includes all forms of prions causing all or any of these diseases or others in any animals used - and in particular in humans and domesticated farm animals.

The term "PrP gene" is used herein to describe genetic material which expresses proteins including known polymorphisms and pathogenic mutations. The term "PrP gene" refers generally to any gene of any species which encodes any form of a prion protein. Some commonly known PrP sequences are described in Gabriel et al., Proc. Natl. Acad. Sci. USA 89:9097-9101 (1992) and U.S.

Patent No. 5,565,186, incorporated herein by reference to disclose and describe such sequences. The PrP gene can be from any animal, including the "host" and "test" animals described herein and any and all polymorphisms and mutations thereof, it being recognized that the terms include other such PrP genes that are yet to be discovered. The protein expressed by such a gene can assume either a PrP^c (non-disease) or PrP^Sc (disease) form.

The terms "standardized prion preparation", "prion preparation", "preparation" and the like are used interchangeably herein to describe a composition (e.g., brain homogenate) obtained from the brain tissue of mammals which exhibits signs of prion disease: the mammal may (1) include a transgene as described herein; (2) have and ablated endogenous prion protein gene; (3) have a high number of prion protein gene from a genetically diverse species; and/or (4) be a hybrid with an ablated endogenous prion protein gene and a prion protein gene from a genetically diverse species. Different combinations of 1-4 are possible, e.g., 1 and 2. The mammals from which standardized prion preparations are obtained exhibit clinical signs of CNS dysfunction as a result of inoculation with prions and/or due to developing the disease of their genetically modified make up, e.g., high copy number of prion protein genes. Standardized prion preparations and methods of making such are described and disclosed in U.S. Patent 5,908,969 issued June 1, 1999 and application serial no. 09/199,523 filed November 25, 1998 both of which are incorporated herein by reference in their entirety to disclose and describe standardized prion preparations.

The term "Alzheimer's disease" (abbreviated herein as "AD") as used herein refers to a condition associated with formation of neuritic plaques comprising amyloid β protein, primarily in the hippocampus and cerebral cortex, as well as impairment in both learning and memory. "AD" as used herein is meant to encompass both AD as well as AD-type pathologies.

The term "AD-type pathology" as used herein refers to a combination of CNS alterations including, but not limited to, formation of neuritic plaques containing amyloid β protein in the hippocampus and cerebral cortex. Such AD-type pathologies can include, but are not necessarily limited to, disorders associated with aberrant expression and/or deposition of APP, overexpression of APP, expression of aberrant APP gene products, and other phenomena associated with AD. Exemplary AD-type pathologies include, but are not necessarily limited to, AD-type pathologies associated with Down's syndrome that is associated with overexpression of APP.

The term "phenomenon associated with Alzheimer's disease" as used herein refers to a structural, molecular, or functional event associated with AD, particularly such an event that is readily assessable in an animal model. Such events include, but are not limited to, amyloid deposition, neuropathological developments, learning and memory deficits, and other AD- associated characteristics.

The term "cerebral amyloid angiopathy" (abbreviated herein as CAA) as used herein refers to a condition associated with formation of amyloid deposition within cerebral vessels which can be complicated by cerebral parenchymal hemorrhage. CAA is also associated with increased risk of stroke as well as development of cerebellar and subarachnoid hemorrhages (Vinters (1987) Stroke 18:311-324; Haan et al. (1994) Dementia 5:210-213; Itoh et al. (1993) /.

Neurol. Sci. 116: 135-414). CAA can also be associated with dementia prior to onset of hemorrhages. The vascular amyloid deposits associated with CAA can exist in the absence of AD, but are more ftequendy associated with AD.

The term "phenomenon associated with cerebral amyloid angiopathy" as used herein refers to a molecular, structural, or functional event associated with CAA, particularly such an event that is readily assessable in an animal model. Such events include, but are not limited to, amyloid deposition, cerebral parenchymal hemorrhage, and other CAA-associated characteristics.

The term "β-amyloid deposit" as used herein refers to a deposit in the brain composed of Aβ as well as other substances. Abbreviations used herein include:

CNS for central nervous system;

BSE for bovine spongiform encephalopathy;

CJD for Creutzfeldt-Jakob Disease; FFI for fatal familial insomnia;

GSS for Gerstmann-Straussler-Scheinker Disease;

AD for Alzheimer's disease;

CAA for cerebral amyloid angiopathy;

Hu for human; HuPrP for human prion protein;

Mo for mouse;

MoPrP for mouse prion protein;

SHa for a Syrian hamster;

SHaPrP for a Syrian hamster prion protein; PAMAM for polyamidoamide dendrimers

PEI for polyethyleneimine

PPI for polypropyleneimine

PrP^Sc for the scrapie isoform of the prion protein;

PrP^c for the cellular contained common, normal isoform of the prion protein; PrP 27-30 or PrP^Sc 27-30 for the treatment or protease resistant form of PrP^Sc;

MoPrP^Sc for the scrapie isoform of the mouse prion protein;

N2a for an established neuroblastoma cell line used in the present studies;

ScN2a for a chronically scrapie-infected neuroblastoma cell line;

ALS for amyotrophic lateral sclerosis; HD for Huntington's disease;

FTD for frontotemporal dementia;

SOD for superoxide dismutase

GENERAL ASPECTS OF THE INVENTION The invention comprises compositions of compounds found to be effective in rendering conformationaUy altered proteins non-infective. The compositions are preferably low pH solutions comprised of a non-toxic weak acid such as acetic acid having dissolved therein a branched polycation. Prefened compositions of the invention are in the form of aqueous or alcohol solutions which are comprised of a branched polycation, an antibacterial, an antifungal and an antiviral compound. The compositions are coated on, mixed with, injected into or otherwise brought into contact with a material to be sterilized. The composition is applied in a manner so that the branched polycation is maintained at a low pH (e.g. 5 or less and preferably 3.5 ± 1) in an amount of 1 μg or more polycation per ml or mg of material to be sterilized. The composition is maintained in the desired pH range at normal temperature (e.g., 15 °C to 30°C) for a sufficient period of time (e.g. 1 hour to 1 week) to cause conformationaUy altered protein present on or in the material to be destroyed (e.g. hydrolyzed) or rendered non-infective. Prefened compositions of the invention are useful in cleaning and sterilizing and may be comprised of a polycationic dendrimers, a detergent, and an acid proving a pH of about 3.5 ±1.

DENDRIMER COMPOUNDS WHICH CLEAR PRIONS

Dendrimers are branched compounds also known as "starburst" or "star" polymers due to a characteristic star-like structure (see Figure 1). Dendrimers of the invention are polymers with structures built from AB_n monomers, with n>2, and preferably n=2 or 3. Such dendrimers are highly branched and have three distinct structural features: 1) a core, 2) multiple peripheral end-groups, and 3) branching units that link the two. Dendrimers may be cationic (full generation dendrimers) or anionic (half generation dendrimers). For a review on the general synthesis, physical properties, and applications of dendrimers, see, e.g. , Tomalia et. al, Angew. Chem. Int. Ed. Engl. , 29: 138-175, (1990); Y. Kim and C. Zimmerman, Curr Opin Chem Biol, 2:733-7421 (1997). In a preferred embodiment, sterilizing compositions of the invention comprise a cationic dendrimer preferably dissolved in a low pH solvent such as acetic acid. Examples of suitable dendrimers are disclosed in U.S. Pat. Nos. 4,507,466, 4,558, 120, 4,568,737, 4,587,329, 4,631,337, 4,694,064, 4,713,975, 4,737,550, 4,871,779, and 4,857,599 to D. A. Tomalia, et al., which are hereby incorporated by reference to disclose and describe such compounds. Dendrimers typicaUy have tertiary amines which have a pKa of 5.7. The dendrimers can optionally be chemically or heat treated to remove some of the tertiary amines. Other suitable cations include polypropylene imine, polyethyleneimine (PEI), which has tertiary amines with a pKa of 5.9, and poly(4'-aza-4'-methylheptamethylene D-glucaramide), which has tertiary amines with a pKa of 6.0. The cationic dendrimer is preferably dissolved in the low pH solvent such as vinegar in a concentration of 0.0001 % or more, preferably 0.01 % or more and more preferably about 1 %.

Preferably, the dendrimers for use in the invention are polyamidoamines (hereinafter "PAMAM"). PAMAM dendrimers are particularly biocompatible, since polyamidoamine groups resemble peptide bonds of proteins.

44- Dendrimers are prepared in tiers called generations (see generations 0, 1 and 2 in Figure 1) and therefore have specific molecular weights. The full generation PAMAM dendrimers have amine terminal groups, and are cationic, whereas the half generation dendrimers are carboxyl terminated. Full generation PAMAM dendrimers are thus preferred for use in the present invention. PAMAM dendrimers may be prepared having different molecular weights and have specific values as described in Table 1 below for generations 0 through 10.

TABLE A

LIST OF PAMAM DENDRIMERS AND THEIR MOLECULAR WEIGHTS (Ethylene Diamine core, amine terminated),

GENERATION TERMINAL GROUPS MOL. WT. g/mole

0 4 517

1 8 1430 2 216 3256

3 32 6909

4 64 14,215

5 128 28,795

6 256 58,048 7 512 116,493

8 1024 233,383

9 2048 467,162

10 4096 934,720

As shown in Table A, the number of terminal amine groups for PAMAM dendrimers generations 0 through 10 range from 4 to 4,096, with molecular weights of from 517 to 934,720. PAMAM dendrimers are available commercially from Aldrich or Dendritech. Polyethyleneimine or polypropylene dendrimers or quaternized forms of amine-terminated dendrimers may be prepared as described by Tomalia et. al, Angew, Chem. Int. Ed. Engl., 29: 138-175 (1990) incorporated by reference to describe and disclose methods of making dendrimers.

STERILIZING COMPOSITIONS Examples provided here show that highly-branched polycations, e.g. dendrimer compounds, affect the extent and distribution of PrP^Sc protein deposits in scrapie-infected ceUs. The presence of dendrimers in a low pH environment and at relatively low, non-cytotoxic levels results in a significant reduction in detectable PrP^Sc in cells and brain homogenates. Thus, the present invention encompasses compositions for reducing, inhibiting, or otherwise mitigating the degree of infectivity of a protein. A composition of the invention is comprised of any compound capable of destroying conformationaUy altered proteins when in a low pH environment, (e.g. a polycationic dendrimer) in solution, suspension or mixture.

STERILIZING FORMULATIONS Sterilizing compositions of the invention preferably contain highly branched polycations, e.g. polycationic dendrimer, in a concentration from 0.0001 to 10% of the formulation. The following methods and excipients are merely exemplary and are in no way limiting.

In addition to including the compound such as a highly branched cationic compound in the formulation it is important to maintain that compound in a low pH environment. Any number of known acids or mixtures of acids could be used with the invention. Non-limiting examples of commercially available products which could be supplemented with the cationic compounds are described below. In these formulations the percentage amount of each ingredient can vary. In general a solvent ingredient (e.g. water or alcohol) is present in amounts of 40% to 100% and the last listed ingredient is present in a range of 0.5% to 5%. The other ingredients are present in an amount in a range of 1 % to 60% and more generally 5% to 20% . In each case the polycationic compounds of the invention are added in amounts of about 0.01 % to 5% and preferably 0J % to 2% and more preferably about 1 % . The amount added is an amount needed to obtain the desired effect.

49-

By using the disclosure provided here and other information such as taught in U.S. Patents 5,767,054; 6,007,831; 5,830,488; 5,968,539; 5,416,075; 5,296,158; and patents and publications cited therein those skilled in the art can produce countless other formulations of the invention. Further, such formulations can be used as described in such publications and can be packaged in any suitable container or dispenser device, e.g. taught in 5,992,698.

Formulations of the invention used with a cell culture have the advantage that they are non-toxic. For example, parenteral administration of a solution of the formulations of the invention is preferably nontoxic at a dosage of 0.1 mg/mouse, which is an LD ₅₀ of less than one at 40 mg/Kg. Various nutrient formulations and/or injectable formulations of the type known to those skilled in the art can be used to prepare formulations for treating cell cultures.

Those skilled in the art will understand that m some situations it may be desirable to further reduce the pH environment to obtain the desired results This can be accomplished by adding any desired acid If desired, the pH can be raised to a normal level after treatment is complete, l e after a sufficient amount of any conformationaUy altered protem present are destroyed

Compounds effective m stenhzmg compositions containing conformationaUy altered protems are determined via a cell culture assay and an organ homogenate assay each of which is described below m detail

ScN2a CELL BASED ASSAY

Efforts were made to optimize the transfection of ScN2a cells with pSPOX expression plasmids (Scott, M.R., Kohler, R , Foster, D & Prusiner, S B Chunenc pnon protem expression m cultured cells and transgemc mice. Protem Sci 1, 986-997 (1992)) In connection with those effects an evaluation was made of a transfection protocol that used SuperFect reagent (QIAGEN®) It was found that epitope-tagged (MHM2) PrP^Sc (Scott, M R , Kohler, R , Foster, D & Prusiner, S.B

Chimeric pπon protein expression m cultured cells and transgemc mice. Protem Sci 1, 986-997 (1992)) could not be detected in ScN2a cells following SuperFect-mediated transfection, whereas MHM2 PrP^Sc was efficiently formed when a cationic hposome method for DNA delivery was used Close scrutiny revealed that, pπor to protease digestion, SuperFect-transfected samples expressed MHM2 bands, which are not seen in the background pattern of an untransfected sample The 3F4 monoclonal antibody does not react with MoPrP but does exhibit high background staining on

Western blots of mouse ScN2a cells Increased lmmunostaimng in the 20-30 kDa region was observed compared to the non-transfected sample These observations led us to conclude that MHM2 PrP was successfully expressed usmg SuperFect transfection reagent, but that conversion of MHM2 PrP^c to protease-resistant MHM2 PrP^Sc was inhibited by SuperFect To mvestigate this apparent inhibition, a Western blot was reprobed with R073 polyclonal antiserum to detect endogenous MoPrP^Sc, the presence of which is diagnostic for pπon infection m ScN2a cells (Butler, D A , et al Scrapie-infected munne neuroblastoma cells produce protease- resistant pnon protems J Virol 62, 1558-1564 (1988)) Surpnsingly, it was found that the SuperFect-treated ScN2a cells no longer contained detectable quantities of MoPrP^Sc - also confirmed m Western blots To mvestigate the mechamsm by which SuperFect reduced the level of pre-existing p_rps^c _m chrojucaiiy infected ScN2a cells, measurements were made of endogenous PrP^Sc in ScN2a cells exposed to vaπous concentrations of SuperFect in the absence of plasmid DNA The results showed that treatment with SuperFect (a branched polycation) caused the disappearance of PrP^Sc from ScN2a cells m a dose-dependent manner The concentration of SuperFect reqmred to elmunate >95% of pre-existing PrP^Sc with a three hour exposure was found to be about 150 μg/ml Duration of treatment also influenced the ability of SuperFect to remove PrP^Sc from ScN2a cells exposure to 150 μg/ml SuperFect for 10 mm did not affect PrP^Sc levels, whereas 7 5 μg/ml SuperFect eliminated all detectable PrP^Sc with a tV_= 8 h

SuperFect is a mixture of branched polyamines deπved from heat-mduced degradation of a PAMAM dendnmer (Tang, M X , Redemann, C T & Szoka, F C J In vitro gene delivery by degraded polyamidoamine dendrimers Bwconjug Chem 7, 703-714 (1996)) Knowing this structure the ability of several other branched and unbranched polymers to eliminate PrP^Sc from ScN2a cells (Table 1) The branched polymers investigated mclude vanous preparations of PEI, as weU as intact PAMAM and PPI dendrimers Dendrimers are manufactured by a repetitive divergent growth technique, allowing the synthesis of successive, well-defined "generations" of homodisperse structures (Figure 1) The potency of both PAMAM and PPI dendrimers in eliminating PrP^Sc from ScN2a cells mcreased as the generation level mcreased The most potent compounds with respect to eliminating PrP^Sc were PAMAM generation 4 0 and PPI generation 4 0, whereas PAMAM generation 1.0 showed very little ability to eliminate PrP^Sc (Table 1). Similarly, a high MW fraction of PEI was more potent than low MW PEI.

From the foregoing data, it is clear that for all three branched polyamines tested, increasing molecular size corresponded to an increased potency for eliminating PrP^Sc . To determine whether this trend was directly attributable to increased surface density of amino groups on the larger molecules, PAMAM-OH generation 4.0 was tested. This is a dendrimer that resembles PAMAM generation 4.0 except that hydroxyls replace amino groups on its surface. Unlike PAMAM generation 4.0, PAMAM-OH generation 4.0 did not cause a reduction of PrP^Sc levels even at the highest concentration tested (10 mg/ml), establishing that the amino groups are required for the elimination of PrP^Sc by PAMAM (Table 1).

In an effort to assess the contribution of the branched architecture to the clearing ability of polyamines for PrP^Sc, the linear molecules poly-(L)lysine and linear PEI were also tested. Both of these linear compounds were less potent than a preparation of branched PEI with similar average molecular weight (Table 1), establishing that a branched molecular architecture optimizes the ability of polyamines to eliminate PrP^Sc, presumably because the branched structures achieve a higher density of surface amino groups.

Kinetics of PrP^c elimination by polyamines.

The preceding results demonstrate the potent ability of branched polyamines to clear PrP^Sc from ScN2a cells within a few hours of treatment. The utility of these compounds to act as therapeutics for treatment of prion disease was tested by determining whether they were cytotoxic for ScN2a cells, using as criteria cell growth, morphology, and viability as measured by trypan blue staining. None of the compounds was cytotoxic to ScN2a cells after exposure for one week at concentrations up to 7.5 μg/ml. To determine whether branched polyamines can cure ScN2a cells of scrapie infection without affecting cell viability, the kinetics of prion clearance was examined in the presence of a non-cytotoxic concentration (7.5 μg/ml) of three different branched polyamines. ScN2a ceUs were exposed to SuperFect, PEI, or PAMAM generation 4.0 for varying periods of time. The kinetics of PrP^Sc elimination were assessed by Western blotting. AU three compounds caused a substantial reduction in PrP^Sc levels after 8-16 h of treatment, and of the three compounds, PEI appeared to remove PrP^Sc most quickly, with a \V_= 4 h.

Curing neuroblastoma cells of scrapie infection.

The above results show that it is possible to reverse the accumulation of PrP^Sc in ScN2a cells under non-cytotoxic conditions. It was also found that extended exposure to even lower levels of the branched polyamines (1.5 μg/ml) was sufficient to eliminate PrP^Sc. Based on these findings, this protocol was used to determine whether the severe reduction in PrP^Sc levels following exposure to branched polyamines would persist after removal of the compounds. Following the exposure of ScN2a cells to a 1.5 μg/ml SuperFect for 1 week, PrP^Sc was reduced to <1% of the baseline level, but then increased back to ~5% of the baseline level after 3 additional weeks in culture in the absence of polyamine. In contrast, following exposure to 1.5 μg/ml of either PEI or PAMAM generation 4.0 for 1 week, PrP^c was completely eliminated and did not return even after 3 weeks in culture without polyamines. A more intensive course of treatment with 1.8 μg/ml SuperFect for 9 d also cured ScN2a cells of scrapie infection fully, manifested by the absence of PrP^Sc 1 month after removal of SuperFect.

Evidence for polyamines acting within an acidic compartment.

The above results showed the potent activity of branched polyamines in rapidly clearing scrapie prions from cultured ScN2a cells. Based on these results the mechanism by which these compounds act was investigated. AU of the compounds which effect removal of PrP^^c from ScN2a cells are known to traffic through endosomes (Boussif, O., et al. A versatile vector for gene and oligonucleotide transfer into cells in culture and in vivo: polyethyleneimine. Proc. Natl. Acad. Sci. U.S.A. 92, 7297-7301 (1995); Haensler, J. & Szoka, F.C.J. Polyamidoamine cascade polymers mediate efficient transfection of cells in culture. Bioconfug. Chem. 4, 372-379 (1993)). Since PrP^c is converted into PrP^Sc in caveolae-like domains (CLDs) or rafts (Gorodinsky, A. & Harris, D.A. Glycolipid-anchored proteins in neuroblastoma cells form detergent-resistant complexes without caveolin. J. Cell Biol. 129, 619-627 (1995); Taraboulos, A., et al. Cholesterol depletion and modification of COOH-terminal targeting sequence of the prion protein inhibits formation of the scrapie isoform. J. Cell Biol. 129, 121-132 (1995); Vey, M., et l. Subcellular colocalization of the cellular and scrapie prion proteins in caveolae-like membranous domains. Proc. Natl. Acad. Sci. USA 93, 14945-14949 (1996); Kaneko, K., et al. COOH-terminal sequence of the cellular prion protein directs subcellular trafficking and controls conversion into the scrapie isoform. Proc. Natl. Acad. Sci. USA 94, 2333-2338 (1997)) and is then internalized through the endocytic pathway (Caughey, B., Raymond, G.J., Ernst, D. & Race, R.E. N-terminal truncation of the scrapie- associated form of PrP by lysosomal protease(s): implications regarding the site of conversion of PrP to the protease-resistant state. J. Virol. 65, 6597-6603 (1991); Borchelt, D.R., Taraboulos, A. & Prusiner, S .B . Evidence for synthesis of scrapie prion proteins in the endocytic pathway. J. Biol. Chem. 267, 16188-16199 (1992)), it was deduced that polyamines act upon PrP^Sc in endosomes or lysosomes. This deduction was investigated by determining the effect of pretreatment with the lysosomotropic agents chloroqume and NH₄C1 on the ability of polyamines to elmunate PrP^Sc These lysosomotropic agents alkalmize endosomes and have no effect on PrP ^c levels when administered to ScN2a cells (Taraboulos, A . Raeber, A J . Borchelt, D R , Serban, D & Prusiner, S B Synthesis and traffickmg of pnon proteins in cultured cells Mol Biol Cell 3, 851-863 (1992)) Experimental results obtained shows that 100 μM chloroqume, but not 30 μM NH₄C1, blocked the ability of PEI to eliminate PrP^Sc Similar results were obtained with SuperFect and PAMAM, generation 4 0 Although the failure of NH₄C1 to affect PrP^Sc levels is not easily explained, the ability of chloroqume to attenuate the ability of branched polyamines to remove PrP^Sc is consistent with the notion that these agents act in endosomes or lysosomes

ORGAN HOMOGENATE ASSAY The above results with cell cultures prompted investigating the possibility that m an acidic environment branched polyamines, either by indirectly interacting with PrP^Sc or with another cellular component, could cause PrP^Sc to become susceptible to hydrolases present in the endosome/lysozome An in vitro degradation assay was developed to evaluate the effect of pH on the ability of polyamines to render PrP^Sc sensitive to protease Crude homogenates of scrapie-mfected mouse brain were exposed to a broad range of pH values m the presence or absence of SuperFect and then treated with protemase K pπor to Western blotting Whereas PrP^So remained resistant to protease hydrolysis throughout the pH range (3 6-9 6) m the absence of Superfect, addition of the branched polyamine at pH 4 0 or below caused PrP^Sc to become almost completely degraded by protease

Polyamine addition showed a dramatic effect on clearance in vitro which was optimized at pH 4 or less These results show that polyamines act on PrP^So m an acidic compartment To establish that the in vitro degradation assay is a valid approximation of the mechamsm by which branched polyamines enhance the clearance of PrP^Sc from cultured cells, a structure activity analysis was performed with several of the compounds tested m culture cells An excellent conelation was found between the clearance of PrP^Sc m cultured ScN2a cells (Table 1) and the ability to render PrP^Sc susceptible to protease at acidic pH in vitro Notably, PAMAM-OH generation 4 0 failed to render PrP^Sc susceptible to protease, whereas PAMAM generation 4 0 and PPI, generation 4 0 exhibited an even stronger activity than Superfect in vitro, as expected from their observed potency in cultured ScN2a cells (Table 1) MECHANISM OF ACTION The results discussed here show that certain branched polyammes cause the rapid elimination of PrP^Sc from ScN2a cells in a dose- and time-dependent manner These compounds demonstrate a potent ability to remove pπons from cultured cells at concentrations that are completely non-cytotoxic The cells may be maintained indefinitely in culture m the presence of therapeutic levels of branched polyammes Furthermore, when ScN2a cells were exposed to these compounds for ~ 1 week. PrP^Sc was reduced to undetectable levels and remained so for at least one month after removal of the polyamine

Claπfication of the exact mechamsm of PrP^Sc elimination by branched polyammes is an important objective Although a number of possible scenanos exist, several possibilities may be excluded already One possibility that was eliminated was that polyammes act by mduction of chaperones such as heat shock protems that mediate pnon protem refolding because the above results show that it was possible to reproduce the phenomenon in vitro Furthermore polyammes seem to offer advantages over other putative therapeutics that would seek to promote refoldmg at very high concentrations, dimethyl sulfoxide (DMSO) and glycerol act as direct "chemical chaperones" and inhibit the formation of new PrP^So (Tatzelt, J , Prusiner, S B & Welch, W J Chemical chaperones interfere with the formation of scrapie pnon protem EMBO J 15, 6363-6373 (1996)), but these compounds cannot reduce pre-existing PrP^Sc levels Furthermore, polyammes inhibit PrP^Sc formation at much lower concentrations than these agents The ability of polyammes to effect the rapid clearance of PrP^Sc also contrasts with the activity of other potential pnon therapeutics Sulfated polyamons may inhibit PrP^Sc accumulation m ScN2a cells by directly binding to PrP^c (Gabizon, R , Meiner, Z , Halimi, M & Ben-Sasson, S A Hepann-like molecules bmd differentially to pπon- protems and change their intracellular metabolic fate J Cell Physiol 157, (1993), Caughey, B , Brown, K , Raymond, G J , Katzenstein, G E & Thresher, W Binding of the protease-sensitive form of PrP (pπon protem) to sulfated glycosammoglycan and Congo red J Virol 68, 2135-2141

(1994)), but because branched polyammes are able to clear pre-existing PrP^Sc, their mechamsm of action cannot simply involve binding to PrP^c and inhibiting de novo synthesis

Another possible mechamsm which can be excluded is endosomal rupture The branched polyamines which were effective in clearing PrP^Sc from ScN2a cells m our experiments, PEI, SuperFect and PAMAM, are also potent lysosomotropic, osmotic agents which can swell m acidic environments and rupture endosomes (Boussif, O , et al A versatile vector for gene and ohgonucleotide transfer mto cells m culture and m vivo polyethyleneimine Proc Natl Acad Sc USA 92, 7297-7301 (1995), Haensler, J & Szoka, F C J Polyamidoamine cascade polymers mediate efficient transfection of cells m culture Bioconjug Chem 4, 372-379 (1993)) This might suggest that branched polyamines clear PrP^Sc from ScN2a cells by rapturing endosomes and exposing PrP^Sc to cytosolic degradation processes. However, it is known that the lysosomotropic, endosome-rapturing agents NH₄C1, chloroquine, and monensin do not interfere with the formation of PrP^Sc in ScN2a cells (Taraboulos, A., Raeber, A.J., Borchelt, D.R., Serban, D. & Prusiner, S.B. Synthesis and trafficking of prion proteins in cultured cells. Mol. Biol. Cell 3, 851-863 (1992)).

Furthermore, the results also show that chloroquine interferes with the ability of branched polyamines to clear PrP^Sc and that polyamines can clear PrP^Sc in vitro at acidic pH in the absence of cell membranes. Together, these observations rule out endosome rapture as the mechanism by which branched polyamines remove PrP^Sc. Without committing to any particular mechanism of action it appears likely that branched polyamines require the acidic environment of intact endosomes or lyzosomes to destroy PrP^Sc. The structure-activity profile of polymers tested reveals that the most active compounds possess densely packed, regularly-spaced amino groups, suggesting that these compounds may bind to a ligand which has periodically-spaced negative charges. Several scenarios remain possible. (1) Branched polyamines may bind directly to PrP^Sc aπanged as an amyloid with exposed negatively-charged moieties and induce a conformational change under acidic conditions. (2) Treatment of PrP 27-30 with acid decreases turbidity and increases a-helical content, suggesting that such conditions might dissociate PrP^Sc into monomers (Safar, J., Roller, P.P., Gajdusek, D.C. & Gibbs, C.J., Jr. Scrapie amyloid (prion) protein has the conformational characteristics of an aggregated molten globule folding intermediate). It is therefore possible that polyamines bind to an equilibrium unfolding intermediate of PrP^Sc present under acidic conditions. (3) Alternatively, polyamines might sequester a cryptic, negatively charged component bound to PrP^Sc that is essential for protease resistance, but which is only released when PrP^Sc undergoes an acid-induced conformational change. Such a component might act as a chaperone for PrP^Sc inside endosomes or lysosomes. (4) Finally, another possibility is that polyamines activate an endosomal or lysosomal factor which can induce a conformational change in PrP^Sc. Clearly, more work will be required to determine the precise mechanism by which branched polyamines destroy PrP^Sc.

GENERAL APPLICABILITY OF ASSAY The in vitro assay described here is generally applicable in the search for compounds that effectively clear conformationaUy altered proteins present in food thereby preventing a number of degenerative diseases, where the accumulation of proteins seems to mediate the pathogenesis of these illnesses. By simulating lysosomes, where proteases hydrolyze proteins under acidic conditions, the in vitro brain homogenate assay is able to rapidly evaluate the efficacy of a variety of polyamines to induce degradation of PrP^Sc.

The in vitro assay which used scrapie infected brain homogenate to test for compounds which clear PrP^Sc could be modified to assay for compounds which would clear any conformationaUy altered protein. The assay is caπied out by homogenizing the organ or tissue where the conformationaUy altered protein is present in the highest concentration. The pH of the homogenate is then reduced to less than 5.0 and preferably 4.0 or less. For example pancreatic tissue can be homogemzed to produce an assay to test for compounds which clear amylin which is associated with type II Diabetes. Homogemzed kidney could be used to test for compounds which clear β₂ - microglobulin and homogemzed heart or vascular tissue used to test for compounds which clear atrial natriuretic factor. Those skilled in the art will recognize other organs and tissue types which can be homogemzed to test for other compounds which clear other conformationaUy altered proteins.

Besides using the in vitro assay to screen for potential drags, the compounds found via the assay such as branched polyamines provide a new tool for exploring the conversion of a protein to conformationaUy altered protein, e.g. PrP^c into PrP^Sc. The mechanism by which branched polyamines render PrP^Sc susceptible to proteolysis, remains to be established. Whether the interaction of branched polyamines with PrP^Sc is reversible is unknown. In addition, we do not know whether branched polyamines are able to solubilize PrP^Sc without ineversibly denaturing the protein. Whatever the mechanism by which branched polyamines interact with PrP^So, it is likely to be different from that found with chaotropes as well as denaturing detergents and solvents (Prusiner,

S.B., Groth, D., Serban, A., Stahl, N. & Gabizon, R. Attempts to restore scrapie prion infectivity after exposure to protein denaturants. Proc. Natl. Acad. Sci. USA 90, 2793-2797 (1993))

Using the assays described and disclosed here certain specific branched polyamines have been found which mediate the clearance of PrP^Sc from cultured cells under non-cytotoxic conditions. These compounds offer the intriguing possibility of being added to a wide range of low pH food products to neutralize conformational altered proteins present. Since the compounds found act by stimulating normal cellular pathways of protein degradation to destroy PrP^Sc, this class of compounds would also likely be of value in the treatment of other degenerative and hereditary disorders where abnormally folded, wild-type or mutant proteins accumulate. Such an approach may find merit in developing an effective therapeutics for one or more of the common, degenerative illnesses including Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, froπtotemporal dementia, adult onset diabetes mellitus and the amyloidoses (Beyreuther, K. & Masters, C.L. Serpents on the road to dementia and death. Accumulating evidence from several studies points to the normal function of presenilin 1 and suggests how the mutant protein contributes to deposition of amyloid plaques m Alzheimer's disease Nature Medicine 3, 723-725 (1997), Masters, C L & Beyreuther, K Alzheimer's disease BMJ 316, 446-448 (1998), Selkoe, D J The cell biology of beta-amyloid precursor protem and preseniun in Alzheimer's disease Trends in Cell Biol 8, 447-453 (1998), Selkoe, D J Translating cell biology into therapeutic advances m Alzheimer's disease Nature 399, A23-31 (1999) Wong, P C , et al An adverse property of a familial ALS -linked SOD1 mutation causes motor neuron disease charactenzed by vacuolar degeneration of mitochondria Neuron 14, 1105-1116 (1995), Spillantini, M G , Crowther, R A , Jakes, R , Hasegawa, M & Goedert, M a-Synuclein in filamentous inclusions of Lewy bodies from Parkinson's disease and dementia with Lewy bodies Proc Natl Acad Sci USA 95, 6469-6473 (1998), Hutton, M , et al Association of missense and 5'-sphce-sιte mutations m tau with the mhented dementia FTDP-17 Nature 393, 702-705 (1998), Stone, M J Amyloidosis a final common pathway for protem deposition m tissues Blood lS , 531-545 (1990)) Whether branched polyammes might also prove efficacious m a vanety of inherited disorders where the accumulation of abnormal protems is a hallmark of the illness remains to be established, these genetic maladies mclude heπtable forms of pπon disease, Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, frontotemporal dementia, Pick's disease and amyloidosis, as well as the tnplet repeat diseases mcludmg Huntington's disease, spinal cerebellar ataxias and myotomc dystrophy (Fu, Y -H , et al An unstable tnplet repeat m a gene related to myotomc muscular dystrophy Science 255, 1256-1259 (1992), Group, T H s D C R A novel gene containing a tnnucleotide repeat that is expanded and unstable on Huntington's disease chromosomes Cell 72, 971-983 (1993))

Compounds identified via assays of the mvention such as branched polyammes will find utility m preventing or delaying the onset of these genetic diseases where earners can often be identified decades m advance of detectable neurologic or systemic dysfunction

The mvention is based on the discovery that several dendntic polycations, mcludmg the starburst dendrimers Superfect™ (QIAGEN®, Valencia, CA), polyamidoamide (PAMAM), and the hyperbranched polycation polyethyleneimine (PEI), were surpnsingly found to eliminate PrP^Sc from cultured scrapie-infected neuroblastoma cells These highly-branched, polycatiomc compounds provide a novel class of therapeutic agents to combat pnon diseases and other degenerative disease mcludmg the amyloidoses The removal of PrP^Sc is dependent on both the concentration of dendntic polymer and length of exposure Dendntic polymers were able to clear PrP^Sc at concentrations which were not cytotoxic Repeated exposures to heat-degraded starburst PAMAM dendnmer or PEI caused a dramatic reduction m PrP^Sc levels which persisted for a month even after removal of the compound Dendntic polycations did not appear to destroy punfied PrP^Sc in vitro, and therefore may act through a generalized mechamsm Dendntic polycations represent a class of compounds which can be used as therapeutic agents in prion diseases and other disorders involving insoluble protein deposits, such as the amyloidoses.

EXAMPLES The following examples are put forth so as to provide those of ordinary skill in the art with a complete disclosure and description of how to make and use the present invention, and are not intended to limit the scope of what the inventors regard as their invention nor are they intended to represent that the experiments below are all or the only experiments performed. Efforts have been made to ensure accuracy with respect to numbers used (e.g. amounts, temperature, etc.) but some experimental enors and deviations should be accounted for. Unless indicated otherwise, parts are parts by weight, molecular weight is weight average molecular weight, temperature is in degrees Centigrade, and pressure is at or near atmospheric.

METHODS AND MATERIALS Chemicals. High molecular weight PEI was purchased from Fluka. DOTAP cationic lipid was purchased from Boehringer Mannheim and SuperFect transfection reagent was purchased from QIAGEN®. All other compounds were purchased from Sigma-Aldrich. AU test compounds were dissolved in water at stock concentration of 3 mg/ml and filtered through a Millipore 0.22 m m filter.

Cultured cells. Stock cultures of ScN2a cells were maintained in MEM with 10% FBS,

10% Glutamax (Gibco BRL), 100 U penicillin, and 100 mg/ml streptomycin (supplemented DME). Immediately prior to addition of test compounds, the dishes were washed twice with fresh supplemented DME media. After exposure to test compounds, dishes were drained of media and cells were harvested by lysis in 0.25-1 ml 20 mM Tris pH 8.0 containing 100 mM NaCl, 0.5% NP-40, and 0.5% sodium deoxycholate to obtain a total protein concentration of 1 mg/ml measured by the BCA assay. Nuclei were removed from the lysate by centrifugation at 2000 rpm for 5 min. For samples not treated with proteinase K, 40 μl of whole lysate (representing 40 μg total protein) was mixed with an equal volume of 2x SDS reducing sample buffer. For proteinase K digestion, 20 μg/ml proteinase K (Boehringer Mannheim) (total protein:enzyme ratio = 50:1) was added, and the sample was incubated for 1 h at 37° C. Proteolytic digestion was terminated by the addition of

Pefabloc to a final concentration of 5 mM. One ml samples were centrifuged at 100,000 x g for 1 h at 4°C, the supernatants were discarded, and the pellets were resuspended in 80 μl of reducing SDS sample buffer for SDS-PAGE. Brain homogenates. Brain homogenates from RML scrapie-affected CD-I mice (10% (w/v) in sterile water) were prepared by repeated extrusion through syringe needles of successively smaller size, from 18 to 22 gauge. Nuclei and debris were removed by centrifugation at 1000 x g for 5 min. The bicinchnoninic acid (BCA) protein assay (Pierce) was used to determine protein concentration. Homogenates were adjusted to 1 mg/ml protein in 1% NP-40. For reactions, 0.5 ml homogenate was incubated with 25 ml 1.0 M buffer (sodium acetate for pH 3-6 and Tris acetate for pH 7-10) plus or minus 10 ml of polyamine stock solution (3 mg/ml) for 2 h at 37° C with constant shaking. The final pH value of each sample was measured directly with a calibrated pH electrode (Radiometer Copenhagen). Following incubation, each sample was neutralized with an equal volume 0.2 M HEPES pH 7.5 containing 0.3 M NaCl and 4% Sarkosyl. Proteinase K was added to achieve a final concentration of 20 μg/ml, and samples were incubated for 1 h at 37° C. Proteolytic digestion was terminated by the addition of Pefabloc to a final concentration of 5 μM. Ten μl of digested brain homogenate was mixed with equal volume 2x SDS sample buffer and analyzed by SDS-PAGE followed by Western blotting.

Western blotting. Following electrophoresis, Western blotting was performed as previously described (Scott, M., et al. Transgenic mice expressing hamster prion protein produce species- specific scrapie infectivity and amyloid plaques. Cell 59, 847-857 (1989)). Samples were boiled for 5 min and cleared by centrifugation for 1 min at 14,000 rpm in aBeckman ultrafuge. SDS-PAGE was carried out in 1.5 mm, 12% polyacrylamide gels(Laemmli, U.K. Cleavage of structural proteins during the assembly of the head of bacteriophage T-4. Nature 227, 680-685 (1970)). Membranes were blocked with 5% non-fat milk protein in PBST (calcium- and magnesium-free PBS plus 0.1% Tween 20) for 1 h at room temperature. Blocked membranes were incubated with primary R073 polyclonal antibody (to detect MoPrP) (Serban, D., Taraboulos, A., DeArmond, S.J. & Prusiner, S.B. Rapid detection of Creutzfeldt-Jakob disease and scrapie prion proteins. Neurology 40, 110-

117 (1990)) or 3F4 monoclonal antibody (to detect MHM2 PrP) (Kascsak, R.J., et al. Mouse polyclonal and monoclonal antibody to scrapie-associated fibril proteins. J. Virol. 61, 3688-3693 (1987)) at 1:5000 dilution in PBST overnight at 4°C. Following incubation with primary antibody, membranes were washed 3 x 10 min in PBST, incubated with horseradish peroxidase-labeled secondary antibody (Amersham Life Sciences) diluted 1:5000 in PBST for 30 to 60 min at 4°C and washed again for 3 x 10 min in PBST. After chemiluminescent development with ECL reagent (Amersham) for 1 min, blots were sealed in plastic covers and exposed to ECL Hypermax film (Amersham). Films were processed automatically in a Konica film processor. EXAMPLE 1A

Branched polyamines inhibit formation of nascent PrP^Sc and induce clearance of pre-existing PrP^Sc

Western blots were probed with 3F4 monoclonal antibody which recognizes newly expressed MHM2 PrP. ScN2a cells were exposed to SuperFect for 3 h and harvested 3 d after removal of

SuperFect. Gells were ran on both undigested, control sample and a sample subjected to limited proteolysis. The samples were run in separate lanes 1-6 with a control and limited proteolysis sample for each of the 6 lanes as follows: Lane 1: DOTAP -mediated transfection. Lane 2: 30 μg/ml SuperFect, 5 μg pSPOX MHM2. Lane 3: 75 μg/ml SuperFect, 5 μg pSPOX MHM2. Lane 4: 150 μg/ml SuperFect, 5 μg pSOX MHM2. Lane 5: 150 μg/ml SuperFect, 10 μg pSPOX MHM2.

Lane 6: No addition of either transfection reagent or DNA. Forty μl of undigested brain homogenate was used in these studies while those samples subjected to limited digestion with proteinase K were concentrated 25-fold prior to SDS-PAGE. One ml of the digest were centrifuged at 100,000 x g for 1 h at 4 ° C and the pellets suspended in 80 μl of SDS sample buffer prior to SDS-PAGE followed by Western blotting. Apparent molecular weights based on migration of protein standards are 34.2,

28.3, and 19.9 kDa.

AU of the control lanes 1-6 show multiple bands as expected. However, of the samples subjected to limited proteolytic only lane 1 shows bands. Unexpectedly, all of the partially digested sample lanes 2-5 show no bands and as expected no bands in the partially digested lane 6. These results show the effect of using SuperFect in clearing PrP^Sc.

EXAMPLE IB The blot described above was stripped of antibody, exposed to labeled R073 and redeveloped. The antibody 3F4 used in Example 1 binds to PrP^c but not to PrP^Sc. However, R073 binds to PrP^Sc and PrP^c. Lanes 1, 2 and 3 show decreasing amounts of PrP^Sc and lanes 4 and 5 show no detectable PrP^Sc.

EXAMPLE 2A Gels were run on undigested controls 1-4 and as above, samples subjected to limited proteolysis. The lanes were as follows: Lane 1 : No SuperFect. Lane 2: 30 μg/ml SuperFect. Lane 3: 75 μg/ml SuperFect. Lane 4: 150 μg ml SuperFect. ScN2a cells were exposed to SuperFect for 3 h and harvested 3 d after removal of SuperFect. Apparent molecular weights based on migration of protein standards are 33.9, 28.8, and 20.5 kDa. In that each sample was tested after the same time penod the results show the dose-dependent effect of SuperFect on PrP^Sc removal Lanes 1, 2 and 3 show decreasmg amounts of PrP^Sc and lane 4 shows no detectable PrP^Sc

EXAMPLE 2B To determine the time-dependent effect of SuperFect three different panels with four lanes each were prepared and run as follows ScN2a cells were exposed to 7 5 μg/ml SuperFect (lanes 1-4), PEI (average molecular weight ~60,000)(lanes 5-8), or PAMAM, generation 4 0 (lanes 9-12) Time of exposure times for each polyamine 0 hours (lanes 1, 5, and 9), 4 hours (lanes 2, 6, and 10), 8 hours (lanes 3, 7, and 11), 16 hours (lanes 4, 8, and 12) AU samples were subjected to limited proteolysis to measure PrP^Sc Apparent molecular weights based on migration of protem standards are 38, 26, and 15 kDa Lanes of each of the three panels show decreasmg amounts of PrP^Sc

EXAMPLE 3 In this example four panels A,B, C and D were created with panels having three double (control and test) lanes each ScN2a cells were exposed to 1 5 μg/ml (A) SuperFect, (B) PEI

(average molecular weight -60,000), (C) PAMAM, generation 4 0, or (D) no addition Cells were harvested Lane 1, before addition, Lane 2, immediately following 1 week contmuous exposure to test compounds, and Lane 3, three weeks after removal of test compounds Mmus (-) symbol denotes undigested, control sample and plus (+) symbol designates sample subjected to limited proteolysis Apparent molecular weights based on migration of protem standards are 33 9, 28 8, and 20 5 kDa Test lanes 3 m panel A showed slight PrP^Sc after three weeks and test lanes 3 m panels B and C showed no detectable PrP^Sc whereas PrP^Sc was present in all lanes m panel D

EXAMPLE 4A Four separate gels were ran to demonstrate the effect of adding chloroqume would have on

PrP^Sc levels The lanes 1 control and 3 where chloroqume was added show clear bands for PrP^Sc whereas lanes 2 and 4 with no chloroqume show barely detectable amounts of PrP^Sc The four lanes were prepared as follows ScN2a cells were treated Lane 1 Control media Lane 2 7 5 μg/ml PEI (average molecular weight ~60,000) Lane 3 PEI plus 100 μM chloroqume Lane 4 PEI plus 30 μM NH₄C1 Chloroqume and NH₄C1 were added 1 h pπor to addition of PEI Cells were harvested 16 hours after addition of PEI AU samples shown were subjected to limited proteolysis to measure PrP^Sc Apparent molecular weights based on migration of protem standards are 38, 26, and 15 kDa EXAMPLE 4B Eight lanes with SuperFect (+SF) and eight lanes without SuperFect (-SF) were prepared. Lanes 1-8 of each group had an adjusted pH of 3.6„ 4, 5, 6, 7, 8, 9 and 9.6. In vitro mixture of crude mouse brain homogenates with SuperFect under a range of pH conditions was performed as described in methods (measured final pH of each sample denoted above the lanes). Addition of 60 μg/ml SuperFect denoted as "+SF" and control with no addition as "-SF". All samples shown were subjected to limited proteolysis to measure PrP^Sc. Apparent molecular weights based on migration of protein standards are 30 and 27 kDa. AU lanes of the -SF group showed PrP^Sc present. Lanes 3-8 of the +SF group showed PrP^Sc. However, lanes 1 and 2 with respective pH levels of 3.6 and 4.0 showed very slight detectable PrP^Sc. The results show that the ability of a blanched polycation such as SuperFect to clear PrP^Sc is pH dependent.

EXAMPLE 5 Sixteen different lanes were prepared as described. Lanes 1 and 2 were control lanes and each of lanes 3-16 contained a different compound as tested in Table 1. The test compounds were all polyamines. Thus, the results show removal of PrP^Sc from brain homogenate in vitro by various polyamines. Samples were incubated with polyamines at pH 3.6 and processed as described in Methods. Each polyamine was tested at 60 μg/ml concentration. Lanes 1 and 2: control. Lane 3: poly-(L)lysine. Lane 4: PAMAM, generation 0.0. Lane 5: PAMAM, generation 1.0. Lane 6: PAMAM, generation 2.0. Lane 7: PAMAM, generation 3.0. Lane 8: PAMAM, generation 4.0.

Lane 9: PAMAM-OH, generation 4.0. Lane 10: PPI, generation 2.0. Lane 11: PPI, generation 4.0. Lane 12: linear PEI. Lane 13: high MW PEI. Lane 14: low MW PEI. Lane 15: average MW PEI. Lane 16: SuperFect. AU samples shown were subjected to limited proteolysis to measure PrP^Sc. Apparent molecular weights based on migration of protein standards are 30 and 27 kDa.Table 1. Removal of PrP^Sc by polymer compounds. IC50 = approximate concentration of polymer required to reduce PrP^Sc to 50% of control levels in ScN2a cells after exposure for 16 hours. AU compounds were tested at 5 different concentrations. PrP^Sc levels were measured by densitometry of Western blot signals.

TABLE 1

(Note that Table 1 includes information on the characteristics of compounds used but that the list does not conespond directly to lanes 1-16)

Molecular Primary NH2 IC50 (ng/ml)

Weight groups

Compound

PAMAM generation 0.0 517 4 >10,000

PAMAM generation 1.0 1,430 8 >10,000

PAMAM generation 2.0 3,256 16 2,000

PAMAM generation 3.0 6,909 32 400

PAMAM generation 4.0 14,215 64 80

PAMAM-OH generation 4.0 14,279 0 >10,000

PPI generation 2.0 773 8 2,000

PPI generation 4.0 3,514 32 80

Low MW PEI -25,000 2,000

Average MW PEI -60,000 400

High MW PEI -800,000 80

Linear PEI -60,000 2,000 poly-(L)lysine -60,000 >500 10,000

SuperFect 400

Lanes 7, 8, 11 and 13 showed the best results, i.e. best ability to clear PrP^Sc under these conditions. Specifically, PAMAM generation 4.0 in lane 8 showed the best ability to clear PrP^Sc under these conditions whereas PAMAM-OH generation 4.0 showed almost no detectable ability to clear PrP^Sc and was comparable to the control.

EXAMPLE 6 Transfection of PrP^Sc Expressing Cells with Dendrimer Compounds

Cells of neuronal origin expressing PrP^Sc were examined for the ability of compounds to suppress PrP^Sc formation.

Transfection Studies

Stock cultures of N2a and ScN2a cells were maintained in MEM with 10% FBS, 10% Glutamax (Gibco BRL), 100 U penicillin, and 100 μg/ml streptomycin. Cells from a single confluent 100 mm dish were trypsinized and split into 10 separate 60 mm dishes containing DME plus 10% FBS, 10%) Glutamax, 100 U penicillin, and 100 μg/ml streptomycin (supplemented DME) one day prior to transfection. Immediately prior to transfection, the dishes were washed twice with 4 ml supplemented DME media and then drained. For DOTAP -mediated transfection, 15 μg pSPOX MHM2 was resuspended in 150 μl steπle Hepes Buffered Salme (HBS) on the day of transfection The DNA solution was then mixed with an equal volume of 333 μg/ml DOTAP (Boehringer Mannheim) m HBS m Falcon 2059 tubes and mcubated at room temperature for 10 minutes to allow formation of DNA/lipid complexes Supplemented DME (2 5 ml) was added to the mixture, and this was then pipetted onto drained cell monolayers The following day, the medium containing DNA/lipid was removed and replaced with fresh supplemented DME Cells were harvested three days later

For Superfect™ -mediated transfections/exposures, Superfect™ with or without DNA was added to 1 ml supplemented DME m a Falcon 2059 tube to achieve the specific concentrations needed for each experiment This mixture was pipetted up and down twice and then onto dramed cell monolayers After exposure for the mdicated times, the medium containing Superfect™ was removed and replaced with fresh supplemented DME Cells were harvested at specified tunes after removal of Superfect™

Exposures to PPI (DAB-Am-8, Polypropylemimne octaamine Dendnmer, Generation 2 0 Aldnch 46,072-9), Intact PAMAM (Starburst (PAMAM)Dendπmer, Generation 4

Aldnch 41,244-9), PEI (Sigma), poly-(L)lysιne (Sigma), and poly-(D) lysme (Sigma) were performed as descnbed above for Superfect™

Isolation of Protem from Treated Cells Cells were harvested by lysis m 1 2 ml of 20 mM Tns pH 8 0 containing 100 mM NaCl,

0 5% NP-40, and 0 5% sodium deoxycholate Nuclei were removed from the lysate by centrifugation at 2000 rpm for 5 mm This lysate typically had a protem concentration of 0 5 mg/ml measured by the BCA assay For samples not treated with protemase K, 40 μl of whole lysate (representing 20 μg total protem) was mixed with 40 μl of 2x SDS sample buffer For protemase K digestion, 1 ml of lysate was mcubated with 20 μg/ml protemase K (total protem enzyme ratio =

254) for 1 hr at 37°C Proteolytic digestion was terminated by the addition of 8 μl of 0 5M PMSF m absolute ethanol Samples were then centrifuged for 75 mm in a Beckman TLA-45 rotor at 100,000 x g at 4°C The pellet was resuspended by repeated pipetting m 80 μl of IX SDS sample buffer The entire sample (representmg 0 5 mg total protem before digestion) was loaded for SDS-PAGE Western Blot Analysis

Immunoreactive PrP bands from the DOTAP -mediated transfection were detected before and after digestion with protemase K with monoclonal antibody 3F4 The construct used to express PrP^Sc m the ScN2a cells is MHM2 a chunenc construct that differs from wild-type (wt) MoPrP at positions 108 and 111 (Scott et al , (1992) Protein Sci 1 986-997) Substitution at these positions with the conespondmg residues (109 and 112 respectively) from the Synan hamster (SHa) PrP sequence creates an epitope for 3F4 (Kascsak et al , (1987) J Virol 61 3688-3693), which does not recognize endogenous wt MoPrP m ScN2a cells and hence facilitates specific detection of the transgene by Western blot Following electrophoresis, Western blotting was performed as previously descnbed (Scott et al , (1989) Cell 59 847-857) Samples were boiled for 5 minutes and cleared by centnfugation for 1 mmute at 14,000 rpm m a Beckman ultrafuge SDS-PAGE was earned out m 1 5 mm, 12% polyacrylamide gels (Laemmli (1970) Nature 227 661-665) Membranes were blocked with 5% nonfat milk protem m PBST (calcium- and magnesium-free PBS plus 0 1% Tween 20) for 1 hour at room temperature Blocked membranes were mcubated with primary R073 polyclonal or 3F4 monoclonal antibody at a 1 5000 dilution m PBST overnight at 4 °C

Following mcubation with primary antibody, membranes were washed 3 x 10 minutes m PBST, mcubated with horseradish peroxidase-labeled secondary antibody (Amersham Life Sciences) diluted 1 5000 in PBST for 25 minutes at room temperature and washed again for 3x 10 minutes m PBST After chemilummescent development with ECL reagent (Amersham) for 1 mmute, blots were sealed m plastic covers and exposed to ECL Hypermax film (Amersham) Films were processed automaticaUy m a Komca film processor

In contrast to DOTAP-transfected cells, ScN2a cells transfected with varying concentrations of Superfect™ and DNA did not appear to contain protease-resistant MHM2 Close scrutiny revealed that, pπor to protease digestion, Superfect™-transfected samples express MHM2 bands which are not seen m the background pattern of the control sample These observations mdicate that MHM2 PrP was successfully expressed usmg Superfect™ transfection reagent, but conversion of MHM2 PrP^c to protease-resistant MHM2 PrP^Sc was inhibited by Superfect™

To examine whether Superfect™ had affected levels of preexisting PrP^Sc in ScN2a cells, the Western blot probed with 3F4 antibody was reprobed with polyclonal antibody R073, which is able to recognize endogenous MoPrP Remarkably, Superfect™ caused the disappearance of preexisting MoPrP^Sc from ScN2a cells m a dose-dependent manner After treatment with Superfect™, PrP^Sc could not be detected m the nuclear fraction, pellet, supernatant, or media The concentration of Superfect™ reqmred to fully remove preexisting PrP^Sc with a three hour exposure was 300 μg/ml, whereas 30 μg/ml was sufficient to interfere with the formation of new MHM2 PrP^Sc within the same time frame.

Length of exposure dramatically influenced the ability of Superfect™ to remove PrP^Sc from ScN2a cells. Whereas a 3 hour exposure to 150 μg/ml Superfect™ significantly lowered PrP^Sc levels in ScN2a cells, exposure for 10 min to the same dose of Superfect™ did not affect PrP^Sc levels.

When ScN2a cells were exposed to 2 μg/ml Superfect™ continuously for 1 week, PrP^Sc disappeared completely.

The conditions tested did not appear to be toxic for the cells. Neither 150 μg/ml Superfect™ for 3 hrs nor 2 μg/ml Superfect™ continuously for 1 week caused any obvious changes in cell morphology, viability, or growth as judged by phase contrast microscopy.

EXAMPLE 7 Elimination of PrP^Sc by repeated exposures to Superfect™

The duration in the reduction in PrP^Sc levels after exposure to Superfect™ was examined, and it was shown that this reduction could persist for extended periods after removal of Superfect™.

Following the exposure of ScN2a cells to a single dose of 150 μg/ml Superfect™ for 3 hrs, PrP^Sc levels remained low for one week, but returned to near baseline levels after 3 weeks in culture without Superfect™

In contrast, when ScN2a cells were exposed to 4 separate doses of Superfect™ over the course of 16 days, very little PrP^Sc could be detected 4 weeks after the final exposure to Superfect™.

This result offers hope that prolonged exposure to Superfect™ may lead to long term cure of scrapie infection in cultured cells.

EXAMPLE 8 Superfect™ does not destroy PrP^Sc directly

The dendrimer Superfect™ was used to determine if it could exert a similar inhibitory effect on PrP^Sc in either crude brain homogenates or purified PrP 27-30 rods.

Brain homogenates from normal and scrapie-affected Syrian hamsters (10% (w/v) in sterile PBS) were prepared by repeated extrasion through syringe needles of successively smaller size, from 18 to 22 gauge. Nuclei and debris were removed by centrifugation at 1000 x g for 10 min. The bicinchnoninic acid (BCA) protein assay (Pierce) was used to determine protein concentration. Homogenates were adjusted to 10 mg/ml protein with PBS and 50 μl was added to 450 μl of lysis buffer containing 100 mM NaCl, 1 mM EDTA, 0.55% sodium deoxycholate, 0.55% Triton X-100, and 50 mM Tris-HCl pH 7.5. This mixture was then incubated with 0-300 μg/ml Superfect™ for 3 hrs at 37 °C and then centnfuged for 10 mm at 14.000 rpm m a Beckman Ultrafuge The pellet was resuspended m 450 μl lysis buffer without Superfect™ Proteinase K (Boehringer Mannheim) was added to achieve a final concentration of 20 μg/ml, and thus the ratio of total protein/enzyme was 50 1 Samples were mcubated for 1 h at 37 °C Proteolytic digestion was ternunated by the addition of 8 μl of 0 5 M PMSF m ethanol Samples were then centnfuged for 75 mm m a Beckman TLA-45 rotor at 100,000 x g at 4 °C Undigested samples (10 μl) were mixed with an equal volume of 2x SDS sample buffer For digested samples, the pellet was resuspended by repeated pipetting m 100 μl lx SDS sample buffer Twenty μl (equivalent to 100 μg of total protem pnor to protemase K digestion) of each sample was loaded for SDS-PAGE PrP 27-30 rods were punfied from scrapie-affected Synan hamster brains and previously descnbed (Prusiner et al , (1983) Cell 35 349-358) Punfied rods (3 5 μg/ml) were mcubated with or without 900 μg/ml Superfect™ m 100 μl supplemented DME After 16 hrs at 37 °C, the suspension was centnfuged at 100,000 x g at 4 °C The pellet was resuspended m 500 μl of buffer containing 1 mg/ml BSA, 100 mM NaCl, 1 mM EDTA, 0 55% sodium deoxycholate, 0 55% Tnton X-l 00, and 50 mM Tπs-HCl pH 7 5 Protemase K was added to achieve a final concentration of 20 μg/ml Samples were mcubated for 1 h at 37 °C Proteolytic digestion was terminated by the addition of 8 μl of 0 5 M Pefabloc (Boehringer Mannheim) Samples were then centnfuged for 75 mm at 100,000 x g at 4 °C Undigested samples (50 μl) were mixed with an equal volume of 2x SDS sample buffer For digested samples, the pellet was resuspended by repeated pipetting m 100 μl lx SDS sample buffer Forty μl of each sample was loaded for SDS-PAGE

When Superfect™ was mixed with either crude homogenates of scrapie-affected Synan hamsters or with punfied Synan hamster PrP 27-30, there was no significant change m the level of protemase K-resistant PrP^Sc These results suggest that the removal of PrP^Sc from ScN2a cells by Superfect™ depends on the presence of intact cellular machinery

EXAMPLE 9 Clearance of PrP^Sc levels by other dendritic polycations The Superfect™ compound is a high molecular weight component of heat-degraded PAMAM Starburst dendrimers, which is a catiomc, highly-branched, monodisperse polymers (Tang et al , (1996) Bioconjugate Chem 1 703-714) To identify other potentially usefid anti-pnon therapeutic agents, we screened three other dendntic polycations and two lmear catiomc polymers for their ability to clear PrP^Sc from ScN2a cells Among the dendntic macromolecules tested, polyetheleneimine (PEI) was the most potent, removing the majonty of PrP^Sc from ScN2a cells after 3 hrs when used at a concentration of 10 μg/ml Intact PAMAM displayed a potency comparable to Superfect™, removing approximately half of the detectable PrP^Sc when used at a concentration of 50 μg/ml. In contrast, the dendrimer polypropyleneimine (PPI), poly-(L)lysine, and the linear polycation poly-(D)lysine failed to reduce PrP^Sc levels at concentrations between 10-50 μg/ml. These results demonstrate that a branched polymeric architecture is required to clear PrP^Sc. Furthermore, exposure of ScN2a cells to either PEI or intact PAMAM for one week at a concentration of 1.5 μg/ml completely removes PrP^Sc, effectively curing the cells of scrapie infection.

While the present invention has been described with reference to the specific embodiments thereof, it should be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the true spirit and scope of the invention. In addition, many modifications may be made to adapt a particular situation, material, composition of matter, process, process step or steps, to the objective, spirit and scope of the present invention. AU such modifications are intended to be within the scope of the claims appended hereto.

Claims

CLAIMS That which is claimed is:

1. A method of sterilizing an object, comprising the steps of: contacting the object with a composition of a branched polycation at a pH of 5.0 or less; and allowing the composition to remain in contact with the object for a period of time sufficient to render a conformationaUy altered protein non-infectious.

2. The method of claim 1 , further comprising : removing the composition from the object.

3. The method of claim 1 , wherein the branched polycation is a polycationic dendrimer selected from the group consisting of polypropylene imine, polyethyleneimine (PEI) poly(4'-aza-4'-methylheptamethylene D-glucaramide), polyamidoamines and variants or fragments thereof.

4. The method of claim 1, wherein the object is a cell culture.

5. The method of claim 1 , wherein the object is a bovine product.

6. A composition, comprising: water in an amount of from 1% to 99.99% by weight; polycationic dendrimer in an amount of 0.001% to 10% by weight.

7. The composition of claim 6, wherein the composition is a pharmaceutical composition comprising a therapeutically effective amount of a branched polycation and a pharmaceutically acceptable excipient.

8. The composition of claim 6, further comprising a second compound selected from the group consisting of: a detergent, an antibacterial compound, an antiviral compound, and an antifungal compound.

9. A capsule for oral administration of a compound, comprising: gelatin extracted from a cow; and a branched polycation.

10. A cell culture, comprising: cells genetically engineering to produce a pharmaceutical; cell nutrients; and a branched polycation.