WO1989005349A1

WO1989005349A1 - Method of combating viral infections

Info

Publication number: WO1989005349A1
Application number: PCT/AU1988/000474
Authority: WO
Inventors: Andrew John Hapel; Ming-Chiu Fung; Jeffrey Robert Hahn
Original assignee: The Australian National University
Priority date: 1987-12-09
Filing date: 1988-12-09
Publication date: 1989-06-15

Abstract

A method for combating viral infection in a human or animal patient, comprises administering to the patient histocompatible blood cells or bone marrow stem cells which have been transformed with a nucleotide sequence coding for a protein or polypeptide which, on expression by the cells will reduce the rate at which the superinfecting virus particles can enter the cells. The nucleotide sequence may be a sequence or gene coding for all or an immunologically-active portion of a HIV envelope protein such as gp160, gp120 or gp41.

Description

METHOD OF COMBATING VIRAL INFECTIONS

This invention relates to a method of combating viral infections, and in particular it relates to a method of combating infections with retroviruses.

BACKGROUND Retroviruses are RNA viruses that can make a DNA copy of their genome using a virus-encoded enzyme called reverse transcriptase. The DNA copy (ies) can become randomly integrated into the genome of eukaryotic cells. These integrated viral genomes may remain silent, may produce infectious virus, or may be oncogenic. Rarely, infection with a retrovirus is lytic for the infected cell. Large numbers of retroviruses have been isolated from mice and many have no obvious pathologic effect. However because retroviruses contain one genes, which may be derived from cellular analogues that control cell division, they have been extensively studied in an attempt to understand oncogenesis. For many years the relevance of such work to man was obscure but the discovery of three disease-causing retroviruses in man has thrust retroviral research to the forefront of medical research. Retroviruses that affect man include the human T-lymphotropic viruses HTLVI and HLTVII, which can cause leukaemias, and the human immunodeficiency virus (HIV or HTLVIII) which causes the acquired immunodeficiency

*-- syndrome (AIDS) . The AIDS virus is somewhat unique in that it causes a lytic infection of lymphocytes, thus inducing a severe and chronic suppression of the immune response of the host, ultimately resulting in a complete collapse of the body's defences against infection and the

^ like. AIDS sufferers normally die as the result of uncontrolled secondary infections due to viruses, fungi, protozoa and bacteria, or as a result of uncontrolled cancers or the like. The total number of ret ovirus- infected individuals in the western world may be 10

15 million and is in any event increasing. There is at present no cure for AIDS, and the disease seems to be uniformly fatal although the virus can take many years after initial infection to cause disease. World-wide efforts to date to produce a vaccine against AIDS by

20 traditional methods have not been effective, and in the absence of an effective vaccine the main defences against the disease have relied on education directed to prevention of the spread of the virus throughout the community.

25 Retroviruses are divided into groups based on their ability to interfere with infection of their host cell by other retroviruses. When a cell is infected with a virus in a particular interference group, no other virus in that group can subsequently infect the cell, that is the cell

30 cannot be subsequently "superinfected". Infection of the cell by viruses in other interference groups is unaffected. This phenomenon of interference is believed to be most likely due to saturation of available virus-binding sites on the cell surface by viral envelope 35 components made within the infected cell. However, genetic activation of other regulatory mechanisms cannot be excluded.

The mechanism of viral interference was elucidated in 1966 by Steck and Rubin (1,2) who showed that viral interference reduces the rate at which superinfecting virus particles penetrate the cell. Cell surface receptors specific for the envelope of the virus being produced are occupied by virus envelope molecules synthesised within the virus-producing cell, and are thus not available for interaction with superinfecting virus particles.

The AIDS virus, HIV, includes major proteins in its outer envelope which are glycoproteins known as gpl20 and gp41. The virus initially produces a large envelope protein, gpl60, before splitting it into the two smaller proteins. HIV infects cells primarily because the glycoprotein gpl20 which is positioned on the envelope of the virus and on the membrane of cells infected with HIV, binds to a cell surface determinant called CD4, which is found predominantly on helper type thymus-derived lymphocytes (3,4). CD4⁺ thymus-derived lymphocytes, are the primary target of HIV, and infection and subsequent loss of these cells results in immunosuppression and the catastrophic adventitius sequelae that are characteristic of HIV infection.

As previously described, a major defect in AIDS is loss of immune function, particularly T-cell mediated immune function as a result of lymphocyte destruction by the AIDS virus. One means for reconstituting immune function would be by transplantation of histocompatible blood cells or bone marrow stem cells, however in the HIV infected patient these transplanted cells would of course themselves be infected and destroyed. It is one object of the present invention to provide a method whereby such cells can be transplanted without resultant destruction by the virus.

SUMMARY OF THE INVENTION

The present invention provides a method for combating viral infection in a human or animal patient, which comprises administering to the patient histocompatible blood cells or bone marrow stem cells which have been transformed with a nucleotide sequence coding for a protein or polypeptide which, on expression by the cells, will reduce the rate at which superinfecting virus particles can enter the cells.

In another aspect, the present invention provides a therapeutic or prophylactic composition for combating viral infection in a human or animal patient, which comprises histocompatible blood cells or bone marrow stem cells which have been transformed with a nucleotide sequence coding for a protein or polypeptide which, on expression by the cells, will reduce the rate at which superinfecting virus particles can enter the cells.

As previously described, the present invention has particular application in combating retroviral infection, most particularly HIV infection, and in one particularly preferred embodiment of the present invention the histocompatible blood cells or bone marrow stem cells are transformed with a nucleotide sequence or gene coding for all or an immunologically-active portion of a HIV envelope protein. Most preferably, the cells are transformed with a nucleotide sequence or gene coding for all or an immunologically-active portion of the HIV envelope proteins gpl60, gpl20 or gp41, or any portion of the gpl60 gene encoding an "interfering" polypeptide. Further, selected blood cells expressing HIV envelope proteins may be useful as potent immunogens inducing strong cell mediated immunity to HIV.

In recent years, a number of retroviral vectors have become well known (5a, 5b, 6) and available. These vectors can enter cells and express the genes or nucleotide sequences they carry without producing infectious virus. Such vectors include, for example, non-replicating viral genomes which do not contain the gene for reverse transcriptase and so cannot reproduce, or modified viral genomes which do not contain genes for structural components of the virus envelope and so cannot make infectious virus. In the performance of the present invention, for example in the production of cells transformed with HIV gpl60, gpl20 or gp41 nucleotide sequences, retroviral vectors are used to construct artificial HIV-like viral genomes. These constructs, of course, do not have the pathogenicity of HIV since they cannot replicate in the transformed cells, however they do contain the gene or similar sequence for gplβO, gpl20 or gp41 under control of either a modified retroviral promoter or some other promoter.

The transformed cells may be used in accordance with the present invention for combating appropriate viral infections. Thus, they may be used therapeutically in the treatment of infected patients or they may be used prophylactically in order to prevent or minimise infection by the virus.

In one preferred embodiment of the invention, bone marrow stem cells are transformed with a retroviral vector which carries the gene coding for the envelope glycoprotein gpl60 or gpl20 from HIV. This gene enables the transformed bone marrow cells to express gρl60 or gpl20 which will bind to the cell surface determinant CD4 of helper type thymus-derived lymphocytes. The surface receptors of these cells will thus become saturated with gpl20, and not be available for interaction with super-infecting HIV particles. The methods used in this aspect of the invention, include construction of a viral vector containing the gene for gpl60 downstream of a suitable promoter, and the use of this vector to transfect bone marrow stem cells and lymphocytes in vitro. The cells expressing gpl60 or gpl20 and gp41 can then be exposed to HIV, and examined for production of infectious virus and/or reverse transcriptase (an indicator of retroviral infection) .

An alternative, and safer method, for testing cells that express HIV gpl60 or gpl20 for resistance to superinfection would be to use radiolabelled, purified gpl20 antigen to measure available gpl20 binding sites. Cells that already produce gp!20, and have therefore saturated their gpl20 binding sites, will not bind significant amounts of the labelled ligand. As previously described, the present invention particularly relates to combating retroviral infections, and in addition to its use in relation to HIV or HLTVIII described in detail, the invention may be used in therapeutic or prophylactic treatment of leukaemias resulting from HTLVI or HLTVII infections in humans. In the treatment of such leukaemias, known chemotherapy and/or radiotherapy procedures are used to destroy the leukaemic cells, and the patient may then be treated by administration of appropriately transformed cells in accordance with the present invention.

The present invention is further illustrated in one embodiment by the following Example which relates to the construction of cells transformed with the HIV gpl60 gene. EXAMPLE

In this Example, standard techniques were used as described for example, in Maniatis "Molecular Cloning, A

Laboratory Manual". Restriction enzymes were used in accordance with manufacturer's directions. a. Expression of HIV-1 envelope αlycoprotein σpl60 in a retroviral shuttle vector.

The retroviral shuttle vector, fpGV-1, (5a, 5b) was used to express the HIV-1 envelope glycoprotein gpl60. 0 Vector fpGV-1 was derived from the HT-1 strain of Moloney

Sarcoma Virus (MSV) , and contains the bacterial ColEl origin of DNA replication, the neo ycin resistance gene from the transposon Tn5 and the long terminal repeats

(LTRs) of HT-1 MSV. It does not contain any sequences *5 related to the transforming mos gene (Figure 1) . The

HIV-1 envelope glycoprotein gpl60 gene was excised from the commercially available plasmid pBHIO (Biotech Research

Labs., U.S.A.) which contains the HIV-1 9kb partial genome from Sstl to Sstl sites (Figure 2) . The strategy of 0 cloning of the gpl60 gene into the retroviral shuttle vector fpGV-1 is shown in Figure 3. The pBHIO plasmid DNA was digested with restriction endonuclease Xhol and the sticky ends of the DNA were blunt-ended using T4 DNA polymerase. The DNA was then digested with restriction *5 endonuclease Sail and separated on a 1% low melting point agarose gel. A 3.Ikb DNA fragment was isolated from the gel using hot phenol extraction method. Vector fpGV-1 plasmid DNA was digested with restriction endonuclease

EcoRl and the sticky ends of the DNA were blunt-ended 0 using T4 DNA polymerase. The vector DNA was then digested with restriction endonuclease Sail. The linearised vector

DNA was ligated with the 3.Ikb Xhol (blunt-ended)-£§11 DNA fragment isolated from pBHIO and transformed into E.coli

DH5α. A clone containing the 3.Ikb fragment was further analysed with restriction endonuclease digestion : Sall+BamHl (6.2kb and 2.7kb); Hind3 (5.3kb, 2.2kb and 1.4kb). This clone was named as HIV-F1 contains the HIV-1 envelope glycoprotein gpl60 gene which is orientated in the same transcription direction as the SV40 early promoter (shown in Figure 3).

b. Production of CD4*--*¹ cell lines.

Peripheral blood mononuclear cells (10⁶/ml) were stimulated with concanavalin A (10 μg/ml) for 4 days.

Activated T cells were washed, subcultured at 3x10-**/ml in tissue culture medium containing optimum growth concentrations of interleukin-2 (IL-2). The activated cells were stored in liquid N₂. As required, cells were thawed and treated with OKT8 for 30 min on ice followed by rabbit complement for 1 hr at 37°C. Treated cells were washed and cultured in round well trays in IL-2 at 2xl0⁴/well in 200μl. Growth of the activated T cells was inactivated by periodic addition of IL-2 and by stimulation with 5 μg/ml of phytohaemagglutinin and a 0.05% suspension of sheep red blood cells. Activated T cells were monitored by FACs analysis for T cell surface markers. Populations generated were 90-95% CD4⁺, 0% CD8⁺, with remaining cells being CD16⁺ NK cells.

c. Transfection of COS-1 and CD4⁺ lymphocytes. COS-1 cells were seeded at 5 10^ per 60mm diameter petri dish, grown overnight in Dulbecco's modified Eagle's medium (DMEM) (Flow Labs, Sydney, Australia), supplemented with 10% fetal calf serum (FCS), then transfected with HIV-F1 (20 μg DNA per 10⁶ cells) by calcium phosphate precipitation and glycerol shock (15% glycerol for three minutes) . The cells were then washed in DMEM containing 10% FCS, rested in 5ml of the same medium and -incubated at 37°C in 5% C0₂. CD4⁺ lymphocytes produced as described above were transfected by allowing them to settle with the CaP0₄ precipitate, decanting off supernatant, then applying glycerol shock as above. Cells were resuspended in growth medium and plated in 96 well round bottom plates at 2xl0⁴ cells/well.

Cells were fed every three days. After the first 72 hours G418 antibiotic was added to test and control cultures. Nontransfected CD4⁺ cells died within 72 hours and COS-1 cells within 96 hours. Cells transfected with HIV-F1 and selected by their resistance to G418 were tested in a fluorescence antibody test using anti-HIV serum from an AIDS patient. These cells were found to be 100% positive, confirming expression of gpl60 by these cells.

Similar methods to those described above have also been used to transfect human bone marrow cells.

As an alternative to the calcium phosphate precipitation/glycerol shock technique, transfection of large numbers of bone marrow cells or lymphocytes can be most effectively achieved using the electroporation technique. In this technique, cells suspended in buffer containing positive retroviral vector are exposed to an electric pulse. This causes temporary pore formation in the cell membrane allowing the vector to enter the cell. Transplant cells transfected in this way and containing, for example, the gene or part of the gene for gpl60, could be injected directly back into the patient without prolonged culture. REFERENCES:

1. Steck, F.T. and Rubin, H. (1966a). Virology 29: 628-641.

2. Steck, F.T. and Rubin (1966b). Virology 29: 642-653.

3. Mathews, T-J. et.al. Proc.Natl.Acad.Sci♦ (USA) 84: 5424-5428.

4. Dalgleish, A.G. et.al. (1987). Nature 312: 763-766.

5a. Jhappan, C. et.al. (1986) J.Viroloσv 60: 750-753.

5b. Hapel, A.J. et.al. (1987) Anticancer Research 7: 661-668.

6. Hapel, A.J. et.al. (1986) Lymphokine Research 5: 249-254.

Claims

CLAIMS :

1. A method for combating viral infection in a human or animal patient, which comprises administering to the patient histocompatible blood cells or bone marrow stem cells which have been transformed with a nucleotide sequence coding for a protein or polypeptide which, on expression by the cells will reduce the rate at which superinfecting virus particles can enter the cells.

2. A method according to claim 1 for combating infection with the human immunodeficiency virus (HIV), wherein said histocompatible blood cells or bone marrow stem cells have been transformed with a nucleotide sequence or gene coding for all or an immunologically- active portion of a HIV envelope protein.

3. A method according to claim 2, wherein said cells have been transformed with a nucleotide sequence or gene coding for all or an immunologically-active portion of the HIV envelope proteins gpl60, gpl20 or gp41.

4. A therapeutic or prophylactic composition for combating viral infection in a human or animal patient, which comprises histocompatible blood cells or bone marrow stem cells which have been transformed with a nucleotide sequence coding for a protein or polypeptide which, on expression by the cells, will reduce the rate at which superinfecting virus particles can enter the cells.

5. A composition according to claim 4, for combating infection with the human immunodeficiency virus (HIV), wherein said histocompatible blood cells or bone marrow stem cells have been transformed with a nucleotide sequence or gene coding for all or an immunologically- active portion of a HIV envelope protein.

6. A composition according to claim 5, wherein said cells have been transformed with a nucleotide sequence coding for all or an immunologically-active portion of the HIV envelope proteins gpl60, gpl20 or gp41.

7. A method for the preparation of a therapeutic or prophylactic composition according to claim 4, which comprises the steps of preparing a viral vector containing said nucleotide sequence under operative control of a suitable promoter sequence, and then transfecting said cells with said viral vector..

8. A method according to claim 7, wherein said viral vector is a retroviral vector.

9. A method according to claim 8, wherein said retroviral vector contains the nucleotide sequence or gene coding for the HIV envelope proteins gpl60, gpl20 or gp41 downstream of a suitable promoter sequence.