Multiple sclerosis-associated retrovirus particles cause T lymphocyte-dependent death with brain hemorrhage in humanized SCID mice model.

A retroviral element (multiple sclerosis-associated retrovirus, MSRV) defining a family of genetically inherited endogenous retroviruses (human endogenous retrovirus type W, HERV-W) has been characterized in cell cultures from patients with multiple sclerosis. Recently, MSRV retroviral particles or the envelope recombinant protein were shown to display superantigen activity in vitro, but no animal model has yet been set up for studying the pathogenicity of this retrovirus. In the present study, the pathogenicity of different sources of MSRV retroviral particles has been evaluated in a hybrid animal model: severe combined immunodeficiency (SCID) mice grafted with human lymphocytes and injected intraperitoneally with MSRV virion or mock controls. MSRV-injected mice presented with acute neurological symptoms and died within 5 to 10 days post injection. Necropsy revealed disseminated and major brain hemorrhages, whereas control animals did not show abnormalities (P <.001). In ill animals, reverse transcriptase-polymerase chain reaction (RT-PCR) analyses showed circulating MSRV RNA in serum, whereas overexpression of proinflammatory cytokines such as tumor necrosis factor (TNF)-alpha and interferon (IFN)-gamma was evidenced in spleen RNA. Neuropathological examination confirmed that hemorrhages occurred prior to death in multifocal areas of brain parenchyma and meninges. Further series addressed the question of immune-mediated pathogenicity, by inoculating virion to SCID mice grafted with total and T lymphocyte-depleted cells in parallel: dramatic and statistically significant reduction in the number of affected mice was observed in T-depleted series (P <.001). This in vivo study suggests that MSRV retroviral particles from MS cultures have potent immunopathogenic properties mediated by T cells compatible with the previously reported superantigen activity in vitro, which appear to be mediated by an overexpression of proinflammatory cytokines.

Gene transfer of anti-gp41 antibody and CD4 immunoadhesin strongly reduces the HIV-1 load in humanized severe combined immunodeficient mice.

OBJECTIVE: To study the anti-HIV-1 effects of the delivery of anti-gp41 monoclonal antibody (mAb) and soluble CD4 (sCD4) immunoadhesin by genetically modified cells in HIV-1-infected, humanized severe combined immunodeficient (SCID) mice. DESIGN: The complementary DNA of mAb 2F5, an anti-HIV-1 gp41 antibody, and of sCD4-IgG chimeric immunoadhesin were transferred into 3T3 cells using Moloney murine leukaemia virus vectors. The cells were then incorporated into a collagen structure called the neo-organ, which allowed the continuous production of the therapeutic molecules. METHODS: The antiviral effects in vivo of 2F5 or sCD4-IgG or both compounds were evaluated in neo-organ-implanted SCID mice that were grafted with human CD4 CEM T cells and challenged with HIV-1 Lai or MN. RESULTS: In SCID mice implanted with 2F5 neo-organs, antibody plasma levels reached 500-2000 ng/ml. Viral loads after HIV-1 challenge were significantly reduced in neo-organ-implanted HIV-infected mice. Although 29 x 10(7) and 13 x 10(8) HIV-1-RNA copies/ml were detected at 12 days in the controls (mice injected with Lai and MN, respectively) less than 16.5 x 10(3) HIV-1-RNA copies/ml were observed in all implanted mice injected with either Lai or MN. The intracellular viral load was also reduced in CD4 cells recovered from the implanted mice. Comparable antiviral effects were obtained with CD4-IgG neo-organs. CONCLUSION: Our results confirm the anti-HIV properties of 2F5 and sCD4-IgG continuously produced in vivo after ex-vivo gene therapy in SCID mice.

Experimental gene therapy: the transfer of Tat-inducible interferon genes protects human cells against HIV-1 challenge in vitro and in vivo in severe combined immunodeficient mice.

OBJECTIVES: To evaluate in vitro and in vivo a strategy for gene therapy for AIDS based on the transfer on interferon (IFN)-alpha, -beta and -gamma genes to human cells. DESIGN: Human U937 promonocytic cells were stably transfected with Tat-inducible IFN expression vectors conferring an antiviral state against infection with HIV. METHODS: Transfected cells were either infected by HIV-1 in vitro or transplanted into severe combined immunodeficient (SCID) mice for an HIV challenge in vivo. RESULTS: U937 cell lines stably carrying IFN transgenes under the positive control of the HIV-1 Tat protein were highly resistant to HIV-1 replication in vitro. This antiviral resistance was associated with a strong induction of IFN synthesis immediately following the viral infection. HIV-1 proteins were found to be specifically trapped within the genetically modified cells. In contrast, all IFN-U937 cells permitted full HIV-2 replication. Transfected cells injected into SCID mice and challenged against HIV-1 were strongly resistant to infection when cells were transduced with IFN-alpha of IFN-beta genes. However, IFN-gamma-transfected cells permitted HIV-1 infection in vivo despite the induction of a high level of IFN-gamma secretion. The quantity of proviral DNA was 10(5)-fold lower in IFN-alpha- or IFN-beta-transfected U937 cells collected from these SCID mice than that in non-transfected cells. CONCLUSIONS: Our results substantiated the validity of a strategy, bases on the transfer of HIV-1-inducible IFN-alpha or IFN-beta genes, to confer antiviral resistance to human cells.

Cell cultures and associated retroviruses in multiple sclerosis. Collaborative Research Group on MS.

Retroviral particles associated with reverse transcriptase (RT) activity in cell-cultures from MS patients have been reported by different groups. Cell-cultures have been used for the study and characterization of the corresponding retroviral genome which we have shown is related to ERV9 in the pol region. Previously unpublished details of a study with monocyte cultures are presented together with observations on leptomeningeal and choroid-plexus cultures. The generation of self-transformed cultures after inhibition of interferon, followed by the loss of retroviral expression and recurrent apoptosis, is analyzed. Retroviral particles with RT-activity are produced in monocyte cultures with an apparent correlation with MS disease activity. However, though leptomeningeal and choroid plexus cells from MS can be passaged for a limited period, their evolution in vitro is not compatible with stable retroviral expression. These culture limitations greatly hampered progress on the elucidation of the retroviral genome sequence.