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OBJECTIVE The objective of this study is to verify whether HIV activates two endogenous retroviruses of the human endogenous retrovirus (HERV)-W family, multiple sclerosis-associated retrovirus (MSRV) and Syncytin-1, whose neuropathogenic and immunopathogenic properties could contribute to HIV-related neurodegeneration. DESIGN AND METHODS Peripheral blood mononuclear cells, monocyte-macrophages and astrocytes were either infected by HIV or exposed to HIV-Tat, and/or other treatments. The expression of transcripts and proteins of interest was evaluated by real-time RT-PCR and western blotting assays, respectively. RESULTS HIV and Tat increase the levels of MSRVenv mRNAs and HERV-Wenv proteins in astrocytes and in blood cells. In monocyte-macrophages, Tat also induces high levels of CCR2, CD16 and Toll-like receptor 4 (TLR4) molecules. Syncytin-1 response to Tat depends on the cell context: in monocytes, Tat stimulates MSRVenv and inhibits Syncytin-1, while in differentiated macrophages, it stimulates both elements. In primary astrocytes, Tat stimulates MSRV and Syncytin-1 indirectly, through interaction with TLR4 and induction of tumour necrosis factor-alpha (TNFα), without internalization. CONCLUSION In-vivo consequence of the study could be that, through increase of CD16 and CCR2, Tat promotes neuroinvasion not only by HIV-infected monocytes/macrophages but also by the HERV-Ws, with their neuropathogenic potential. Also, the novel finding of TLR4 stimulation by Tat may be of relevance, as TLR4 is critical in neuroinflammation. Within central nervous system (CNS), Tat-induced TNFα could induce high levels of the HERV-Ws, in both macrophages and astrocytes, also without HIV replication. The indirect mechanism by which Tat activates the HERV-Ws through induction of TNFα could add a new piece to the puzzle of CNS pathogenesis, that is the HERV-Wenv contribute to the HIV-related neurodegeneration.

The newly discovered type III interferon lambda (IFN-lambda) has antiviral activity against a broad spectrum of viruses and potent immune-related activities. Its major producers are peripheral blood mononuclear cells (PBMCs) and dendritic cells. The above functions and cells are deeply involved in AIDS pathogenesis, but there is no information so far on IFN-lambda effects on HIV. Therefore we addressed the sensitivity of HIV-1 replication to cell exposure to human IFN-lambda2. Human PBMCs and C8166 T cells were treated with human Type III or Type I IFNs, and the ability of HIV-1 to bind and replicate in untreated and IFN-treated cells was investigated. Virus amounts were quantified by infectivity and p24 assays. In parallel, we evaluated the possible antiproliferative effects of IFN-lambda2 and the expression of CD4, CXCR4, and CCR5 genes, whose transcripts were quantified by real time RT-PCR. Data showed increased adsorption of HIV to IFN-treated cells in a dose-dependent fashion. Virus yields increased accordingly. In both systems the accumulation of CD4, CXCR4, and CCR5 transcripts was increased, particularly in PBMCs. Antiproliferative activity and classical antiviral state were instead detected on PBMCs, but not on C8166 cells. We concluded that pretreatment of PBMCs and C8166 cells with Type III and Type I IFNs causes increased HIV binding and replication. These effects are likely to be due to increased expression of HIV receptors and coreceptors on the plasma membrane. These findings indicate another mechanism utilized by HIV for subversion of host defenses.

Background: Several viruses were reported as co-factors triggering the pathogenesis of multiple sclerosis (MS), including the endogenous retroviruses of the HERV-W family, that were also proposed as biomarkers of disease progression and therapy outcome. Objective: The objective of this article is to clarify whether in MS patients treatment with natalizumab has effects on MSRV/syncytin-1/HERV-W expression and the possible relationship with disease outcome. Methods: Peripheral blood mononuclear cells were collected from 22 patients with relapsing–remitting disease, at entry and after three, six and 12 months of treatment with natalizumab. The cell subpopulations and the expression of MSRV env/syncytin-1/HERV-W env were analyzed by flow cytometry and by discriminatory env-specific RT-PCR assays. Results: By flow cytometry the relative amounts of T, NK and monocyte subpopulations were shown to remain fairly constant. A relative increase of B lymphocytes was observed at three to six months ( p = 0.033). The MSRV env and syncitin-1 transcripts were reduced at six to 12 months of therapy ( p = 0.0001). Accordingly, at month 12, the plasma-membrane levels of the HERV-W env protein were reduced ( p = 0.0001). B cells, NK and monocytes but not T cells expressed the HERV-W env protein. None of the patients relapsed during therapy. Conclusion: Effective therapy with natalizumab downregulates MSRV/syncytin-1/HERV-W expression.

Background: Proposed co-factors triggering the pathogenesis of multiple sclerosis (MS) are the Epstein Barr virus (EBV), and the potentially neuropathogenic MSRV (MS-associated retrovirus) and syncytin-1, of the W family of human endogenous retroviruses. Methodology/Principal Findings: In search of links, the expression of HERV-W/MSRV/syncytin-1, with/without exposure to EBV or to EBV glycoprotein350 (EBVgp350), was studied on peripheral blood mononuclear cells (PBMC) from healthy volunteers and MS patients, and on astrocytes, by discriminatory env-specific RT-PCR assays, and by flow cytometry. Basal expression of HERV-W/MSRV/syncytin-1 occurs in astrocytes and in monocytes, NK, and B, but not in T cells. This uneven expression is amplified in untreated MS patients, and dramatically reduced during therapy. In astrocytes, EBVgp350 stimulates the expression of HERV-W/MSRV/syncytin-1, with requirement of the NF-kB pathway. In EBVgp350-treated PBMC, MSRVenv and syncytin-1 transcription is activated in B cells and monocytes, but not in T cells, nor in the highly expressing NK cells. The latter cells, but not the T cells, are activated by proinflammatory cytokines. Conclusions/Significance: In vitro EBV activates the potentially immunopathogenic and neuropathogenic HERV-W/MSRV/ syncytin-1, in cells deriving from blood and brain. In vivo, pathogenic outcomes would depend on abnormal situations, as in late EBV primary infection, that is often symptomatic, or/and in the presence of particular host genetic backgrounds. In the blood, HERV-Wenv activation might induce immunopathogenic phenomena linked to its superantigenic properties. In the brain, toxic mechanisms against oligodendrocytes could be established, inducing inflammation, demyelination and axonal damage. Local stimulation by proinflammatory cytokines and other factors might activate further HERV-Ws, contributing to the neuropathogenity. In MS pathogenesis, a possible model could include EBV as initial trigger of future MS, years later, and HERV-W/MSRV/syncytin-1 as actual contributor to MS pathogenicity, in striking parallelism with disease behaviour.

Astrocytes play a key role in important neurological diseases such as multiple sclerosis (MS) and neuroAIDS. The multiple sclerosis-associated retrovirus (MSRV) is an active member of the W family of human endogenous retroviruses (HERV), able to produce extracellular particles; another HERV-W element is ERVWE1, producing only an env protein, named syncytin-1, that can be found intracellularly and on the plasma-membrane, but not extracellularly. MSRVenv and syncytin-1 proteins have pro-inflammatory properties that might be pathogenic, as observed in vitro and in animal models: they may cause neuroinflammation, neurodegeneration, alterations of the immune system and stress responses; both have been suggested as co-factors triggering the immunopathogenesis of MS.λ2 has been shown to favour the replication of exogenous retroviruses, such as HIV, we designed studies to detect possible effects of IFNλ2 on the above HERV-W retroelements in U87 MG astrocytes, by using real time RT-PCR assays that can selectively identify either MSRVenv or syncytin-1 transcripts.. Treatment of astrocytes with IFNλ2 was found to enhance the expression of both MSRVenv and syncytin-1, dose-dependently. If cells are infected by HIV, the expression of both elements is modified. Surprisingly, HIV caused opposite effects on the two HERV-W retroelements, since MSRVenv transcription was up-regulated, whilst that of syncytin-1 was down-regulated. Cell pre-treatment with IFNλ2 did not alter the effects of subsequent HIV infection on MSRVenv and syncytin-1. behaves as a pro-inflammatory cytokine, that can facilitate the expression of both exogenous and endogenous human retroviruses. Since Type III IFN. This cell line has the IL-28R receptor, and is sensitive to IFNλ2. It is totally unknown the role played by Type III IFN in neuropathologies like neuro-AIDS and MS, but it could be hypothesized that IFNλ.

Background Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system, with demyelination and gliosis. Proposed pathogenic co-factors triggering MS pathogenesis are the Epstein Barr virus (EBV), and two elements of the W family of human endogenous retroviruses (HERV-W): MSRV, that forms free virions, and syncytin-1, the ERVWE1env protein; both retroelements have neuropathogenic properties. In the past we studied MSRV in MS patients in various temporal and clinical stages; in all cases, striking parallelisms between MS behaviour and MSRV/HERV-W presence/ load were found. By simultaneous detection of MSRV and HHV-6, we found a direct correlation between MS and MSRV presence/load, but not for HHV-6. MS brains over-express MSRVenv and syncytin-1 transcripts, with respect to controls, while EBV presence was not detected. Materials and methods Since late EBV seroconversion is a strong risk factor for MS development, we performed in vitro experiments on PBMC from MS patients and MSRV+ volunteers, as well as on U87-MG astroglioma cells, that were studied as such or were exposed to EBV or to recombinant EBV glycoprotein350 (EBVgp350), or to proinflammatory cytokines. The levels of MSRVenv and syncytin-1 mRNAs were evaluated by discriminatory real time RTPCR assays. Flow cytometry was used to evaluate the HERV-Wenv protein on the plasmamembrane, as well the PBMC subsets. Results Basal expression of MSRVenv and syncytin-1 occurs in astrocytes and in NK, B and monocyte cells, but not in T cells. This uneven expression is amplified in naive MS patients. Astrocyte infection by EBV and exposure to EBVgp350 stimulate the expression of HERV-W/MSRV/ syncytin-1, with requirement of the NF-kB pathway. In EBVgp350-treated PBMC, MSRVenv and syncytin-1 are activated in B cells and monocytes, but not in T cells, nor in the highly expressing NK cells. The latter cells, but not the T cells, are activated by proinflammatory cytokines. Conclusions The study demonstrates that there are interactions among the above proposed MS-cofactors. In vivo, a pathogenic outcome would depend on activation in abnormal situations/tissues, as it may occur in delayed EBV infection, or in the presence of particular host genetic backgrounds, or both.