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    Analysis of macrophage infection by cell-to-cell transfer of HIV-1

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    Rationale and objectives

     

     

    Macrophages are cellular targets of HIV-1 and play important roles in virus dissemination and in the early establishment of persistent virus reservoirs in different host tissues. While HIV-1 replication was extensively analyzed in T lymphocytes during infection by cell-free virus particles and by viral cell-to-cell transfer between T cells, the mechanisms regarding how macrophages could be infected by cell-to-cell transfer have been poorly investigated. It is evident that macrophages can establish tight contacts with infected T lymphocytes leading to the establishment of virus reservoirs in some tissues, such as lymphoid organs, colon and brain, in HIV-infected patients. As indicated by our preliminary results, we have obtained data showing that virus transfer to macrophages is much more effective through close contacts with infected CD4+ T cells compared to the low level of virus transfer measured with cell-free viruses. This viral transfer leads to efficient virus replication and release of fully infectious viruses by the recipient macrophages. Interestingly, our data also indicate that the virus transfer toward macrophages is dependent of the cellular co-receptor used for virus entry, since efficient transfer and virus replication in macrophages was observed with HIV-1 strains using the CCR5 receptor but not with strains using CXCR4 suggesting that virus transfer is related to an envelope-dependent mechanism.

     

     

     

    The goal of this proposal is now to investigate the mechanisms of macrophage infection and early interactions of HIV-1 with certain cellular signaling pathways and cytoskeleton when macrophages are infected through tight contacts with infected T lymphocytes. We will also investigate the contribution of the HIV-1 auxiliary proteins in this viral transfer process. By inducing profound alterations of intracellular trafficking and signaling pathways in virus donor T cells or recipient macrophages, or by counteraction of the antiviral activity of cellular restriction factors, these viral regulatory proteins could modulate virus transfer.

    This proposal will be focused on three main specific objectives:

    1) Cell imaging analysis of virus cell-to-cell transfer toward macrophages to visualize and characterize in fluorescence and electron microscopy, on fixed cells but also on live cells,  initial intercellular interactions involved in HIV-1 transfer from infected lymphocytes toward macrophages.

    2) Analysis of the role of some signaling pathways as well as the specific role of actin cytoskeleton organization and microtubule dynamic in the achievement of the early steps (reverse-transcription of the viral genome, intra-cytoplasmic routing and nuclear import of the viral DNA) of the virus life cycle during cell-to-cell virus transfer from infected T cells toward macrophages.

    3) Analysis of the contribution of the Nef, Vpu, Vif and Vpr auxiliary viral proteins in the modulation of the viral transfer process from donor infected T lymphocytes and viral replication in recipient macrophages.

    This program regarding HIV-1 spreading from infected T cells toward macrophages should give access to crucial information for AIDS pathogenesis regarding how HIV-1 is transferred from infected T cells toward macrophages leading to virus dissemination and formation of long-lived virus reservoirs in host tissues from infected patients.

     

     

     

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