SAMHD1 Restricts HIV-1 Cell-to-Cell Transmission and Limits Immune Detection in Monocyte-Derived Dendritic Cells

Institut Pasteur, Unité Virus et Immunité, Département de Virologie, and CNRS, URA3015, 28 rue du Docteur Roux, F-75015, Paris, France.
Journal of Virology (Impact Factor: 4.44). 12/2012; 87(5). DOI: 10.1128/JVI.02514-12
Source: PubMed


SAMHD1 is a viral restriction factor expressed in dendritic cells and other cells, inhibiting infection by cell-free human
immunodeficiency virus type 1 (HIV-1) particles. SAMHD1 depletes the intracellular pool of deoxynucleoside triphosphates,
thus impairing HIV-1 reverse transcription and productive infection in noncycling cells. The Vpx protein from HIV-2 or simian
immunodeficiency virus (SIVsm/SIVmac) antagonizes the effect of SAMHD1 by triggering its degradation. A large part of HIV-1
spread occurs through direct contacts between infected cells and bystander target cells. Here, we asked whether SAMHD1 impairs
direct HIV-1 transmission from infected T lymphocytes to monocyte-derived dendritic cells (MDDCs). HIV-1-infected lymphocytes
were cocultivated with MDDCs that have been pretreated or not with Vpx or with small interfering RNA against SAMHD1. We show
that in the cocultures, SAMHD1 significantly inhibits productive cell-to-cell transmission to target MDDCs and prevents the
type I interferon response and expression of the interferon-stimulated gene MxA. Therefore, SAMHD1, by controlling the sensitivity
of MDDCs to HIV-1 infection during intercellular contacts, impacts their ability to sense the virus and to trigger an innate
immune response.

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    • "The authors compare HIV-1 replication kinetics in static and continuously shaking lymphocyte cultures, they conclude that shaking culture conditions prevent cell contacts, thus avoiding virus transfer through direct cell contacts. This system of shaking culture is widely used to study differences between cell-free and cell-to-cell HIV-1 transmission [5], [6], [7]. Here we show that shaking culture of HIV-1-infected T cells not only avoids cell contacts preventing the transfer of virus from cell to cell but, after 24 hours, it also affects cell-free virus transmission by inducing loss of HIV-1 infectivity and reduction of envelope proteins from the surface of the viral particles. "
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    ABSTRACT: HIV-1 spreads by cell-free particles and through direct cell contacts. To discriminate between these two modes of dissemination, an assay in which the cells are cultured under shaking conditions impairing cell-to-cell transmission has been described. We addressed the impact of shaking on HIV-1 particle infectivity. Kinetics of HIV-1 infection in static or shaking conditions confirmed that HIV-1 replication is reduced in mobile lymphocyte T cells. Strikingly, the infectivity of viruses produced by mobile lymphocytes was dramatically reduced. In parallel, the amount of envelope protein present on these particles showed a continuous decrease over time. We conclude that inefficient HIV-1 replication in mobile lymphocytes in this experimental system is not only due to avoidance of viral cell-to-cell transfer but also to the loss of infectivity of the viral particles due to the alteration of the composition and functionality of the particles produced by these lymphocytes. It is important to take these observations into account when studying viral transmission under shaking conditions.
    Full-text · Article · Oct 2014 · PLoS ONE
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    • "After a co-culture of 18 h (PBMCs) or 48 h (Gen2.2), type I IFN levels and expression of the protein MxA were measured as described previously (Lepelley et al., 2011; Puigdomènech et al., 2013). required for antibodies to block viral cell–cell spread. "
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    ABSTRACT: The neutralizing activity of anti-HIV-1 antibodies is typically measured in assays where cell-free virions enter reporter cell lines. However, HIV-1 cell to cell transmission is a major mechanism of viral spread, and the effect of the recently described broadly neutralizing antibodies (bNAbs) on this mode of transmission remains unknown. Here we identify a subset of bNAbs that inhibit both cell-free and cell-mediated infection in primary CD4(+) lymphocytes. These antibodies target either the CD4-binding site (NIH45-46 and 3BNC60) or the glycan/V3 loop (10-1074 and PGT121) on HIV-1 gp120 and act at low concentrations by inhibiting multiple steps of viral cell to cell transmission. These antibodies accumulate at virological synapses and impair the clustering and fusion of infected and target cells and the transfer of viral material to uninfected T cells. In addition, they block viral cell to cell transmission to plasmacytoid DCs and thereby interfere with type-I IFN production. Thus, only a subset of bNAbs can efficiently prevent HIV-1 cell to cell transmission, and this property should be considered an important characteristic defining antibody potency for therapeutic or prophylactic antiviral strategies.
    Full-text · Article · Nov 2013 · Journal of Experimental Medicine
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    • "The recently discovered restriction factor SAMHD1 blocks infection of HIV-1 and other retroviruses [20,21,27-31,36,37]. In the crystal structure by Goldstone and colleagues the HD domain of the human SAMHD1 appears as a dimer with extensive dimerization interface [29] (Figure 1A). "
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    ABSTRACT: SAMHD1 is a restriction factor that potently blocks infection by HIV-1 and other retroviruses. We have previously demonstrated that SAMHD1 oligomerizes in mammalian cells by immunoprecipitation. Here we investigated the contribution of SAMHD1 oligomerization to retroviral restriction. Structural analysis of SAMHD1 and homologous HD domain proteins revealed that key hydrophobic residues Y146, Y154, L428 and Y432 stabilize the extensive dimer interface observed in the SAMHD1 crystal structure. Full-length SAMHD1 variants Y146S/Y154S and L428S/Y432S lost their ability to oligomerize tested by immunoprecipitation in mammalian cells. In agreement with these observations, the Y146S/Y154S variant of a bacterial construct expressing the HD domain of human SAMHD1 (residues 109-626) disrupted the dGTP-dependent tetramerization of SAMHD1 in vitro. Tetramerization-defective variants of the full-length SAMHD1 immunoprecipitated from mammalian cells and of the bacterially-expressed HD domain construct lost their dNTPase activity. The nuclease activity of the HD domain construct was not perturbed by the Y146S/Y154S mutations. Remarkably, oligomerization-deficient SAMHD1 variants potently restricted HIV-1 infection. These results suggested that SAMHD1 oligomerization is not required for the ability of the protein to block HIV-1 infection.
    Full-text · Article · Nov 2013 · Retrovirology
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