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APOBEC3G/3F mediates intrinsic resistance of monocyte-derived dendritic cells to HIV-1 infection.

ABSTRACT: HIV-1 infects immature dendritic cells (iDCs), but infection is inefficient compared with activated CD4+ T cells and only involves a small subset of iDCs. We analyzed whether this could be attributed to specific cellular restrictions during the viral life cycle. To study env-independent restriction to HIV-1 infection, we used a single-round infection assay with HIV-1 pseudotyped with vesicular stomatitis virus G protein (HIV-VSVG). Small interfering RNA-mediated depletion of APOBEC3G/3F (A3G/3F), but not TRIM5alpha, enhanced HIV-1 infection of iDCs, indicating that A3G/3F controls the sensitivity of iDCs to HIV-1 infection. Furthermore, sequences of HIV reverse transcripts revealed G-to-A hypermutation of HIV genomes during iDC infection, demonstrating A3G/3F cytidine deaminase activity in iDCs. When we separated the fraction of iDCs that was susceptible to HIV, we found the cells to be deficient in A3G messenger RNA and protein. We also noted that during DC maturation, which further reduces susceptibility to infection, A3G levels increased. These findings highlight a role for A3G/3F in explaining the resistance of most DCs to HIV-1 infection, as well as the susceptibility of a fraction of iDCs. An increase in the A3G/3F-mediated intrinsic resistance of iDCs could result in a block of HIV infection at its mucosal point of entry.

SUBMITTER: Pion M

PROVIDER: S-EPMC2118170 | biostudies-literature | 2006 Dec

REPOSITORIES: biostudies-literature

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APOBEC3G/3F mediates intrinsic resistance of monocyte-derived dendritic cells to HIV-1 infection.

Pion Marjorie M Pion Marjorie M Granelli-Piperno Angela A Mangeat Bastien B Stalder Romaine R Correa Rafael R Steinman Ralph M RM Piguet Vincent V

The Journal of experimental medicine 20061204 13

HIV-1 infects immature dendritic cells (iDCs), but infection is inefficient compared with activated CD4+ T cells and only involves a small subset of iDCs. We analyzed whether this could be attributed to specific cellular restrictions during the viral life cycle. To study env-independent restriction to HIV-1 infection, we used a single-round infection assay with HIV-1 pseudotyped with vesicular stomatitis virus G protein (HIV-VSVG). Small interfering RNA-mediated depletion of APOBEC3G/3F (A3G/3F) ...[more]

PMID: 17145955

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Project description:UnlabelledMonocyte-derived dendritic cells (MDDC) stimulate CD8 cytotoxic T lymphocytes (CTL) by presenting endogenous and exogenous viral peptides via major histocompatibility complex class I (MHC-I) molecules. MDDC are poorly susceptible to HIV-1, in part due to the presence of SAMHD1, a cellular enzyme that depletes intracellular deoxynucleoside triphosphates (dNTPs) and degrades viral RNA. Vpx, an HIV-2/SIVsm protein absent from HIV-1, antagonizes SAMHD1 by inducing its degradation. The impact of SAMHD1 on the adaptive cellular immune response remains poorly characterized. Here, we asked whether SAMHD1 modulates MHC-I-restricted HIV-1 antigen presentation. Untreated MDDC or MDDC pretreated with Vpx were exposed to HIV-1, and antigen presentation was examined by monitoring the activation of an HIV-1 Gag-specific CTL clone. SAMHD1 depletion strongly enhanced productive infection of MDDC as well as endogenous HIV-1 antigen presentation. Time-lapse microscopy analysis demonstrated that in the absence of SAMHD1, the CTL rapidly killed infected MDDC. We also report that various transmitted/founder (T/F) HIV-1 strains poorly infected MDDC and, as a consequence, did not stimulate CTL. Vesicular stomatitis virus glycoprotein (VSV-G) pseudotyping of T/F alleviated a block in viral entry and induced antigen presentation only in the absence of SAMHD1. Furthermore, by using another CTL clone that mostly recognizes incoming HIV-1 antigens, we demonstrate that SAMHD1 does not influence exogenous viral antigen presentation. Altogether, our results demonstrate that the antiviral activity of SAMHD1 impacts antigen presentation by DC, highlighting the link that exists between restriction factors and adaptive immune responses.ImportanceUpon viral infection, DC may present antigens derived from incoming viral material in the absence of productive infection of DC or from newly synthesized viral proteins. In the case of HIV, productive infection of DC is blocked at an early postentry step. This is due to the presence of SAMHD1, a cellular enzyme that depletes intracellular levels of dNTPs and inhibits viral reverse transcription. We show that the depletion of SAMHD1 in DCs strongly stimulates the presentation of viral antigens derived from newly produced viral proteins, leading to the activation of HIV-1-specific cytotoxic T lymphocytes (CTL). We further show in real time that the enhanced activation of CTL leads to killing of infected DCs. Our results indicate that the antiviral activity of SAMHD1 not only impacts HIV replication but also impacts antigen presentation by DC. They highlight the link that exists between restriction factors and adaptive immune responses.

Project description:HIV establishes long-term latent infection in memory CD4+ T cells and also establishes sustained long-term productive infection in macrophages, especially in the central nervous system (CNS). To better understand how HIV sustains infection in macrophages, we performed RNAseq analysis after infection of human monocyte-derived macrophages (MDMs) with the brain-derived HIV-1 strain YU2 and compared this with acute infection of CD4+ T cells. HIV infection in MDM and CD4+ T cells altered many gene transcripts, but with few overlaps between these different cell types. We found interferon pathways upregulated in both MDM and CD4+ T cells, but with different gene signatures. The interferon-stimulated gene RSAD2/Viperin was among the most upregulated genes following HIV infection in MDMs, but not in CD4+ T cells. RSAD2/Viperin was induced early after infection with various HIV strains, was sustained over time, and remained elevated in established MDM infection even if new rounds of infection were blocked by antiretroviral treatment. Immunofluorescence microscopy revealed that RSAD2/Viperin was induced in HIV-infected cells, as well as in some uninfected neighboring cells. Knockdown of RSAD2/Viperin following the establishment of infection in MDMs reduced the production of HIV transcripts and viral p24 antigen. This correlated with the reduction in the number of multinucleated giant cells, and changes in the HIV DNA and chromatin structure, including an increased DNA copy number and loss of nucleosomes and histone modifications at the long terminal repeat (LTR). RNAseq transcriptomic analysis of RSAD2/Viperin knockdown during HIV infection of MDMs revealed the activation of interferon alpha/beta and gamma pathways and the inactivation of Rho GTPase pathways. Taken together, these results suggest that RSAD2/Viperin supports the sustained infection in macrophages, potentially through mechanisms involving the alteration of the LTR chromatin structure and the interferon response.ImportanceHIV infection of macrophages is a barrier to HIV cure and a source of neurocognitive pathology. We found that HIV induces RSAD2/Viperin during sustained infection of macrophages. While RSAD2/Viperin is an interferon-stimulated gene with known antiviral activity, we find RSAD2/Viperin promotes HIV infection in macrophages through multiple mechanisms, including interferon signaling. Therefore, RSAD2/Viperin may be a therapeutic target for the treatment of HIV-infected macrophages.

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APOBEC3G/3F mediates intrinsic resistance of monocyte-derived dendritic cells to HIV-1 infection.

Publications

APOBEC3G/3F mediates intrinsic resistance of monocyte-derived dendritic cells to HIV-1 infection.

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