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CD4 depletion in SIV-infected macaques results in macrophage and microglia infection with rapid turnover of infected cells.

Micci L, Alvarez X, Iriele RI, Ortiz AM, Ryan ES, McGary CS, Deleage C, McAtee BB, He T, Apetrei C, Easley K, Pahwa S, Collman RG, Derdeyn CA, Davenport MP, Estes JD, Silvestri G, Lackner AA, Paiardini M - PLoS Pathog. (2014)

Bottom Line: In rhesus macaques (RMs), experimental depletion of CD4+ T-cells prior to SIV infection results in higher viremia and emergence of CD4-independent SIV-envelopes.In this study we used the rhesus recombinant anti-CD4 antibody CD4R1 to deplete RM CD4+ T-cells prior to SIVmac251 infection and investigate the sources of the increased viral burden and the lifespan of productively infected cells.We believe these findings have important implications for HIV eradication studies.

View Article: PubMed Central - PubMed

Affiliation: Division of Microbiology & Immunology, Yerkes National Primate Research Center, Emory University School of Medicine, Atlanta, Georgia, United States of America.

ABSTRACT
In rhesus macaques (RMs), experimental depletion of CD4+ T-cells prior to SIV infection results in higher viremia and emergence of CD4-independent SIV-envelopes. In this study we used the rhesus recombinant anti-CD4 antibody CD4R1 to deplete RM CD4+ T-cells prior to SIVmac251 infection and investigate the sources of the increased viral burden and the lifespan of productively infected cells. CD4-depleted animals showed (i) set-point viral load two-logs higher than controls; (ii) macrophages constituting 80% of all SIV vRNA+ cells in lymph node and mucosal tissues; (iii) substantial expansion of pro-inflammatory monocytes; (iv) aberrant activation and infection of microglial cells; and (v) lifespan of productively infected cells significantly longer in comparison to controls, but markedly shorter than previously estimated for macrophages. The net effect of CD4+ T-cell depletion is an inability to control SIV replication and a shift in the tropism of infected cells to macrophages, microglia, and, potentially, other CD4-low cells which all appear to have a shortened in vivo lifespan. We believe these findings have important implications for HIV eradication studies.

No MeSH data available.


Related in: MedlinePlus

Massive activation and productive infection of microglia in CD4-depleted RMs.(a) ISH showing the levels of SIV vRNA+ cells in brain from a representative SIV-uninfected control (top), SIV-infected control (middle) and CD4-depleted SIV-infected (bottom) animal. The amount of SIV vRNA+ cells was markedly higher in CD4-depleted animals than in controls. (b) Immunofluorescence staining for CD163 (left panels), HLA-DR (middle panels) and proliferating cell nuclear antigen (PCNA; right panels) in the parenchyma of one representative SIV-uninfected control (top), one SIV-infected control (middle) and one SIV-infected CD4-depleted (bottom) RM. Nuclei are stained in green; markers of interest in red. (c) Quantitative analyses showing the number of cells per mm2 of tissue that stained positively for the markers of interest. Increased expression of CD163, HLA-DR and PCNA was found in CD4-depleted animals (orange square; n = 4) when compared to both groups of controls (SIV- open circle, n = 3; SIV+ closed circle, n = 3). (d) Single and combined staining for IBA-1 (green), CD163 (blue), and SIV-vRNA (red) in the brain of one representative SIV-infected CD4 depleted RM. The box on the right is a magnification of a microglial cell (IBA-1+) that expresses CD163 and is productively infected (SIV vRNA+).
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ppat-1004467-g005: Massive activation and productive infection of microglia in CD4-depleted RMs.(a) ISH showing the levels of SIV vRNA+ cells in brain from a representative SIV-uninfected control (top), SIV-infected control (middle) and CD4-depleted SIV-infected (bottom) animal. The amount of SIV vRNA+ cells was markedly higher in CD4-depleted animals than in controls. (b) Immunofluorescence staining for CD163 (left panels), HLA-DR (middle panels) and proliferating cell nuclear antigen (PCNA; right panels) in the parenchyma of one representative SIV-uninfected control (top), one SIV-infected control (middle) and one SIV-infected CD4-depleted (bottom) RM. Nuclei are stained in green; markers of interest in red. (c) Quantitative analyses showing the number of cells per mm2 of tissue that stained positively for the markers of interest. Increased expression of CD163, HLA-DR and PCNA was found in CD4-depleted animals (orange square; n = 4) when compared to both groups of controls (SIV- open circle, n = 3; SIV+ closed circle, n = 3). (d) Single and combined staining for IBA-1 (green), CD163 (blue), and SIV-vRNA (red) in the brain of one representative SIV-infected CD4 depleted RM. The box on the right is a magnification of a microglial cell (IBA-1+) that expresses CD163 and is productively infected (SIV vRNA+).

Mentions: We then investigated if the observed high viremia, monocyte activation, and infection of macrophages in peripheral tissues were associated with central nervous system (CNS) virus dissemination and pathology. First, we investigated the presence of infected cells in brain sections collected at necropsy from the CD4-depleted and non-depleted (SIV+ controls) SIV-infected RMs included in our previous study (in contrast to the current study, these animals were not treated with antiretroviral drugs at the time of necropsy [7]). For the SIV negative controls, we used brain sections from historically SIV-uninfected RMs present at the Tulane National Primate Research Center (SIV− controls). In CD4-depleted RMs SIV vRNA+ cells were found throughout the parenchyma (Figure 5a) and had a stellate morphology typical of microglia. The high number of infected cells led us to evaluate, in the same brain sections, the levels of activation by IHC/IF staining for CD163, HLA-DR, and proliferating cell nuclear antigen (PCNA, a marker of perivascular macrophages that has been used as a marker of DNA repair in macrophages [14]). As shown in the representative images (b) and in the quantitative analysis (c) of Figure 5, the expression of CD163 (P = 0.0013; P = 0.0047), HLA-DR (P = 0.0571; P = 0.0571), and PCNA (P = 0.0026; P = 0.0121) in cells with location and stellate morphology typical of microglia were significantly higher in CD4-depleted than SIV-uninfected or SIV-infected controls. The surprising finding that a significant number of microglia are activated and productively infected was confirmed by triple fluorescent labeling for SIV vRNA (red), CD163 (blue) and the microglia-specific marker IBA-1 [15] (green) (Figure 5d). Quantification of these stainings showed numbers of SIV vRNA+ IBA-1+ microglia markedly higher in CD4-depleted compared to non-depleted SIV-infected animals (11.3±8.4 vs. 0.2±0.2; P = 0.0286). Of note, we found a direct correlation between the number (cells/mm2) of SIV vRNA+ cells and PCNA+ cells in the eight CD4-depleted animals (r = 0.8289, P = 0.0302).


CD4 depletion in SIV-infected macaques results in macrophage and microglia infection with rapid turnover of infected cells.

Micci L, Alvarez X, Iriele RI, Ortiz AM, Ryan ES, McGary CS, Deleage C, McAtee BB, He T, Apetrei C, Easley K, Pahwa S, Collman RG, Derdeyn CA, Davenport MP, Estes JD, Silvestri G, Lackner AA, Paiardini M - PLoS Pathog. (2014)

Massive activation and productive infection of microglia in CD4-depleted RMs.(a) ISH showing the levels of SIV vRNA+ cells in brain from a representative SIV-uninfected control (top), SIV-infected control (middle) and CD4-depleted SIV-infected (bottom) animal. The amount of SIV vRNA+ cells was markedly higher in CD4-depleted animals than in controls. (b) Immunofluorescence staining for CD163 (left panels), HLA-DR (middle panels) and proliferating cell nuclear antigen (PCNA; right panels) in the parenchyma of one representative SIV-uninfected control (top), one SIV-infected control (middle) and one SIV-infected CD4-depleted (bottom) RM. Nuclei are stained in green; markers of interest in red. (c) Quantitative analyses showing the number of cells per mm2 of tissue that stained positively for the markers of interest. Increased expression of CD163, HLA-DR and PCNA was found in CD4-depleted animals (orange square; n = 4) when compared to both groups of controls (SIV- open circle, n = 3; SIV+ closed circle, n = 3). (d) Single and combined staining for IBA-1 (green), CD163 (blue), and SIV-vRNA (red) in the brain of one representative SIV-infected CD4 depleted RM. The box on the right is a magnification of a microglial cell (IBA-1+) that expresses CD163 and is productively infected (SIV vRNA+).
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ppat-1004467-g005: Massive activation and productive infection of microglia in CD4-depleted RMs.(a) ISH showing the levels of SIV vRNA+ cells in brain from a representative SIV-uninfected control (top), SIV-infected control (middle) and CD4-depleted SIV-infected (bottom) animal. The amount of SIV vRNA+ cells was markedly higher in CD4-depleted animals than in controls. (b) Immunofluorescence staining for CD163 (left panels), HLA-DR (middle panels) and proliferating cell nuclear antigen (PCNA; right panels) in the parenchyma of one representative SIV-uninfected control (top), one SIV-infected control (middle) and one SIV-infected CD4-depleted (bottom) RM. Nuclei are stained in green; markers of interest in red. (c) Quantitative analyses showing the number of cells per mm2 of tissue that stained positively for the markers of interest. Increased expression of CD163, HLA-DR and PCNA was found in CD4-depleted animals (orange square; n = 4) when compared to both groups of controls (SIV- open circle, n = 3; SIV+ closed circle, n = 3). (d) Single and combined staining for IBA-1 (green), CD163 (blue), and SIV-vRNA (red) in the brain of one representative SIV-infected CD4 depleted RM. The box on the right is a magnification of a microglial cell (IBA-1+) that expresses CD163 and is productively infected (SIV vRNA+).
Mentions: We then investigated if the observed high viremia, monocyte activation, and infection of macrophages in peripheral tissues were associated with central nervous system (CNS) virus dissemination and pathology. First, we investigated the presence of infected cells in brain sections collected at necropsy from the CD4-depleted and non-depleted (SIV+ controls) SIV-infected RMs included in our previous study (in contrast to the current study, these animals were not treated with antiretroviral drugs at the time of necropsy [7]). For the SIV negative controls, we used brain sections from historically SIV-uninfected RMs present at the Tulane National Primate Research Center (SIV− controls). In CD4-depleted RMs SIV vRNA+ cells were found throughout the parenchyma (Figure 5a) and had a stellate morphology typical of microglia. The high number of infected cells led us to evaluate, in the same brain sections, the levels of activation by IHC/IF staining for CD163, HLA-DR, and proliferating cell nuclear antigen (PCNA, a marker of perivascular macrophages that has been used as a marker of DNA repair in macrophages [14]). As shown in the representative images (b) and in the quantitative analysis (c) of Figure 5, the expression of CD163 (P = 0.0013; P = 0.0047), HLA-DR (P = 0.0571; P = 0.0571), and PCNA (P = 0.0026; P = 0.0121) in cells with location and stellate morphology typical of microglia were significantly higher in CD4-depleted than SIV-uninfected or SIV-infected controls. The surprising finding that a significant number of microglia are activated and productively infected was confirmed by triple fluorescent labeling for SIV vRNA (red), CD163 (blue) and the microglia-specific marker IBA-1 [15] (green) (Figure 5d). Quantification of these stainings showed numbers of SIV vRNA+ IBA-1+ microglia markedly higher in CD4-depleted compared to non-depleted SIV-infected animals (11.3±8.4 vs. 0.2±0.2; P = 0.0286). Of note, we found a direct correlation between the number (cells/mm2) of SIV vRNA+ cells and PCNA+ cells in the eight CD4-depleted animals (r = 0.8289, P = 0.0302).

Bottom Line: In rhesus macaques (RMs), experimental depletion of CD4+ T-cells prior to SIV infection results in higher viremia and emergence of CD4-independent SIV-envelopes.In this study we used the rhesus recombinant anti-CD4 antibody CD4R1 to deplete RM CD4+ T-cells prior to SIVmac251 infection and investigate the sources of the increased viral burden and the lifespan of productively infected cells.We believe these findings have important implications for HIV eradication studies.

View Article: PubMed Central - PubMed

Affiliation: Division of Microbiology & Immunology, Yerkes National Primate Research Center, Emory University School of Medicine, Atlanta, Georgia, United States of America.

ABSTRACT
In rhesus macaques (RMs), experimental depletion of CD4+ T-cells prior to SIV infection results in higher viremia and emergence of CD4-independent SIV-envelopes. In this study we used the rhesus recombinant anti-CD4 antibody CD4R1 to deplete RM CD4+ T-cells prior to SIVmac251 infection and investigate the sources of the increased viral burden and the lifespan of productively infected cells. CD4-depleted animals showed (i) set-point viral load two-logs higher than controls; (ii) macrophages constituting 80% of all SIV vRNA+ cells in lymph node and mucosal tissues; (iii) substantial expansion of pro-inflammatory monocytes; (iv) aberrant activation and infection of microglial cells; and (v) lifespan of productively infected cells significantly longer in comparison to controls, but markedly shorter than previously estimated for macrophages. The net effect of CD4+ T-cell depletion is an inability to control SIV replication and a shift in the tropism of infected cells to macrophages, microglia, and, potentially, other CD4-low cells which all appear to have a shortened in vivo lifespan. We believe these findings have important implications for HIV eradication studies.

No MeSH data available.


Related in: MedlinePlus