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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

Expansion of activated, pro-inflammatory monocytes in CD4-depleted SIV-infected RMs.(a) Representative flow plots of different monocyte subsets as defined by CD14 and CD16 expression. Levels of Ki-67 and FMO controls are represented for classical (CD14+CD16−), pro-inflammatory (CD14+CD16+), and non-classical (CD14−CD16+) monocytes. (b) Quantification of total and Ki-67+ blood monocyte subsets (cells/µl) in SIV-infected CD4-depleted (orange square; n = 8) and undepleted control (closed circle; n = 4) RMs. In depleted RMs, the number of total and proliferating CD14+CD16+ monocytes was significantly higher than undepleted controls at day 28 and 52 post-infection. (c) In CD4-depleted RMs (orange square; n = 8) plasma levels of soluble CD163 (sCD163) were significantly higher than undepleted controls (closed circle; n = 4) at day 28 and day 52 post-infection, as well as after 12 days of ART. (d) Plasma level of sCD163 significantly correlates with the numbers of CD14+CD16+ and of CD14+CD16+Ki-67+ monocytes in all SIV-infected RMs (day 52 p.i.; n = 12; Spearman rank correlation tests). The gray box in the graphs of panels b and c indicates the 12 days of ART.
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ppat-1004467-g003: Expansion of activated, pro-inflammatory monocytes in CD4-depleted SIV-infected RMs.(a) Representative flow plots of different monocyte subsets as defined by CD14 and CD16 expression. Levels of Ki-67 and FMO controls are represented for classical (CD14+CD16−), pro-inflammatory (CD14+CD16+), and non-classical (CD14−CD16+) monocytes. (b) Quantification of total and Ki-67+ blood monocyte subsets (cells/µl) in SIV-infected CD4-depleted (orange square; n = 8) and undepleted control (closed circle; n = 4) RMs. In depleted RMs, the number of total and proliferating CD14+CD16+ monocytes was significantly higher than undepleted controls at day 28 and 52 post-infection. (c) In CD4-depleted RMs (orange square; n = 8) plasma levels of soluble CD163 (sCD163) were significantly higher than undepleted controls (closed circle; n = 4) at day 28 and day 52 post-infection, as well as after 12 days of ART. (d) Plasma level of sCD163 significantly correlates with the numbers of CD14+CD16+ and of CD14+CD16+Ki-67+ monocytes in all SIV-infected RMs (day 52 p.i.; n = 12; Spearman rank correlation tests). The gray box in the graphs of panels b and c indicates the 12 days of ART.

Mentions: Increased activation and turnover of monocytes predict progression to AIDS in SIV-infected RMs even better than CD4+ T-cell number [9]–[11]. Hence, we quantified the levels and Ki-67 expression of the monocyte subsets in CD4-depleted and control RMs. Monocytes were defined as classical (CD14+CD16−), pro-inflammatory (CD14+CD16+), and non-classical (CD14−CD16+) based on the expression of CD14 and/or CD16 (Figure 3a). In the control animals, stable levels of all monocyte subsets at day 52 p.i. followed their initial expansion. However, classical and pro-inflammatory monocytes in CD4-depleted RMs continued to increase, with numbers of CD14+CD16+ monocytes significantly higher than those of controls at days 28 (P = 0.0283) and 52 (P = 0.0283) p.i. (Figure 3b). Furthermore, and consistent with an activated/pro-inflammatory status and an increased output from bone marrow, the number of CD14+CD16+ monocytes expressing Ki-67+ in CD4-depleted RMs was significantly higher as compared to controls at days 28 (P = 0.0162) and 52 (P = 0.0485) p.i. (Figure 3b). At day 52 p.i. CD4-depleted RMs also have a higher number of proliferating CD14+CD16− and CD14−CD16+ monocytes than controls, although the difference was not statistically significant (Figure 3b). In CD4-depleted RMs plasma levels of soluble CD163 (sCD163), a marker of monocyte activation associated with rapid disease progression [9], [12], [13], were significantly higher than in controls at day 28 (p = 0.016) and day 52 (p = 0.048) p.i. (Figure 3c). Of note, at day 52 p.i., levels of sCD163 strongly correlated with the numbers of total (r = 0.7483, P = 0.0070) and Ki-67+ (r = 0.6923, P = 0.0155) CD14+CD16+ monocytes (Figure 3d), as well as with viremia (r = 0.8322; P = 0.0013) (Figure S2). Thus, depletion of CD4+ T-cells prior to SIV infection results in increased number, activation and turnover of monocytes during early SIV infection. As indicated in Figure 1a, all 12 SIV-infected RMs were started on ART at day 52 p.i. The numbers of pro-inflammatory monocytes (CD14+CD16+; P = 0.0145) and their levels of Ki-67 expression (P = 0.0189) after 12 days of ART (day 64 p.i) were significantly decreased as compared to pre-ART (day 52 p.i.) levels, and become comparable to those found in controls (Figure 3b). Classical (CD14+CD16−) and non-classical (CD14−CD16+) monocyte levels were not significantly affected by ART (Figure 3b). Levels of sCD163 remained significantly higher in CD4 depleted animals than controls after 12 days of ART (Figure 3c). Of note, the interpretation of the effects of ART in the aforementioned parameters, in particular for sCD163, is complicated by the fact that we were able to only treat the animals for a short period. Indeed, and perhaps as a consequence of the fact that CD4-depletion resulted in very high virus replication, seven of the eight depleted RMs had to be euthanized for AIDS-related reasons briefly after ART initiation (Table S1).


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)

Expansion of activated, pro-inflammatory monocytes in CD4-depleted SIV-infected RMs.(a) Representative flow plots of different monocyte subsets as defined by CD14 and CD16 expression. Levels of Ki-67 and FMO controls are represented for classical (CD14+CD16−), pro-inflammatory (CD14+CD16+), and non-classical (CD14−CD16+) monocytes. (b) Quantification of total and Ki-67+ blood monocyte subsets (cells/µl) in SIV-infected CD4-depleted (orange square; n = 8) and undepleted control (closed circle; n = 4) RMs. In depleted RMs, the number of total and proliferating CD14+CD16+ monocytes was significantly higher than undepleted controls at day 28 and 52 post-infection. (c) In CD4-depleted RMs (orange square; n = 8) plasma levels of soluble CD163 (sCD163) were significantly higher than undepleted controls (closed circle; n = 4) at day 28 and day 52 post-infection, as well as after 12 days of ART. (d) Plasma level of sCD163 significantly correlates with the numbers of CD14+CD16+ and of CD14+CD16+Ki-67+ monocytes in all SIV-infected RMs (day 52 p.i.; n = 12; Spearman rank correlation tests). The gray box in the graphs of panels b and c indicates the 12 days of ART.
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Related In: Results  -  Collection

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ppat-1004467-g003: Expansion of activated, pro-inflammatory monocytes in CD4-depleted SIV-infected RMs.(a) Representative flow plots of different monocyte subsets as defined by CD14 and CD16 expression. Levels of Ki-67 and FMO controls are represented for classical (CD14+CD16−), pro-inflammatory (CD14+CD16+), and non-classical (CD14−CD16+) monocytes. (b) Quantification of total and Ki-67+ blood monocyte subsets (cells/µl) in SIV-infected CD4-depleted (orange square; n = 8) and undepleted control (closed circle; n = 4) RMs. In depleted RMs, the number of total and proliferating CD14+CD16+ monocytes was significantly higher than undepleted controls at day 28 and 52 post-infection. (c) In CD4-depleted RMs (orange square; n = 8) plasma levels of soluble CD163 (sCD163) were significantly higher than undepleted controls (closed circle; n = 4) at day 28 and day 52 post-infection, as well as after 12 days of ART. (d) Plasma level of sCD163 significantly correlates with the numbers of CD14+CD16+ and of CD14+CD16+Ki-67+ monocytes in all SIV-infected RMs (day 52 p.i.; n = 12; Spearman rank correlation tests). The gray box in the graphs of panels b and c indicates the 12 days of ART.
Mentions: Increased activation and turnover of monocytes predict progression to AIDS in SIV-infected RMs even better than CD4+ T-cell number [9]–[11]. Hence, we quantified the levels and Ki-67 expression of the monocyte subsets in CD4-depleted and control RMs. Monocytes were defined as classical (CD14+CD16−), pro-inflammatory (CD14+CD16+), and non-classical (CD14−CD16+) based on the expression of CD14 and/or CD16 (Figure 3a). In the control animals, stable levels of all monocyte subsets at day 52 p.i. followed their initial expansion. However, classical and pro-inflammatory monocytes in CD4-depleted RMs continued to increase, with numbers of CD14+CD16+ monocytes significantly higher than those of controls at days 28 (P = 0.0283) and 52 (P = 0.0283) p.i. (Figure 3b). Furthermore, and consistent with an activated/pro-inflammatory status and an increased output from bone marrow, the number of CD14+CD16+ monocytes expressing Ki-67+ in CD4-depleted RMs was significantly higher as compared to controls at days 28 (P = 0.0162) and 52 (P = 0.0485) p.i. (Figure 3b). At day 52 p.i. CD4-depleted RMs also have a higher number of proliferating CD14+CD16− and CD14−CD16+ monocytes than controls, although the difference was not statistically significant (Figure 3b). In CD4-depleted RMs plasma levels of soluble CD163 (sCD163), a marker of monocyte activation associated with rapid disease progression [9], [12], [13], were significantly higher than in controls at day 28 (p = 0.016) and day 52 (p = 0.048) p.i. (Figure 3c). Of note, at day 52 p.i., levels of sCD163 strongly correlated with the numbers of total (r = 0.7483, P = 0.0070) and Ki-67+ (r = 0.6923, P = 0.0155) CD14+CD16+ monocytes (Figure 3d), as well as with viremia (r = 0.8322; P = 0.0013) (Figure S2). Thus, depletion of CD4+ T-cells prior to SIV infection results in increased number, activation and turnover of monocytes during early SIV infection. As indicated in Figure 1a, all 12 SIV-infected RMs were started on ART at day 52 p.i. The numbers of pro-inflammatory monocytes (CD14+CD16+; P = 0.0145) and their levels of Ki-67 expression (P = 0.0189) after 12 days of ART (day 64 p.i) were significantly decreased as compared to pre-ART (day 52 p.i.) levels, and become comparable to those found in controls (Figure 3b). Classical (CD14+CD16−) and non-classical (CD14−CD16+) monocyte levels were not significantly affected by ART (Figure 3b). Levels of sCD163 remained significantly higher in CD4 depleted animals than controls after 12 days of ART (Figure 3c). Of note, the interpretation of the effects of ART in the aforementioned parameters, in particular for sCD163, is complicated by the fact that we were able to only treat the animals for a short period. Indeed, and perhaps as a consequence of the fact that CD4-depletion resulted in very high virus replication, seven of the eight depleted RMs had to be euthanized for AIDS-related reasons briefly after ART initiation (Table S1).

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