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Dynamics of SIV-specific CXCR5+ CD8 T cells during chronic SIV infection.

ABSTRACT: A significant challenge to HIV eradication is the elimination of viral reservoirs in germinal center (GC) T follicular helper (Tfh) cells. However, GCs are considered to be immune privileged for antiviral CD8 T cells. Here, we show a population of simian immunodeficiency virus (SIV)-specific CD8 T cells express CXCR5 (C-X-C chemokine receptor type 5, a chemokine receptor required for homing to GCs) and expand in lymph nodes (LNs) following pathogenic SIV infection in a cohort of vaccinated macaques. This expansion was greater in animals that exhibited superior control of SIV. The CXCR5+ SIV-specific CD8 T cells demonstrated enhanced polyfunctionality, restricted expansion of antigen-pulsed Tfh cells in vitro, and possessed a unique gene expression pattern related to Tfh and Th2 cells. The increase in CXCR5+ CD8 T cells was associated with the presence of higher frequencies of SIV-specific CD8 T cells in the GC. Following TCR-driven stimulation in vitro, CXCR5+ but not CXCR5- CD8 T cells generated both CXCR5+ as well as CXCR5- cells. However, the addition of TGF-? to CXCR5- CD8 T cells induced a population of CXCR5+ CD8 T cells, suggesting that this cytokine may be important in modulating these CXCR5+ CD8 T cells in vivo. Thus, CXCR5+ CD8 T cells represent a unique subset of antiviral CD8 T cells that expand in LNs during chronic SIV infection and may play a significant role in the control of pathogenic SIV infection.

SUBMITTER: Mylvaganam GH

PROVIDER: S-EPMC5338410 | biostudies-literature | 2017 Feb

REPOSITORIES: biostudies-literature

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Dynamics of SIV-specific CXCR5+ CD8 T cells during chronic SIV infection.

Mylvaganam Geetha H GH Rios Daniel D Abdelaal Hadia M HM Iyer Smita S Tharp Gregory G Mavigner Maud M Hicks Sakeenah S Chahroudi Ann A Ahmed Rafi R Bosinger Steven E SE Williams Ifor R IR Skinner Pamela J PJ Velu Vijayakumar V Amara Rama R RR

Proceedings of the National Academy of Sciences of the United States of America 20170203 8

A significant challenge to HIV eradication is the elimination of viral reservoirs in germinal center (GC) T follicular helper (Tfh) cells. However, GCs are considered to be immune privileged for antiviral CD8 T cells. Here, we show a population of simian immunodeficiency virus (SIV)-specific CD8 T cells express CXCR5 (C-X-C chemokine receptor type 5, a chemokine receptor required for homing to GCs) and expand in lymph nodes (LNs) following pathogenic SIV infection in a cohort of vaccinated macaq ...[more]

PMID: 28159893

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Project description:CD8+ lymphocytes play an important role in suppressing in vivo viral replication in HIV infection. However, both the extent to which and the mechanisms by which CD8+ lymphocytes contribute to viral control are not completely understood. A recent experiment depleted CD8+ lymphocytes in simian immunodeficiency virus (SIV)-infected rhesus macaques (RMs) on antiretroviral treatment (ART) to study the role of CD8+ lymphocytes. CD8+ lymphocytes depletion resulted in temporary plasma viremia in all studied RMs. Viral control was restored when CD8+ lymphocytes repopulated. We developed a viral dynamic model to fit the viral load (VL) data from the CD8 depletion experiment. We explicitly modeled the dynamics of the latent reservoir and the SIV-specific effector cell population including their exhaustion and their potential cytolytic and noncytolytic functions. We found that the latent reservoir significantly contributes to the size of the peak VL after CD8 depletion, while drug efficacy plays a lesser role. Our model suggests that the overall CD8+ lymphocyte cytolytic killing rate is dynamically changing depending on the levels of antigen-induced effector cell activation and exhaustion. Based on estimated parameters, our model suggests that before ART or without ART the overall CD8 cytolytic killing rate is small due to exhaustion. However, after the start of ART, the overall CD8 cytolytic killing rate increases due to an expansion of SIV-specific CD8 effector cells. Further, we estimate that the cytolytic killing rate can be significantly larger than the cytopathic death rate in some animals during the second phase of ART-induced viral decay. Lastly, our model provides a new explanation for the puzzling findings by Klatt et al. and Wong et al. that CD8 depletion done immediately before ART has no noticeable effect on the first phase viral decay slope seen after ART initiation Overall, by incorporating effector cells and their exhaustion, our model can explain the effects of CD8 depletion on VL during ART, reveals a detailed dynamic role of CD8+ lymphocytes in controlling viral infection, and provides a unified explanation for CD8 depletion experimental data.

Project description:CD8+ T-cells inhibit virus replication in SIV-infected rhesus macaques (RM). However, it is not clear how SIV infection is controlled in germinal center during chronic SIV infection and limited information exists on the characteristics of CXCR5+ CD8 T cells during chronic SIV/HIV infection. In this study, we used functional genomics to investigate characteristic features and potential mechanisms of CXCR5+ and CXCR5- SIV specific CD8 T cells for the control of pathogenic SIV infection. Six chronically SIV infected RMs, three SIVE660 infected and three SIV mac251 infected that are positive for Mamu A01 allele were selected and SIV-specific CXCR5+ and CXCR5- CD8 T cells were sorted based on CXCR5 expression. RNA from sorted cells were extracted and microarray were performed and analysed. Principal component analysis demonstrated that overall gene expression difference between CXCR5+ and CXCR5- SIV-specific CD8 T cells. Interestingly, the CXCR5+ CD8 T cells revealed a distinct gene signature pattern when compared to CXCR5- CD8 T cells. Unlike the CXCR5- CD8 T cells, the CXCR5+ CD8 T cells expressed higher levels of genes associated with Tfh CD4 T cells such as the master transcription factor Bcl6, CD200, and CTLA4 as well as markers associated with Th2 CD4 T cells such as IL-4R (CD124), CCR4, STAT6, NFATC, and IL-10. Effector molecules typically observed in cytotoxic CD8 T cells such as granzyme A, B, and K were expressed at lower levels on CXCR5+ CD8 T cells compared to their CXCR5- counterparts. CXCR5+ CD8 T cells also expressed higher levels of molecules associated with co-stimulation/antigen presentation such as CD40, CD83, 41BBL and MAMU-DRA. The CXCR5+ CD8 also expressed higher levels of inhibitory receptors such as CD200 and SPRY2 but lower levels of other inhibitory receptors CD160 and CD244. The functional consequence of the expression of these molecules is yet to be determined. Additionally, CXCR5+ CD8 T cells expressed higher levels of the anti-apoptotic gene Bcl-2 and lower levels of the pro-apoptotic gene annexin, suggestive of their better survival potential during chronic SIV infection. Collectively, these results demonstrate that SIV specific CXCR5+ CD8 T cells possess a unique gene expression signature compared to SIV-specific CXCR5- CD8 T cells.

Dataset Information

Dynamics of SIV-specific CXCR5+ CD8 T cells during chronic SIV infection.

Publications

Dynamics of SIV-specific CXCR5+ CD8 T cells during chronic SIV infection.

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