HIV-specific CD4 T cells

Screen Shot 2013-06-03 at 3.57.39 PMAssociation of HLA-DRB1–restricted CD4+ T cell responses with HIV immune control

Srinika Ranasinghe, Sam Cutler, Isaiah Davis, Richard Lu, Damien Z. Soghoian, Ying Qi, John Sidney, Gregory Kranias, Michael Flanders, Madelene Lindqvist, Bjorn Kuhl, Galit Alter, Steven G. Deeks, Bruce D. Walker, Xiaojiang Gao, Alessandro Sette, Mary Carrington and Hendrik Streeck

The contribution of HLA class II–restricted CD4+ T cell responses to HIV immune control is poorly defined. Here, we delineated previously uncharacterized peptide-DRB1 restrictions in functional assays and analyzed the host genetic effects of HLA-DRB1 alleles on HIV viremia in a large cohort of HIV controllers and progressors. We found distinct stratifications in the effect of HLA-DRB1alleles on HIV viremia, with HLA-DRB1*15:02 significantly associated with low viremia and HLA-DRB1*03:01 significantly associated with high viremia. Notably, a subgroup of HLA-DRB1 variants linked with low viremia showed the ability to promiscuously present a larger breadth of peptides with lower functional avidity when compared to HLA-DRB1 variants linked with high viremia. Our data provide systematic evidence that HLA-DRB1 variant expression has a considerable impact on the control of HIV replication, an effect that seems to be mediated primarily by the protein specificity of CD4+ T cell responses to HIV Gag and Nef.

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HIV-specific CD4 T cell responses to different viral proteins have discordant associations with viral load and clinical outcome.

Ranasinghe S, Flanders M, Cutler S, Soghoian DZ, Ghebremichael M, Davis I, Lindqvist M, Pereyra F, Walker BD, Heckerman D, Streeck H.J Virol. 2012 Jan;86(1):277-83.

A successful prophylactic vaccine is characterized by long-lived immunity, which is critically dependent on CD4 T cell-mediated helper signals. Indeed, most licensed vaccines induce antigen-specific CD4 T cell responses, in addition to high-affinity antibodies. However, despite the important role of CD4 T cells in vaccine design and natural infection, few studies have characterized HIV-specific CD4 T cells due to their preferential susceptibility to HIV infection. To establish at the population level the impact of HIV-specific CD4 T cells on viral control and define the specificity of HIV-specific CD4 T cell peptide targeting, we conducted a comprehensive analysis of these responses to the entire HIV proteome in 93 subjects at different stages of HIV infection. We show that HIV-specific CD4 T cell responses were detectable in 92% of individuals and that the breadth of these responses showed a significant inverse correlation with the viral load (P = 0.009, R = -0.31). In particular, CD4 T cell responses targeting Gag were robustly associated with lower levels of viremia (P = 0.0002, R = -0.45). Importantly, differences in the immunodominance profile of HIV-specific CD4 T cell responses distinguished HIV controllers from progressors. Furthermore, Gag/Env ratios were a potent marker of viral control, with a high frequency and magnitude of Gag responses and low proportion of Env responses associated with effective immune control. At the epitope level, targeting of three distinct Gag peptides was linked to spontaneous HIV control (P = 0.60 to 0.85). Inclusion of these immunogenic proteins and peptides in future HIV vaccines may act as a critical cornerstone for enhancing protective T cell responses.

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HIV-1-specific interleukin-21+ CD4+ T cell responses contribute to durable viral control through the modulation of HIV-specific CD8+ T cell function

Chevalier MF, Jülg B, Pyo A, Flanders M, Ranasinghe S, Soghoian DZ, Kwon DS, Rychert J, Lian J, Muller MI, Cutler S, McAndrew E, Jessen H, Pereyra F, Rosenberg ES, Altfeld M, Walker BD, Streeck H. . J Virol. 2011 Jan;85(2):733-41.

Functional defects in cytotoxic CD8(+) T cell responses arise in chronic human viral infections, but the mechanisms involved are not well understood. In mice, CD4 cell-mediated interleukin-21 (IL-21) production is necessary for the maintenance of CD8(+) T cell function and control of persistent viral infections. To investigate the potential role of IL-21 in a chronic human viral infection, we studied the rare subset of HIV-1 controllers, who are able to spontaneously control HIV-1 replication without treatment. HIV-specific triggering of IL-21 by CD4(+) T cells was significantly enriched in these persons (P = 0.0007), while isolated loss of IL-21-secreting CD4(+) T cells was characteristic for subjects with persistent viremia and progressive disease. IL-21 responses were mediated by recognition of discrete epitopes largely in the Gag protein, and expansion of IL-21(+) CD4(+) T cells in acute infection resulted in lower viral set points (P = 0.002). Moreover, IL-21 production by CD4(+) T cells of HIV controllers enhanced perforin production by HIV-1-specific CD8(+) T cells from chronic progressors even in late stages of disease, and HIV-1-specific effector CD8(+) T cells showed an enhanced ability to efficiently inhibit viral replication in vitro after IL-21 binding. These data suggest that HIV-1-specific IL-21(+) CD4(+) T cell responses might contribute to the control of viral replication in humans and are likely to be of great importance for vaccine design.

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