Abstract
BACKGROUND: HIV-2 infection is characterised by a longer asymptomatic phase and slower AIDS progression than HIV-1 infection. Identifying unique immune signatures associated with HIV-2 pathogenesis may thus provide therapeutically useful insight into the management of HIV infection. This study examined the dynamics of the CD4(+)T cell compartment, critical in disease progression, focussing on chronic HIV-2 and HIV-1 infected individuals at various stages of disease progression. METHODS: A total of 111 participants including untreated and treated HIV infected individuals and seronegative individuals were enrolled in this study. The relative proportion of CD4(+)T cell subsets, expressing CD25 (IL-2Rα) and CD127 (IL-7R), in HIV infected individuals and seronegative controls were assessed by multiparametric flow cytometry. Additionally, levels of immune activation and cytotoxic T lymphocytes in both the CD4(+)T and CD8(+)T cell compartments was evaluated. RESULTS: Both treated and untreated, HIV-1 and HIV-2 infected individuals showed apparent dysregulation in CD4(+) T cell subset frequency that was associated with disease progression. Furthermore, longitudinal sampling from a group of HIV-1 infected individuals on virologically effective ART showed no significant change in dysregulated CD4(+)T cell subset frequency. For both ART naïve and receiving groups associations with disease progression were strongest and significant with CD4(+) T cell subset frequency compared to per cell expression of IL-2Rα and IL-7Rα. In untreated HIV-2 infected individuals, T cell activation was lower compared to ART naïve HIV-1 infected individuals and higher than seronegative individuals. Also, the level of Granzyme-B expressing circulating T cells was higher in both ART-naïve HIV-1 and HIV-2 infected individuals compared to seronegative controls. CONCLUSION: Dysregulation of IL-2 and IL-7 homeostasis persists in CD4(+)T cell subsets irrespective of presence or absence of viremia or antiretroviral therapy in HIV infection. Furthermore, we report for the first time on levels of circulating Granzyme-B expressing CD4(+)T and CD8(+)T cells in chronic HIV-2 infection. Lower immune activation in these individuals indicates that persistent immune activation driven CD4(+)T cell depletion, as observed in untreated HIV-1 infected individuals, may not be as severe and provides evidence for a disparate pathogenesis mechanism. Our work also supports novel immunomodulatory therapeutic strategies for both HIV-1 and HIV-2 infection.