In vitro replication of SIVcpz is suppressed by beta-chemokines and CD8+ T cells but not by natural killer cells of infected chimpanzees

Highly dampened HIV-specific cytolytic effector T cell responses define viremic non-progression

This study reports on HIV-specific T cell responses in HIV-1 infected Viremic Non-Progressors (VNPs), a rare group of people living with HIV that exhibit asymptomatic infection over several years accompanied by stable CD4+ T cell counts in spite of ongoing viral replication. We attempted to identify key virus-specific functional attributes that could underlie the apparently paradoxical virus-host equilibrium observed in VNPs. Our results revealed modulation of HIV-specific CD4+ and CD8+ effector T cell responses in VNPs towards a dominant non-cytolytic profile with concomitantly diminished degranulation (CD107a+) ability. Further, the HIV specific CD8+ effector T cell response was primarily enriched for MIP-1β producing cells. As expected, concordant with better viral suppression, VCs exhibit a robust cytolytic T cell response. Interestingly, PuPs shared features common to both these responses but did not exhibit a CD4+ central memory IFN-γ producing Gag-specific response that was shared by both non-progressor (VC and VNP) groups, suggesting CD4 helper response is critical for non-progression. Our study also revealed that cytolytic response in VNPs is primarily limited to polyfunctional cells while both monofunctional and polyfunctional cells significantly contribute to cytolytic responses in VCs. To further understand mechanisms underlying the unique HIV-specific effector T cell response described here in VNPs we also evaluated and demonstrated a possible role for altered gut homing in these individuals. Our findings inform immunotherapeutic interventions to achieve functional cures in the context of ART resistance and serious non AIDS events.

Characterization of γδT cells in naïve and HIV-infected chimpanzees and their responses to T-cell activators in vitro

BACKGROUND

γδT cells are effector cells that eliminate cancer and virus-infected cells. Chimpanzees are an endangered species that can naturally and experimentally be infected with SIV and HIV, respectively, but no information about the functionality of γδT cells during chronic lentiviral infection is currently available.

METHODS

Healthy and HIV-infected chimpanzee γδT cells were characterized by flow cytometry. γδT subsets were studied after stimulation with T-cell activators, and the release of cytokines was analyzed by Luminex assay.

RESULTS

γδT-cell subsets, Vδ1 and Vδ2Vγ9, showed different patterns in the expression of CD4, CD195, CD159a, and CD159c. Stimulation of γδT cells resulted in increased levels of CD4 and HLA-DR, which is more pronounced in Vδ1 T cells. Distinct cytokine patterns were found between healthy and HIV-infected chimpanzees.

CONCLUSIONS

Analyses of major chimpanzee γδT subsets show similarities to human γδT cells and suggest different functionality and roles in their immune response against HIV infection.

Influence of interleukin-15 on CD8+ natural killer cells in human immunodeficiency virus type 1-infected chimpanzees

Chimpanzees are susceptible to human immunodeficiency virus type-1 (HIV-1) and develop persistent infection but generally do not progress to full-blown AIDS. Several host and immunological factors have been implicated in mediating resistance to disease progression. Chimpanzees have a higher prevalence of circulating natural killer (NK) cells than humans; however, their role in mediating resistance to disease progression is not well understood. Furthermore, NK cell survival and activity have been shown to be dependent on interleukin-15 (IL-15). Accordingly, the influence of IL-15 on NK cell activity and gamma interferon (IFN-gamma) production was evaluated in naive and HIV-1-infected chimpanzees. In vitro stimulation of whole-blood cultures with recombinant gp120 (rgp120) resulted in enhanced IFN-gamma production predominantly by the CD3(-) CD8(+) subset of NK cells, and addition of anti-IL-15 to the system decreased IFN-gamma production. Moreover, in vitro stimulation with recombinant IL-15 (rIL-15) augmented IFN-gamma production from this subset of NK cells and increased NK cell cytotoxic activity. Stimulation with rgp120 also resulted in a 2- to 7-fold increase in IL-15 production. These findings suggest that chimpanzee CD3(-) CD8(+) NK cells play a vital role in controlling HIV-1 infection by producing high levels of IFN-gamma, and that IL-15 elicits IFN-gamma production in this subpopulation of NK cells in HIV-1-infected chimpanzees.

Human and simian immunodeficiency virus-infected chimpanzees do not have increased intracellular levels of beta-chemokines in contrast to infected humans

This study was undertaken to explain why chimpanzees infected with HIV-1 (human immunodeficiency virus type 1) or SIV(cpz) (simian immunodeficiency virus of chimpanzee) are relatively resistant to AIDS (acquired immunodeficiency syndrome). The numbers of beta-chemokine-positive cells were compared between uninfected and infected humans and chimpanzees using three-color cytofluorometry. In humans, the percentage of beta-chemokine-positive cells was significantly higher in CD8(+) T and natural killer (NK) cells than in CD4(+) T cells in both uninfected and HIV-1-infected individuals. In the presence of HIV-1 infection, however, both CD8(+) and CD4(+) T cell subsets contained significantly more beta-chemokine-positive cells than in the absence of infection. Interestingly, in chimpanzees two important differences were noted. First, their percentage of beta-chemokine-positive CD8(+) T and NK cells was significantly higher than in uninfected humans. Second, in contrast to humans, infection with either HIV-1 or with SIV(cpz) was not associated with increased numbers of beta-chemokine-positive cells. These results indicate that: constitutive high levels of intracellular beta-chemokines in chimpanzees' CD8 lymphocytes and NK cells do not necessarily correspond to lower levels of virus replication during the chronic phase of infection; and increased percentages of beta-chemokine-positive cells in HIV-infection are not a correlate of disease resistance. The data suggest that neither pre-nor post-exposure levels of intracellular beta-chemokines are correlated with the subsequent control of disease progression.