Objective

Both protective T-cell genotypes and natural killer (NK) cell genotypes have been associated with delayed progression to AIDS and shown to be co-inherited in HIV-1-infected individuals who limit viral replication in absence of antiretroviral therapy ('controllers'). However, a comparative analysis of the genotype and function of the innate and adaptive immune compartments in HIV-1-infected controller individuals has been understudied to date.

Design

Here, we simultaneously tested NK and T-cell function in controllers to investigate the mechanism(s) that might account for host immune control over viral replication.

Methods

We measured CD8 T-cell responses against HIV-1 utilizing overlapping 15-mer peptides spanning the HIV-1 consensus clade B Gag protein and tested NK cell degranulation and cytokine secretion against tumor target cells following interferon-α (IFNα) stimulation.

Results

Among a cohort of 37 controllers, the presence of protective major histocompatibility complex class I human leukocyte antigen (HLA) alleles (such as HLA-B*57) was not correlated with HIV-specific CD8 responses. In contrast, the inheritance of a protective killer inhibitory receptor KIR3DL1*h/*y receptor genotype along with the corresponding HLA-Bw4*80I ligand was associated with significantly heightened target cell-induced NK degranulation and cytokine secretion following IFNα stimulation (P = 0.0201, n = 13). Interestingly, we observed a significant inverse association between the IFNα stimulated NK response to K562 cells and the HIV-specific CD8 T-cell response to Gag among elite controllers (rho = -0.8321, P = 0.0010, n = 12).

Conclusion

Together, these results suggest that heightened NK responses can be evidenced independently of HIV-specific T-cell responses in HIV-1-infected elite controllers.

Persistence of latent HIV-1 in long-lived resting memory CD4+ T cells is a major barrier to curing HIV-1 infection, and thus a biomarker for latently infected cells would be of great scientific and clinical importance.,,,, Through an elegant discovery-based approach, Descours et al. reported that CD32a, an Fcγ receptor not normally expressed on T cells, is a potential biomarker for latently infected cells. Using the quantitative viral outgrowth assay, we show that CD32+ CD4+ T cells do not harbor the majority of intact proviruses in the latent reservoir and that the enrichment found by Descours et al. may in part reflect the use of an ultrasensitive ELISA for HIV-1 p24 antigen that does not predict exponential viral outgrowth. Our studies show that CD32 is not a biomarker for the major population of latently infected CD4+ T cells.

The persistence of HIV reservoirs, including latently infected, resting CD4⁺ T cells, is the major obstacle to cure HIV infection. CD32a expression was recently reported to mark CD4⁺ T cells harboring a replication-competent HIV reservoir during antiretroviral therapy (ART) suppression. We aimed to determine whether CD32 expression marks HIV latently or transcriptionally active infected CD4⁺ T cells. Using peripheral blood and lymphoid tissue of ART-treated HIV⁺ or SIV⁺ subjects, we found that most of the circulating memory CD32⁺ CD4⁺ T cells expressed markers of activation, including CD69, HLA-DR, CD25, CD38, and Ki67, and bore a T_H2 phenotype as defined by CXCR3, CCR4, and CCR6. CD32 expression did not selectively enrich for HIV- or SIV-infected CD4⁺ T cells in peripheral blood or lymphoid tissue; isolated CD32⁺ resting CD4⁺ T cells accounted for less than 3% of the total HIV DNA in CD4⁺ T cells. Cell-associated HIV DNA and RNA loads in CD4⁺ T cells positively correlated with the frequency of CD32⁺ CD69⁺ CD4⁺ T cells but not with CD32 expression on resting CD4⁺ T cells. Using RNA fluorescence in situ hybridization, CD32 coexpression with HIV RNA or p24 was detected after in vitro HIV infection (peripheral blood mononuclear cell and tissue) and in vivo within lymph node tissue from HIV-infected individuals. Together, these results indicate that CD32 is not a marker of resting CD4⁺ T cells or of enriched HIV DNA-positive cells after ART; rather, CD32 is predominately expressed on a subset of activated CD4⁺ T cells enriched for transcriptionally active HIV after long-term ART.