UC San Diego

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.