Follicular Immune Landscaping Reveals a Distinct Profile of FOXP3^hiCD4^hi T Cells in Treated Compared to Untreated HIV

Follicular helper CD4^hi T cells (T_FH) are a major cellular pool for the maintenance of the HIV reservoir. Therefore, the delineation of the follicular (F)/germinal center (GC) immune landscape will significantly advance our understanding of HIV pathogenesis. We have applied multiplex confocal imaging, in combination with the relevant computational tools, to investigate F/GC in situ immune dynamics in viremic (vir-HIV), antiretroviral-treated (cART HIV) People Living With HIV (PLWH) and compare them to reactive, non-infected controls. Lymph nodes (LNs) from viremic and cART PLWH could be further grouped based on their T_FH cell densities in high-T_FH and low-T_FH subgroups. These subgroups were also characterized by different in situ distributions of PD1^hi T_FH cells. Furthermore, a significant accumulation of follicular FOXP3^hiCD4^hi T cells, which were characterized by a low scattering in situ distribution profile and strongly correlated with the cell density of CD8^hi T cells, was found in the cART-HIV low-TFH group. An inverse correlation between plasma viral load and LN GrzB^hiCD8^hi T and CD16^hiCD15^lo cells was found. Our data reveal the complex GC immune landscaping in HIV infection and suggest that follicular FOXP3^hiCD4^hi T cells could be negative regulators of T_FH cell prevalence in cART-HIV.