Dynamic changes in immune cell subsets in blood and lymph node over the course of acute HIV infection

Innate, cellular and humoral immunity in acute HIV infection (AHI) play crucial roles in dictating immunological and pathological outcomes. However, understanding immune cell dynamics in different compartments during AHI is limited. In this study, we characterized immune cells from matched blood and lymph node samples in the RV254 Thai AHI cohort, the RV304 Thai chronic HIV infection cohort, and HIV-negative individuals, using flow cytometry. Our results showed a significant loss of the CD4:CD8 ratio in both PBMCs and LNMCs during AHI. Similarly, we observed increased immune activation of CD4⁺ and CD8⁺ T cells in both blood and lymph node compartments during AHI. In contrast, we found no increase in T follicular helper cells (Tfh) and a lack of association between circulating Tfh and lymph node Tfh during AHI. Furthermore, early B cell depletion, particularly in resting memory B cells, was observed in blood but not in lymph nodes during AHI. Additionally, during AHI, plasmacytoid dendritic cell activation was increased in lymph nodes but not in blood. These findings suggest that certain immune cell phenotypes and dynamics are unique in lymph nodes compared to blood during AHI. Understanding the immune cell alteration in these compartments during AHI may help define the mechanisms leading to lack of immune control in natural HIV infection.