T follicular helper cells (Tfh), defined as CD3+CD4+PD-1+CXCR5+, are specialized T cells, residing in the B cell follicles that assist in B cell survival, proliferation, antibody class switching, and differentiation. The loss of Tfh cells, in chronically infected individuals, is associated with immune dysfunction. Tfh cells have also been implicated as a persistent reservoir of virus-infected cells in persons treated with antiretrovirals (ART) with undetectable plasma HIV RNA levels. Herein, we studied the dynamics of Tfh cells in lymph nodes (LN) before and shortly after ART initiation.
ART-naïve patients with CD4 counts <100cells/µL were enrolled in a prospective study, Inguinal LNs were collected at baseline (pre-ART) and 4-8 weeks post-ART and cells were extracted for immunophenotyping for flow cytometry. Mann-Whitney test and Wilcoxon matched pair test was used to compare groups, while Spearman’s rank correction coefficient was used to test associations.
22 patients, with a median age of 36 (22-53), 6 females and 16 males, were included and underwent LN biopsies including 13 with paired (pre/post-ART) sampling. Median CD4 count at baseline was 23 cells/µL, and median HIV-RNA was 136,677 cp/mL. Median CD4 count after ART was 82 cells/µL, while median HIV-RNA was 78 c/mL (Table). In addition, median CD8 T cells counts in peripheral blood also increased post-ART from 527 to 713 cells/µL. Subsets of CD4 T cells (naïve, effector, central memory and Treg) did not differ significantly post-ART in LN. The CD8 percentage in LN decreased significantly (X vs y, P) post-ART. The percent of CD4 T cells in LN increased post-ART although the difference was only significant in paired analysis of the 13 paired sample subgroup (X vs Y, P). In contrast, the percentage of Tfh cells increased post-ART treatment in both paired and unpaired analysis (Figure). This increase of Tfh cells was not associated with baseline or post-ART HIV-RNA or CD4 count recovery.
Tfh emergence in lymph nodes of advanced patients initiating ART occurs early after ART initiation and is independent of plasma viremia or CD4 restoration. The mechanisms of this accumulation are unclear and may have implications in their functionality and their role as HIV reservoirs.