Tregs including follicular regulatory T cells (TFR) are expanded in lymph nodes of untreated HIV+ people. TFR impair TFH responses and humoral immunity in untreated disease. Little is known about the impact of antiretroviral therapy (ART) on Treg and TFR populations in secondary lymphoid organs.
Frequencies of Tregs (FoxP3+CD8-) and TFR (Tregs located in CD20+ B cell follicles) were determined by immunostaining of formalin fixed paraffin embedded lymph node (LN) tissue sections and quantitative image analysis. Frequencies of HIV RNA+ cells were determined in the same tissue section using in situ hybridization (RNAscope). Data were analyzed using descriptive and nonparametric statistics.
LN were evaluated from 6 HIV+ men receiving ART for a median of 20 years (range, 7-29 years) with documented plasma HIV RNA <20 copies/mL at the time of screening. For comparison, LN sections from 8 HIV+ men not receiving ART, and 6 HIV seronegative men (SN) were also evaluated. As expected, frequencies of Tregs in the tissue cross sections were significantly higher in untreated HIV+ compared to SN men (medians, 56 vs 21 cells/mm2; p=0.008), and a similar trend was seen for TFR within follicles (medians, 59 versus 22 cells/mm2; p=0.10). In ART treated HIV+, Tregs (median, 36 cells/mm2) and TFR (median, 76 cells/mm2) did not differ significantly from either group. Tregs and TFR from ART-treated HIV+ demonstrated a clear dichotomy; 3 subjects had elevated levels similar to what was seen in untreated HIV+, and 3 had low levels of TFR similar to SN. HIV RNA+ cells were detected in LN of all ART-treated HIV+ (range, 0.05 to 0.5 cells/mm2) and were significantly fewer than those detected in untreated HIV+ (range, 0.2 to 2.6 cells/mm2; p=0.04). Higher concentrations of HIV RNA+ cells were found in the LN follicles of all ART treated individuals (median, 0.4 cells/mm2) compared to extrafollicular regions (median, 0.2 cells/mm2) with median F:EF ratio of 1.8 (range, 1.5 to 3.2). Frequencies of both Tregs and TFR in LN of ART-treated individuals correlated directly with frequencies of HIV RNA+ cells (r=0.88; p=0.03 for both).
Persistent expansion of Tregs including TFR is seen in LN of some ART-treated individuals with plasma virus suppression and is related to tissue HIV RNA expression. Expansions in TFR may contribute to impairments in humoral immunity seen in some ART-treated individuals.