Follicular Helper CD4+ (TFh) are antigen experienced T cells found in secondary lymphoid organs such as lymph nodes (LN). Recently, different TFh subsets has been described during chronic SIV infection based on chemokine receptors expression including CXCR3-Tfh1, CCR4-Tfh2 and CCR6-Tfh17. We characterized TFh subsets proportions and activation patterns during chronic HIV infection and its association with disease progression and viral control.
Cervical LN mononuclear cells (LNMC) from 22 chronic-untreated (CHR) and 7 treated-undetectable (ART) patients were characterized by flow cytometry including CXCR5hiPD-1hi (TFh), chemokine receptors (R5, R4, R6, X3, X5) and activation markers (CD38, HLA-DR, CD69). LNMC and PBMC HIV CA-DNA were measured by qPCR. T cell counts were assessed by BD True count kit. pVL was determined by m2000 system. Analysis were performed on Cytobank and Prism6 using non-parametric tests.
CHR participants had an average CD4+Tc count of 454 cells/ul. CD4+Tc represented 21.43% of LNMC. TFh were 3.11% of total LN CD4+Tc. Significant negative correlation was detected between TFh% and CD8+Tc count (Spearman r=-0.56, P=0.006). We found low beta chemokine receptors expression on TFh (Tfh2=2.6%, Tfh17=0.7%). CCR5 expression on TFh was 5.2% on CHR and 11.6% on ART, p=0.005. Of note, CXCR3+ Tfh1 are a prevalent population on both CHR (45.8%) and TAR (44.1%). Interestingly, Tfh1% from CHR negatively correlates with pVL (r=-0.55, P=0.007), PB CA-DNA (r=-0.58, P=0.004) and LN CA-DNA (r=-0.47, P=0.02). Tfh1 clustered as separated population on viSNE analysis. Furthermore, Tfh1 expressed significantly higher levels of CCR5, HLA-DR, CD38, CD69 when compared to CXCR3 negative TFh (p<0.0001 in all markers). Finally, CCR5 expressing Tfh1 were significantly higher on treated participants (9.5% CHR vs 26% ART; p<0.0001).
Our study defined preferential chemokine receptors expression patterns on TFh during HIV infection including higher proportions of CXCR3+ Tfh1 cells. Tfh1 levels were associated with lower pVL and CA-DNA on LN and PB. Likewise, Tfh1 were found to be highly activated. These results suggest that Tfh1 have a role controlling HIV during chronic infection. Furthermore, we showed that Tfh1 express higher CCR5 levels compared to other TFh populations. CCR5 expressing Tfh1 are increased in treated individuals suggesting preferential infection on this subset. Our results encourage further Tfh1 studies to detail their role on HIV control and persistence