Frequencies of circulating Th1-biased T follicular helper cells in acute HIV-1 infection correlate with the development of HIV-specific antibody responses and lower set point viral load

Despite decades of focused research, the field has yet to develop a prophylactic vaccine. In the RV144 vaccine trial, non-neutralizing antibody responses were identified as a correlate for prevention of HIV acquisition. However, factors that predict the development of such antibodies are not fully elucidated. We sought to define the contribution of circulating T follicular helper (cTfh) cell subsets to the development of non-neutralizing antibodies in HIV-1 clade C infection. Study participants were recruited from an acute HIV-1 clade C infection cohort. Plasma anti-gp41, -gp120, -p24 and -p17 antibodies were screened using a customized multivariate Luminex assay. Phenotypic and functional characterization of cTfh were performed using HLA class II tetramers and intracellular cytokine staining. In this study, we found that acute HIV-1 clade C infection skewed differentiation of functional cTfh subsets towards increased Tfh1 (p=0.02) and Tfh2 (p<0.0001) subsets, with a concomitant decrease in overall Tfh1-17 (that shares both Tfh1 and Tfh17 properties) (p=0.01) and Tfh17 subsets (p<0.0001) compared to HIV negative subjects. Interestingly, the frequencies of Tfh1 during acute infection (5.0-8.0 weeks post-infection) correlated negatively with set point viral load (p=0.03, r=-60) and were predictive of p24-specific plasma IgG titers at one year of infection (p=0.003, r=0.85). Taken together, our results suggest that circulating the Tfh1 subset plays an important role in the development of anti-HIV antibody responses and contributes to HIV suppression during acute HIV-1 infection. These results have implications for vaccine studies aimed at inducing long lasting anti-HIV antibody responses.\n\nImportanceThe HIV epidemic in southern Africa accounts for almost half of the global HIV burden with HIV-1 clade C being the predominant strain. It is therefore important to define immune correlates of clade C HIV control that might have implications for vaccine design in this region. T follicular helper (Tfh) cells are critical for the development of HIV-specific antibody responses and could play a role in viral control. Here we showed that the early induction of circulating Tfh1 cells during acute infection correlated positively with the magnitude of p24-specific IgG and was associated with lower set point viral load. This study highlights a key Tfh cell subset that could limit HIV replication by enhancing antibody generation. This study underscores the importance of circulating Tfh cells in promoting non-neutralizing antibodies during HIV-1 infection.