Background: HIV controllers, who spontaneously contain HIV replication to very low levels, develop particularly efficient antiviral T cell responses. To gain insights into the contribution of the CD4 helper subset to HIV control, we characterized the differentiation status of HIV-specific CD4+ T cells at the single cell level.
Methods: CD4+ T cells reactive with MHC-II tetramers specific for the most immunodominant HIV epitope (Gag293) were analyzed by multiplexed real-time qPCR (Biomark, Fluidigm) combined with multiparametric flow cytometry. HIV controllers from the ANRS CODEX-CO21 cohort with a viral load < 50 copies/mL were compared to efficiently treated patients with an equivalently low viral load.
Results: Gag293-specific cells from HIV controllers proved to express lower levels of CCR5 and PD-1 than those of treated patients, while CCL5 and TRBV2 expression were increased. As low expression of the HIV coreceptor CCR5 may inhibit HIV entry, we tested the susceptibility of Gag293-specific CD4+ T cells to fusion with an HIV-1 JRFL-BlaM-Vpr reporter virus. HIV controller specific cells proved less susceptible to HIV fusion than those of treated patients (P=0.017). Moreover, CCR5 expression in specific cells correlated with HIV fusion (R=0.83, P< 0.005). CCR5 expression in total CD4+ T cells did not reveal significant differences between groups. However, a negative correlation was observed between CCR5 expression in total CD4+ T cells and the frequency of Gag293-specific cells, indicating that the subset of controllers with low CCR5 expression maintained strong CD4 responses. Genetic analysis of one controller with particularly low fusion susceptibility uncovered biallelic mutations that impaired CCR5 expression.
Conclusions: Taken together, these findings reveal a lower susceptibility of HIV controller specific CD4+ T cells to HIV entry, and point to a role for low CCR5 expression in promoting spontaneous HIV control.