Memory CD4+ T cells (mCD4s) containing integrated HIV DNA are considered the main barrier to a cure for HIV infection. Here we analysed HIV DNA reservoirs in antigen-specific subsets of mCD4s to delineate the mechanisms by which HIV reservoirs persist during ART.
HIV Gag, Cytomegalovirus (CMV) and Tetanus Toxoid (TT) specific mCD4s were isolated from peripheral blood samples obtained from 11 individual subjects, 2-11 years after commencing ART. Antigen-specific mCD4s were identified by the sensitive OX40 assay and purified by cell sorting. Total HIV DNA levels were quantified by real-time PCR, and clonal viral sequences generated from mCD4 subsets and pre-ART plasma samples. Quantitative results and sequence analysis were restricted to 5 and 3 study participants respectively, likely due to the low frequency of the antigen-specific mCD4s and relatively low HIV DNA proviral loads. Median HIV Gag-, CMV-, and TT-specific mCD4s were 0.61%, 2.46% and 0.78% of total mCD4s, and contained a median of 2.50, 2.38, and 2.55 log10 copies of HIV DNA per 106 cells respectively. HIV DNA sequences derived from antigen-specific mCD4s clustered with sequences derived from pre-ART plasma samples. There was a trend towards increased viral diversity in clonal viral sequences derived from CMV-specific relative to TT-specific mCD4s.
Despite limitations, this study provides direct evidence that HIV reservoirs persist in memory CD4+ T cell subsets maintained by homeostatic proliferation (TT) and adds to growing evidence against viral evolution during ART. Similar future studies require techniques that sample diverse HIV reservoirs and with improved sensitivity.
- HIV reservoirs
- Antigen-specific CD4 T cells
- HIV DNA