Background:
HIV-specific T-cells targeting Nef but not other HIV proteins are associated with levels of total HIV DNA and cell-associated (CA)-RNA that persist on ART, suggesting ongoing Nef antigenic stimulation. It is not known, however, if HIV-specific T-cells impact either proviral persistence or expression. We hypothesized that decay of intact proviral DNA and CA-RNA levels on ART would be associated with cytotoxic T-cell (CTL) responses.
Methods:
49 participants from the ACTG A5321 cohort on suppressive ART (plasma HIV RNA < 40 copies/mL) were studied at weeks 24 and 168 post-entry (median 7 years on ART at entry). HIV DNA and CA-RNA were measured by droplet digital PCR (IPDA for DNA, 5’ unspliced and 3’ total poly(A) for RNA). T-cell responses were measured by IFN-γ and granzyme B [GrB] ELISPOT to each HIV gene product (Gag, Env, Pol, Nef, Tat, Rev, and summed HIV). Non-parametric statistics were used to evaluate associations and to compare time points.
Results:
5’ unspliced CA-RNA decreased significantly from week 24 to 168 (p=0.001), and decline in intact (p=0.053) but not defective (p=0.22) HIV DNA approached significance. CA-RNA levels at weeks 24 and 168, and changes from 24 to 168 weeks were not found associated with IPDA levels or changes over time. There were no apparent associations between measures of HIV-specific T-cell responses (both IFN-γ-producing and GrB-producing) with the changes in intact or defective proviruses, nor with the changes in CA-RNA levels – including after controlling for time on ART, pre-ART viral load, and pre-ART CD4 count. As examples, the correlations between magnitudes of IFN-γ-producing Nef-specific responses and changes in intact HIV (r=-0.11, p=0.61) and 5’ CA-RNA (r=0.06, p=0.71), or GrB-producing Nef-specific responses and changes in intact HIV (r=0.10, p=0.66) and 5’ CA-RNA (r=-0.14, p=0.37), were small and not significant.
Conclusions:
While both intact proviral DNA and CA-RNA levels (5’ unspliced) decayed over the 144-week period, contrary to our primary hypothesis no associations were observed between decay of intact HIV DNA or CA-RNA with HIV-specific T-cell responses, including with cytotoxic function (GrB) and despite controlling for time on ART. These findings suggest either a limited role for CTLs in reservoir decay after multiple years of suppressive ART, or that other unmeasured parameters are important, such as variation in susceptibility of reservoir cells to CTL-mediated killing.