Background
In the PULSE clinical trial, 68 people living with HIV underwent three consecutive analytical treatment interruptions (ATIs). Of note, 10% of the participants transiently controlled HIV rebound during the 3rd ATI. We investigated whether this virological control is associated with improved antiviral CD8 T-cell function and response to mutationally-constrained and highly-conserved HIV epitopes.
Methods
We obtained blood-derived mononuclear cells from four participants enrolled in PULSE: two non-controllers (NCs) with rapid viral rebound during all ATIs and two transient controllers (TCs) with virological control during the 3rd ATI. To evaluate CD8 T-cell functionality during the ATIs, CD8 T-cells were stimulated with HIV peptides to assess cytokine production (IFN-γ/TNF-α) and stained with CellTrace Far-Red to quantify proliferation by flow cytometry. To compare CD8 T-cell cytotoxicity across the ATIs, autologous CD4 T-cells were infected with HIV-NL4-3, co-cultured with CD8 T-cells from each ATI timepoint, and p24 levels were measured by ELISA. Using our novel Immunoinformatics Analysis Pipeline (IMAP), we identified 33 mutationally-constrained and unique Gag-derived HIV epitopes (Gag-IMAP-peptides). The response to these peptides was determined in NC- and TC-derived CD8 T-cells by measuring IFN-γ/TNF-α expression.
Results
For TCs, CD8 T-cell proliferation and cytokine production (3- to 34-fold) increased during the viral control timepoints. In contrast, the capacity for CD8 T-cells to proliferate and produce cytokines did not increase across the ATI timepoints for NCs. Moreover, TC-derived CD8 T-cells from the 3rd ATI, where viral rebound is delayed, eliminated HIV-infected CD4 T-cells more efficiently (2- to 5-fold p24 decrease) compared to CD8 T-cells from earlier ATI timepoints. In contrast, within NCs, we observed no consistent enhancement of CD8 T-cell cytolytic response. Both NC- and TC-derived CD8 T-cells responded to the Gag-IMAP-peptides, with a 49-fold higher response observed for TC-derived cells.
Conclusions
For some participants, repeated exposure to viral antigens during consecutive ATIs results in enhanced CD8 T-cell proliferation, cytokine production and cytotoxicity. The higher potential of CD8 T-cells from transient controllers to recognize mutationally-constrained HIV epitopes may also contribute to their virological control. Importantly, these results indicate that enhanced CD8 T-cell responses are pivotal for achieving viral remission after consecutive ATIs.