Background:
The mechanisms by which emerging immunotherapies (e.g., broadly neutralizing antibodies [bNAbs], vaccines) contribute to post-ART control are unknown. Robust HIV-specific CD8+ T cell proliferation (after in vitro peptide stimulation) has been consistently associated with sustained (elite) virus control. To determine the relevance of this relationship in vivo, we studied early T cell proliferation in response to reactivating virus in two prospective studies with an analytic treatment interruption (ATI).
Methods:
We previously reported a higher-than-expected rate of post-intervention control after a single-arm combination clinical trial (NCT04357821) in which people with treated HIV received a DNA/MVA vaccine regimen, followed by two bNAbs (10-1074, VRC07-523LS) plus a TLR-9 agonist (lefitolimod), then two bNAbs at the time of ATI. Seven of 10 participants achieved a low viral load (VL) set point ~1000 copies/mL while three had typical rebound (median set point 48,043 cpm). Before rebound and at an early timepoint (within 1 month) after rebound (median VL 775 cpm; n=8), we performed intracellular cytokine staining (by flow cytometry with overlapping peptide pools) and CyTOF on PBMCs. In a second study (NCT04359186), we performed single cell transcriptional analysis (10X 5′ scRNA/TCRseq) of lymph node (LN) mononuclear cells before an ATI and at or near the time of rebound in 5 participants, two of whom had controlled HIV pre-ART and then re-controlled post-ATI.
Results:
In the trial, early post-rebound, the frequency of IFNg+ HIV-specific CD8+ T cells (sum: Gag+Pol+Nef+Env) increased in those who exhibited control (median fold-change [FC] vs pre-rebound: 1.8x) but not in those who failed to control (FC 0.9x). Similarly, the frequency of proliferating (Ki67+) non-naïve CD8+ T cells increased robustly in controllers (FC 2.8x; 2.7 to 8.8%) but not in non-controllers (FC 1.2x; 2.8 to 3.3%). Higher %Ki67+ non-naïve CD8+ T cells early post-rebound was associated with lower VL set point (r=-0.81, p=0.02). Similarly, post-ATI in the second study, the fraction of proliferating CD8+ T cells (expressing MKI67) in the LN was higher in controllers vs non-controllers (3.6% vs 0.8%).
Conclusions:
To our knowledge, these studies are the first to demonstrate a relationship between the early in vivo CD8+ T cell proliferative response to viral reactivation and HIV control post-ART. The results support continued focus on developing HIV cure strategies that enhance HIV-specific CD8+ T cell proliferative capacity.
