Blockade of the PD-1 axis alone is not sufficient to activate HIV-1 virion production from CD4+ T cells of individuals on suppressive ART

Abstract

Blockade of the programmed cell death protein/ligand 1 (PD-1/PD-L1) pathway with monoclonal antibodies (mAb) is now commonly used for cancer immunotherapy and has therapeutic potential in chronic viral infections including HIV-1. PD-1/PD-L1 blockade could augment HIV-1-specific immune responses and reverse HIV-1 latency, but the latter effect has not been clearly shown. We tested the ability of the human anti-PD-L1 mAb BMS-936559 and the human anti-PD-1 mAb nivolumab to increase HIV-1 virion production ex vivo from different peripheral blood mononuclear cell populations obtained from donors on suppressive antiretroviral therapy (ART). Fresh peripheral blood mononuclear cells (PBMC), CD8-depleted PBMC, total CD4+ T cells, and resting CD4+ T cells were purified from whole blood of HIV-1-infected donors and cultured in varying concentrations of BMS-936559 (20, 5, or 1.25μg/mL) or nivolumab (5 or 1.25μg/mL), with or without anti-CD3/CD28 stimulatory antibodies. Culture supernatants were assayed for virion HIV-1 RNA by qRT-PCR. Ex vivo exposure to BMS-936559 or nivolumab, with or without anti-CD3/CD28 stimulation, did not consistently increase HIV-1 virion production from blood mononuclear cell populations. Modest (2-fold) increases in virus production were observed in a subset of donors and in some cell types but were not reproducible in longitudinal samples. Cell surface expression of PD-1 and PD-L1 were not associated with changes in virus production. Ex vivo blockade of the PD-1 axis alone has limited effects on HIV-1 latency.

Fig 1. Virion production and cell viability in response to BMS-936559.

Median HIV-1 virion production across all donors after 7 days of stimulation with BMS-936559 (Fig 1A). Median fold-change in cell viability across all donors from no-Ab control after 7 day treatment with BMS-936559 (Fig 1B). * = multiplicity adjusted, p<0.05 by Wilcoxon matched-pairs signed rank test with Bonferroni correction. NAC = no-Ab control; IC = isotype control; 3/28 = anti-CD3/CD28. Error bars = Interquartlie range (IQR).

Fig 2. Virion production and cell viability in response to nivolumab.

Median virion production across all donors in response to nivolumab (Fig 2A). Median-fold difference in cell viability across all donors in response to nivolumab or anti-CD3/CD28 stimulation compared to isotype control (Fig 2B). Median virion production in response to nivolumab in cells stimulated with anti-CD3/CD28 (Fig 2C). Median cell viability in response to nivolumab in cells stimulated with anti-CD3/CD28 (Fig 2D). NAC = no-Ab control; IC = isotype control; 3/28 = anti-CD3/CD28; nivo = nivolumab. Error bars = IQR.