Background
Sustained expression of adeno-associated virus (AAV)-vectored anti-HIV-1 broadly neutralizing antibodies (bNAbs) could prevent and treat HIV-1 infection. However, durable expression of AAV-vectored bNAbs in vivo is limited by host immune responses, impeding efficacy studies in preclinical nonhuman primate (NHP) models. Programmed cell death protein (PD)-1 is an immune checkpoint protein on T cells that inhibits T-cell activity upon binding to programmed cell death protein ligand (PD-L)1. We hypothesized that PD-L1 co-expression on AAV.bNAb-transduced cells maintains bNAb expression by suppressing host anti-bNAb antibodies and T-cell responses. The goal of this research is to develop a model for prolonged AAV-vectored bNAb production in NHPs and possibly advance AAV-delivery of bNAbs for human clinical trials.
Methods
Five groups of six rhesus macaques each received the following vectors: 1) AAV9.PD-L1; 2) AAV9.10-1074; 3) AAV9.PD-L1 and AAV9.10-1074; 4) AAV9.3BNC117; and 5) AAV9.PD-L1 and AAV9.3BNC117. Serum antibody concentrations were determined by gp120 ELISA and B and T cell reactivity were assessed by anti-drug antibody ELISA and by ELISpot assay, respectively. Beginning at 20- or 30-weeks post AAV9 administration, all animals were challenged biweekly via low-dose, intrarectal challenge using SHIV-AD8. Protection from SHIV challenge was determined by monitoring plasma viremia by qPCR. Additionally, to assess the safety of our approach, we have ongoing studies to determine the immunomodulatory effect of AAV9.PD-L1 in PBMCs by RNASeq and off-target AAV transduction by ddPCR post necropsy.
Results
All six macaques that received AAV9.10-1074 and AAV9.PD-L1 had sustained concentrations of 10-1074 throughout the study compared to four of six macaques that only received AAV.10-1074. Similarly, five of six macaques that received AAV9.3BNC117 and AAV9.PD-L1 compared to three of six macaques that only received AAV9.3BNC117 had sustained expression of 3BNC117. We observed a negative correlation between bNAb serum titers and both host anti-bNAb antibodies and T cell reactivity. All macaques that achieved sustained expression of 10-1074 were significantly protected from SHIV challenges. Macaques that received AAV9.3BNC117 and AAV9.PD-L1 were significantly protected against SHIV challenge.
Conclusions
We have developed a strategy for sustained bNAb expression in NHPs. This will allow the prophylactic and therapeutic efficacy of AAV-delivered bNAbs to be studied in preclinical NHP models.
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