Abstract
Adeno-associated virus (AAV)-vectored delivery of HIV-1 broadly neutralizing antibodies (bNAbs) holds promise for achieving durable HIV-1 immunity in a practical and scalable way, yet AAV-encoded bNAbs often elicit antidrug antibody (ADA) responses that limit transgene expression. Engagement of T cell-expressed CD28 with its ligands CD80/CD86 on professional antigen-presenting cells is crucial for initiating adaptive immunity. Because the immunoglobulin-fusion protein CTLA4Ig can outcompete CD28 for binding to CD80/CD86, CTLA4Ig can inhibit T cell activation and prevent immune responses. Hence, we hypothesized that co-delivering CTLA4Ig during AAV/bNAb administration would prevent ADAs in primates. Six rhesus macaques (RMs) were treated intramuscularly with AAV-1 vectors encoding “rhesusized” (rh) versions of the bNAbs 3BNC117 (IgG1) and 10-1074 (IgG2). The experimental monkeys (n = 3) were dosed intravenously with 20 mg/kg of rh-CTLA4Ig on days 0, 2, 7, and 14, while the control animals (n = 3) did not receive any additional intervention. The experimental monkeys mounted ADAs that inhibited bNAb expression, albeit at different rates for rh-3BNC117-IgG1 (66%) and rh-10-1074-IgG2 (33%). In the control group, the incidence of ADAs leading to loss of bNAb expression was 100% for rh-3BNC117-IgG1 and 0% for rh-10-1074-IgG2. There was no significant difference between the groups in their cumulative levels of ADAs or bNAb expression measured over 20 weeks. Despite the development of ADAs against rh-3BNC117-IgG1 in five out of six animals, and in one out of six against rh-10-1074-IgG2, macaques in both groups exhibited minimal T cell responses to both bNAbs. AAV-1 capsid-specific CD4+ T cells trended higher in the control animals. In conclusion, a short course rh-CTLA4Ig did not significantly reduce the immunogenicity of AAV-encoded bNAbs in RMs. Although our study was not powered to detect marginal effects, robust improvements in AAV-driven expression of hypermutated HIV-1 bNAbs may require combination approaches, such as multiple co-stimulation blockers, pharmacological immunosuppression, and/or muscle-specific promoters.
Get full access to this article
View all access options for this article.
References
Supplementary Material
Please find the following supplemental material available below.
For Open Access articles published under a Creative Commons License, all supplemental material carries the same license as the article it is associated with.
For non-Open Access articles published, all supplemental material carries a non-exclusive license, and permission requests for re-use of supplemental material or any part of supplemental material shall be sent directly to the copyright owner as specified in the copyright notice associated with the article.
