AAV vectors are ideally suited for long-term delivery of a combination of broadly neutralizing antibodies to achieve sterilizing
immunity to HIV. Unfortunately, host immune responses to the delivered
antibody have severely limited the
efficacy. The TLR9 pathway has been identified in initiating adaptive immune responses against AAV and delivered bNAbs. To enhance this strategy, we validated
Hydroxychloroquine, a known
drug inhibitor of the TLR9 pathway, as a pretreatment to AAV delivery to avoid anti-
drug antibody responses. TLR9 signaling inhibition was validated using a HEK-Blue hTLR9 reporter
cell line and CpG stimulation.
Hydroxychloroquine was also validated in a 3-
macaque trial where AAV9-3BNC117 and AAV9-10-1074 were administered along with 3 doses of
hydroxychloroquine once a week starting 1 week before AAV
inoculation. Unlike historical controls, where 3BNC117 and 10-1074 expression is lost within the first 4-5 weeks, 2 macaques maintained 10-1074 expression and 1
macaque maintained 3BNC117 for the duration of the trial. Anti-3BNC117 antibodies were only observed in 2 of the 3 macaques and were significantly delayed. Anti-10-1074
antibody responses were a log lower than typically observed in historic controls. The use of
hydroxychloroquine as a pretreatment for AAV
inoculation is a promising strategy. The significant decrease in anti-10-1074 antibody levels and the successful delivery of 10-1074 in 2 macaques and 3BNC117 in 1
macaque was very encouraging. Extending the dosage of
hydroxychloroquine beyond 3 doses may be sufficient to observe long-term bNAb expression in all animals and further decrease ADA responses. Together, these data suggest that the short-term treatment of hydroxychloroquine at the time of AAV
inoculation has a meaningful
impact on
tolerance induction to our AAV-delivered bNAbs.