Immunomodulatory drug interventions for the prevention of host immune responses toward AAV-delivered anti-HIV antibodies - Project Summary - Abstract Long-term delivery of potent broadly neutralizing antibodies (bnAbs) using adeno-associated virus (AAV)- mediated gene transfer represents a promising approach for the prevention and treatment of HIV infection. However, the effectiveness of AAV-antibody gene transfer has been hindered by the emergence of unwanted immune responses including anti-drug antibodies (ADAs), which have been observed in both monkeys and humans. Here we present strategies that aim at preventing or eliminating host immune responses toward AAV- delivered bnAbs. A wide array of immunomodulatory drugs has been successfully used in the fields of autoimmunity, transplantation, and cancer medicine. Therefore, a well-defined drug combination regimen could be employed to increase the efficacy of AAV gene therapy. The experimental project will enroll ten naive AAV- negative rhesus monkeys that will be segregated into two groups. In our first aim, we will attempt to induce tolerance toward AAV-delivered antibodies by a synergistically acting drug treatment prior to, during, and following AAV administration. In group 1, five rhesus monkeys will receive intramuscular injections of rapamycin and ibrutinib three times a week for the duration of ten weeks. At week 2 following the initiation of the drug treatment, the monkeys will be given AAV9 encoding the C-rh 3BNC117 anti-HIV bnAb. The five rhesus monkeys in group 2 will serve as controls and will only be given AAV9 encoding C-rh 3BNC117 in the absence of any drug treatment. Levels of AAV-delivered antibody and ADAs will be monitored in serum and compared among the two groups through week 26. In our second aim, we will explore the use of nucleoside-modified mRNA delivery for its potential to induce antigen-specific tolerance. In mouse experiments, this approach has been demonstrated to prevent de novo immune responses against a foreign protein and to have immunomodulatory properties when used as treatment of autoimmune disease (Krienke et al., Science 371, 145–153, 2021). At week 26, nucleoside- modified mRNA lipid nanoparticles encoding the C-rh PGT145 bnAb will be given to the five control animals of group 2 with the goal to preventing de novo immune responses toward AAV8-delivered C-rh PGT145 that will be administered at week 32. At week 26, the animals of group 2 will also receive nucleoside-modified mRNA lipid nanoparticles encoding the C-rh 3BNC117 bnAb with the goal to reverting expected ADAs toward the previously AAV9-delivered C-rh 3BNC117. Serum levels of C-rh PGT145 and C-rh 3BNC117 and ADAs will be monitored through week 48 and the data will be compared among the two groups and against historical control animals that consistently elicited ADAs toward the two bnAbs following AAV administration. These experiments will define which of several conditions will, or will not, result in consistent tolerance to AAV-delivered anti-HIV antibodies. The use of synergistically acting drugs and immunomodulatory mRNA intervention hold promise to solve the ADA problem with the ultimate goal of preventing and eliminating HIV infection in the human population.
