PROJECT SUMMARY / ABSTRACT The quest for an HIV cure remains incomplete, nearly half a century since the onset of the epidemic. Antiretroviral drug cocktails can suppress HIV infection, but suffer in their success owing to side effects and limitations in access and compliance. Injection of broadly neutralizing antibodies (bNAbs) to prevent HIV rebound has had some success, but requires regular re-injection of multiple antibodies to maintain suppression and viral escape. Thus, cost and continued access remain limitations. Genetic engineering of patient cells has been proposed to overcome all of these shortfalls, and could constitute a one-time treatment with lifelong therapeutic value if successful. In this proposal, we leverage a novel approach developed by Dr. Justin Taylor’s laboratory to genetically engineer B cells to express bNAbs for the treatment of human immunodeficiency virus (HIV). This strategy has already been used to engineer B cells to produce antibodies protective against influenza virus, respiratory syncytial virus, Epstein-barr virus and HIV [Moffett et al., Science Immunology, 2019]. While this approach can ensure protective antibody production, the genetic engineering process required 10 days of complicated ex vivo manufacturing and is not broadly distributable. To overcome these barriers, we will co-opt a novel, synthetic nanoparticle that was developed in Dr. Jennifer Adair’s laboratory to deliver genetic engineering in a single, passive step [Shahbazi et al., Nature Materials, 2019]. We show that this nanoparticle can be assembled in less than a day to genetically engineer unstimulated, primary human blood cells and can be modified to specifically interact with target blood cell types in vivo. Here we will develop this scalable nanoformulation as a vaccine-like in vivo delivery system to direct humoral immunity with multiple bNAbs in a clinically-relevant nonhuman primate model of HIV infection. We will use these nanoparticles to directly genetically engineer native primary B cell subtypes, and hematopoietic stem and progenitor cells, which can provide lifelong replenishment of antibody- producing B cells. This research will not only develop a unique tool set against HIV but will provide transformative advances in equitable distribution of gene editing therapies.