Summary Antiretroviral pre-exposure prophylaxis (PrEP) is an important tool for preventing transmission to virus naïve individuals and plays an important role in current efforts to end the HIV epidemic. If taken daily current oral PrEP strategies reliably block HIV transmission. However, the requirement of strict adherence to daily pill uptake, pill fatigue and other institutional barriers to access leave oral PrEP underutilized. Long-acting injectable PrEP strategies have the potential to address many of the problems associated with oral PrEP but the realization of drug formulations and delivery strategies that ensure sustained drug release for at least three months has remained challenging and motivates the development of entirely new long-acting PrEP strategies. This project develops a long-acting injectable PrEP strategy based on membrane-wrapped nanoparticles (NPs) that establish cellular depots for sustained maintenance of inhibitory concentrations of antiretrovirals (ARVs) at primary tissue sites of HIV-1 transmission in the female genital tract (FGT) and rectum. Selective targeting of CD169-expressing macrophages and dendritic cells is accomplished through incorporation of the ganglioside GM3 in the NP membrane. GM3-CD169 binding triggers uptake and sequestration of NPs in non-endolysosomal compartments that share distinct similarities with virus containing compartments (VCCs) in tissue-associated macrophages and dendritic cells. These compartments represent protected sites from where NPs can release drugs into the surrounding tissue for an extended period of time. Membrane-wrapped inverse micelles of block copolymers will be engineered as a GM3-NP platform for long-acting PrEP. A combination of long-acting tenofovir (TFV) and emtricitabine (FTC) prodrugs will be used as active compounds to validate the approach. The block copolymer NPs will contain TFV covalently linked to a polymer shell that encapsulates an aqueous core holding FTC conjugated to dendrimers. After quantifying drug loading and release in vitro, the GM3-mediated targeting of CD169+ myeloid cells in the FGT and rectum of a humanized mouse model will be tested. In parallel, the GM3- NP platform will be optimized to achieve sustained drug release in the target tissues. The hypothesis that the optimized NPs provide protection from mucosal HIV infection in a humanized mouse model for at least three months will be tested. The specific aims of this application are: Aim 1: To develop membrane-wrapped multicomponent NPs for sustained release of TFV/FTC. Aim 2: To target CD169-expressing myeloid cells in the FGT and SLTs for sustained TFV/FTC release. Aim 3: To demonstrate long-term protection from mucosal HIV-1 transmission in humanized mice by TFV/FTC incorporating GM3-NPs.

Improved Nanoparticle Targeting of Tissue Myeloid Cells for HIV-1 Long-acting Pre-exposure Prophylaxis Relevance to Public Health The female genital tract and rectum are primary tissue sites of HIV transmission. This project develops nanoparticle-based strategies to achieve long-acting antiretroviral pre-exposure prophylaxis (PrEP) against mucosal HIV transmission in the female genital tract and rectum of a humanized mouse model. The proposed work provides the basis for future long-acting PrEP in humans.