A novel HIV triple broadly neutralizing antibody (bNAb) combination-based passive immunization of infant rhesus macaques achieves durable protective plasma neutralization levels and mediates anti-viral effector functions

To eliminate vertical HIV transmission and achieve therapy-free viral suppression among children living with HIV, novel strategies beyond antiretroviral therapy (ART) are necessary. Our group previously identified a triple bNAb combination comprising of 3BNC117, PGDM1400 and PGT151 that mediates robust in vitro neutralization and non-neutralizing effector functions against a cross-clade panel of simian human immunodeficiency viruses (SHIVs). In this study, we evaluated the safety, pharmacokinetics, and antiviral potency of this bNAb combination in infant rhesus macaques (RMs). We demonstrate that subcutaneous infusion of the triple bNAb regimen was well tolerated in pediatric monkeys and resulted in durable systemic and mucosal distribution. Plasma obtained from passively-immunized RMs demonstrated potent HIV-neutralizing and Fc-mediated antiviral effector functions. Finally, using the predicted serum neutralization 80% inhibitory dilution titer (PT80) biomarker, which was recently identified as a surrogate endpoint for evaluation of the preventative efficacy (PE) of bNAbs against mucosal viral acquisition in human clinical trials, we demonstrated that our regimen has a predicted PE≥90% against a large panel of plasma and breast milk-derived HIV strains and cross-clade SHIV variants. This data will guide the development of combination bNAbs for eliminating vertical HIV transmission and for achieving ART-free viral suppression among children living with HIV. ### Competing Interest Statement S.R.P serves as a consultant for Merck, Moderna, Pfizer, Hoopika, Dynavax, and GSK on their CMV vaccine programs, and has led sponsored programs with Merck and Moderna on CMV vaccines. Other authors have no conflict of interest to disclose.