Mentored Scientist Award

Polymorphisms in human APOBEC3H (A3H) affect the transmission dynamics of HIV-1, with stable and active A3H being maintained at high frequencies in populations of African descent, creating a natural barrier to viral spread. However, many European and Asian populations express unstable and inactive A3H variants, leading to higher susceptibility. HIV-1 counters A3H activity by encoding the viral infectivity factor (Vif), which recruits host protein CBF- and an E3 ligase complex, facilitating polyubiquitination and degradation of A3H via the 26S proteasome. Laboratory-adapted HIV-1 Vif exhibits only weak antagonistic activity against stable A3H (A3H hap II), while patient-derived Vif variants display strong neutralization of A3H hap II. This adaptation in Vif is crucial for overcoming A3H-mediated restriction, yet the molecular details governing this adaptation remain unknown. This project aims to elucidate the structural and biochemical mechanisms through which patient-adapted HIV-1 Vif antagonizes stable A3H hap II. Co-expression of patient-derived Vif, A3H hap II, CBF-, and E3 ligase subunits (Cul5, ELOB, and ELOC) in insect cells will enable the structural determination of the Vif- A3H complex via single-particle cryo-electron microscopy (cryo-EM). Key Vif residues involved in antagonism and adaptation will be identified through biochemical and virological assays, supported by deep mutational scanning to systematically map mutations impacting Vif’s ability to neutralize A3H hap II. This research will provide critical insights into how HIV-1 Vif evolves to overcome A3H-mediated immunity, contributing to our understanding of viral adaptation and informing the development of therapeutic strategies targeting Vif to bolster innate immune defenses against HIV-1.