Unraveling the Structural Architecture and Molecular Mechanisms of HIV-1 Cell-to-Cell - Project summary HIV-1 cell-to-cell transmission is a highly efficient mode of viral spread that evades immune surveillance and antiviral therapy, contributing to reservoir formation and disease persistence. Despite this critical role, the mechanism by which cell-to-cell transmission enables this evasion of antiretroviral therapies and immune responses remains poorly understood. In particular, the architecture of HIV-1 transmission sites in their native, frozen-hydrated state has been challenging. Previous imaging techniques, such as traditional electron microscopy, have been limited by sample preparation artifacts that obscure the true structural details of these transmission sites. Our proposal aims to use advanced in situ correlative cryoimaging techniques to explore the ultrastructure of HIV-1 cell-to-cell transmission in primary T lymphocytes. Preliminary data using this approach challenges the prevailing hypothesis that viral transmission requires numerous viruses in a large intercellular space. Instead, our findings suggest that transmission occurs in small, confined spaces containing only 1-3 viruses, enclosed by narrow membrane interfaces that may hinder access by broadly neutralizing antibodies and antiviral drugs. Through two specific aims, we will (1) determine the architecture of HIV-1 transmission sites in primary T cells using correlative in situ cryoimaging and (2) investigate the molecular determinants of viral entry and infection in both free-virus and cell-to-cell transmission. The outcome of this research are insights into the mechanisms driving efficient viral spread which can inform therapeutic strategies specifically designed to target and impair cell-to-cell transmission—a critical aspect currently overlooked in existing treatments.
