Systematic discovery of pro- and anti-HIV host factors in primary human CD4+ T cells.

Host factors that promote or restrict human immunodeficiency virus (HIV) infection in human CD4+ T cells have not been comprehensively identified. We employed orthogonal genome-wide CRISPR activation (CRISPRa) and CRISPR knockout screens in primary CD4+ T cells to discover pro- and anti-HIV host factors systematically. Secondary pooled screens and individual perturbations validated high-confidence hits and revealed diverse mechanisms of action. CRISPRa uncovered multiple potent antiviral factors, including PI16, PPID, SHISA3, and ITM2A. PI16 interacts with host factors involved in HIV fusion and inhibits viral entry, whereas PPID (Cyp40), a paralog of the proviral cyclophilin CypA, binds capsid and reduces nuclear import of the HIV core. Structural modeling, evolutionary analyses, and targeted mutagenesis revealed domains and residues required for PPID-mediated HIV restriction, including non-human primate ortholog substitutions that enhance antiviral activity. Together, these data define the functional HIV-host interaction landscape in primary human T cells and uncover new mechanisms modulating infection.