For instance, knockout of previously known HIV-1 interactors Cyclin T1 (CCNT1), Peptidylprolyl isomerase A (CYPA) and Lens epithelium–derived growth factor (LEDGF) reduced susceptibility to HIV-1 infection of primary human CD4+ T cells to approximately 20 percent of wild-type T cells. This evidence concerns the gene CD4 and HIV-1 infection.