The aim of this project was to identify cellular factors enriched with HIV-1 virions after filtration and ultracentrifugation of culture surpernatants of HIV-1 producer cells compared to a control. To this end, HeLa cells were transfected with HIV-1 NL4-3 provirus and, 48 hours after transfection, culture surpernatants of HIV-1 producer cells were collected, filtered and ultracentrifugated on a 20% sucrose cushion to pellet viruses released in the supernatants. As a control, supernatant from mock-transfected HeLa cells was collected and prepared as the supernatant of HIV-1 producer cells. The same volume of filtered and ultracentrifugated supernatants from mock- and HIV-1-producing cells were then subjected to LC-MS analysis.