2.8 Viral infectivity assay
5×105 293T cells were seeded in 6-well plates 12 h before transfection. 293T cells were co-transfected with pcDNA3.1-FLAG-GP-ΔMLD/VSV-G, pNL-Luc-ΔEnv, and MARCH expression vectors. Forty-eight hours post-transfection, virion-containing supernatants were collected to infect the indicator Vero cells. Before infection, supernatants were subjected to ultracentrifugation at 40000 × g for 1 h, and pellets were used for WB or P24Gag ELISA quantity assay. Thirty-six hours post-infection, Vero cells were lysed, and viral infectivity was assessed via luciferase activity assay.