2.3. Virus Infectivity Assays

For the HIV-1 infectivity assay, p24-normalized HIV-1 particles produced in the presence of PSGL-1, CD43, CD164, TMEM123, CD34, PODXL1, PODXL2, TIM-1, MUC1, MUC4, or empty vector were used to infect Rev-A3R5-GFP cells (0.2 to 0.5 million cells per infection). The percentage of GFP+ cells was quantified by flow cytometry at 48 or 72 h post infection. The IC₅₀ inhibition curves were generated using GraphPad Software. For the influenza A virion infectivity assay, influenza A-GFP reporter viruses were assembled in the presence of PSGL-1, CD43, CD164, TMEM123, CD34, PODXL1, PODXL2, TIM-1, MUC1, MUC4, or empty vectors. Virions were harvested at 48 h and used to infect MDCK cells (3 × 10⁴ cells per infection). GFP expression was quantified at 24 h post infection by flow cytometry. For Ha-CoV-2 infectivity assay, HEK293T(ACE2/TMPRSS2) cells were infected for 2 h with Ha-CoV-2 particles assembled in the presence of each individual SHREK-expressing vector or an empty vector. Infected cells were washed and cultured for 18 h. Cells were lysed with Luciferase Assay Lysis Buffer (Promega, Madison, WI, USA). Luminescence was measured on GloMax^® Discover Microplate Reader (Promega).