Gal-9 reduces HIV-1 infection in CD4⁺ T cells that are already HIV-infected. (A) Percentages of p24 suppression in activated CD4⁺ T cells that were exposed to Gal-9 (1 μg/mL) for 2 hours after HIV-1 infection with X-4 and R-5-tropic isolates. (B) Percentages of CD4⁺p24⁺ cells in activated CD4⁺ T cells in the presence of Gal-9 (1 μg/mL) 2 hours after HIV-1 infection with X-4-tropic (HIV-1_LAI) and R-5 (HIV-1_JR-CSF) isolates. Significance was tested using paired t test. (C) Representative flow cytometry dot plots from CD4⁺ T cells infected, and then stimulated with 1 μg/mL Gal-9 after infection with X-4-tropic or R5-tropic HIV-1 isolates, respectively. (D) Representative flow cytometry dot plots from CD4⁺ T cells incubated for 2 hours with 0.5 μg/mL Gal-9 prior or after infection with GFP-labeled T-cell tropic single-cycle HIV-1_SF2. CD4⁺ T cells from 6 HIV-1 seronegative donors were used for each viral isolate. The number of infected cells was quantified by intracellular GFP detection 40 hours after infection for SF2 isolate and viral p24 antigen staining using flow cytometry on day 5 after infection for other viral isolates. Data are from 6 HIV-1 seronegative individuals infected with both X4-and R5-tropic viral isolates in vitro with duplicate cultures per condition. Error bars indicate mean ± SEM from duplicate cell cultures from 6 HIV-1 seronegative individuals infected 4 separate times with both X4-and R5-tropic viral isolates in vitro. Each point represents an individual.