Inhibition of HIV-1 infection by decidual soluble factors. Decidual mononuclear cells were cultured for 24 hours without stimulation, then infected with R5 or X4 HIV-1 isolates (10-4 MOI), following with or without a washing step. Viral replication was measured by p24 viral antigen assay in culture supernatants 7 and 10 days post-infection. Results represent the percentage inhibition of HIV-1 infection induced by decidual soluble factors compared with experiments including a washing step. Mean viral p24 levels in culture supernatants were 367 pg/ml at day 7 and 6839 pg/ml at day 10 for R5 HIV-1; and respectively 42 at day 7 and 613 pg/ml at day 10 for X4 HIV-1. Experiments used 9 different donors, each represented by a different symbol, and lines indicate the mean inhibition. Mean inhibition of R5 HIV-1 infection was statistically significant at day 7 (mean 28.64% p = 0.039) but not at day 10 (mean 18.69% p = 0.088). Inhibition of X4 HIV-1 infection observed at day 10 was not statistically significant (mean 11.25% p = 0.375).