Conditioned media (CM) was recovered from EM stromal fibroblasts, diluted 1:1 in X-Vivo 15 media and incubated with R5-tropic HIV-1 BaL (A) or X4-tropic HIV-1 IIIB (D) (MOI=0.1) for 1hr prior to addition to CD4+ T cells for 1hr, followed by extensive washout, and incubation with fresh media. Infection was determined by assessing levels of secreted p24 by ELISA after 7 days. * P<0.05, ** P<0.01 compared to CM from untreated cells. Bars and horizontal lines represent the percent mean HIV infection +/− SEM respectively, of independent experiments from 6 different individual donors. Statistical analysis was performed using the non-parametric Wilcoxon Signed Rank test.