MDDC mediated trans-infection of CD4+ T-cells by Env+ pseudovirions. (A) Trans-infection of CD4+ T-cells following virion capture by MDDCs is substantially more efficient than cell free infection of T-cells or MDDCs alone. T/F/acute and late disease non-mac- and mac-tropic R5 Env+ pseudovirions are all enhanced. Note that for late disease non-mac-tropic and mac-tropic R5 Envs, trans-infectivity titers are not significantly different. Infectivities are shown as the number of FFU/ml (GFP+ cells per ml) of input virus. (B) Infectivity as a percent of infection for TZM-bl cells suggests that trans-infection preferentially enhances non-mac-tropic R5 Env+ pseudovirions, although differences are not significant. Symbol colour designations are the same as described in Figure 1. Please also refer to Additional file 1: Figure S5, where FFU/ml for each Env+ pseudovirus is presented in a bar graph with standard deviation bars shown, while the column scatter plot of infectivity as a percent of TZM-bl infectivity is presented with each point labeled for Env used. Median values are marked.