FIG. 2.

Role of VP4 in the plasma-dependent enhancement of CVB-induced IFN-α production by PBMC. Plasma samples obtained from 5 healthy subjects were preincubated for 1 h at 37°C in the absence or presence of the VP4 fraction (a and c) or H antigen (b and d) dissociated from CVB3 or CVB4 (CVB4E2) at various concentrations before the addition of CVB3 or CVB4 (CVB4E2) (MOI, 1) for one additional hour at 37°C. PBMC were then infected with these mixtures. Culture supernatant samples were harvested 48 h postinfection. IFN-α levels in culture supernatants were determined by DELFIA. For each plasma sample, the experiments were performed in duplicate and the culture supernatants obtained for each plasma sample were pooled before the IFN-α assay was performed. Each individual result is presented. Mock protein means protein from mock-infected cells.