FIG. 3.

Inhibition of MV binding to CD46 receptor and of virus-cell membrane fusion. (A) U373 cells (7.5 × 10⁵) were first incubated with serial dilutions of monoclonal anti-CD46 IgG for 1 h, then infected with MV at an MOI of 2 for 24 h. Inhibition of RANTES production by anti-CD46 IgG was calculated by taking the amount of RANTES produced in the absence of antibody (∼370 pg/ml) as indicating 0% inhibition. (B) U373 cells (5 × 10⁶) were incubated with varying concentrations of the tripeptide X-Phe-Phe-Gly together with MV at an MOI of 5 for 48 h. Supernatants were assayed for RANTES expression by ELISA (left panel), and cell pellets were examined for MV nucleocapsid and fusion protein mRNA expression by Northern blotting (right panel). The amount of RANTES protein produced in the absence of the tripeptide (TP) (12,000 pg/ml) was taken as indicating 0% inhibition (left panel). The band densities of MV nucleocapsid and fusion mRNAs expressed without tripeptide treatment were taken as indicating 0% inhibition (right panel). The nucleocapsid and fusion mRNAs were similarly inhibited by the tripeptide.