Figure 1.

In vitro antiviral effect of RWJ‐56110. (A) Cytotoxicity of TFLLR‐NH₂, AY‐NH₂, RWJ‐56110 and argatroban was determined by the MTS test. (B, C) Selectivity of RWJ‐56110 to PAR1 was evaluated by studying its capacity to inhibit PAR1 activation‐induced ERK phosphorylation in NIH/3T3 cells and to modulate the viral replication in A549 cells transfected with siRNA targeting PAR1 (n = 6 per group, *P < 0.05 control siRNA/RWJ‐56110; PAR1 siRNA or PAR1 siRNA/RWJ‐56110 vs. control siRNA). (D) The capacity of RSV and hMPV to activate PAR1 was investigated in A549 cells by Western blot analysis. (E, F) Antiviral effect of RWJ‐56110 was investigated in A549 cells. The cells were treated with DMSO, TFLLR‐NH₂ or RWJ‐56110 and then infected with RSV or hMPV. Virus‐infected cells were identified by immunostaining and counted [n = 6 per group, *P < 0.05 RWJ‐56110 5, 10, 20, 40, 80 or 160 μM vs. DMSO (0 μM)]. In addition to the evaluation of viral replication, Western blot analysis was used to study ERK phosphorylation.