Verapamil inhibits respiratory syncytial virus infection by regulating Ca2+ influx

Aims The study evaluated the antiviral effect of Verapamil against respiratory syncytial virus (RSV) and investigated its underlying mechanism. Materials and methods RSV-infected BALB/c mice were treated with Verapamil. Body weight, survival rates, viral load, lung damage, inflammatory factors, and the expression of RSV fusion (F) protein were analyzed. In cellular studies, intracellular Ca 2+ and viral titers were measured in the presence of Verapamil, Calcium Chloride, and EGTA. A time-of-addition assay assessed the antiviral effect of Verapamil. Key findings Mice infected with RSV and treated with Verapamil exhibited a significant decrease in weight loss, an increase in survival rates, and reductions in viral titers, RSV F protein expression, inflammatory responses, and lung tissue injury. Verapamil reduced intracellular calcium levels, which correlated with reduced viral titers. The addition of calcium chloride reversed the anti-viral effects mediated by Verapamil, while EGTA potentiated them. The antiviral activity of Verapamil was observed during the early phase of RSV infection, likely by blocking Ca 2+ channels and inhibiting virus replication. Significance Verapamil effectively inhibits RSV infection by blocking calcium channels and reducing intracellular calcium levels, thereby impeding viral replication. Thus, Verapamil shows promise as a treatment for RSV.