Effect of bafilomycin A1 on the growth of Japanese encephalitis virus in Vero cells

We studied the effect of bafilomycin A1 (Baf-A1), a novel and highly specif ic inhibitor for vacuolar-type proton (V-H+) pump, on the growth of Japanes e Encephalitis virus (JEV) in Vero cells. Viral fluorescence microscopic st udy showed that Baf-A1 induced the complete disappearance of acidified comp artments such as endosomes and lysosomes in Vero cells by the treatment wit h 0.1 mu M Baf-A1 for Ih at 37 degrees C. In proportion to the disappearanc e of acidified compartments, virus growth was inhibited when Baf-A1 was pre sent from 1 h before infection to the end of incubation in a dose-dependent manner, or added within as early as 5 min after infection. Conversely, the virus growth was recovered in correlation with the reappearance of acidifi ed compartments after removal of Baf-A1. These results suggest that a low p H condition, which is regulated by Baf-A1-sensitive V-H+ pumps, is essentia l for the early stage of JEV growth.