Effect of microbubbles on the infectivity of HSV-1. (A) Microbubbles (9.8 × 107/100 μl) were mixed with viral solution (1 × 107 PFU of R849/900 μl). These mixtures were placed at 4°C. After incubation for 10, 30, and 60 min, the mixtures were subjected to plaque assays on Vero cell monolayers. (B) HSV-1 strain HF was also tested for sensitivity to microbubbles. Microbubbles and 3 × 107 PFU of HF were mixed as described for R849.