FIG 4.

Effect of multiple, sequential low-pH exposures on HSV-1 infectivity. Extracellular HSV-1 KOS virions were treated for 10 min with pH 5.0 and then neutralized to pH 7.4 for 10 min (1×). This treatment was repeated for a total of two (2×) or four (4×) times. Virus titers were determined on Vero cells. Nonsequential samples were treated with pH 5.0 for 40 min and neutralized to pH 7.4 for 40 min. Data are the means from four replicates with standard errors. The P values were determined using Student's t test (*, P < 0.01; **, P < 0.001). Results are representative of three independent experiments.