TABLE 1.

Titers of supernatant and cell-associated VHSV at different adsorption and infection pHs^a

pH, adsorption + infection	VHSV titer,b FFU (106)/ml		Cell-associated virus, %	Cytopathic effect
	Supernatant	Cell lysate
7.5 + 7.5	250.0000	≤0.1000	≤0.05	Yes
7.5 + 6.5	0.0067	0.0059	45.38	No
6.5 + 6.5	0.0025	0.0027	52.90	No
6.5 + 7.5	300.0000	≤0.0800	≤0.02	Yes

^aEPC cell monolayers in 25-cm² flasks seeded with 9 × 10⁶ cells per flask were incubated for 2 h with VHSV at an MOI of 0.01 at pH 7.5 or 6.5 (adsorption step). After washing, 7 ml of cell culture medium at pH 7.5 or 6.5 was added per flask, and the cultures were incubated for 7 days at 14°C (infection step). The supernatants (extracellular viral particles) and cell lysates (intracellular viral particles) were then titrated. Cell-associated virus was calculated as VHSV titer in cell lysate/VHSV titer in supernatant × 100.

^bMean from two experiments.