Infectivity of a multiploid-forming mutant of western equine encephalitis virus.

(Simizu et al., 1973; Hashimoto et al., 1975). Infected culture fluids were harvested in 24 hr after infection for preparing a crude virus suspension. The virus suspension was purified according to the procedures described elsewhere (Hashimoto et al., 1975). Physical particles of viruses were counted by the loop-drop method of Watson, Russell and Wildy (1963). One-tenth milliliter of virus suspension was mixed with 0.1 ml of a polystyrene latex (109 nm in diameter, Dow Chemical, Indiana-