Some properties of a new virus of Pieris rapae

A new insect virus of Pieris rapae was purified using a chloroform-butanol treatment followed by two differential and sucrose gradient centrifugations. The sedimentation coefficient of the purified virion was approximately 132 S, and it banded at a density of 1.39 g/cm³ in cesium chloride. The virion has a nonenveloped capsid with icosahedral symmetry. Several virions were shown to have a regular hexagonal contour about 25 nm in diameter and to be composed of many capsomeres. Full and empty viral particles, with 12 capsomeres around the periphery of the capsid, were noted. In some particles a small core has been observed which is spherical, about 15 nm in diameter. Both purified virus and partially purified virus preparations from dead, infected larvae gave only one precipitin band with a reaction of identity when tested against the antiserum to partially purified virus. When crude extracts of uninfected larvae and purified virus were tested against antiserum to partially purified virus, the pure virus produced a precipitin band. The band was formed independently and did not join to the band of the uninfected insect producing a typical reaction of nonidentity.