Biochemical comparison of virion proteins from five nuclear polyhedrosis viruses infecting plusiine larvae (Lepidoptera: Noctuidae)

The virions of six isolates of five nuclear polyhedrosis viruses (NPV) infecting plusiine larvae (Lepidoptera: Noctuidae) were reproducibly separated by sucrose density gradient centrifugation and fractionation. Purity of the preparations was established by electron microscopy. Virion proteins were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE); each produced 12 distinct polypeptides ranging from 10,300 to 82,900 mw. Qualitative and quantitative differences were found between most of the polypeptide patterns. The singly embedded viron (SEV)-type isolates had two major components with mw in the range of 32,900–35,200; multiply embedded virion (MEV)-type isolates had a major component of ca. 12,500 mw. SEV isolates showed almost no within-group differences, while minor differences were found among the MEV banding patterns in both intensity and presence of certain bands. Capsids and envelopes from MEV had two to four polypeptides with mw between 10,800 and 26,900. The presence of more than one polypeptide and electron microscopy of sample composition suggested that the capsid and envelope are composed of several distinct proteins.