AUTOGRAPHA-CALIFORNICA NUCLEAR POLYHEDROSIS-VIRUS, PDV, AND ECV VIRALENVELOPES AND NUCLEOCAPSIDS - STRUCTURAL PROTEINS, ANTIGENS, LIPID AND FATTY-ACID PROFILES

Autographa californica nuclear polyhedrosis virus (AcMNPV) infection r esults in the production of two types of infectious, enveloped viruses . As both of these viral forms play significantly different roles in t he virus life cycle, the different functional characteristics in the r oles of the virus may be explained, in part, by the protein and lipid composition and source of the viral envelopes. Both viruses utilize di fferent maturation and envelopment strategies: Extracellular virus (EC V) obtains an envelope by budding from the host cell plasma membrane, while the envelope of polyhedra-derived virus (PDV) is obtained within the nucleus of the host cell. There is compelling evidence for differ ences between ECV and PDV structural proteins; however, no previous st udy directly compares ECV and PDV purified from the same source and li ttle data are available on the protein and lipid composition of the vi ral envelopes. This study begins the systematic comparison of ECV, PDV , and their envelopes to target proteins for use as probes to study th e molecular and biochemical basis of viral envelopment within the nucl eus. AcMNPV ECV and PDV were isolated from infected Spodoptera frugipe rda cells and fractionated into their respective envelope and nucleoca psid fractions. The structural protein, glycoprotein, and phosphoprote in composition of ECV, PDV, and their envelope and nucleocapsid fracti ons are analyzed and compared, and antigens of ECV and PDV viral envel ope are identified. A number of structural proteins are different betw een ECV and PDV. ECV is enriched for proteins at 67, 45, and 35 kDa, w hile proteins at 89, 70, 60, 50, and 25 kDa are enriched in PDV. At le ast two proteins, PDV-E66 and PDV-E43, are identified to be specific f or the PDV envelope. There are more N-glycosylated proteins in ECV tha n in PDV, with ECV-specific proteins found at 137, 128, 89, 45, and 40 kDa. PDV glycoproteins are 70, 53, 49, 42, 40, and 31 kDa. Most phosp hoproteins of both ECV and PDV are predominantly found in the viral en velopes. The predominant phosphoprotein of ECV is 85 kDa, whereas PDV major phosphoprotein is 36 kDa. This study presents the first report o f the phospholipid and fatty acid content of ECV and PDV viral envelop es. The major phospholipid of ECV is phosphatidylserine (50%), while p hosphatidylcholine and phosphatidylethanolamine are the major phosphol ipids of PDV (39 and 30%, respectively). Since PDV is enveloped within the nucleus of the host cell, the PDV phospholipid composition is com pared with the phospholipid composition of purified S. frugiperda (Sf9 ) nuclei and this analysis demonstrates significant differences betwee n these two membrane systems. (C) 1994 Academic Press, Inc.