CHARACTERIZATION OF VIRAL ENHANCING ACTIVITY FROM TRICHOPLUSIA NI GRANULOSIS-VIRUS

A factor present in the granules of Trichoplusia ni granulosis virus, when fed together with a nuclear polyhedrosis virus, can enhance viral infection and accelerate death in T. ni neonate larvae. Occlusion bod ies of T. ni granulosis virus were dissolved in alkali and soluble pro teins were separated by gel filtration chromatography. These fractions were assayed for enhancement of nuclear polyhedrosis infection in T. ni neonates. Denaturing gel electrophoresis of the fractions revealed that enhancin, a protein homologous to the synergistic factor of Pseud aletia unipuncta, eluted as a discrete peak. Viral enhancing activity eluted over a large volume covering this peak and a wide molecular wei ght range following this peak. Moreover, we show that the 98-kDa enhan cin protein is released from a larger 150-kDa complex, by heating in t he presence of detergent. Once released, the enhancin protein is subje ct to extensive proteolysis, yielding smaller protein fragments. These results suggest the possibility that fragments of the enhancin protei n, or other components of the 150-kDa complex, may be active viral enh ancing agents. (C) 1995 Academic Press, Inc.