The Lymantria dispar nucleopolyhedrovirus enhancins are components of occlusion-derived virus

Abstract

Enhancins are metalloproteinases, first identified in granuloviruses, that can enhance nucleopolyhedrovirus (NIPV) potency. We had previously identified two enhamin genes (El and E2) in the Lymantria dispar multinucleocapsid NPV (LdMNPV) and showed that both were functional. For this study, we have extended our analysis of LdMNPV enhancin genes through an immunocytochemical analysis of El and E2 expression and localization. El and E2 peptide antibodies recognized proteins of ~84- kDa and 90-kDa, respectively, on Western blots of extracts from L. dispar 65ZY cells infected with wild-type virus. The 84- and 90-kDa proteins were first detected at 48 h postinfection (p.i.) and were present through 96 h p.i. El and E2 peptide antibodies detected El and EZ in polyhedron extracts, and the antibodies were shown to be specific for El and E2, respectively, through the use of recombinant virus strains lacking the enhancin genes. El and E2 were further localized to occlusion-derived virus (ODV). The enhancins were not found in budded virus. Immunoelectron microscopy indicated that El and E2 were present in ODV envelopes and possibly in nucleocapsids. Fractionation studies with several detergents suggested that the enhancins were present in ODV envelopes in association with nncleocapsids. In contrast, enhancins in granuloviruses are located within the granulin matrix. The presence of LdMNPV enhancins within ODV provides a position for the proteins to interact directly on the peritrophic membrane as ODV traverses this host defense barrier.

Citation

Slavicek, James M.; Popham, Holly J.R. 2005. The Lymantria dispar nucleopolyhedrovirus enhancins are components of occlusion-derived virus. Journal of Virology. 79(16): 10578-10588.