Choristoneura murinana Nuclear Polyhedrosis Virus: Comparative Biochemical and Biological Examination of Replication in vivo and in vitro

Abstract
Summary An in vitro replication system for the Choristoneura murinana nuclear polyhedrosis virus (CmMNPV) was established and used (i) to characterize this baculovirus biochemically; (ii) to study the cytoplasmic spindle-shaped inclusions (CSIs) associated with CmMNPV replication; and (iii) to compare the cytopathic changes during CmMNPV replication in vivo and in vitro as well as the properties of virions, polyhedra and CSIs from both systems. It was shown that the processes occurring during, and the products of, CmMNPV replication in vitro closely resemble those in vivo, i.e. in larval hosts. Genome analysis by restriction endonucleases, as well as infectivity studies with polyhedra from both sources did not reveal major differences between virus produced in vivo and that produced in vitro. The CSIs were found exclusively in the cytoplasm of infected cells and were shown to consist of a single protein of M r 50000. Although the biological significance of these spindles, which are produced in large quantities, is not known, they do not seem to be of importance for the infectivity of this baculovirus in vivo.