The Non-Permissive Infection of Insect (Gypsy Moth) LD-652 Cells by Vaccinia Virus

Abstract

The members of Poxviridae family are among the most complex of animal viruses and subfamily members infect both vertebrate (Chordopoxvirinae) and invertebrate (Entomopoxvirinae) hosts, respectively. Vaccinia virus (VV) is the most commonly studied vertebrate virus and the entomopoxvirus of Amsacta moorei (AmEPV) is the prototypic insect virus. AmEPV, while not able to productively infect vertebrate cells, does enter vertebrate cells and expresses early genes after which the infection aborts although the cells survive (Y. Li, R. L. Hall, and R. W. Moyer. J.Virol. 71(12), 95579562, 1997). We show here that a recombinant VV, containing the lacZ gene regulated by the cowpox virus A-type inclusion (ATI) late promoter, likewise does not productively infect insect cells. Our results suggest that the recombinant VV enters insect cells, host protein synthesis is inhibited, early gene expression is normal, and viral DNA replication occurs as does late protein synthesis. However, little if any proteolytic processing of late viral proteins, typical of morphogenesis, is observed. Electron micrographs of infected cells suggest that while cytoplasmic virosomes (factories) are formed, there is little indication of further morphogenesis or any formation of mature virions. Therefore, while both orthopoxviruses and entomopoxviruses fail to replicate in heterologous hosts, the nature of abortive infections is quite different.

Biological Transmission of Arboviruses: Reexamination of and New Insights into Components, Mechanisms, and Unique Traits as Well as Their Evolutionary Trends

“…This mode of transmission (termed circulative, nonpropagative mode) of geminiviruses thus appears to be in the intermediate mode between mechanical transmission and biological transmission. Some insect poxviruses (genus Entomopoxvirus) share with mammalian poxviruses similar cell entry and uncoating mechanisms as well as biochemical strategy for replication, the major difference being that the former viruses are defective in late gene expression in vertebrate cells, while the latter are defective in proteolytic processing of late viral proteins in insect cells (180,181). Polydnaviruses are obligate, symbiotic, double-stranded DNA viruses that infect insects.…”

Ectopic Transgene Expression in Butterfly Imaginal wing Discs using Vaccinia Virus

“…The vaccinia viral vector and reporter gene used appeared to have no overt effect on the health of the insect or wing color pattern formation, an important property if vaccinia virus is to be used to express genes thought to be involved in this process. In addition, the fact that vaccinia virus, which is a vertebrate poxvirus, has the ability to infect butterflies in vivo as well as gypsy moth cells in vitro (9), suggests that vaccinia virus will also be a useful gene expression tool in other arthropod species for which classical genetic methods are either impractical or unavailable.…”

“…It has been reported that vaccinia virus, a vertebrate poxvirus, is able to infect gypsy moth cell lines in vitro (9). The vaccinia virus enters the gypsy moth cells and carries out both early and late viral protein synthesis as well as viral DNA replication (9).…”

“…Because vaccinia virus does not productively infect insect cells (9), and thus the infections will be centered around the initial site of inoculation only, the ability to inject specific sites of the larval wing disc will allow us to directly target gene expression to particular areas of the wing at specific developmental times. This will enable us to further define the roles that a specific gene plays during color pattern formation.…”

“…The vaccinia virus enters the gypsy moth cells and carries out both early and late viral protein synthesis as well as viral DNA replication (9). However, processing of viral late proteins does not occur, and therefore infectious virions are not produced.…”