Submitted to: Journal of Virology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 4/22/2005
Publication Date: 8/1/2005
Citation: Shapiro, A.M., Green, T.B., Rao, S., White, S.E., Carner, G., Mertens, P.P., Becnel, J.J. 2005. Morphological and molecular characterization of a cypovirus (reoviridae) from the mosquito uranotaenia sapphirina (diptera: culicidae). Journal of Virology. 79:(15) Interpretive Summary: A naturally occurring virus that infects mosquitoes has been discovered by ARS scientists at the Center for Medical, Agricultural and Veterinary Entomology, Gainesville Florida. This report is an analysis of the biology, morphology and molecular characteristics of this virus from the mosquito Uranotaenia sapphirina and designated UsCPV. These data indicate that using the species parameters published by the International Committee on Taxonomy of Viruses, UsCPV belongs to a distinct group of viruses in the genus Cypovirus and can now be identify as 'Cypovirus 17' (strain UsCPV-17). UsCPV is the first confirmed cypovirus from a mosquito host. Oral transmission of UsCPV-17 to mosquito larvae was found to be enhanced by magnesium and inhibited by calcium. UsCPV-17 has a relatively broad host range including Culex quinquefasciatus, Aedes aegypti, Ochlerotatus triseriatus, Ur. lowii, and Anopheles albimanus, although it was not transmitted to An. quadrimaculatus or the lepidopteran host Helicoverpa zea. This fundamental knowledge contributes to our basic understanding of these pathogens and will enable the evaluation and development of viruses as biopesticides for the control of mosquitoes that vector deadly diseases of man and animals.
Technical Abstract: A novel cypovirus was isolated from the mosquito Uranotaenia sapphirina (UsCPV) and shown to cause a chronic infection confined to the cytoplasm of epithelial cells of the gastric caecae and posterior stomach. The production of large numbers of virions and occlusion bodies, and their arrangement into paracrystalline arrays gives the gut of infected insects a distinctive blue iridescence. The virions, which were examined by electron microscopy, are icosahedral (55 to 65 nm in diameter) with a central core that is surrounded by a single capsid layer. They are usually packaged individually within cubic inclusion bodies (polyhedra, ~100 nm across), although 2-8 virus particles were sometimes occluded together. The virus was experimentally transmitted per os to several mosquito species. The transmission rate was enhanced by the presence of magnesium ions but was inhibited by calcium ions. Most of the infected larvae survived to adulthood and the adults retained the infection. Electrophoretic analysis of the UsCPV genome segments (using 1% agarose gels) revealed an electropherotype that is different to that of the sixteen Cypovirus species already recognized. UsCPV genome segment 10 (Seg-10) did not show significant nucleotide sequence similarity to the equivalent segment of the cypoviruses previously analysed. In addition, a Blast search of UsCPV deduced amino acid sequences showed low level similarity to Antheraea mylitta CPV- 4 (67/290 = 23%) and Choristoneura fumiferana CPV-16 (33/111 = 29%). We conclude that UsCPV should be recognized as a member of a new Cypovirus species (Cypovirus 17: Strain UsCPV-17).