Submitted to: Journal of Invertebrate Pathology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 10/11/2005
Publication Date: 1/15/2006
Citation: Green, T.B., Shapiro, A.M., White, S.E., Rao, S., Mertens, P.P., Carner, G., Becnel, J.J. 2006. Molecular and biological characterization of a cypovirus from the mosquito culex restuans. Journal of Invertebrate Pathology 91:27-34. Interpretive Summary: A naturally occurring virus that infects mosquitoes has been characterized by ARS scientists at the Center for Medical, Agricultural and Veterinary Entomology, Gainesville Florida. Mosquito species susceptible to this virus are important vectors of St. Louis Encephalitis, Eastern Equine Encephalitis and West Nile Virus in the United States. We have conducted biological and molecular study and determined that transmission of the virus to mosquitoes was enhanced by the presence of magnesium. We have also determined that this RNA virus has a 10 segmented genome and sequence analysis of the occlusion body protein has determined this species (CrCPV) is a new member of the Cypoviruses (CrCPV-17). This new virus from mosquitoes expands the genetic diversity base required to investigate and understand basic mechanisms involved in infectivity and host range that will enhance capabilities to use these viruses for mosquito control.
Technical Abstract: A cypovirus (cyptoplasmic polyhedrosis virus, CPV) from mosquito Culex restuans was isolated and its morphology, genomic, and molecular characteristics are reported. CrCPV is characterized by small (0.1 to 1.0µm), irregularly shaped inclusion bodies that are multiply embedded. The divalent cation, magnesium, enhanced CrCPV transmission by ~73% while calcium repressed it to ~5%. CrCPV is the 2nd cypovirus from a mosquito that has been confirmed by using molecular analysis. CrCPV has a genome of 10 segmented dsRNAs with an electropherotype similar to the recently discovered UsCPV-17 (Uranotaenia sapphirina), but distinct from the lepidopteran cypoviruses BmCPV-1 (Bombyx mori), TnCPV-15 (Trichoplusia ni) and others. Nucleotide and deduced amino acid sequence analysis of CrCPV segment 10 (polyhedrin) suggests that CrCPV is closely related (83% nucleotide sequence identity and 87% amino acid sequence identity) to the newly characterized UsCPV-17 but is unrelated to the sixteen remaining CPV species from lepidopteran hosts. Furthermore, examination of the terminal regions, an additional method for differentiating various cypovirus species, shows CrCPV and UsCPV-17 are quite comparable. Therefore, we propose that CrCPV is a member of the Cyprovirus-17 species group and designated CrCPV-17.