Submitted to: Journal of Virology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/9/2001
Publication Date: N/A
Interpretive Summary: In this report, we describe the complete genome sequence of CuniNPV and compare it to the genomes of other baculoviruses. CuniNPV is highly pathogenic to C. nigripalpus and C. quinquefasciatus, both of which are important vectors of St. Louis and Eastern encephalitis viruses and it is responsible for epizootics in field populations of C. nigripalpus larvae. This is the first complete genome sequence and analysis of a baculovirus infecting mosquitoes and provides novel information on genome composition, basic replicative functions and host range functions which may lead to the development of novel mosquito control strategies. The comparison with lepidopteran baculoviruses provides insight on baculovirus diversity and evolution. The Baculoviridae is a large and diverse family of occluded viruses with double stranded DNA genomes that are pathogenic for insects particularly of the lepidopteran, hymenopteran and dipteran orders. Because a number of dipteran (mosquito) species are important vectors for variety of human and veterinary diseases, extensive investigations to identify pathogens of these insects have been undertaken and in the last 20 years NPVs were isolated from at least ten mosquito species of the genera Aedes, Anopheles, Culex, Psorophora, Uranotenia and Wyeomia. Recently, the Center for Medical, Agricultural and Veterinary Entomology in Gainsville (USDA) have identified conditions for the isolation and trans- mission of a NPV pathogenic for C. nigripalpus, thus allowing the study and use this virus for mosquito control purposes. These genera are all members of the Culicidae which contains approximately 3,500 species of mosquitoes.
Technical Abstract: In this report we describe the complete genome sequence of a nucleopoly- hedrovirus that infects larval stages of the mosquito Culex nigripalpus (CuniNPV). The CuniNPV genome is a circular dsDNA molecule of 108,252 base pairs and is predicted to encode 109 genes- 37 of these genes show homology to genes from other baculoviruses (BV's) their orientation and order exhibit little conservation relative to the genomes of lepidopteran BV's. CuniNPV genes homologous to those from other BV's includes those involved in early and late gene expression, DNA replication, and structural functions. Auxiliary genes include homologues of genes encoding the p35 anti-apoptosis protein, and a novel insulin binding related protein. In contrast to these conserved genes, CuniNPV lacks apparent homologues of BV genes essential (ie-1, lef-3) or stimulatory (ie-2, lef-7, pe38) for DNA replication. Also BV genes essential or stimulatory for early-late (ie-1, ie-2), early (ie-0 and pe-38) and late (lef-6, lef-11, pp31) gene trans- cription are not identifiable. In addition, CuniNPV lacks homologues of genes involved in the formation of virogenic stroma (pp31), nucleocapsid (orf1629, p87 and p24), envelope of occluded virions (odv-e25, odv-e66, odv-e18), and polyhedra and budded virus envelope fusion protein gp64. The absence of homologues of occlusion derived virion (ODV) envelope proteins and occlusion body (OB) protein (polyhedrin) suggests that both CuniNPV occlusion bodies ODV and OB may be structurally and compositionally different from those found in terrestrial lepidopteran hosts. The striking difference in genome organization, the low level of conservation of homologous genes, and the lack of many genes conserved in other BV's suggest a large evolutionary distance between CuniNPV & lepidopteran BV's.