Isolation of a novel species of flavivirus and a new strain of Culex flavivirus (Flaviviridae) from a natural mosquito population in Uganda

Abstract

The genus Flavivirus, which contains approximately 70 single-stranded, positive-sense RNA viruses, represents a unique model for studying the evolution of vector-borne disease, as it includes viruses that are mosquito-borne, tick-borne or have no known vector. Both theoretical work and field studies suggest the existence of a large number of undiscovered flaviviruses. Recently, the first isolation of cell fusing agent virus (CFAV) was reported from a natural mosquito population in Puerto Rico, and sequences related to CFAV have been discovered in mosquitoes from Thailand. CFAV had previously been isolated from a mosquito cell line in 1975 and represented the only known ‘insect-only’ flavivirus, appearing to replicate in insect cells alone. A second member of the ‘insect-only’ group, Kamiti River virus (KRV), was isolated from Kenyan mosquitoes in 2003. A third tentative member of the ‘insect-only’ group, Culex flavivirus (CxFV), was first isolated in 2007 from Japan and further strains have subsequently been reported from the Americas. We report the discovery, isolation and characterization of two novel ‘insect-only’ flaviviruses from Entebbe, Uganda: a novel lineage tentatively designated Nakiwogo virus (NAKV) and a new strain of CxFV. The individual mosquitoes from which these strains were isolated, identified retrospectively by using a reference molecular phylogeny generated using voucher specimens from the region, were Mansonia africana nigerrima and Culex quinquefasciatus, respectively. This represents the first isolation, to our knowledge, of a novel insect-only flavivirus from a Mansonia species and the first isolation of a strain of CxFV from Africa.

A tick-borne segmented RNA virus contains genome segments derived from unsegmented viral ancestors

“…Images of thin sections were observed under a transmission electron microscope (JEM 1230; JEOL). The supernatant was also harvested and subject to negative staining EM as described previously (20).…”

Novel Flaviviruses Detected in Different Species of Mosquitoes in Spain

“…It was the first ''insect flavivirus'' (e.g viruses that propagate only in mosquito cells but not in mammalian cells) discovered. To date, six other ''insect flaviviruses'' have been described: Kamiti River virus (KRV), isolated from field collected Aedes macintoshi in Africa in 2003 (Crabtree et al 2003); Culex Flavivirus (CxFV), isolated mainly from Culex mosquitoes in Japan, Indonesia (Hoshino et al 2007), Guatemala (Morales-Betoulle et al 2008), México (Farfan-Ale et al 2009), United States, Trinidad (Kim et al 2009), and Uganda (Cook et al 2009); Aedes Flavivirus (AEFV), isolated from Aedes albopictus mosquito in Japan (Hoshino et al 2009); Quang Binh virus (QBV) isolated from Culex tritaeniorhynchus in Vietnam (Crabtree et al 2009); Nakiwogo virus (NAKV) isolated from Mansonia africana nigerrima in Uganda (Cook et al 2009); and Calbertado virus detected mainly in Cx. tarsalis mosquitoes in Canada (Pabbaraju et al 2009).…”

Culex Flavivirus and West Nile Virus Mosquito Coinfection and Positive Ecological Association in Chicago, United States

“…CxFV was first isolated from Culex pipiens Linnaeus mosquitoes in Japan (Hoshino et al 2007) but appears to have a global distribution, with additional variants identified in other Culex species and subspecies from Mexico, Uganda, Trinidad, and the United States (Morales-Betoulle et al 2008, Blitvich et al 2009, Cook et al 2009, Farfan-Ale et al 2009, Kim et al 2009). The insect-specific designation of CxFV derives from the observation that it has been cultured in the laboratory only in mosquito cell lines and, additionally, that it has been identified in many natural populations of Culex mosquitoes (Hoshino et al 2007).…”