A new flavivirus and a new vector: characterization of a novel flavivirus isolated from uranotaenia mosquitoes from a tropical rain forest

Abstract

A novel flavivirus was isolated from Uranotaenia mashonaensis, a mosquito genus not previously known to harbor flaviviruses. Mosquitoes were caught in the primary rain forest of the Taï National Park, Côte d'Ivoire. The novel virus, termed nounané virus (NOUV), seemed to grow only on C6/36 insect cells and not on vertebrate cells. Typical enveloped flavivirus-like particles of 60 to 65 nm in diameter were detected by electron microscopy in the cell culture supernatant of infected cells. The full genome was sequenced, and potential cleavage and glycosylation sites and cysteine residues were identified, suggesting that the processing of the NOUV polyprotein is similar to that of other flaviviruses. Phylogenetic analyses of the whole polyprotein and the NS3 protein showed that the virus forms a distinct cluster within the clade of mosquito-borne flaviviruses. Only a distant relationship to other known flaviviruses was found, indicating that NOUV is a novel lineage within the Flaviviridae.

FIG. 1.

Phylogenetic trees of NOUV and other flaviviruses showing the association of virus groups with their invertebrate vectors and vertebrate hosts and associated human diseases. The trees are based on the amino acid sequences of the entire ORF (A) or on the NS3 protein (B). Trees were constructed using the NJ method. CFAV was used as an outgroup. Bootstrap values were calculated with 1,000 replicates. ALF, Alfuy virus; ALK, Alkhurma hemorrhagic fever virus; APOI, Apoi virus; DEN, dengue virus; ENT, Entebbe bat virus; ILH, Ilheus virus; JE, Japanese encephalitis virus; KR, Kamiti River virus; KOK, Kokobera virus; LI, louping ill virus; MML, Montana myotis leukoencephalitis virus; MVE, Murray Valley encephalitis virus; NOU, nounané virus; OHF, Omsk hemorrhagic fever virus; POW, Powassan virus; RB, Rio Bravo virus; ROC, Rocio virus; SEP, Sepik virus; SLE, St. Louis encephalitis virus; TBE, tick-borne encephalitis virus; USU, Usutu virus; WN, West Nile virus; YF, yellow fever virus; ZIK, Zika virus.

FIG. 2.

Transmission electron micrograph of ultrathin sections of C6/36 cells infected with NOUV. Enveloped virions are located in the endoplasmatic reticulum (A) and in vesicles (B), as indicated by arrows. Scale bar, 100 nm.