Work

Characterization of a Culex theileri flavivirus variant in field-collected mosquitoes from Turkey

Year: 2016

Type: article

Abstract: Purpose: The Flaviviridae family includes several strains that only replicate in mosquitoes or mosquito-derived cell lines, generally called as insect-specific flaviviruses, along with the well-known mosquito-borne important human pathogens. Recent evidence indicates wider-than-expected prevalence and dispersion insect-specific flaviviruses in mosquito populations. Here, we describe the near-complete genomic characterization of flaviviruses isolated during a field survaillance campaign in Turkey. Methods & Materials: Four virus strains, isolated using C6/36 cells from mosquito pool extracts with positive results in screening via generic flavivirus PCR were evaluated. The pools originated from collection sites in Aegean and Thrace regions, and comprised individuals previously identified as Culex theileri via morphology and DNA barcoding. Culture supernatants of the 3rd passage were subjected to nucleic acid purification, cDNA synthesis, library preparation and sequencing via Illumina HiSeq 1500 sequencing platform. Assembly of the contigs, alignment with the complete or-near-complete insect flavivirus genomes deposited in public databases and further analyses were performed with relevant software. Results: Near-complete genomes of 10299-10420 nucleotides, that cover the complete coding region of the flavivirus polyprotein were assembled. Neighbor-joining analyses placed all isolates within a distinct group, which further forms a cluster with two culex theileri flavivirus isolates from Portugal. No association of nucleotide/aminoacid variations with collection sites was observed. The putative polyprotein comprised 3357 amino acids and followed the universal flavivirus polyprotein organization of structural proteins C, preM and E, and nonstructural proteins NS1, NS2a, NS2b, NS3, NS4a, NS4b and NS5. The putative protease cleavage sites were noted as identical to the Culex theileri flaviviruses. Pairwise amino acids comparions demonstrated 0.99-1.33% diversity rates among intramural and phylogenetically-related strains. Conclusion: The findings indicate the circulation of a novel culex theileri flavivirus variant, tentatively called as the “Culex Theileri Flavivirus Turkey (CTFT)”, in various regions of Turkey. This report constitutes the first detailed characterization of insect-specific flaviviruses in Asia Minor.

Source: International Journal of Infectious Diseases

DOI: 10.1016/j.ijid.2016.11.302