Identificação de vírus inseto-específicos e Wolbachia pipientis em culicídeos vetores capturados em Cuiabá-MT

Abstract

Interference in arbovirus replication in vectors by concomitant infection with endosymbiont microorganisms has been demonstrated experimentally. Insect-specific viruses(ISVs) comprise a group of viruses capable of replicating only in invertebrate cells. Culex flavivirus (CxFV), genus Flavivirus, is an ISV isolated from Culex spp. in many countries. New ISVs belonging to different viral families have been described. The present study aimed to investigate the frequency of adult mosquitoes naturally infected by ISVs and Wolbachia (W.) pipientis in the city of Cuiabá, Mato Grosso. Adult females of Cx. quinquefasciatus Say 1823 (n = 3,425) collected in 200 urban census tracts, separated into pools (1-20 females) according to species, date and place of collection were subjected to RT-PCR for the NS5 gene region of Flavivirus genus, viral isolation in C6/36 cells, Semi-Nested-PCR to wsp gene, supergroup B of W. pipientis and to nucleotide sequencing and to Ion-Torrent platform. The obtained sequences were analyzed to confirm viral species and phylogenetic analysis. Culex flavivirus was detected in 16/403 pools of Cx. quinquefasciatus, the most abundant species in the city. The sequences obtained in this study presented high similarity with sequences from isolates obtained in Mexico, Uganda and Brazil. Complete genome phylogeny revealed that the Cuiabá isolate is closely related to samples belonging to the African / Caribbean / Latin American genotype (genotype II). The estimate of monthly maximum likelihood ranged from 1.81 to 9.94 per 1000 mosquitoes. This is the first report of CxFV in Midwest Brazil. In addition to the complete genome of CxFV, 1 Cx quinquefasciatus pool was also positive for a ORF1 region (756 bp) of a new virus belonging to Sandewavirus supergroup, taxon Negevirus with 77.1% of similarity with the previously described Santana virus. A region of the RNA-dependent RNA polymerase (1081 bp) belonging to a new Rhabdovirus similar (44%) to the Wuhan mosquito virus 9 was identified in another pool. CxFV was the only virus isolated after three passages in C6/36 cells. 217/403 Cx. quinquefasciatus females pools were identified positive for W. pipientis supergroup B. Of these, 20 were also positive for arboviruses in previous studies. The most prevalent administrative region were South. The sequences obtained for wsp gene presented 97-100% of identity with other isolates from Cx. quinquefasciatus, Cx. pipiens and other arthropods. Phylogentic analysis reveals that the supergroups A and B presented as sistergroups and more external to the supergroups C, D e F that comprise isolates from other invertebrates. The pathogenicity of ISVs and their interference in arbovirus replication in competent vectors needs to be better clarified, however, studies have suggested that as endosymbionts, ISVs can alter mosquito vector competence for some arboviruses, resulting in exclusion of superinfection or by altering the vector immune response.