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Mosquito-specific flaviviruses comprise a group of insect-specific viruses with a single positive RNA, which can affect the duplication of mosquito-borne viruses and the life growth of mosquitoes, and which have the potential to be developed as a vaccine platform for mosquito-borne viruses. In this study, a strain of mosquito flavivirus (MFV) YN15-283-02 was detected in Culicoides collected from Yunnan, China. The isolation of the purified MFV YN15-283-02 from cell culture failed, and the virus was then rescued by an infectious clone. To study the biological features of MFV YN15-283-02 in vitro and in vivo, electron microscopy, phylogenetic tree, and viral growth kinetic analyses were performed in both cell lines and mosquitoes. The rescued MFV (rMFV) YN15-283-02 duplicated and reached a peak in C6/36 cells at 6 d.p.i. with approximately 2 × 106 RNA copies/μL (RNA to cell ratio of 0.1), but without displaying a cytopathic effect. In addition, the infection rate for the rMFV in Ae.aegypti show a low level in both larvae (≤15%) and adult mosquitoes (≤12%). [ABSTRACT FROM AUTHOR]

Background: Aedes vexans (Meigen) is considered a nuisance species in central Europe and the Mediterranean region. It is an anthropophilic and mammalophilic floodwater mosquito involved in the transmission of several arboviruses. Rift Valley fever (RVF) is a relevant mosquito-borne zoonosis, affecting mainly humans and ruminants, that causes severe impact in public health and economic loses. Due to globalization and climate change, the European continent is threatened by its introduction. The main purpose of the present study was to evaluate the vector competence of a European field-collected Ae. vexans population. Methods: Aedes vexans field-collected larvae were reared in the laboratory under field-simulated conditions. To assess the vector competence for Rift Valley fever phlebovirus (RVFV) transmission, adult F0 females were exposed to infectious blood meals containing the 56/74 RVFV strain. Additionally, intrathoracic inoculations with the same virus strain were performed to evaluate the relevance of the salivary gland barriers. Natural circulation of alphavirus, flavivirus and phlebovirus was also tested. Results: To our knowledge, an autochthonous Ae. vexans population was experimentally confirmed as a competent vector for RVFV for the first time. This virus was capable of infecting and disseminating within the studied Ae. vexans mosquitoes. Moreover, infectious virus was isolated from the saliva of disseminated specimens, showing their capacity to transmit the virus. Additionally, a natural infection with a circulating Mosquito flavivirus was detected. The co-infection with the Mosquito flavivirus seemed to modulate RVFV infection susceptibility in field-collected Ae. vexans, but further studies are needed to confirm its potential interference in RVFV transmission. Conclusions: Our results show that field-collected European Ae. vexans would be able to transmit RVFV in case of introduction into the continent. This should be taken into consideration in the design of surveillance and control programmes. [ABSTRACT FROM AUTHOR]