Arboviruses and Hemorrhagic Fever Viruses Unit, Virology Department, Institut Pasteur de Dakar, BP220 Dakar, Senegal; Department of Animal Biology, Faculty of Science et Technics, Université Cheikh Anta Diop de Dakar (UCAD), Fann, BP 5005 Dakar, Senegal.
Unité d'Entomologie Médicale, Institut Pasteur de Dakar, BP220 Dakar, Senegal.
Virus Res. 2019 Nov;273:197753. doi: 10.1016/j.virusres.2019.197753. Epub 2019 Sep 12.
Usutu virus (USUV) previously restricted to Africa where it caused mild infections, emerged in 2001 in Europe and caused more severe infections among birds and humans with neurological forms, suggesting an adaptation and increasing virulence. This evolution suggests the need to better understand USUV transmission patterns for assessing risks and to develop control strategies. Phylogenetic analysis conducted in Africa showed low genetic diversity of African USUV strains except for one human and the USUV subtype (USUVsub) strains, which exhibited a deletion in the 3'UTR and nucleotide substitutions throughout the genome. Here we analyzed their viral replication in vitro in mosquito and mammalian cells, and vector competence of Culex quinquefasciatus, compared to a reference strain. Growth kinetics of the different strains showed comparable replication rates however variations in replication and translation efficiency were observed. Vector competence analysis showed that all strains were able to infect Culex quinquefasciatus the main peridomestic Culex species in Africa, with detection of USUV viral genomes and infectious particles. Dissemination and transmission were observed only for USUVsub, but infectious particles were not detected in Culex quinquefasciatus saliva. Our findings suggest that genetic variability can affect USUV in vitro replication in a cell type-dependent manner and in vivo in mosquitoes. In addition, the results show that Culex quinquefasciatus is not competent for the USUV strains analyzed here and also suggest an aborted transmission process for the USUVsub, which requires further investigations.
乌苏图病毒（USUV）先前局限于非洲，在那里它引起了轻度感染，于 2001 年在欧洲出现，并在鸟类和人类中引起了更严重的感染，表现出适应和毒力增加。这种进化表明需要更好地了解 USUV 的传播模式，以评估风险并制定控制策略。在非洲进行的系统发育分析表明，非洲 USUV 株的遗传多样性较低，除了一种人类和 USUV 亚型（USUVsub）株之外，这些株在 3'UTR 中表现出缺失，并且整个基因组中的核苷酸取代。在这里，我们分析了它们在蚊子和哺乳动物细胞中的体外复制情况，以及库蚊的媒介能力，与参考株进行了比较。不同菌株的生长动力学显示出可比的复制率，但是在复制和翻译效率方面观察到了变化。媒介能力分析表明，所有菌株都能够感染库蚊，这是非洲主要的半家栖库蚊种，可检测到 USUV 病毒基因组和感染性颗粒。仅 USUVsub 观察到传播和传播，但在库蚊唾液中未检测到感染性颗粒。我们的研究结果表明，遗传变异可以以细胞类型依赖性的方式影响 USUV 的体外复制，以及在蚊子体内的复制。此外，结果表明库蚊对分析的 USUV 株不具有媒介能力，并且也表明 USUVsub 的传播过程被中止，这需要进一步调查。
