Vertical transmission (VT) of arboviruses (arthropod-borne viruses) can serve as an essential link in the transmission cycle during adverse environmental conditions. The extent of VT among mosquito-borne arboviruses can vary significantly among different virus families and even among different viruses within the same genus. For example, orthobunyaviruses exhibit a higher VT rate than orthoflaviviruses and alphaviruses. Mosquitoes are also the natural hosts of a large number of insect-specific viruses (ISV) that belong to several virus families, including Bunyaviridae, Flaviviridae, and Togaviridae. Cell fusing agent virus (CFAV), an insect-specific orthoflavivirus, displays higher VT rates than other dual-host orthoflaviviruses, such as Zika and dengue viruses. High VT rates require establishment of stabilized infections in the germinal tissues of female vectors. To delve deeper into understanding the mechanisms governing these differences in VT rates and the establishment of stabilized infections, the ovary infection patterns and VT of Zika virus (ZIKV) and CFAV were compared. Laboratory colonized Aedes aegypti females were infected with either ZIKV or CFAV by intrathoracic injection. Ovary infection patterns were monitored by in situ hybridization using virus-specific probes, and VT was determined by detecting the presence of the virus among the progeny, using a reverse-transcription quantitative polymerase chain reaction (PCR) assay. Both ZIKV and CFAV infect mosquito ovaries after intrathoracic injection. Infections then become widespread following a non-infectious blood meal. VT rates of ZIKV are similar to previously reported results (3.33%). CFAV, on the contrary transmits vertically very rarely. VT was not observed in the first gonotrophic cycle following intrathoracic injection, and only rarely in the second gonotrophic cycle. VT of CFAV is mosquito population independent, since similar results were obtained with Aedes aegypti collected from two different geographic locations. Although CFAV infects mosquito ovaries, the occurrence of VT remains infrequent in artificially infected Ae. aegypti, despite the observation of high VT rates in field-collected mosquitoes. These results suggest that infections of insect-specific viruses are stabilized in mosquitoes by some as yet unidentified mechanisms.

中文翻译：

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细胞融合剂病毒很少在人工感染的实验室定植埃及伊蚊中垂直传播

虫媒病毒（节肢动物传播的病毒）的垂直传播（VT）可以作为不利环境条件下传播周期的重要环节。蚊媒虫媒病毒的 VT 程度在不同病毒科甚至同一属的不同病毒之间可能存在显着差异。例如，正布尼亚病毒表现出比正黄病毒和甲病毒更高的VT率。蚊子也是大量昆虫特异性病毒 (ISV) 的天然宿主，这些病毒属于多个病毒科，包括布尼亚病毒科、黄病毒科和披膜病毒科。细胞融合剂病毒 (CFAV) 是一种昆虫特异性正黄病毒，与其他双宿主正黄病毒（例如寨卡病毒和登革热病毒）相比，表现出更高的 VT 率。高VT率需要在雌性媒介的生发组织中建立稳定的感染。为了更深入地了解控制 VT 率差异和稳定感染建立的机制，比较了寨卡病毒 (ZIKV) 和 CFAV 的卵巢感染模式和 VT。实验室定植的雌性埃及伊蚊通过胸腔注射感染 ZIKV 或 CFAV。使用病毒特异性探针通过原位杂交监测卵巢感染模式，并使用逆转录定量聚合酶链反应（PCR）测定通过检测子代中病毒的存在来确定VT。 ZIKV 和 CFAV 均在胸腔内注射后感染蚊子卵巢。在非传染性的血餐后，感染就会广泛传播。 ZIKV 的 VT 发生率与之前报道的结果相似 (3.33%)。相反，CFAV 很少垂直传输。在胸腔内注射后的第一个促性腺营养周期中未观察到 VT，并且在第二个促性腺营养周期中很少观察到 VT。 CFAV 的 VT 与蚊子种群无关，因为从两个不同地理位置收集的埃及伊蚊获得了类似的结果。尽管 CFAV 感染蚊子卵巢，但在人工感染的伊蚊中，VT 的发生率仍然很少。埃及伊蚊，尽管观察到现场采集的蚊子的 VT 率很高。这些结果表明，昆虫特异性病毒的感染通过一些尚未确定的机制在蚊子中得到稳定。