Arbovirus Laboratory, Wadsworth Center, New York State Department of Health, 5668 State Farm Road, Slingerlands, NY, 12159, USA.
Parasit Vectors. 2024 Apr 4;17(1):177. doi: 10.1186/s13071-024-06232-6.
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.
垂直传播（VT）的虫媒病毒（节肢动物传播的病毒）可以作为不良环境条件下传播周期的重要环节。虫媒病毒中的 VT 程度在不同病毒科之间甚至同一属内的不同病毒之间差异很大。例如，正粘病毒的 VT 率高于黄病毒和甲病毒。蚊子也是大量昆虫特异性病毒（ISV）的天然宿主，这些病毒属于几个病毒科，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）是一种昆虫特异性黄病毒，其 VT 率高于其他双宿主黄病毒，如寨卡病毒和登革热病毒。高 VT 率需要在雌性载体的生殖组织中建立稳定的感染。为了更深入地了解这些 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。
通过胸内注射感染实验室饲养的埃及伊蚊雌性，用病毒特异性探针进行原位杂交监测卵巢感染模式，并用逆转录定量聚合酶链反应（PCR）检测病毒在后代中的存在来确定 VT。
ZIKV 和 CFAV 经胸内注射均可感染蚊子卵巢。感染后，在非传染性血餐后广泛传播。ZIKV 的 VT 率与之前的报道结果相似（3.33%）。相反，CFAV 很少垂直传播。在胸内注射后的第一个生殖周期中未观察到 VT，在第二个生殖周期中也很少观察到。CFAV 的 VT 与蚊群无关，因为从两个不同地理位置采集的埃及伊蚊获得了相似的结果。
尽管 CFAV 感染蚊子卵巢，但在人工感染的埃及伊蚊中 VT 仍然很少见，尽管在野外采集的蚊子中观察到高 VT 率。这些结果表明，昆虫特异性病毒的感染在蚊子中通过一些尚未确定的机制得到稳定。
