Department of Biomedical Sciences and Pathobiology, Virginia Tech, VA-MD College of Veterinary Medicine, Blacksburg, Virginia, USA.
Center for Emerging, Zoonotic, and Arthropod-borne Pathogens, Virginia Tech, Blacksburg, Virginia, USA.
Insect Mol Biol. 2023 Dec;32(6):648-657. doi: 10.1111/imb.12863. Epub 2023 Jun 19.
Chikungunya virus (CHIKV) is an alphavirus that has re-emerged globally over the last two decades and has the potential to become endemic in the United States due to the presence of competent mosquito vectors, Aedes aegypti and Aedes albopictus. CHIK disease is characterised by fever, rash, and joint pain, and causes chronic debilitating joint pain and swelling in >50% of infected individuals. Given the disease severity caused by CHIKV and the global presence of vectors to facilitate its spread, strategies to reduce viral transmission are desperately needed; however, the human biological factors driving CHIKV transmission are poorly understood. Towards that end, we have previously shown that mosquitoes fed on alphavirus-infected obese mice have reduced infection and transmission rates compared to those fed on infected lean mice despite similar viremia in lean and obese mice. One of the many host factors that increase in obese hosts is insulin, which was previously shown to impact the infection of mosquitoes by several flaviviruses. However, insulin's impact on alphavirus infection of live mosquitoes is unknown and whether insulin influences mosquito-borne virus transmission has not been tested. To test this, we exposed A. aegypti mosquitoes to bloodmeals with CHIKV in the presence or absence of physiologically relevant levels of insulin and found that insulin significantly lowered both infection and transmission rates. RNA sequencing analysis on mosquito midguts isolated at 1-day-post-infectious-bloodmeal (dpbm) showed enrichment in genes in the Toll immune pathway in the presence of insulin, which was validated by reverse transcription-quantitative polymerase chain reaction (RT-qPCR). We then sought to determine if the Toll pathway plays a role in CHIKV infection of Ae. aegypti mosquitoes; therefore, we knocked down Myd88, a critical immune adaptor molecule for the Toll pathway, in live mosquitoes, and found increased CHIKV infection compared to the mock knockdown control group. Overall, these data demonstrate that insulin reduces CHIKV transmission by Ae. aegypti and activates the Toll pathway in mosquitoes, suggesting that conditions resulting in higher serum insulin concentrations may reduce alphavirus transmission. Finally, these studies suggest that strategies to activate insulin or Toll signalling in mosquitoes may be an effective control strategy against medically relevant alphaviruses.
基孔肯雅病毒（CHIKV）是一种甲病毒，在过去二十年中在全球再次出现，并有可能由于存在有能力的蚊子媒介埃及伊蚊和白纹伊蚊而成为美国的地方病。CHIK 病的特征是发热、皮疹和关节痛，并导致 >50%感染个体出现慢性衰弱性关节痛和肿胀。鉴于 CHIKV 引起的疾病严重程度和传播它的全球存在的媒介，急需减少病毒传播的策略；然而，驱动 CHIKV 传播的人类生物学因素理解甚少。为此，我们之前曾表明，与感染瘦鼠相比，感染肥胖鼠的蚊子在摄入感染的肥胖鼠的血餐后感染和传播率降低，尽管瘦鼠和肥胖鼠的病毒血症相似。肥胖宿主中增加的宿主因素之一是胰岛素，它以前被证明会影响几种黄病毒对蚊子的感染。然而，胰岛素对活体蚊子感染的影响尚不清楚，也没有测试胰岛素是否影响蚊媒病毒传播。为了测试这一点，我们在存在或不存在生理相关水平的胰岛素的情况下，使 A. aegypti 蚊子接触含 CHIKV 的血餐，并发现胰岛素显著降低了感染和传播率。在感染含 CHIKV 的血餐后 1 天（1-day-post-infectious-bloodmeal，1-dpbm）分离的蚊子中肠的 RNA 测序分析显示，在胰岛素存在时，Toll 免疫途径中的基因富集，通过反转录定量聚合酶链反应（RT-qPCR）进行验证。然后，我们试图确定 Toll 途径是否在 CHIKV 感染埃及伊蚊中起作用；因此，我们在活体蚊子中敲低了 Toll 途径的关键免疫衔接分子 Myd88，与模拟敲低对照组相比，发现 CHIKV 感染增加。总体而言，这些数据表明胰岛素降低了埃及伊蚊传播 CHIKV 的能力，并激活了蚊子中的 Toll 途径，表明导致血清胰岛素浓度升高的情况可能会降低甲病毒的传播。最后，这些研究表明，在蚊子中激活胰岛素或 Toll 信号的策略可能是针对具有医学意义的甲病毒的有效控制策略。
