探討埃及斑蚊唾液蛋白對登革病毒複製與病媒蚊攝食行為之影響

Abstract

登革病毒隸屬於黃病毒屬，而埃及斑蚊為傳播此病毒的重要病媒蚊之一，目前全球大約有1/3的人口暴露於受登革病毒感染的風險之中。登革病毒在病媒蚊體內的複製過程中，會與蚊子體內之蛋白有相互作用，而此階段對於病毒的繁殖極為關鍵。於過往的實驗裡，我們發現蚊子體內的一個唾腺蛋白並命名為AaSG34，其具有影響登革病毒複製與傳播之能力。AaSG34會促進登革病毒於蚊子唾腺內的複製，進而提高人類受病媒蚊叮咬後染疫的機率。然而，關於AaSG34於蚊子唾腺內如何調控登革病毒之複製，其詳細的分子機制則尚待釐清。因而本篇研究中，我們著重於探討AaSG34與登革病毒兩者間相互作用之詳盡分子機制。由於AaSG34特定表現於埃及斑蚊的唾腺，所以首先我們想了解埃及斑蚊的唾液是否會改變病毒的穩定性，我們的結果顯示，埃及斑蚊的唾液具有提升四型登革病毒穩定度與感染力之效益。透過Far-Western blotting assay及免疫沉澱法，我們也發現AaSG34與登革病毒之NS1、E此兩種病毒蛋白之間具有交互作用。並且在抑制AaSG34的情況下，會促進蚊子體內部分的抗菌?(Antimicrobial peptides, AMP)的表現上升致使登革病毒的複製量降低。此外，我們同時發現AaSG34表現量降低會影響部分嗅覺結合蛋白(olfactory binding protein, OBP)的基因表現，進而使埃及斑蚊的吸血行為產生改變。綜觀我們的研究結果，AaSG34除具有調控登革病毒的複製能力外，尚與病媒蚊吸血行為存在著關聯性，此二者與登革病毒之傳播脣齒相依。因而我們認為此篇研究在未來，將有助於病蚊媒傳播疾病防治策略之制定。

Dengue virus (DENV) is a member of the genus Flavivirus that causes dengue fever and is responsible for tremendous human morbidity and mortality worldwide. DENV is transmitted to humans by Aedes aegypti mosquitoes. During viral replication in the mosquito and transmission to a new host, DENV interacts with a variety of mosquito proteins, which are important for each step of the viral cycle. We have recently investigated the effect of a salivary protein AaSG34 on DENV replication and transmission. We demonstrated that AaSG34 increases DENV replication in mosquito salivary glands and promotes the viral transmission to the mammalian host. However, the detailed molecular mechanisms of how AaSG34 regulates DENV replication and the role of AaSG34 in mosquito salivary glands remain largely unknown. In this study, we aim to investigate the detailed molecular interactions between AaSG34 and DENV. Given that AaSG34 is a salivary gland-specific protein, we first determined the effect of mosquito saliva in maintaining virus stability. We showed that the saliva of Aedes aegypti significantly stabilizes DENV and promotes the infectivity of four serotypes of DENV. We also showed that AaSG34 interacts with DENV NS1 and E proteins by Far-Western blotting analysis and immunoprecipitation assay. Inhibition of AaSG34 enhanced several antimicrobial peptides (AMPs) and suppressed dengue viral replication in mosquitoes. In addition, we have observed that silencing of AaSG34 resulted in the impairment of mosquito feeding frequency probably which were through regulating olfactory binding proteins (OBPs). Taken together, our results suggested that AaSG34 plays a dual role in the promotion of dengue virus replication and the host-seeking behavior of mosquitoes. In consequence, clarifying the function of AaSG34 provides new tools for generating novel vector control strategies in the future.