Abstract
Mosquitoes are natural vectors for many etiologic agents of human viral diseases. Mosquito-borne flaviviruses can persistently infect the mosquito central nervous system without causing dramatic pathology or influencing the mosquito behavior and lifespan. The mechanism by which the mosquito nervous system resists flaviviral infection is still largely unknown. Here we report that an Aedes aegypti homologue of the neural factor Hikaru genki (AaHig) efficiently restricts flavivirus infection of the central nervous system. AaHig was predominantly expressed in the mosquito nervous system and localized to the plasma membrane of neural cells. Functional blockade of AaHig enhanced Dengue virus (DENV) and Japanese encephalitis virus (JEV), but not Sindbis virus (SINV), replication in mosquito heads and consequently caused neural apoptosis and a dramatic reduction in the mosquito lifespan. Consistently, delivery of recombinant AaHig to mosquitoes reduced viral infection. Furthermore, the membrane-localized AaHig directly interfaced with a highly conserved motif in the surface envelope proteins of DENV and JEV, and consequently interrupted endocytic viral entry into mosquito cells. Loss of either plasma membrane targeting or virion-binding ability rendered AaHig nonfunctional. Interestingly, Culex pipien pallens Hig also demonstrated a prominent anti-flavivirus activity, suggesting a functionally conserved function for Hig. Our results demonstrate that an evolutionarily conserved antiviral mechanism prevents lethal flaviviral infection of the central nervous system in mosquitoes, and thus may facilitate flaviviral transmission in nature.
Highlights
Mosquitoes transmit many human pathogens of medical importance throughout the world
The central nervous system plays a predominant role in organisms associated with cognition and higher-order functions, which is key to their normal behavior and successful survival
Mosquitoes are highly permissive to flaviviral infection that can be persistent in the mosquito nervous system
Summary
Mosquitoes transmit many human pathogens of medical importance throughout the world. Flaviviruses, such as West Nile (WNV), Japanese Encephalitis (JEV), Dengue (DENV) and Yellow Fever (YFV) viruses that are transmitted by mosquitoes are the etiologic agents of human hemorrhagic fever, encephalitis and meningitis [1]. Mosquitoes are very permissive to and allow systematic and persistent flavivirus infection [2,3]. The head of mosquitoes, where the central neural system locates, can maintain productive flavivirus infection [4]. The ability of the neural antiviral mechanisms to control viral replication and to maintain a normal mosquito lifespan may facilitate viral dissemination in nature. The machinery that controls flavivirus infection of the mosquito nervous system is still largely unknown
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