Why do Aedes mosquitoes catch and transmit dengue virus?

Biology

A number of viral diseases, such as dengue, Zika, Chikungunya, and yellow fever are transmitted to humans by the same intermediary: the Aedes aegypti mosquito. However, like other insects, this mosquito possesses antiviral defenses based the mechanism of RNA interference: small RNA molecules that can specifically degrade the genetic material of the virus, thereby blocking its multiplication and dissemination in the organism. Yet why is this system seemingly incapable of stopping dengue virus in the Aedes mosquito?

Teams from the laboratory Modèles insectes de l'immunité innée (CNRS/Inserm) and the Federal University of Minas Gerais (Brazil) have just discovered the existence in Aedes of a gene called Loqs2, which is indispensable to the proper functioning of RNA interference in the mosquito, but is not operative in its intestine! Without it, the viruses in the blood on which the mosquito feeds can multiply and subsequently infect its salivary glands. Aedes then transmits this virus during its next meal. Surprisingly, Loqs2 is not present in the genome of other related mosquitoes, which are not vectors of the virus. Researchers deduced that this gene could provide a key to understanding this distinctive feature of Aedes mosquitoes.

Aedes aegypti mosquitoes are vectors of multiple viral diseases, such as dengue, Zika, Chikungunya, and yellow fever. Mosquitoes that bite an infected human can become infected and capable of transmitting the disease to another human, thereby maintaining the cycle of transmission. © Roenick Olmo
Loqs2 is a newly discovered element of the antiviral defenses of Aedes aegypti mosquitoes. It plays an important role in controlling the dengue and Zika viruses during their systemic dissemination within mosquitoes, however it has no effect on the infection of the intestine. The expression of the Loqs2 gene artificially provoked in the intestine of mosquitoes makes them more resistant to the dengue and Zika viruses by decreasing viral replication and dissemination toward other tissue. © Roenick Olmo

 

Bibliography

Control of dengue virus in the midgut of Aedes aegypti by ectopic expression of the dsRNA-binding protein Loqs2. Roenick P. Olmo, Alvaro G. A. Ferreira, Tatiane C. Izidoro-Toledo, Eric R. G. R. Aguiar, Isaque J. S. de Faria, Kátia P. R. de Souza, Kátia P. Osório, Lauriane Kuhn, Philippe Hammann, Elisa G. de Andrade, Yaovi Mathias Todjro, Marcele N. Rocha, Thiago H. J. F. Leite, Siad C. G. Amadou, Juliana N. Armache, Simona Paro, Caroline D. de Oliveira, Fabiano D. Carvalho, Luciano A. Moreira, Eric Marois, Jean-Luc Imler and João T. Marques. Nature Microbiology, October 29, 2018. DOI : 10.1038/s41564-018-0268-6

Contact

Jean-Luc Imler
Enseignant-chercheur Université de Strasbourg
Joao Marques
Chercheur CNRS - Université fédérale de Minas Gerais
François Maginiot
CNRS Press Officer