Mosquito vector competence for dengue is modulated by insect-specific viruses

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Aedes mosquitoes are the main vectors of dengue virus (DENV) and other arboviruses, including Zika virus (ZIKV), for which neither vaccine nor antiviral treatment is currently available. Understanding the factors that influence the transmission of arboviruses from mosquitoes to humans is therefore a priority because it could guide the implementation of public health measures that could limit or even prevent epidemics. In a study published on January 5, 2023 in the journal Nature Microbiology (https://pubmed.ncbi.nlm.nih.gov/36604511/), researchers from the team of Joao Marques at the Institute of Molecular and Cellular Biology in Strasbourg (CNRS UPR9022-ERL INSERM U1257) and at the Federal University of Minas Gerais in Belo Horizonte, Brazil, describe the collection of viruses (the virome) present in 800 mosquitoes collected in 6 countries and 4 continents. They identify 12 insect-specific viruses and show that two of them increase the multiplication of dengue and Zika viruses and their transmission to mammals. The mechanism involved reveals a new cellular factor hijacked by arboviruses in mosquitoes.

The mosquito Aedes aegypti is notoriously capable of transmitting viruses responsible for causing dengue, Zika, yellow fever, and chikungunya. In nature, these blood sucking mosquitoes enter in contact with viruses once biting in an infected individual. After the extrinsic incubation period, time between the mosquito acquiring the virus and effective release of infectious virus in the saliva, they can transmit the virus to another host upon feeding on their blood. This cycle can be affected by diverse factors such as virulence of circulating viruses, genetics of mosquito population, microbiota composition, or even by other viruses concurrently infecting the mosquito. In this work we show that two insect-specific viruses present worldwide, Humaita-Tubiacanga virus (HTV) and Phasi Charoen-like virus (PCLV), interact positively with dengue virus (DENV) and Zika virus (ZIKV) in the mosquito Ae. aegypti. This interaction leads to higher DENV and ZIKV loads and shortening of the extrinsic incubation period, accelerating virus transmission from the mosquito to another mammal and potentially impacting the progression of Aedes-borne disease outbreaks.

11 January 2023

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