A recent study sheds light on the Aedes aegypti mosquito and its role in transmitting viral diseases, as well as new ways to understand its immune system and utilize it in fighting infection.
The Aedes aegypti mosquito, also known as the yellow fever mosquito, is a highly adapted invasive species and is considered one of the world’s major health threats, as it is a major vector for a number of serious diseases, most notably dengue fever, in addition to yellow fever, chikungunya fever and Zika virus.
Health authorities rely on regular monitoring of this mosquito to detect the viruses it carries and track its spread. However, this monitoring mostly depends on traditional techniques such as reverse transcription polymerase chain reaction (RT-PCR), which only detect previously known viruses for which specific tests have been developed.
In recent years, high-throughput RNA sequencing techniques have provided a broader understanding of mosquito-associated viruses, also known as "insect viruses," which live inside the mosquito's body. However, important questions remain about how these viruses persist within mosquito colonies, how they interact with the mosquito's immune system, and their transmissibility.
In this context, researchers from Boston University School of Medicine (Chopanian and Avedesian) conducted a new study that focused on the immune response of mosquitoes with the aim of discovering additional unknown viruses.
The study is based on the idea that viruses that infect mosquitoes produce double-stranded RNA molecules, which activate a defense mechanism within the mosquito known as RNA interference (RNAi). This mechanism breaks down the virus's genetic material and converts it into smaller fragments (vsmRNAs), which help to limit infection.
Researchers were able to track these fragments to discover viruses present inside Aedes aegypti mosquitoes, which are prevalent in warm-weather cities like Miami and Sacramento. The results showed that these mosquitoes carry a large number of viruses, some of which are globally widespread, while others are confined to specific regions, such as the Formosus virus, which has been detected in mosquito strains originating in Africa.
The study also revealed an ongoing conflict between these viruses and the mosquito's immune system, showing that some viruses are able to evade or hide from the basic defense mechanism (RNAi).
Researchers collected samples of Aedes aegypti mosquitoes from multiple regions, including North and Central America, Africa, and Asia. They then analyzed the small RNA (immune response) and compared it to the active viral RNA. This analysis contributed to the discovery of new viruses and a deeper understanding of disease transmission mechanisms.
Dr. Nelson Lau, an associate professor at Boston University, explained that these findings could open the door to using elements of the mosquito's own immune system as a future tool to reduce the spread of viruses, and perhaps to develop ways to make mosquitoes more resistant to pathogens that are transmitted through them to humans.
The study's findings were published in the journal Nature Communications.
