A protein present in the saliva of mosquitoes, vectors of Zika and dengue, promotes viral infection in humans.
- A protein found in the saliva of mosquitoes that transmit the Zika and dengue viruses promotes viral infection, a new study suggests.
- It’s called Nest1. It binds to a molecule called CD47 and thus blocks several human immune functions.
- This discovery could help in the development of treatments against mosquito-borne diseases.
Zika, dengue, chikungunya, yellow fever… The mosquito Aedes aegypti is a vector of many diseases. Researchers at Yale School of Medicine have reportedly found the key to this ability to contaminate. A protein called Nest1, present in the saliva of these insects, promotes viral infection.
Their work was the subject of an article published in the journal Science Immunology.
Aedes aegypti mosquitoes: a protein in their saliva inhibits the immune system
Mosquito saliva contains many other molecules that affect their hosts. “Many of these compounds are thought to help the mosquito feed, for example by preventing blood clots. We wanted to know if mosquito saliva contained compounds that could increase viral infectivity.”explains Dr. Erol Fikrig, co-senior author of the study.
The researchers were particularly interested in the Nest1 protein present in the saliva of Aedes aegypti mosquitoes, which had been highlighted in previous studies. First, the team exposed human skin samples to the Zika virus in the presence or absence of Nest1. They found that the virus replicated much faster in human skin when it was associated with the protein. The scientists concluded that Nest1 interacts with biological molecules in the epidermis. To identify which ones, they tested the mosquito protein with more than 2,600 human proteins. They noticed that Nest1 bound strongly to a molecule called CD47 (Cluster of Differentiation 47). The latter is known to be involved in a number of immune processes.
“Through its interaction with CD47, Nest1 was able to inhibit key immune functions such as phagocytosis (in which a cell ingests and neutralizes pathogens or cellular debris), reduce the activity of several protective immune pathways, and increase the activity of pathways involved in virus replication, the researchers found. The overall effect was to suppress antiviral responses in the skin and boost viral activity.”explain the authors in their press release.
The discovery could lead to the development of new treatments for mosquito-borne diseases, the team said. “For example, we could develop a treatment that would block Nest1, perhaps with a monoclonal antibody, which would decrease the favorable environment that Nest1 creates for the virus at the site of the mosquito bite,” Fikrig said. “This could be done alone or in combination with a traditional pathogen-based vaccine, which would make the vaccine more effective.”
Triple E, dengue fever…: an increase in diseases transmitted by mosquitoes
The mosquito is not just an insect with annoying noises and an itchy bite. Responsible for 800,000 deaths each year, the insect is the most dangerous animal for humans. Thus, the expansion of the tiger mosquito in Europe and the growing number of cases of imported or indigenous dengue fever in France raises fears. Last June, the European Center for Disease Prevention and Control (ECDC) warned of the increase in mosquito-borne diseases in the EU. The agency recalled that it had recorded 130 “local” cases and more than 4,900 imported cases of dengue fever in 2023, compared to 71 and 1,572 cases respectively in 2022. Regarding the circulation of the West Nile virus last year, “The number of affected regions is the highest since the peak in 2018, indicating a wide geographical circulation of the virus,” noted the ECDC.
Europeans are not the only ones worried about these insects and the viruses they carry. American authorities have been on high alert since the identification in August of two human cases of Eastern equine encephalitis, a disease transmitted by mosquitoes. Melanura Culiseta. Both patients were infected in northeastern states of the country. The death of one of them was announced on August 27.
In the United States, encephalitis is fatal in 30% of cases
This disease also called Triple E is “rare, but serious”. While the majority of those affected do not show symptoms, some have flu-like symptoms (fever, headaches, chills, joint pain). In severe cases, Eastern equine encephalitis causes central nervous system damage that is fatal in 30% of cases. In addition, neurological sequelae have been observed in 50% of patients who survive the infection. To reduce the risk of contamination, several states in the northwest of the United States, including New Hampshire and Massachusetts, have taken measures such as closing parks or spraying mosquito repellent.