Targeting mosquito spitting to stop the spread of the virus

A molecule present in the saliva of mosquitoes has been identified as a potential target for vaccination against a series of diseases for which there is neither protection nor medicine.

Researchers from the Virus-Host Interaction Team at the University of Leeds have found that the molecule, called sialokinin, facilitates the passage of a number of viruses from mosquitoes to humans, where they can then s install, leading to nasty and life-threatening illnesses.

These viruses include yellow fever, which causes severe illness in approximately 15% of those infected; dengue, which can progress to dengue fever, a life-threatening disease, and Zika, which caused a global medical emergency in 2016.

Our research suggests that blocking sialokinin may be an exciting new approach that prevents serious disease from infection with many different viruses.

Previous research determined that sialokinin was able to alter the function of blood vessel cells grown in the laboratory, allowing for increased blood flow and more efficient feeding of the mosquito. But experts were unsure what role it played in helping the virus infect the body.

By inspecting the behavior of sialokinin on mouse skin cells, the team discovered that the molecule makes blood vessels permeable, allowing contents to seep into the skin – which inadvertently helps viruses infect the skin. host.

Research Director Dr Clive McKimmie, Associate Professor at Leeds Medicine Schoolsaid: “We have identified sialokinin as a key component of mosquito saliva that aggravates infection in the mammalian host.

“Our research suggests that blocking sialokinin, for example through a vaccine or topical treatment, may be an exciting new approach that prevents serious disease following infection with many distinct viruses.”

Lead author Dr Daniella Lefteri worked on the study as a PhD researcher at Leeds Medical School. She is now a postdoctoral researcher at the University of Glasgow.

She said: ‘Our findings may also explain why some mosquitoes can transmit infection to humans, while others cannot. Anopheles mosquitoes cannot spread most viruses. Basically, we show that their saliva, which cannot leak blood vessels and cannot increase virus infection in the mammalian host, does not contain sialokinin.

“Our work has increased our understanding of how mosquito-derived factors influence infection in a host’s body.”

Virus transmitted by mosquitoes

Viruses transmitted by mosquitoes are known as arboviruses. They can affect humans and other mammals, such as cattle. In humans, symptoms usually appear three to 15 days after exposure and can last three to four days. The most common symptoms are a debilitating fever and headache, but more serious illnesses can occur and some infections can be fatal.

The mosquito genus Aedes, present on all continents except Antarctica, spreads arboviruses. Species include the Asian tiger mosquito and the yellow fever mosquito.

• Yellow fever infects people living in and visiting parts of South America and Africa. Symptoms include fever, chills, headache, back pain and muscle aches. About 15% of cases progress to serious illness that can be fatal.
• Dengue is contracted by people visiting or living in Asia, the Americas or the Caribbean. According to the World Health Organization5.2 million people contracted the disease in 2019. Half of the world’s population is now at risk of infection.
• The Zika virus is present in parts of South and Central America, the Caribbean, the Pacific Islands, Africa and Asia. It can harm a developing baby. In 2016, thousands of babies were born with brain damage after their mothers were infected during pregnancy.

There is currently no specific treatment or vaccine for dengue fever, Zika and other potentially serious mosquito-borne viruses including Chikungunya, West Nile virus, Semliki forest virus and Rift Valley fever.

The research team says future work should focus on identifying the other factors in mosquito saliva that help viruses infect hosts, and developing therapies to target and block them.

Dr McKimmie said: “One way to do that would be to develop a vaccine that generates neutralizing antibodies that bind to these factors, and so stop them from working and helping the virus.”