Targeted mosquito spit to stop the spread of viruses

A molecule in mosquito saliva has been identified as a potential target for vaccination against a range of diseases for which there is no protection or cure.

Researchers from the Virus Host Interaction Team at the University of Leeds have found that the molecule, called sialokinin, makes it easier for a number of viruses to pass from mosquitoes to humans, where they can then burrow – leading to unpleasant and potentially deadly diseases.

These viruses include yellow fever, which causes serious illness in about 15% of infected people; dengue fever, which can develop into the potentially deadly disease dengue fever, and Zika, which caused a worldwide medical emergency in 2016.

Our research suggests that blocking sialokinin may be an exciting new approach that prevents severe disease after infection with numerous different viruses.

Previous research found that sialokinin could alter the function of lab-grown blood vessel cells, allowing increased blood flow and more effective nutrition for the mosquito. But experts weren’t sure what role it played in helping the virus infect the body.

When inspecting the behavior of sialokinin on mouse skin cells, the team found that the molecule causes blood vessels to become permeable, allowing its contents to leak into the skin — inadvertently helping viruses infect the host.

Research Supervisor Dr Clive McKimmie, Associate Professor at Leeds’ Medical Facultysaid: “We have identified sialokinin as a key component in mosquito saliva that exacerbates the 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 severe disease after infection with a variety of viruses.”

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

She said: “Our findings may also explain why some mosquitoes can spread infections to humans, while others can’t. Anopheles mosquitoes cannot spread most viruses. Crucially, we show that their saliva, which cannot cause leaky blood vessels.” and cannot potentiate the infection of the virus in the mammalian host, does not contain sialokinin.

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

Mosquito-borne viruses

Viruses spread by mosquitoes are called arboviruses. They can affect humans and other mammals, such as livestock. In humans, symptoms usually appear three to 15 days after exposure and can last for three to four days. The most common symptoms are debilitating fever and headaches, but more serious illnesses can occur and some infections are fatal.

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

• Yellow fever affects people who live in and visit parts of South America and Africa. Symptoms include fever, chills, headache, backache, and muscle aches. About 15% of cases develop into a serious illness that can be fatal.
• Dengue is contracted by people who visit or live in Asia, America 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 being infected.
• The Zika virus is found 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 became infected during pregnancy.

There are currently no specific treatments or vaccines for dengue, Zika, and other potentially serious mosquito-borne viruses, including Chikungunya, West Nile virus, Semliki Forest virus, and Rift Valley fever virus.

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 this would be to develop a vaccine that generates neutralizing antibodies that bind to these factors, thereby preventing them from working and helping the virus.”