Mosquito spit triggers surprising immune response: Study reveals

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Representational Image
Representational Image

New Delhi : Talk about mosquito and you will find them flying here and there all the year round. They are source of potentially serious diseases, generally transmitted by their bite. Researchers predict that mosquito saliva plays a key role in spreading diseases. To study the subject, a team of researchers at Baylor College of Medicine has observed the effect of mosquito saliva alone and found that it can trigger an unexpected variety of immune responses in an animal model of the human immune system. 

"Billions of people worldwide are exposed to diseases transmitted by mosquitoes, and many of these conditions do not have effective treatments," said corresponding author Dr. Rebecca Rico-Hesse, professor of molecular virology and microbiology at Baylor College of Medicine. "One of the interests of my lab is to study the development of dengue fever, which is caused by the dengue virus transmitted by mosquito Aedes aegypti."

Health experts at World Health Organization have calculated that 100 million dengue virus infections and 22,000 deaths occur yearly across the globe, and children are mostly affected. According to the Centers for Disease Control and Prevention, more than one-third of the world's population lives in areas at risk of infection, making the dengue virus a leading cause of illness and death in the tropics and subtropics.

"One of the main limitations for studying dengue fever is that the dengue virus only causes the disease in humans; no other animals can be used as models of the condition to develop preventive and therapeutic measures," Rico-Hesse said. "To overcome this challenge, we have been working with a mouse model of the human immune system."

"In 2012, we demonstrated in these humanized mice that mosquito-bite delivery and needle-injection delivery of dengue virus led to significantly different disease developments," Rico-Hesse said. "Importantly, mosquito-bite delivery of the virus resulted in a more human-like disease than the one we observed after needle-injection delivery of the virus. When the mosquitoes delivered the virus, the mice had more of a rash, more fever and other characteristics that mimic the disease presentation in humans."

Therefore, the observations meets the idea that mosquitoes are not just act like 'syringes,' but also inject viruses into the animals they feed on. And, their saliva seems to contribute to the development of the disease, which has prompted Rico-Hesse and her colleagues to investigate what this role might be. They began by determining the effect of bites from virus-free mosquitoes on the human immune response of humanized mice.

The results and the complete study is being published in the journal PLOS Neglected Tropical Diseases.