Researchers at Baylor College of Medicine found that mosquito saliva can affect immune system resulting infections caused by a mosquito bite more severe than those caused by needle injection of parasite.
"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."
The World Health Organization [WHO] has estimated that over 100 million dengue virus infections and 22,000 deaths occur yearly worldwide, mostly among children.
The main limitations for studying dengue fever is that dengue virus only causes the disease in humans, so no other animals can be used as models of the condition to develop preventive and therapeutic measures. To overcome this situation, researchers have worked with mice engineered to have human immune system.
Previous studies have shown that in these humanized mice, mosquito-bite delivery and needle-injection delivery of dengue virus led to significantly different disease developments. Mosquito-bite delivery of the virus resulted more human-like disease than the needle-injection delivery of the virus. When the mosquitoes delivered the virus, the mice had more of rash, more fever and other characteristics that mimic the disease presentation in humans.
Those observations support the theory that mosquitoes are not just acting like 'syringes', merely injecting viruses into the animals they feed on, their saliva seems to contribute significantly to the development of the disease.
To test it, researchers took blood and a number of other tissue samples from anesthetized humanized mice that were bitten by a handfulof mosquitoes. They compared these data with those obtained from humanized mice that had not been bitten by mosquitoes.
After thoroughly examining the results, the researchers found that mosquito saliva alone can trigger long-lasting immune responses - up to seven days post-bite - in multiple tissue types, including blood, skin and bone marrow.
The researchers will continue this study by investigating which of the more than 100 proteins in mosquito saliva are mediating the effects on the immune system, or may help the virus become more infectious.
Identifying these proteins could help design strategies to fight transmission of dengue fever, as well as other diseases caused by viruses also transmitted by Aedes aegypti, such as Zika, chikungunya and yellow fever.
Original Source: Baylor College of Medicine
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