It is believed that the protein in the mosquito’s saliva could assist in the production of a universal vaccine against all the pathogens that mosquitoes carry: malaria, dengue fever, chikungunya, Zika, yellow fever, West Nile viruses and Mayaro, claims Jessica Manning, a researcher at the National Institute of Allergies and Infectious Diseases in the US.
On June 11th, British publication The Lancet published the first result of the research: the first clinical study ever conducted on a vaccine produced from mosquito saliva against diseases they cause in humans. The study showed that the vaccine triggered antibody and human cell responses.
Michael McCracken, a researcher not involved in the study, called the preliminary results “fundamental.” McCracken has worked at the Walter Reed Army Research Institute in Maryland and has studied immune responses to mosquito-borne viruses for several years. Malaria alone kills more than 400,000 people each year, according to the World Health Organization.
What Manning is looking for is called a vector-based vaccine. A vector is the living organism – like a mosquito – that transmits a pathogen such as malaria – to humans or from animals to humans. All existing vaccines for humans target a pathogen. Manning follows the vector. Her idea is to find a stimulus for the immune system to recognize the proteins in the mosquito’s saliva and give a reply to prevent infection with the viruses that come from it.
Scientists have been concerned with this subject for many years. A study on macaques, published in 2015, showed that vaccination with mosquito saliva reduced the size of lesions caused by leishmaniasis and the parasitological load. Another, performed on mice, published in 2018, showed that immunization with products derived from the saliva of anopheles mosquitoes reduced malaria. Another scientific report based on research on mice last year showed that the saliva of the Aedes mosquito improves the survival of animals infected with the Zika virus. The study published in The Lancet was conducted in 2017.
At Bethesda Clinic, Maryland, people were tested. 49 healthy volunteers participated. The volunteers were randomly assigned. Some received a placebo and others a version of the vaccine. After a few weeks, the hungry mosquitoes were placed on the arms of the study participants. The study measured the immune response to mosquito saliva proteins, but did not involve pathogens.
Several tests are needed to validate the effect of the vaccine on those infected with mosquito-borne pathogens. No major problems were identified, the Reuters correspondent said. Only one participant in the study had their skin reddened to an area of 8 centimeters around the injection site and was treated with steroids and antihistamines.
“I’m not as worried about redness as I would be if something systemic, like fever, headache, muscle aches, nausea, or vomiting, came in,” said Stephen Thomas, an infectious disease expert at SUNY Upstate Medical University. who was not involved in the study, Thomas previously worked in the US Department of Defense and helped manage Ebola, dengue and Zika vaccine programs.
Another scientist from the University of Maryland is researching a different vaccine formula, also from mosquito saliva. Meanwhile, Manning returned to Cambodia. She is working on the genomic sequencing of pathogens found in Aedes and Culex mosquitoes, some of which can infect humans. He discovered something worrying. “These mosquitoes carry a lot of different viruses than we already know,” he told Reuters.