This is a study to file under "impracticable, but very cool." A group of Japanese researchers has developed a mosquito that spreads vaccine instead of the disease. Even the researchers admit, however, that regulatory and ethical issues prevent the creatures to ever take wing at least for the delivery of human vaccines.
scientists have devised various ways tinkering with the DNA of insects to fight against the disease. One option is to create strains of mosquitoes that are resistant to infection with parasites or viruses, or who are unable to pass the pathogens to humans. Ceux- it would somehow have to replace mosquitoes, carriers of natural disease, which is a challenge. another strategy closer to becoming reality is to release transgenic mosquitoes when they mate with their wild-type counterparts, do not produce viable offspring. It would reduce the population over time.
The new study is based on a very different mechanism: Use mosquitoes to become what scientists call "flying vaccinators" Normally, when biting mosquitoes, they inject a tiny drop of saliva prevents blood. host of coagulation. the Japanese group decided to add a compound-an antigen that elicits an immune response to the combination of proteins in the saliva of the insect.
a group led by Shigeto Yoshida the molecular geneticist from Jichi medical University in Tochigi, Japan, identified a region of the genome of Anopheles stephensi -a malaria mosquito called a promoter that turns on genes only in the saliva of insects. for this promoter they attached SP15, a candidate vaccine against leishmaniasis, a parasitic disease transmitted by sand flies that can cause skin damage and organ damage. in fact, mosquitoes SP15 products in their saliva, reports the team in the current issue of Insect Molecular Biology . And when the insects were allowed to feast on mice, the mice developed antibodies against SP15.
The antibody levels are not very high, and the team has yet to check whether they protect rodents against the disease. (Only a few laboratories have facilities for so-called challenge studies with this disease, says Yoshida.) In the experiment, the mice were bitten some 1,500 times on average; this may seem very high, but studies show that in areas where malaria is endemic, people are bitten more than 100 times a night, Yoshida says. In the meantime, the group mosquito also produce a vaccine against the malaria candidate.
Other researchers are impressed by the achievement. "Science is really beautiful," says Jesus Valenzuela of the National Institute of Allergy and Infectious Diseases in Bethesda, Maryland, who developed the SP15. David O'Brochta vaccine, a molecular geneticist insects at the University of Maryland , College Park, calls "a fascinating proof of concept."
So why not fly? There is a huge variation in the number of mosquito bites a person received in relation to the other, so people exposed to transgenic mosquitoes would get very different doses of the vaccine; it would be like to give some people a jab measles and other 500 of them. No regulator would sign it, said molecular biologist Robert Sinden from Imperial College London. The release of mosquitoes also mean vaccinating people without their informed consent, ethical no-no. Yoshida concedes that the mosquito would be "unacceptable" as a delivery mechanism of human vaccines.
However, vaccinators, or "flying syringes" as some have dubbed them -may have potential in the fight against the flying animal diseases, O'Brochta said. Animals shall not give consent, and the variable dosage would matter less.
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