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Genetically engineered mosquito vaccinates as it bites

An Anopheles mosquito ingesting a blood meal along with malarial parasites.
An Anopheles mosquito ingesting a blood meal along with malarial parasites.
Photo: CDC/James Gathany, 2004

Malaria is a parasitic infection that most individuals are familiar with.  It is a disease that is transmitted between individuals by the bite of an Anopheles mosquito.  Globally, there are several hundred million cases of malaria every year with over one million fatalities.  There are certainly treatments, yet as treatment resistance builds, prevention may become increasingly important.  Certainly, eradication of the disease would be the most favored outcome.

Over the years, scientists have looked at a multitude of ways to stop the spread of the parasite.  A new approach, reported in the journal Insect Molecular Biology, would genetically alter the Anopheles mosquito itself.  The approach would modify the salivary glands of the mosquito and turn it into a “flying vaccinator” of sorts.  The desired outcome would be a bite by a mosquito that would cause the body to produce a protective immune response.  Over a period of time, repeated exposure to the mosquito bites would serve the same function as getting a “booster shot,” high levels of immunity that last a long time.

Japanese scientists have already engineered a mosquito that produces a natural vaccine protein in its saliva.  The engineered mosquito carries a vaccine against Leishmania, a potentially fatal parasitic disease spread by sand flies.  Leishmania infections can cause painful sores, fever and weight loss, and if not treated may destroy the liver and spleen.  Laboratory mice bitten by the “engineered” mosquito produced antibodies against the Leishmania parasite, indicating immunization.  An effective vaccine for malaria has not been developed, and as such, this study is a “proof of concept.”  The study leader was Professor Shigeto Yoshida, from Jichi Medical University in Shimotsuki, Japan.

To the casual observer, bringing this concept to fruition would be a great scientific breakthrough, and could spur research into controlling other vector-borne diseases.  However, it could also present an interesting dilemma for medical ethicists.  A strategy that allows the mass delivery of vaccines, via biting insects, would have to be weighed against the need to obtain patient consent and monitor dosage.

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