Using mosquitoes to vaccinate humanity

Image credit: Nature Journal

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Krishna: Yes, scientists are trying this method.

For instance, scientists have developed a new vaccination strategy for malaria — boosting immunity through bites from mosquitoes carrying a genetically engineered version of the parasite that causes malaria. Bites from insects infected with modified malaria parasites boosted immunity and stopped people from contracting the disease (1).

Scientists have genetically modified malaria parasites so that a mosquito bite is protective rather than pathogenic.

After decades of research, two new breakthrough vaccines were developed in recent years that promise to help reduce infections. And a new trial published in the New England Journal of Medicine could pave the way for a new vaccine delivered by mosquito bite.

The researchers genetically modified the parasite so that it dies six days after a mosquito bite sends it into the body, when it is still in the first stage of its life cycle in the liver. Normally, it moves from this liver stage into the bloodstream, where it causes infection and symptoms begin.

But because the parasite dies before it infects the blood cells and evolves into its deadly phase, it instead acts as a way of priming the immune system, as a vaccination usually would.

The researchers developed a genetically modified parasite that they called GA1, and then created a second iteration they called GA2 in which development was arrested later on in the liver stage.

They decided to test both on a small group of participants by exposing them to mosquitoes.

One group (eight people) were bitten by mosquitoes with GA1 parasites, a second group (nine people) with GA2, and the third group (three people) were in the placebo group (they were bitten by uninfected mosquitoes).

After three weeks, all participants were exposed to malaria-carrying mosquitoes to test the vaccine’s efficacy.

The results were striking. Before being exposed to malaria-carrying mosquitoes, both groups who had been bitten with modified mosquitoes showed increased antibody levels. However, the GA2 group had a strong immune protection of 89% compared with the GA1 group (13%). The only reported side effects were minor itching from the mosquito bites. (2)

The researchers noted that although this was a very small study and this approach will need further investigation, the efficacy of the vaccine and the lack of breakthrough infections were promising.

Footnotes:

1. This malaria vaccine is delivered by a mosquito bite
2. https://www.nejm.org/doi/10.1056/NEJMoa2313892