Wednesday, 30 May 2012

Backyard algae may yield malaria vaccine

People living in malarial areas could produce their own vaccine against the killer disease by growing genetically engineered algae in their backyards at very low cost, researchers say.

The algae is being researched as a candidate vaccine for malaria because it blocks the reproductive cycle of the mosquito-borne parasite, Plasmodium falciparum.
The new developments could mean that people are able to grow their own vaccine against malaria, for which there is currently no effective vaccine.

Several potential vaccines are being developed, but many of them involve complex proteins which are hard to produce in the laboratory, as well as expensive.

Writing in the online open-access journal PLoS One, researchers in the United States said that algal cells were a very cheap way of cultivating vaccine candidates, and could break the transmission path from mosquitoes to humans.

The potential vaccine hinges on an edible green microalgae called Chlamydomonas reinhardtii, which was engineered to produce the protein Pfs25 by Stephen Mayfield, of the San Diego Center for Algae Biotechnology at the University of California.

This protein is normally produced by the Plasmodium parasite when it is inside the gut of the host mosquito.

The proteins would stimulate the production of antibodies that can block the parasite's reproductive cycle in the gut of the mosquito.

According to Joseph Vinetz, a professor of medicine at the University of California San Diego, the vaccine would be given to humans, but it would only act once inside the mosquitoes.

Effectively, humans would be acting as antibody delivery devices to the mosquito population which bit them, he said.

Laboratory mice that were injected with Pfs25 produced these antibodies, researchers said.

Mayfield described the research as a "game-changer" for the developing world.

Such a vaccine could be made at very little cost at a local level by local people, who could feed it to themselves and each other by adding it to existing foods.

The algae, which are cultivated in other developing countries in Africa, South Asia and East Asia, could easily be grown in water tanks with access to sunlight.

Conventional vaccines currently require large investments in their delivery networks, distribution, production and correct storage.

According to Colin Sutherland of the London School of Hygiene and Tropical Medicine, the algal system is a promising development towards solving the technical challenges in producing these proteins.

But some experts said there was a danger that self-administered vaccines could end up producing resistance in the organisms they targeted. They also said that the protein itself remained untested in humans.

According to Peter Seeberger, director of the Max Planck Institute of Colloids and Interfaces in Germany, the best strategy would be to develop a vaccine that combines different modes of action, targeting different aspects of the parasite at once.

The researchers will now move on to test the safety and efficacy of the algal-borne vaccine administered to mice via their food supply.

The first human clinical trials could take place as soon as the summer of 2013, if the necessary funding is in place.


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