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Gambia News: Immune Gambians provide malaria vaccine hope

A vaccine for malaria looks tantalisingly close: researchers have isolated antibodies from the blood of people who have a natural immunity to the disease. When injected, the antibodies protected against malaria infection in a mouse study, researchers say.

The original antibodies – from 10 Gambians with a rare, natural immunity – were refined and strengthened using a novel animal testing system which for the first time mimics in mice the way malaria infects humans.

The new mouse model developed in the experiment could prove a useful screening tool to test other experimental antibodies, the researchers say.

Richard Pleass at the University of Nottingham, UK, and colleagues, who isolated and re-engineered the antibodies, are now hoping to start clinical trials to test the antibodies in humans.

Modified mice

At present, no reliable animal model exists for malaria. Mice do not get ill when infected by Plasmodium falciparum, the blood-borne parasite that causes malaria in people. And the immune system of mice shows a different response to humans when it comes into contact with the parasite.

This meant that, despite making a promising human antibody vaccine that had worked against the parasite in a lab dish, the team could not test it in a living animal.

Pleass's team got around the problem by creating a mouse model of the human malaria infection. They took a closely related mouse parasite, Plasmodium berghei, and genetically modified it to produce an antigen that the human immune system recognises.

Best model

Next, they genetically altered the mouse's immune system to produce a "human molecule" on its white blood cells that recognises the parasite and destroys it. The team hoped that the Gambian antibodies in the mouse's blood would find and capture the parasite, allowing the modified white blood cells to destroy it.

“We have made the best possible animal model you can get in the absence of working on humans or higher primates,” says Pleass.

In trials using the modified rodents, the team showed the antibodies protected mice from the parasite - all the mice that did not receive the antibody injection died.