New malaria vaccine is off to promising start

An experimental vaccine against malaria induces an immune response in people over the course of 1 year similar to that mustered over a lifetime by people living in malarial zones, a study in the November PLoS Medicine shows.

People exposed to malaria churn out countless antibodies against the disease-causing parasite, but these immune system proteins fail to induce instant immunity, says physician Pierre Druilhe of the Pasteur Institute in Paris. Protection is built up through a combination of immune processes only gradually with constant exposure to the parasite, he says.

Some antibodies play key roles in fostering this natural immunity. One in particular responds to a protein on the parasite’s surface by activating white blood cells called monocytes. Lab tests of monocytes taken from infected people have shown that, once activated, these cells can kill the parasite.

Druilhe and his colleagues gave a vaccine based on a synthetic version of the surface protein in three injections to 30 European volunteers who had never been exposed to malaria. The protein is called malaria merozoite surface protein 3, or MSP3.

Blood tests after 5 and 12 months showed that 23 of the 30 volunteers had produced significant antibodies against MSP3. Furthermore, 29 volunteers had geared up an army of other immune cells, called T cells, against the parasite. The responses rival those seen in African adults who routinely fend off malaria, say the researchers.

The vaccine caused no serious side effects. Druilhe’s team is now preparing to vaccinate African children in malarial zones to test the new vaccine against the actual disease.

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