Malaria vaccine trials are qualified success.

Malaria vaccine trials are qualified success

The first vaccine against the disease-causing stages of the malaria parasite induced partial immunity in a small number of human volunteers, scientists report. Using a prototype vaccine made from three synthesized proteins, Manuel Patarroyo and his colleagues at the National University of Colombia and the Central Military Hospital in Bogota reduced the severity of disease in 3 of the 5 people who were given the vaccine in the trial, according to a report published in the March 10 NATURE.

Malaria is a major public health problem in developing countries, killing millions each year and causing the death of one-quarter of all children born in central Africa. Because some strains of the parasite have grown resistant to antimalaria drugs, many groups around the world have been searching for a vaccine.

The synthesized proteins in the Colombian vaccine were copies of proteins carried by the malaria parasite Plasmodium falciparum during its asexual erythrocyte stages. In these stages, which make up one phase of the parasite's complex life cycle, the organisms can multiply asexually in the host's red blood cells, or erythrocytes, damaging organs and causing fever.

P. falciparum enters the body when a mosquito injects the sporozoite form of the parasite while feeding on blood. The sporozoite travels to the liver and lodges there, emerging seven days later in the first of the asexual erythrocyte forms. While the new vaccine can provide partial protection against the symptoms that result from parasite reproduction in blood cells, it does not protect against the sporozoite form of the parasite. A vaccinated person could still be infected with the sporozoite if bitten by a carrier mosquito, but would not be totally debilitated by disease.

In an article in the same issue of NATURE, malaria researcher Louis Miller of the National Institute of Allergy and Infectious Diseases notes that human trials of vaccines against asexual forms of malaria carry risks for the subjects. Now that the Colombian trials have shown some success, he suggests, researchers should use monkeys to determine if they can improve the vaccine by using other malaria proteins and to test it against other strains of P. falciparum.