An antidrug malaria pump?

An antidrug malaria pump?

The drug resistance of malaria-causing parasites may be due to a highly effective "sump pump' that can expel a common antimalaria medication, scientists reported last week. But, say the scientists, this mechanism can be inhibited by other drugs that could be added to the therapy regimen for malaria.

Researchers at Washington University in St. Louis and Walter Reed Army Institute of Research in Washington, D.C., say that Plasmodium falciparum parasites resistant to the commonly used drug choloroquine apparently release the drug 40 to 50 times more rapidly than do P. falciparum killed by chloroquine. The scientists report in the Nov. 27 SCIENCE that this "rapid efflux phenomenon' can be found in drug-resistant malarial parasites from Africa, South America and Asia. But by adding other drugs--including two that block the entry of calcium into cells--to P. falciparum cultures, the researchers were able to significantly slow chloroquine release. They say that results suggest this choloroquine resistance may be similar to multidrug resistance in mammalian cells. This similarity was noted previously by researchers studying the response of resistant P. falciparum to the anticancer drug verapamil (SN: 3/7/87, p.148).

Other researchers are working on vaccines against P. falciparum (SN: 3/21/87, p.181), but results from the first clinical trials of an antimalaria vaccine have been disappointing. Made by the U.S. Army, the potential vaccine protected only one of the six subjects immunized and then exposed to the parasite, according to an Army spokesman.