Apical membrane antigen 1 protects monkeys against malaria.

2003 FEB 5 - (NewsRx.com & NewsRx.net) -- by Maria G. Essig, MS, ELS, senior medical writer - Monkeys immunized with a vaccine containing Plasmodium falciparum apical membrane antigen 1 (AMA1) were protected against blood-stage malaria, according to a report in the journal Infection and Immunity.

"A major challenge facing malaria vaccine development programs is identifying efficacious combinations of antigens," said Anthony W. Stowers and colleagues at the Malaria Vaccine Development Unit of the U.S. National Institute of Allergy and Infectious Diseases. "To date, merozoite surface protein 1 (MSP1) is regarded as the leading asexual vaccine candidate. Apical membrane antigen 1 has been identified as another leading candidate for an asexual malaria vaccine, but without any direct in vivo evidence that a recombinant form of Plasmodium falciparum AMA1 would have efficacy."

Stowers and his collaborators evaluated the effectiveness of a recombinant form of AMA1 produced in the yeast, Pichia pastoris. After immunizing Aotus vociferans monkeys with a vaccine containing the antigen, the investigators challenged the monkeys with a potentially lethal dose of P. falciparum organisms.

Patency was delayed in five of the six (83%) animals treated. Two of the five remained subpatent throughout the study. In two other animals, the level of parasitized red blood cells remained below 0.75%.

"The protection induced by AMA1 was ...