Immune-mediated parasite clearance in mice infected with Plasmodium berghei following treatment with manzamine A

Manzamine A, a sponge-derived alkaloid, was recently shown to possess in vi vo antimalarial activity against the blood stages of the rodent malaria par asite Plasmodium berghei. A single intraperitoneal dose of 100 mu mol/kg of manzamine A suppressed parasite growth but was followed by parasite recrud escence. Forty percent of mice with recrudescing parasites were able to rec over and clear the fulminating parasitaemia. Examination of sera from these mice revealed that infected mice treated with manzamine A had a suppressed IFN-gamma production but an increase in their IL-10 and IgG production. Th e prolonged survival of infected mice treated with manzamine A and the even tual clearance of recrudescing parasites in some of these mice involve a do wn-regulation of Th1 responses and a switch to antibody dependent-Th2 respo nses.