IMMUNE-RESPONSE AND LACK OF IMMUNE-RESPONSE TO PLASMODIUM-FALCIPARUM P126 ANTIGEN AND ITS AMINO-TERMINAL REPEAT IN MALARIA-INFECTED HUMANS

A parasitophorous vacuole protein of Plasmodium falciparum, p126, is a potential candidate for a malaria vaccine. Its N-terminal region, com posed of six repeats of eight amino acids, appears to be involved in t he induction of protective immunity against P. falcipartum challenge i n monkeys. This study evaluated the immune response to p126 and to its N-terminal region (Nt47) in patients (n = 45) living in a malaria-end emic area of Brazil (Colina, Porto Velho, Rondonia). Cellular prolifer ative responses against Nt47 were low and infrequent. The study of the humoral immune response demonstrated that 95% of the patients had det ectable anti-p126 antibodies and 77% had anti-Nt47 antibodies. Analysi s of the antibody isotypes specific for Nt47 revealed that all four Ig G subclasses were present and individuals with higher levels of anti-N t47 cytophilic IgG antibody (IgG1 + IgG3/IgG2 + IgG4) had significantl y lower parasitemia levels, suggesting that antibodies to the N-termin al region of the p126 protein may contribute to acquisition of immunit y to P, falciparum malaria.