IMMUNE-RESPONSES TO BAND-3 NEOANTIGENS ON PLASMODIUM-FALCIPARUM-INFECTED ERYTHROCYTES IN SUBJECTS LIVING IN AN AREA OF INTENSE MALARIA TRANSMISSION ARE ASSOCIATED WITH LOW PARASITE DENSITY AND HIGH HEMATOCRIT VALUE

During the intracellular development of the human malarial parasite, P lasmodium falciparum, cryptic regions of the erythrocyte band 3 protei n are exposed. Antibodies against these band 3-related neoantigens blo ck cytoadherence, and peptides based on amino acid sequences of putati ve exofacial loops of band 3 protein block the in vitro and in vivo ad herence of P. falciparum-infected erythrocytes. At present, it is not known whether reactivity to these antigens is related to exposure to t he malaria parasite or is correlated with protective immunity. The rea ctivities of plasma to peptides containing amino acid sequences of put ative exofacial loops 3 and 7 of human band 3 protein were determined for children and adults living in an area of perennial malaria transmi ssion (Liberia) and for donors who had never been exposed to malaria ( Denmark). Plasma samples from children and adults living in an area of intense malaria transmission showed a much higher reactivity with the band 3 peptides than did those from nonimmune individuals. High react ivity to the loop 3 peptide (amino acids 546 to 555) was correlated wi th lower mean parasite density in children in the 5- to 9-year-old age group. The presence of antibodies against loop 3 and 7 peptides was n ot associated with a low packed erythrocyte volume (hematocrit); in fa ct, higher-than-average reactivities to both peptides were positively correlated with high hematocrit values, indicating that antibodies whi ch specifically recognize the band 3-related neoantigens are not invol ved in hemolysis (autoimmunity).