SEROLOGICAL DIVERSITY OF ANTIGENS EXPRESSED ON THE SURFACE OF ERYTHROCYTES INFECTED WITH PLASMODIUM-FALCIPARUM

We have studied the surface-antigen phenotypes of infected erythrocyte s from children with acute falciparum malaria in the Punjab, Pakistan. Infected erythrocytes from 15 children and their homologous acute and convalescent sera, as well as hyperimmune sera from adults living in the same area, were used to analyse the serological diversity of paras ite-associated antigens expressed on the surface of erythrocytes infec ted with Plasmodium falciparum. Analysis included agglutination, cytoa dherence/inhibition of cytoadherence to melanoma cells, and rosette fo rmation/disruption of rosettes formed between infected and non-infecte d erythrocytes. We found that isolate-specific antibodies were acquire d by all children during convalescence and that there was a high degre e of diversity of surface-antigen phenotypes. A majority of the sera e ither acquired or increased by 2- to 3-fold the capacity to inhibit cy toadherence and/or agglutinate the patient's own infected erythrocytes during convalescence and a strong correlation was found between these 2 activities. Hyperimmune sera from adults agglutinated and/or inhibi ted cytoadherence of many, but not all, of the isolates. Rosette forma tion was observed in 11 of the 15 isolates; 38% of the acute and 75% o f the convalescent sera had anti-rosette activity on rosettes formed b y the patient's own parasites. Among the isolates there was no correla tion between rosette formation and binding of infected erythrocytes to melanoma cells. Our data provide good evidence that the children deve loped isolate-specific antibodies during convalescence from an acute a ttack of falciparum malaria and suggest that there was a high degree o f heterogeneity of antigens expressed on the surface of infected eryth rocytes.