DIVERSITY OF AGGLUTINATING PHENOTYPE, CYTOADHERENCE, AND ROSETTE-FORMING CHARACTERISTICS OF PLASMODIUM-FALCIPARUM ISOLATES FROM PAPUA-NEW-GUINEAN CHILDREN

The relationship between antigenic variation, cytoadherence, rosette f ormation, and the pathogenesis of malaria has led to great interest in the diversity of these properties in Plasmodium falciparum isolates f rom different communities. In this study, we extend previous investiga tions by delineating the spectrum of agglutinating phenotypes, adheren ce to C32 melanoma cells, human umbilical vein endothelial cells (HUVE C), CD36, and intracellular adhesion molecule-1 (ICAM-1), and rosette- forming ability of a group of 20 P. falciparum isolates from Papua New Guinean children. Agglutination phenotypes were determined by using b oth the children's convalescent serum and a panel of adult immune sera . The wide range of variant antigenic types in the community was demon strated by the failure of the agglutination assays to identify any two isolates with the same agglutinating phenotype in this, the largest s tudy of its kind. Comparison of agglutination profiles from fresh and cryopreserved isolates demonstrated the general acceptability of cryop reservation before testing, but cautioned that some isolates may under go selection and phenotypic change during the process. Nineteen isolat es were able to bind to at least one of the four ligands studied and s howed marked variation in both avidity and specificity of binding. The purified proteins ICAM-1 and CD36 proved to be the most useful assay ligands for investigating field isolates, with 18 isolates binding to at least one protein and 14 to both. No correlation was found between the binding of isolates to any two ligands nor between the binding of a standardized inoculum and the level of the patient's presenting para sitemia. All isolates from the study group were found to form rosettes (at a mean rate of 14.6% of cultured trophozoites involved in rosette s). A lack of correlation between rosette formation and CD36 binding s uggests that the previously reported role of CD36 as a rosette formati on receptor may not be important for isolates from Papua New Guinea.