ASSESSMENT OF THE HUMORAL AND CELL-MEDIATED-IMMUNITY AGAINST THE PLASMODIUM-FALCIPARUM VACCINE CANDIDATES CIRCUMSPOROZOITE PROTEIN AND SPF66 IN ADULTS LIVING IN HIGHLY ENDEMIC MALARIOUS AREAS OF PAPUA-NEW-GUINEA

To assess natural immunity against the circumsporozoite (CS) protein a nd the synthetic vaccine SPf66, immunologic studies were carried out i n a highly endemic malarious area of Papua New Guinea. Antibody preval ence, antibody titers, and T cell proliferation against both antigens were measured in 214 adults. Immunologic data were analyzed with respe ct to longitudinal malariologic and morbidity data. Evidence of geneti c traits such as glucose-6-phosphate dehydrogenase deficiency and oval ocytosis was analyzed. Antibody prevalence was high, with 79% and 84% for CS protein and SPf66, respectively, while T cell proliferation was infrequent and low, with 14% and 12% responders, respectively. Anti-C S protein antibodies increased with age but showed no association to m alaria indices or morbidity. No protective value was observed with T c ell responses or with humoral response to SPf66. These results provide a first description of naturally developed immunity against SPf66 and suggest further studies in to fully understand the mechanism of immun ity against this antigen.