HUMORAL RESPONSE TO PLASMODIUM-FALCIPARUM PF155 RING-INFECTED ERYTHROCYTE SURFACE-ANTIGEN AND PF332 IN 3 SYMPATRIC ETHNIC-GROUPS OF BURKINA-FASO/

The humoral immune response against synthetic peptides of two Plasmodi um falciparum blood-stage antigens, Pf155/ring-infected erythrocyte su rface antigen (RESA) (EENV)(6) and Pff32 (SVTEEIAEEDK)(2), in individu als belonging to three sympatric ethnic groups (Mossi, Rimaibe, and Fu lani) living in the same conditions of hyperendemic transmission in a Sudan savanna area northeast of Ouagadougou, Burkina Faso were examine d, The Mossi and Rimaibe are Sudanese Negroid populations with a long tradition of sedentary farming, while the Fulani are nomadic pastorali sts partly settled and characterized by non-Negroid features of possib le Caucasoid origin. A total of 764 subjects (311 Mossi, 273 Rimaibe, and 180 Fulani) were tested. A lower P, falciparum prevalence was obse rved in the Fulani of all age groups. The serologic results clearly in dicate the existence of interethnic differences in the capacity to res pond to these two P. falciparum antigens. The Mossi and Rimaibe showed similar responses, whereas the Fulani displayed consistently higher p revalences and levels of antibodies against both epitopes tested. ;The anti-(EENV)(6) and anti-(SVTEEIAEEDK)(2) seroprevalences were 29.9% a nd 38.9% in Mossi, 29.7% and 39.2% in Rimaibe, 86.1% and 76.1% in Fula ni (all P values of Fulani-Mossi and Fulani-Rimaibe comparisons much l ess than 0.001). Anti-RESA and anti-Pf332 antibody levels were approxi mately 65% (P much less than 0.001) and 45% (P much less than 0.001), respectively, higher in seropositive Fulani than in seropositive Mossi and Rimaibe, who showed very similar values. The observed differences cannot be explained in terms of interethnic heterogeneity of malaria exposure since these communities have lived in the same area for more than 30 years and the P. falciparum inoculation rate, measured during two consecutive years, was substantially uniform for the three ethnic groups. The possibility of remarkable heterogeneities in the capacity to mount immune responses against P. falciparum antigens among populat ions with different genetic backgrounds must be taken into account in the development of anti-malaria vaccines.