EFFECT OF IVERMECTIN PROPHYLAXIS ON ANTIBODY-RESPONSES TO ONCHOCERCA-VOLVULUS RECOMBINANT ANTIGENS IN EXPERIMENTALLY INFECTED CHIMPANZEES

Antibody responses to recombinant Onchocerca volvulus antigens were st udied in experimentally infected chimpanzees. Sera from 3 groups of 6 animals were tested by ELISA with recombinant antigens OC 3.6 and OC 9 .3. Groups I and Il were treated with 200 mu g/kg of ivermectin on the day of infection or on day 28, respectively. Group III were untreated controls. Antibodies to OC 3.6 developed during the prepatent period in all 3 groups. In contrast, antibodies to OC 9.3 were usually first detected around the time of onset of patency. Several animals had earl y antibody responses to OC 9.3, but these animals subsequently failed to develop microfilarial patency. Only 1 of 6 animals in group I produ ced a strong antibody response to OC 9.3 while all 12 animals in group s II and III developed antibodies to this antigen. Although there was some inconsistency in antibody responses observed in each treatment gr oup, the results suggest that OC 9.3 may be more useful than OC 3.6 fo r monitoring the efficacy of prophylactic drugs or vaccines for onchoc erciasis while OC 3.6 may be useful for detecting exposure to the para site and early infection, regardless of the later outcome of the infec tion.