Human serological response to louse-borne relapsing fever.

Serological response to louse-borne relapsing fever in Ethiopia was determined by immobilization tests using Borrelia recurrentis cultures. Isolates from 26 patients tested with autologous convalescent sera showed from 90 to 100% of the organisms had been immobilized. Sera from thirteen patients were tested with autologous and heterologous strains. Several reacted with the majority and two showed high titers against all strains tested. Screening of day 2 and day 8 sera frequently showed heterologous antibody present before autologous antibody appeared, suggesting multiple antigenic challenge to infected patients. Some strains appeared to be antigenically related, but because of the wide diversity of serological responses, no definite serological groupings could be ascertained.