Immunoblot analysis of humoral immune responses to Leucocytozoon caulleryi in chickens.

The humoral antibody responses of chickens infected or immunized with Leucocytozoon caulleryi were analyzed by immunoblot comparing with protection against challenge infection, agar-gel precipitation (AGP) test, enzyme-linked immunosorbent assay (ELISA), and parasitemia. IgG antibodies in the sera from chickens infected with L. caulleryi were found to react with 20-35 bands of approximate molecular weights 25-300 kDa, such as 33, 44, 58, 79, 94, and 141 kDa from 3 to 50 wk after infection. In chickens immunized with schizont antigens from L. caulleryi, several bands were reacted with sera 2 wk after the second immunization, e.g., 36, 58, 71, 81, 97, 112, and 123 kDa. Chickens that recovered from the primary infection showed complete protection against reinfection, whereas immunized chickens showed partial protection against challenge infection. These results suggest that the difference in antibody response to schizont antigen might cause the difference in protection between immunized and infected chickens.