Production and characterization of mouse monoclonal antibodies against Afipia felis

A series of 10 monoclonal antibodies reacting with Afipia felis antigens were selected from mice immunized with live organisms of the reference strain ATCC 53690. Immunoblotting against SDS-PAGE-separated A felis sonicate allowed the antibodies to be classified into three groups: 1) 168-4, -6, -7 and -10 reacted with a 53 kDa antigen, 2) 168-1, -3 and -9 reacted with both 53 kDa and 60 kDa antigens, and 3) 168-2, -5 and -9 reacted with other antigens. Antibodies of group 1 did not cross-react with other Afipia species or 36 unrelated bacteria, whereas those of groups 2 and 3 reacted with other Afipia species and some unrelated bacteria. Immunoblots of crossed immunoelectrophoretic patterns of A. felis sonicate against rabbit antiserum showed that antibodies of groups 1 and 2 bound to the same precipitin arcs. Antibodies of group 1 reacted with a species-specific epitope on the 53 kDa antigen, while those of group 2 reacted with other epitopes shared by the 53 kDa and 60 kDa antigens. The binding of antibodies of group 1 to A. felis sonicate was inhibited by post-infection rabbit serum, whereas no inhibition was observed for antibodies of group 2. The species-specific epitope of the 53 kDa antigen and the early appearance of antibodies against this epitope after infection suggest that this antigen can be used in a serodiagnostic test for A. felis infection.