Termination of pregnancy in mice following antiserum administration to modified chicken riboflavin carrier protein.

Rabbit antibodies to native riboflavin carrier protein (RCP), are to a large extent directed towards conformational epitopes and antibodies to disulphide bond reduced carboxymethylated RCP (RCM-RCP) are towards sequential epitopes. The major cyanogen bromide (CNBr) fragments and tryptic fragments of RCM-RCP interact with both antiserum to RCM-RCP and RCP. Passive immunization of pregnant mice with antibodies to RCM-RCP results in bioneutralization, leading to termination of pregnancy. Recently, a major tryptic fragment of RCM-RCP (24 +/- 2 kd) which could assume conformation at the antibody combining site of native RCP, obtained following mild trypsinization has been identified [Natraj et al. J. Biosci, 15 (1990) 341]. Rabbit antibodies to RCM-RCP treated with trypsin generated antibodies of low titer which interacted with RCM-RCP as well as RCP. The interaction of this antibody with RCP was of high affinity and could be displaced with RCP. The bioneutralizing ability of the antibody was demonstrated by its ability to cause termination of pregnancy in mice.