Immunological relatedness of chicken and human riboflavin carrier protein

Polyclonal antibodies (pAbs) to riboflavin carrier protein (RCP) purified from human amniotic fluid were raised in two rabbits. These pAbs apart from recognizing the parent antigen, reacted significantly with chicken RCP as well. When all the 212 octapeptides overlapping by one amino acid residue and covering the entire primary amino acid sequence of chicken RCP immobilized on polyethylene rods were probed with rabbit anti-human RCP antibodies, it was found that these antibodies recognize five epitopic sequences (residues 37-42, 73-76, 133-140, 174-176 and 200-207) in chicken RCP primary structure common to both the rabbits. In addition, the antisera from the two individual animals also recognized additional epitopes characteristic to that particular animal. The reactivities of these antigenic determinants have been confirmed with polyclonal anti-human RCP sera by using synthetic peptides harbouring these chicken RCP sequences in inhibition ELISA. This high level of immunological similarities among linear epitopes observed may reflect the degree of conservation of local conformations among linear antigenic determinants shared by the two evolutionarily distant homologous proteins.