In Vitro Trial
Abstract Natural and synthetic peptides representing COOH terminal sequences of the beta subunit of human chorionic gonadotropin (hCG) were coupled to tetanus toxoid and rabbits immunized with the conjugates. Sera were evaluated for antibody levels, antibody affinity and antibody class. Conditions for appropriate estimation of these parameters were also studied. Findings revealed that iodination of hCG or peptides did not alter their immunological properties and that reaction of labelled antigens with antisera require differing periods of time for the establishment of equilibrium. Peak titers to the hCG antigens were reached at 70 days of immunization. Antibodies to natural peptide 109–145 of β-hCG and synthetic peptides 109–145, 111–145, and 115–145 reacted to hCG approximately 90% as well as they reacted to the peptide used for immunizations whereas antibodies to synthetic peptide 125–145 reacted only 60–70% as well. Mean antibody affinities to peptides were not significantly higher than affinities of the same sera to hCG. The affinity of antisera to synthetic peptide 125–145 to both antigens and the mean ratio of hCG affinity : peptide affinity was somewhat lower than those to longer peptides. After 70 days of immunization, antibodies were predominantly of the IgG class. The findings indicate that antibodies raised to natural or synthetic peptides of the COOH region of hCG beta subunit are highly cross-reactive to native hCG but have affinities somewhat lower than those generated to the intact hormone or its beta subunit.
J. Powell, Arthur C. Lee, G. Tregear
Journal of Reproductive Immunology