Antigens in penicillin allergy. I. A radioimmunoassay for detection of penicilloylated protein contaminants in penicillin preparations.

This communication presents a sensitive and discriminative method for detection of protein impurities in penicillin preparations. Antibodies against various penicilloyl derivatives of high avidities and specificities raised in rabbits were coupled to microcrystalline cellulose. The amount of penicilloyl antigen present in a sample was calculated from the relative uptake of a radioiodinated penicilloylated albumin competing with the sample for binding to the antipenicilloyl immunosorbent. As little as 0.048 pmol/ml of penicilloylated human serum albumin could be detected. The accuracy of the determination was within +/- 23% (p less than 0.05). The pronounced specificities against the penicillin side chains demonstrated by the various immunosorbents were not displayed by the antibodies in passive cutaneous anaphylaxis experiments in guinea pigs. Furthermore, the immunosorbents showed the same pattern of specificity against monomeric penicillins as for penicilloylated proteins, but the former were considerably less efficiently recorded. The relatively small quantities of protein impurities in penicillin preparations, however, necessitated a separation from penicillin prior to analyses with the RIA. This was accomplished by fractionation on Sephadex G-50 fine, ginving a recovery of 80-90% of 0.1-2.5 ppm of penicilloylated protein.