Epitope analysis of aztreonam by antiaztreonam monoclonal antibodies and possible consequences in beta-lactams hypersensitivity.

Three cell lines producing monoclonal antibodies, Az-1 (IgG1), Az-2 (IgG1) and Az-3 (IgM) against aztreonam were established. The epitopes and the cross-reactions of the antibodies with various beta-lactams, which were conjugated with human serum albumin (HSA), were examined by enzyme-linked immunosorbent assay (ELISA) and ELISA inhibition test. In ELISA, Az-1 and Az-2 reacted only with aztreonam and ceftazidime, which have the same acyl side chain. Furthermore, Az-2 showed a strong cross-reaction with carumonam. In the ELISA inhibition test, Az-1 and Az-2 were inhibited from binding to aztreonam-HSA by aztreonam, ceftazidime, aztreonam hydrolysate, aztreonam-epsilon-amino-n-caproic acid (EACA) and ceftazidime-EACA. Az-2 was also inhibited with carumonam. From the above results, it seems that Az-1 can recognize only the degraded structure of monobactam nucleus, and Az-2 can recognize the degraded nucleus moiety and the acyl side chain. On the other hand, Az-3 displayed broad cross-reaction to various beta-lactams in ELISA. Furthermore, the MAb showed no inhibitory reaction with various beta-lactams except aztreonam- and ceftazidime-EACA conjugates in the ELISA inhibition test, suggesting that Az-3 recognize a new antigenic determinant (NAD), which is formed by the conjugation of beta-lactam and carrier protein. The above results indicate that antibodies can recognize at least three epitopes of the degraded product(s) of aztreonam nucleus, acyl side chain and NAD in aztreonam-protein conjugate.