IMMUNOGENICITY STUDIES OF A SYNTHETIC ANTIGEN OF ALPHA-METHYL DOPA

Since the idiosyncratic liver toxicity of methyl dopa (L-alpha-methyl- 3,4-dihydroxy-phenylalanine) may be due to immune mediated mechanisms, immunologic tools are needed to detect methyl dopa induced antibody a nd antigen. Hapten (methyl dopa) - carrier (albumin) conjugates were s ynthesized to generate antibodies reactive with this drug. Studies wer e also conducted to test the immunogenicity of this hapten-carrier con jugate and its cross reactivity with methyl catechol and levodopa. Met hyl dopa (MD), levodopa (LD) or methyl catechol (MC) were conjugated t o rabbit serum albumin (RSA) under high pH (base) conditions or by a t yrosinase (tyr) catalyzed reaction. Under the base conjugation conditi ons, MD-RSA, LD-RS4 and MC-RSA conjugates were produced at higher hapt en: carrier ratios than conjugates produced by the enzyme catalyzed re action. Rabbits were subsequently immunized with either MD-RSA(base) o r MD-RSA(tyr). Antibodies elicited by MD-RSA(base) had marked reactivi ty to the carrier protein, albumin, whereas antibodies elicited by MD- RSA(tyr) did not. In addition, reactivity of anti-MD antibody was equa l to or greater with MC-RSA than reactivity with either MDRSA or LD-RS A. This work suggests that the conjugation method using the tyr cataly zed reaction produces the optimal immunogen with minimal modification of the carrier protein. In addition, the catechol moiety of MD, MC and LD appears to be the immunogenic epitope on these haptens.