Expression of autoantibodies to specific cytochromes P450 in a case of disulfiram hepatitis

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Abstract

Background/Aims:

Immunological mechanisms are involved in many adverse drug reactions. In certain forms of drug-induced hepatitis, patients have been reported to express specific autoantibodies to hepatic drug-metabolising enzymes. The alcohol deterrent disulfiram is associated with a low frequency of severe liver toxicity, including hepatitis, but the mechanism of the toxicity is unknown. We investigated whether autoantibodies to cytochrome P450 enzymes were expressed in the serum of a 28-year-old male patient, who developed hepatitis after 7 weeks of disulfiram treatment and in whom possible causes of hepatitis other than disulfiram had been ruled out.

Methods:

Patient serum IgG reactivity was analysed by immunoblotting or ELISA against test antigens consisting of recombinant/purified human or rat liver P450 enzymes, or isolated rat liver microsomes.

Results:

A significant serum reactivity was found in immunoblotting against human cytochromes P450 1A2 and rat P450 3A1, using serum dilutions of up to 1:900 and 1:2400, respectively. In contrast, the reactivity against cytochromes P450 2E1, 2C9, 2D6, 3A4, and rat liver P450 reductase was either very low or undetectable. ELISA reactivity was low in general, indicating that the P450 epitopes were not surface exposed. Immunoblotting of rat liver microsomes revealed that autoantibodies recognised one major polypeptide corresponding to P450 3A. Autoantibody titres remained stable for at least 6 months after acute hepatitis. A similar reactivity was not found in any of ten control sera.

Conclusions:

The expression of autoantibodies directed against specific cytochromes P450 in a case of disulfiram hepatitis suggests that immunological mechanisms are involved in this adverse drug reaction, and that these P450 proteins should be evaluated as possible diagnostic test antigens in disulfiram hepatotoxicity.

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