S-Ethylthiotrifluoroacetate Enhancement of the Immune Response to Halothane in the Guinea Pig

Abstract

Halothane hepatitis appears to be a hypersensitivity reaction to neoantigens formed when halothane reactive intermediates covalently bind to liver proteins. Production of an animal model for halothane hepatitis has been largely unsuccessful, possibly due to inadequate cytochrome P-450 mediated biotransformation of halothane to reactive intermediates. S-ethylthiotrifluoroacetate (SETFA) reacts rapidly and efficiently with protein lysine groups to form trifluoroacetylated proteins. The advantage to this procedure is that cytochrome P-450 mediated activation is not required. Male Hartley guinea pigs (600–700 g) were injected (ip) with SETFA (50 ml) emulsified in an adjuvant-mycobacterial protein mixture. Subsequent exposure to halothane produced a 10x increase in anti-trifluoro acetylated albumin antibody response compared to controls, as well as centrilobular lesions consistent with halothane toxicity. Western-type immunoblot analysis demonstrated three unique antigen bands in microsomal fractions from SETFA-treated guinea pigs. The adjuvant-mycobacterial mixture alone caused only minor liver lesions and minimal immune response. SETFA may be effective for producing the reactive intermediate of halothane metabolism, bypassing the need to induce atypical halothane metabolism to produce an im munopathological response.