A novel assay for detecting antibodies to cytochrome P4502D6, the molecular target of liver kidney microsomal antibody type 1

Liver Kidney Microsomal type 1 (LKM1) antibody, the diagnostic marker of au toimmune hepatitis type 2, is also found in a proportion of patients with h epatitis C virus infection (HCV). It is detected conventionally by the subj ective immunofluorescence technique. Our aim was to establish a simple and objective enzyme-linked immunosorbent assay (ELISA) that measures antibodie s to cytochrome P4502D6 (CYP2D6), the target of LKM1. An indirect ELISA usi ng eukaryotically expressed CYP2D6 was designed. Absorbance values obtained against a reference microsomal preparation were subtracted from those obta ined against a microsomal preparation over-expressing CYP2D6, thus removing the non-CYP2D6-specific reaction. Sera from 51 LKM1 positive patients (21 autoimmune hepatitis and 30 with HCV infection), 111 LKM1 negative patients with chronic liver disease (including 20 with HCV infection) and 43 health y controls were tested. Of 51 patients positive by immunofluorescence, 48 w ere also positive by ELISA while all the 154 LKM1 negative subjects were al so negative by ELISA. There was a high degree of association between IFL an d ELISA as demonstrated by a kappa reliability value of 0.96. The absorbanc e values by ELISA correlated with immunofluorescence LKM1 titres both in au toimmune hepatitis (r = 0.74, p < 0.001) and HCV infection (r = 0.67, p < 0 .001). The simple, objective ELISA described has the potential to replace t he standard immunofluorescence technique. (C) 1999 Elsevier Science B.V. Al l rights reserved.