Anti-rat liver microsomal and cytosolic antibodies in hepatitis C virus infection

Anti-LC1 autoantibodies in patients with chronic hepatitis C virus infection

Various autoantibodies have been reported in patients chronically infected by hepatitis C virus. 2% to 10% of theses patients have anti-liver-kidney microsome type 1 (anti-LKM1) autoantibodies. In type 2 autoimmune hepatitis, anti-LKM1 autoantibodies are frequently associated with anti-liver-cytosol type 1 (anti-LC1) autoantibodies.

AIMS

To determine the prevalence of anti-LC1 autoantibodies in a hepatitis C-positive population and characterize their reactivity.

METHODS

146 patients suffering from liver diseases, of which 99 were chronically infected by hepatitis C virus, were tested by Western blotting and immunoprecipitation to detect and characterize anti-LC1 autoantibodies.

RESULTS

12% of this hepatitis C population had anti-LC1 autoantibodies. LC1 positivity by Western blotting was 30% of LC1+ sera. Epitopes were found throughout the protein but linear epitopes were situated in the 395-541 amino acid region of formiminotransferase cyclodeaminase. Three putative conformational epitopes were identified by phage display.

CONCLUSIONS

Anti-LC1 autoantibodies are as prevalent as anti-LKM1 autoantibodies in patients infected with hepatitis C virus and their production is not dependent of anti-LKM1 autoantibodies formation. Autoantibody reactivity against the anti-LC1 antigen is different in hepatitis C than in type 2 autoimmune hepatitis. Anti-LC1 autoantibodies can now be regarded as a serological marker of autoimmunity in chronic hepatitis C infection.

Features and outcome of autoimmune hepatitis type 2 presenting with isolated positivity for anti-liver cytosol antibody

BACKGROUND AND AIMS

Autoimmune hepatitis (AIH) type 2 is identified by the presence in the serum of anti-liver/kidney microsome type 1 autoantibody. Anti-liver cytosol autoantibody has been reported in children with autoimmune liver disorders mostly in association with anti-liver/kidney microsome reactivity. However, its role as a sole marker of AIH type 2 is debated. We describe here a series of 18 children and adolescents (15 girls, 3 boys) with AIH with serum anti-liver cytosol type 1 (aLC1) as the only autoimmune marker.

METHODS

A retrospective review was conducted from 3 pediatric hepatology units of all children with an autoimmune liver disease associated with aLC1 as found by immunofluorescence and/or immunodiffusion or immunoblotting.

RESULTS

Age at first symptoms ranged from 11 months to 14 years; 12 children presented with acute hepatitis, 1 with progressive jaundice, and 5 were asymptomatic. Anti-liver/kidney microsome, antimitochondria, and anti-actin autoantibodies were not detected. Signs of cirrhosis were present in 11 children. Immunosuppressive treatment was effective in all except 2 children who had subfulminant hepatic failure and who required liver transplantation. Sixteen patients (14 with their native liver) currently are alive; 14 patients still are on immunosuppressive therapy after 1 to 22 years. According to the international scoring system for the diagnosis of AIH, 16 patients corresponded to a definite diagnosis and 2 corresponded to a probable diagnosis.

CONCLUSIONS

The presence of aLC1 in children with acute or chronic liver disease of unknown origin strongly supports a diagnosis of AIH and is an indication for early immunosuppressive therapy.

Sera of children with hepatitis C infection and anti-liver-kidney microsome-1 antibodies recognize different CYP2D6 epitopes than adults with LKM+/HCV+ sera

BACKGROUND

Liver-kidney microsome type 1 (LKM1) antibodies are specific markers of autoimmune hepatitis (AIH) type 2. Antibodies to LKM1 have been found in 2% to 3% of adults infected with hepatitis C virus (HCV) without AIH. Thirty percent of these antibodies are directed against linear sequences of CYP2D6 protein. LKM1 antibodies in HCV+/LKM1+ sera and in sera of AIH patients do not recognize the same CYP2D6 epitopes. The current study was conducted to determine whether LKM1 antibodies in HCV+/LKM1+ children's sera are the result of the same immune response as the antibodies described in AIH type 2 and in HCV+/LKM1+ adult patients.

METHODS

Sera from 10 HCV+/LKM1+ children were tested against human liver microsomal and cytosolic proteins by Western blot analysis and against synthetic peptides of the CYP2D6 sequence between amino acids 200 and 429 by dot blot. The same sera were tested against radiolabeled CYP2D6 by immunoprecipitation.

RESULTS

Four of 10 sera tested by Western blot analysis showed immunoglobulin (Ig) G-type antibodies against CYP2D6, and 2 had antibodies against proteins of 58, 66, and 84 kDa. One of the sera also contained IgM-type anti-66-kDa and 84-kDa proteins. The radioligand test detected anti-CYP2D6 antibodies in 9 of 10 patients. Five of the anti-CYP2D6-positive sera recognized a peptide between amino acids 200 and 429 including amino acids 254-271.

CONCLUSIONS

Most HCV+/LKM1+ sera from children recognize conformational epitopes of the CYP2D6 antigen, and half recognize linear epitopes. Some HCV+/LKM1+ sera demonstrated antibodies against the AIH type 2 main antigenic site of the CYP2D6. Screening of HCV RNA should be performed before starting treatment of presumed autoimmune hepatitis associated with LKM1.

Clinical manifestations of hepatitis C

Hepatitis C is a common cause of viral hepatitis that progresses to chronic infection in the majority of patients. Clinically, the infection is generally asymptomatic, but it may present with a wide variety of symptoms. Cirrhosis, hepatocellular carcinoma, cryoglobulinemia, auto-antibodies, and glomerulonephritis have been strongly associated with HCV. There is a probable association with autoimmune disease and NHL. More information is needed to determine whether lichen planus, PCT, and other disorders are part of the growing clinical spectrum or just coincidental associations with chronic liver disease.