Anti-HCV testing in autoimmune hepatitis and primary biliary cirrhosis

Hepatitis C virus infection in patients with primary biliary cirrhosis

BACKGROUND AND AIM

The aim of this study is to evaluate the role of hepatitis C virus (HCV) infection in patients with primary biliary cirrhosis (PBC).

MATERIAL AND METHODS

On the basis of a retrospective review of medical records, all patients consecutively diagnosed with PBC or HCV infection between 1999 and 2011 and who had a regular follow-up of at least 3 years were included in the study. Clinical characteristics, especially the severity of cirrhosis, were analyzed in PBC patients with HCV infection (PBC-HCV), PBC patients without HCV infection (PBC-only), and patients with only HCV infection (HCV-only).

RESULTS

A total of 76 patients with PBC, including 9 patients with HCV infection, were analyzed. Of the PBC-HCV patients, 7 (7/9, 77.8%) were women with a mean age of 55.11 ± 14.29 years. Age- and sex-matched PBC-only patients (n = 36) and HCV-only patients (n = 36) were used as control groups. In comparison to the PBC-only controls, PBC-HCV patients had a greater severity of cirrhosis based on Child-Pugh (p = 0.019) and Model for End-Stage Liver Disease (MELD) (p = 0.01) scores. However, no significant difference in the severity of cirrhosis was found between the PBC-HCV and HCV-only control patients (p = 0.94 in Child-Pugh scores; p = 0.64 in MELD scores).

CONCLUSIONS

In PBC patients with concomitant HCV infection, aggressive management may be warranted in view of the associated more severe liver cirrhosis.

Anti-Soluble Liver Antigen (SLA) Antibodies in Chronic HCV Infection

Hepatitis C infection is associated with autoimmune disorders, such as the production of autoantibodies. Anti-LKM1 and anti-LC1, immunomarkers of type 2 autoimmune hepatitis, have been previously associated with a HCV infection. Anti-Soluble-Liver-Antigen autoantibodies (SLA) are specifically associated with type 1 and type 2 autoimmune hepatitis and more closely related to patients who relapse after steroid therapy. The recent molecular cloning of the soluble liver antigen provides the opportunity to develop more specific tests for the detection of antibodies against it. The aim of this work is to characterize anti-soluble-liver autoantibodies in sera from patients chronically infected by HCV. A recombinant cDNA from activated Jurkat cells coding for the full length tRNP(Ser)Sec/SLA antigen was obtained. ELISA, Western Blot and immunoprecipitation tests were developed and used to search for linear and conformational epitopes recognized by anti-SLA antibodies in sera from patients chronically infected by HCV. Anti-soluble liver antigen antibodies were found in sera from 10.4% of HCV-infected patients. The prevalence was significantly increased to 27% when anti-LKM1 was also present. Most anti-SLA reactivity was directed against conformational epitopes on the antigen. The means titers by ELISA were lower than those obtained in type 2 AIH. The result of autoantibody isotyping showed a subclass restriction to IgG1 and also IgG4. This study shows the presence of anti-SLA antibodies in approximately 10% of HCV infected patients. The prevalence of SLA autoantibodies in HCV infected patients increases when LKM1 autoantibodies are also present. The relationship between the prevalence of this characteristic autoimmune hepatitis autoantibody and the implication of an autoimmune phenomenon in the liver injury of patients chronically infected by HCV needs further investigation.

LKM1 autoantibodies in chronic hepatitis C infection: a case of molecular mimicry?

Anti-liver-kidney microsome type 1 (LKM1) autoantibodies directed against the cytochrome P450 2D6 (CYP2D6) are considered specific markers of type 2 autoimmune hepatitis, but are also found in 5% of sera from patients chronically infected by hepatitis C virus (HCV). Molecular mimicry between HCV proteins and CYP2D6 has been proposed to explain the emergence of these autoantibodies. Anti-LKM1 autoantibodies from hepatitis C-infected patients were affinity-purified against immobilized CYP2D6 protein and used to screen a phage display library. CYP2D6 conformational epitopes were identified using phage display analysis and the identification of statistically significant pairs (SSPs). Cross-reactivity between CYP2D6 and HCV protein candidates was tested by immunoprecipitation. Nineteen different clones were isolated, and their sequencing resulted in the mapping of a conformational epitope to the region of amino acids 254-288 of CYP2D6. Candidate HCV proteins for molecular mimicry included: core, E2, NS3 and NS5a. Affinity-purified autoantibodies from HCV+/LKM1+ patients immunoprecipitated either NS3, NS5a, or both, and these reactivities were specifically inhibited by immobilized CYP2D6. In conclusion, HCV+/LKM1+ sera recognize a specific conformational epitope on CYP2D6 between amino acids 254 to 288, the region that contains the major linear epitope in type 2 autoimmune hepatitis patients. Cross-reactivity due to molecular mimicry at the B-cell level was shown between the CYP2D6 and the HCV NS3 and NS5a proteins and could explain the presence of anti-LKM1 in patients chronically infected with HCV. Further investigation of the role played by this molecular mimicry in HCV-infected patients may lead to more specific strategies for diagnosis and treatment.

Primary biliary cirrhosis and hepatitis C virus infection

OBJECTIVE

The aim of this study was to describe the clinical characteristics of hepatitis C virus (HCV)-infected patients with primary biliary cirrhosis (PBC) by comparison to patients with both antimitochondrial (AMA) positive and AMA negative PBC.

METHODS

All patients consecutively diagnosed as having PBC between 1973 and 1999 who had a regular follow-up of at least 2 yr were prospectively included in the study. The mean follow-up was 8.3 +/- 5.7 yr. Survival was calculated according to Kaplan-Meier curves.

RESULTS

A total of 170 patients with PBC were considered. The syndrome with PBC and HCV infection (HCV-infected PBC patients) was recorded in 14 patients (13 women and one man), whereas 135 patients had AMA positive PBC and 18 had AMA negative PBC. Only three patients fulfilled the criteria for overlap syndrome involving PBC and autoimmune hepatitis. At presentation, the HCV-infected PBC group had significantly lower levels of ALP, gamma-glutamyl transpeptidase, and IgM than the AMA positive or AMA negative PBC patients (p < 0.01). With regard to the autoantibody profile, there was a significant association with LKM and HCV-infected PBC patients (21.4%), whereas ANA was significantly higher in AMA negative PBC patients than in the other two groups (83% vs 21.4% in the HCV-infected PBC patients and 38.5% in the AMA positive PBC group). No differences were found regarding the association with autoimmune conditions. During follow-up, hepatocellular carcinoma (HCC) developed more frequently in the PBC/HCV overlap group (i.e., three of 14 vs four of 135 patients with AMA positive PBC, p < 0.05). Survival curves were similar in HCV-infected PBC patients and AMA positive PBC, whereas the AMA negative group had a significantly slower decline (relative risk (RR) = 2.44, p < 0.05).

CONCLUSION

HCV-infected PBC patients are characterized by a biochemical profile with a modest rise in cholestatic enzymes but a high risk of developing HCC during follow-up.

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.

Auto-antibodies in hepatitis C

Hepatitis C virus (HCV) has been implicated in the development of a variety of autoimmune phenomena, some of which are well documented and include a panel of auto-antibodies shared with autoimmune hepatitis (AIH). Anti-nuclear (ANA) and smooth muscle (SMA) antibodies (markers of AIH type 1 [AIH-1]), have been demonstrated in 9-38% and 5-91% of cases respectively, whereas anti-liver/kidney microsomal type 1 (anti-LKM-1) and anti-liver cytosol type 1 antibodies (anti-LC1) (markers of AIH type 2 [AIH-2]), are definitely rarer, especially in adults. The presence of these auto-reactivities in chronic hepatitis C generates clinical overlaps and dilemmas in the correct classification and treatment of such patients. The immunopathological characterization of the auto-antibodies, anti-nuclear and smooth muscle antibodies in particular, combined with internationally defined criteria for the diagnosis of AIH is helpful in this clinical process. Thyroid auto-antibodies and cryoprecitable rheumatoid factors are also commonly detected in hepatitis C, while the occurrence of other auto-antibodies still awaits confirmation.

[Autoimmune hepatitis and hepatitis C]

From autoimmune hepatitis (AIH) classification which recognizes three types of AIH, we discuss the main relations between hepatitis C virus (HCV) infection and AIH. Type I AIH is associated with antinuclear and antismooth muscle antibodies, and with other autoimmune diseases. There is no relation between type I AIH and HCV. Type I anti-liver kidney microsome and anti-liver cytosol I antibodies represent the hallmark of type II AIH. Among type II AIH, two subgroups emerged: type IIa AIH (10-40%) are true AIH (sensitive to steroids but worsens with interferon alpha), whereas type IIb AIH (60-90%) appear as a particular form of HCV hepatitis. Type IIb AIH have a moderate activity, a low titer of autoantibodies, anti-GOR antibodies but never anti-liver cytosol I, no sensitivity to steroids but are sensitive to interferon alpha. The hallmark of type III AIH are anti-cytosol antibodies, but these AIH have the same characteristics as type I AIH. The classification between true AIH (I, IIa, III) or "pseudo-AIH" due to HCV infection has major therapeutic implications. Steroids or immunosuppressive treatments are effective in type I, IIa and III AIH but have no efficacy in type IIb AIH. Alpha interferon has an efficacy in type IIb AIH, but it has no efficacy and may even worsen hepatitis in type I, IIa and III AIH.

Heterogeneity of liver/kidney microsomal antibody type 1 in autoimmune hepatitis and hepatitis C virus related liver disease

Liver/kidney microsomal antibody type 1 (LKM-1), the serological marker of a subset of autoimmune hepatitis, is also present in a proportion of patients with hepatitis C virus (HCV) related chronic liver disease. To characterise further this autoreactivity and to evaluate whether an autoantibody giving an identical immunofluorescence staining, and detected in two different clinical conditions, involves the same antigenic target(s), sera from autoimmune and HCV infected patients were tested with native, recombinant, and synthetic antigens. Sixty five sera were selected on the basis of the typical immunofluorescence pattern: 50 patients had serological markers of HCV infection, the remaining 15 suffered from autoimmune hepatitis. The reactivity of each serum with rat and human microsomal fractions, full length human recombinant CYP2D6, and two synthetic peptides spanning the amino acid regions 257-269 and 373-398 of CYP2D6 was systematically investigated by immunoblotting. Fourteen (93%) sera from autoimmune hepatitis patients and 39 (78%) from HCV infected patients reacted with rat and/or human microsomal polypeptides of 39 kD, 50 kD, 58 kD, and 66 kD in different associations, the 50 kD band being the most frequently observed. Reactivity to CYP2D6 and its amino acid sequence 257-269 was significantly more common in autoimmune hepatitis than in HCV infected patients (p < 0.001 and p < 0.0003, respectively). LKM-1 reactivity is directed against heterogeneous and not entirely defined autoantigens. The main target in autoimmune sera is CYP2D6 and its 257-269 amino acid region, while sera from patients with HCV infection are more likely to recognise other microsomal targets, the molecular identity of which is currently unknown.

Liver cytosolic 1 antigen-antibody system in type 2 autoimmune hepatitis and hepatitis C virus infection

Within the multiform liver/kidney microsomal (LKM) family, a subgroup of sera that reacts with a liver cytosolic (LC) protein has been isolated and the new antigen-antibody system is called LC1. Unlike LKM antibody type 1 (anti-LKM1), anti-LC1 is said to be unrelated to hepatitis C virus (HCV) infection and has therefore been proposed as a marker of 'true' autoimmune hepatitis type 2. Altogether 100 LKM1 positive sera were tested by immunodiffusion (ID). Twenty five gave a precipitation line with human liver cytosol; 17 of the 25 also reacted with rat liver cytosol. Thirteen of the 25 sera were anti-HCV positive by second generation ELISA: anti-HCV positive patients were significantly older (p < 0.001) and tended to have less active disease. No difference in anti-LC1 titre or ID immunoreactivity was found between anti-LC1/anti-HCV positive and anti-LC1/anti-HCV negative cases. In Western blotting experiments, 14 of 24 ID positive sera recognised a 58 kD protein of the human cytosolic fraction and 11 gave a similar reactivity when tested with human microsomes, suggesting the presence of the LC1 target antigen also in the microsomal preparation. Western blotting reactivity was similar for both anti-HCV positive and negative sera. These data confirm the existence of the LC1 antigen-antibody system that partially overlaps with LKM1, and that it is an additional marker of juvenile autoimmune hepatitis type 2. It does not, however, discriminate between patients with and without HCV infection.

Autoimmune hepatitis and hepatitis C virus infection

The identification of the hepatitis C virus (HCV) and the availability of serological tests for the identification of its infection has deeply changed our view of autoimmune hepatitis. In fact, we have learned that autoantibodies such as anti-nuclear, anti-smooth muscle and anti-liver kidney microsomes, cannot be considered specific any longer for the diagnosis of autoimmune hepatitis, since they are frequently found in association with HCV. The new clinical entity characterized by the association of autoantibodies with signs of HCV infection is presently under evaluation. This, in order to understand what is the prevalent pathogenetic mechanism, viral or autoimmune, operating in these patients and to chose the best treatment regimen.

Primary and secondary liver/kidney microsomal autoantibody response following infection with hepatitis C virus

Liver/kidney microsomal autoantibody type 1 (LKM-1), which characterizes a subtype of autoimmune hepatitis, is also found in some patients with chronic hepatitis C virus (HCV) infection. Whether HCV and LKM-1 are accidentally or causally related is unknown. This case report describes a child who became infected by HCV after liver transplantation for end-stage liver disease caused by alpha 1-antitrypsin deficiency. LKM-1 was detected by immunofluorescence, anti-microsomal reactivity by Western blotting, anti-HCV and anti-GOR by immunoenzymatic assays, and HCV RNA by polymerase chain reaction. Two weeks after HCV infection, immunoglobulin (Ig) M LKM-1 appeared, followed by IgG1 LKM-1, with titers increasing to 1/2560; antibodies to a 50-kilodalton liver microsomal protein appeared 2 months later. Sera from day 1 posttransplant became positive for HCV RNA. HCV RNA was also detected in a liver biopsy specimen obtained 3 months after surgery. The patient did not produce anti-HCV and anti-GOR antibodies throughout the study and had no histological evidence of hepatitis. The temporal relationship between HCV infection and LKM-1 production suggests that HCV may trigger a primary autoimmune response. The lack of liver damage attributable to autoimmunity or viral infection may be caused by immunosuppression.

Cryoglobulinemia in chronic liver diseases: role of hepatitis C virus and liver damage

BACKGROUND/AIMS

Mixed cryoglobulinemia is frequently associated with liver diseases. The respective role of hepatitis C virus (HCV) and liver damage in the pathogenesis of cryoglobulinemia is investigated in this study.

METHODS

The prevalence of cryoglobulinemia in 226 consecutive patients with chronic liver diseases (hepatitis C, 127; hepatitis B, 40; other diseases, 59) was studied, and the epidemiological, biological, histological, and virological features in these three groups were analyzed. Anti-HCV antibodies, HCV proteins, and HCV RNA were searched in the cryoprecipitates.

RESULTS

The prevalence of mixed cryoglobulinemia was high (41.5%) in patients with liver diseases and higher in patients with hepatitis C (54.3%) than in patients with hepatitis B (15%) or other causes of liver disease (32%). Patients with cryoglobulinemia had cirrhosis more frequently and had a longer history of hepatitis. In patients with hepatitis C, HCV RNA sequences and HCV proteins were detected in the cryoprecipitate. Cryoglobulins became undetectable in 21 of 43 patients treated with interferon.

CONCLUSIONS

These findings suggest that HCV is a major cause of cryoglobulinemia. Besides viral infection itself, multiple factors appear to be responsible for the production of cryoglobulins, including cirrhosis and duration of liver disease.

Hepatitis C virus in autoimmune liver disease in the UK: aetiological agent or artefact?

Hepatitis C virus antibody titres (anti-HCV) were measured in serum from 122 patients with autoimmune liver disease (96 with primary biliary cirrhosis and 26 with autoimmune chronic active hepatitis using three generations of enzyme immunoassay (EIA): first generation--Ortho, EIA1; second generation--Abbott, EIA2; and third generation--Murex, EIA3. Anti-HCV was below the positive cut-off level in all 26 autoimmune chronic active hepatitis patients for all tests, while seropositivity values in primary biliary cirrhosis were 31% (EIA1), 14% (EIA2), and 0% (EIA3). In primary biliary cirrhosis, anti-HCV values as measured by all three tests correlated positively with serum IgG concentrations, serum storage time, and a number of other indices of hepatic dysfunction. Multiple regression analysis showed that anti-HCV values were independently affected by both serum IgG and the length of storage time, although the magnitude of the effects varied between tests. When all three multiple regression models were applied to an extreme clinical example, however, EIA3 was least likely to give a false-positive result. The difference in test performance was emphasised further by examination of anti-HCV values in nine primary biliary cirrhosis patients (confirmed negative by recombinant immunoblot assay 2) in whom serial samples were tested (seven to 14 per patient, stored for one to 138 months). Apparent anti-HCV values (EIA1 and EIA2) increased with increasing serum storage time, but were unchanged when measured by EIA3. A similar pattern was evident in a limited study of five autoimmune chronic active hepatitis patients. As the second generation EIA is in widespread use and confirmatory testing is not always available, the effect of serum storage in addition to hyperglobulinaemia should be considered in the interpretation of positive results in auto immune and in other types of chronic liver disease.

Anti-LKM-1 antibodies determined by use of recombinant P450 2D6 in ELISA and western blot and their association with anti-HCV and HCV-RNA

Several subtypes of anti-liver-kidney microsome antibodies (LKM) are known. LKM-1 antibodies associated with autoimmune chronic active hepatitis recognize P450 2D6, a cytochrome P450 mono-oxygenase. The frequent association of anti-LKM-1 antibodies and hepatitis C virus (HCV) infections and the probable existence of an infectious and autoimmune form of anti-LKM-1-associated hepatitis, requiring different therapeutical strategies, necessitates the exact determination of anti-LKM-1 specificities. Therefore, we compared various antibody tests (immunofluorescence, ELISA with recombinant P450 2D6, and Western blot with recombinant and natural antigens and agargel double diffusion) with sera of 27 anti-LKM-1-positive chronic active hepatitis (CAH) patients, with 61 sera harbouring anti-mitochondrial antibodies, 100 sera each from HCV-RNA-positive and HCV-RNA-negative patients, and 50 sera of healthy persons. Western blot techniques using recombinant MS2-polymerase P450 2D6 fusion protein were found to be the most sensitive and specific method for anti-LKM-1 antibody determination in routine laboratory. The recently recognized association of anti-LKM-1 antibody and HCV infection was confirmed by the results of this study. In anti-HCV and HCV-RNA-positive patients with anti-LKM-1 antibodies there was a preponderance of males with higher mean age and lower antibody titres. The results support the hypothesis of the existence of an autoimmune as well as an infectious (HCV triggered) subgroup of anti-LKM-1-positive hepatitis.

Liver/kidney microsome antibody type 1 and hepatitis C virus infection

Recent studies have shown that hepatitis C virus antibodies are present in a large proportion of patients with autoimmune hepatitis type 2. We have studied 83 patients with liver/kidney microsome antibody-positive type 1 hepatitis. Hepatitis C virus antibodies were sought in every case by second-generation tests (hepatitis C virus enzyme-linked immunosorbent assay and recombinant immunoblot assay). Hepatitis C virus RNA sequences were sought in 22 patients (12 with recombinant immunoblot assay-positive results and 10 with recombinant immunoblot assay-negative results) by means of polymerase chain reaction and by use of primers located in the 5' noncoding region. Sixty-four patients (77%) had positive results for hepatitis C virus antibodies in the enzyme-linked immunosorbent assay test, and 41 (49.3%) were confirmed by recombinant immunoblot assay. Hepatitis C virus RNA sequences were found in all the recombinant immunoblot assay-positive patients but in none of the 10 who were recombinant immunoblot assay-negative. The recombinant immunoblot assay-negative patients were younger than those who were positive (13 +/- 11 vs. 50 +/- 11 years) and had higher gamma-globulin levels and liver/kidney microsome antibody-positive type 1 titers (61% had a titer of 1:1,000 or more, vs. only 17% of the recombinant immunoblot assay-positive patients).(ABSTRACT TRUNCATED AT 250 WORDS)

Hepatitis C virus testing in primary biliary cirrhosis

We retrospectively investigated anti-HCV prevalence in a series of 160 consecutive patients with primary biliary cirrhosis who presented between 1980 and 1989. Of these, 19 (12%) were positive for anti-HCV by C-100 ELISA. Serum IgG levels were significantly higher in anti-HCV-positive patients and correlated to optical density values. A serum sample was again collected from all the patients from the same series who were seen in 1990 for follow-up, after a median period of 32 months. Anti-HCV positivity was found to be substantially unchanged in this subgroup of patients when the freshly drawn blood samples were retested with C-100 ELISA, while it increased from 10% to 17% when second generation ELISA was used. Three of the C-100 ELISA positive samples were C-100 RIBA reactive, and six of the second generation ELISA positive samples were 4-RIBA reactive. The HCV genome was not detected in any of the seven anti-HCV C-100 ELISA and second generation ELISA positive sera which were studied by polymerase chain reaction, including four cases confirmed by 4-RIBA. Life expectancy, as determined by survival analysis, did not differ significantly between anti-HCV-positive and -negative patients. These findings suggest that anti-HCV positivity does not influence the clinical presentation and course of primary biliary cirrhosis.

Anti-GOR and hepatitis C virus in autoimmune liver diseases

Anti-GOR is an autoantibody found in hepatitis C virus (HCV) infection. We have studied the specificity of this antibody for HCV infection in various groups of autoimmune liver diseases. Anti-HCV was detected by a second generation HCV enzyme-linked immunosorbent assay in 14 of 29 patients with liver-kidney-microsomal (LKM-1) -antibody-positive autoimmune hepatitis type 2 and in all 6 control patients with HCV-RNA-positive chronic hepatitis C. Anti-HCV was not found in those with antinuclear-antibody-positive autoimmune hepatitis type 1 (10 patients), with soluble-liver-protein-antibody-positive autoimmune hepatitis type 3 (8), with primary biliary cirrhosis (9), with systemic lupus erythematosus (SLE) (10), or in healthy controls (13). Anti-GOR was detected in 11 of 14 patients with autoimmune hepatitis type 2 who were all positive for anti-HCV but only in 1 of 15 LKM-1 patients who were negative for anti-HCV. We did not find anti-GOR in any other group of autoimmune liver disease, SLE, or control sera, but this antibody was detected in 3 of 6 patients with chronic hepatitis C. Autoimmune hepatitis type 2 patients who were anti-GOR positive and anti-HCV positive were less likely to be female, were older (p less than 0.001), and had lower LKM-1 antibody titres (p less than 0.001), lower disease activity, and responded less effectively to immuno- suppression than did those who were anti-HCV negative/anti-GOR negative. The findings show that anti-GOR reflects HCV-specific autoimmunity. HCV seems to induce autoimmunity to both GOR (an HCV-specific autoepitope) and LKM-1 (an epitope that is also recognised by autoimmune hepatitis sera of a different cause). Anti-GOR and LKM-1 antibodies contribute to a better differentiation of chronic hepatitis, a finding that has therapeutic implications.

Antibodies to hepatitis C virus in primary biliary cirrhosis

We investigated the prevalence of anti-HCV in 160 consecutive patients with primary biliary cirrhosis. By ELISA, 19 (12%) were positive, as compared to a 68% prevalence in 135 patients with chronic non-A, non-B hepatitis. Serum IgG levels were significantly higher in the anti-HCV positive group. By RIBA, seropositivity was confirmed for 4 patients, whereas 7 were indeterminate. A slight, non-significant reduction of life expectancy was found in anti-HCV positive patients. Until reliable and independent confirmatory tests become available, definitive conclusions on the importance of anti-HCV positivity in primary biliary cirrhosis are improper.

LKM-1 autoantibodies recognize a short linear sequence in P450IID6, a cytochrome P-450 monooxygenase

LKM-1 autoantibodies, which are associated with autoimmune chronic active hepatitis, recognize P450IID6, a cytochrome P-450 monooxygenase. The reactivities of 26 LKM-1 antisera were tested with a panel of deletion mutants of P450IID6 expressed in Escherichia coli. 22 sera recognize a 33-amino acid segment of P450IID6, and 11 of these recognize a shorter segment, DPAQPPRD. PAQPPR is also found in IE175 of herpes simplex virus type 1 (HSV-1). Antibodies for HSV-1 proteins were detected by ELISA in 17 of 20 LKM-1 sera tested. An immobilized, synthetic peptide, DPAQPPRDC, was used to purify LKM-1 antibodies. Affinity purified LKM-1 autoantibodies react on immunoblots with a protein in BHK cells after infection with HSV-1. 11 of 24 LKM-1 sera, including 3 that recognize DPAQPPRD, also exhibit antibodies to the hepatitis C virus (HCV) protein, C100-3. Affinity purified LKM-1 antibodies did not recognize C100-3. However, partial sequence identity was evident between portions of the immunopositive 33-amino acid segment of P450IID6 and other portions of the putative HCV polyprotein. Immune cross-recognition of P450IID6 and HCV or HSV-1 proteins may contribute to the occurrence of LKM-1 autoantibodies.

Hepatitis C viraemia in adults with type 2 autoimmune hepatitis

Sera from 14 patients with type 2 autoimmune hepatitis (anti-LKM1 positive) were investigated for evidence of hepatitis C virus (HCV) infection. Antibodies to HCV were detected in 13 patients by both commercial and "in-house" ELISAs and also by a second generation recombinant immunoblot assay. Nine of the 13 (69%) anti-HCV positive patients were shown to be viraemic by a polymerase chain reaction-based assay for serum HCV RNA. Neither anti-HCV nor serum HCV RNA were detected in any of 6 controls with primary biliary cirrhosis or in 39 healthy blood donors. These findings strongly suggest a role for HCV in the pathogenesis of type 2 autoimmune hepatitis.