Gerd Michel

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.

In vitro secretion of anti-GOR protein and anti-hepatitis C virus antibodies in patients with chronic hepatitis C

BACKGROUND/AIMSnAnti-GOR antibodies may reflect hepatitis C virus (HCV)--related autoimmunity or cross-reactivity with HCV core antigen. This study aimed to evaluate the clinical significance of anti-GOR antibodies.nnnMETHODSnPeripheral blood mononuclear cells (PBMCs) were isolated from 35 patients with HCV and 48 controls and cultured for 8 days. The in vitro antibody secretion by PBMC was determined using specific enzyme-linked immunosorbent assays and recombinant immunoblot assay.nnnRESULTSnIn 22 of 35 patients with HCV (62.9%), PBMCs secreted anti-c22-3 or anti-c33c antibodies. However, in 3 of 48 controls (6.2%), PBMCs secreted anti-c33c antibodies alone. A significant in vitro anti-GOR response was found in 13 of 35 patients (37.1%) with HCV in relation to 4 of 48 controls (8.3%). In 12 of these patients (92.3%), anti-GOR were found in vitro and in serum. Two patients with HCV produced in vitro anti-GOR but not anti-c22-3 antibodies. Regarding disease activity, in vitro anti-GOR-positive patients with HCV had significantly higher alanine aminotransferase levels (108.8 +/- 17.8 U/L vs. 64.5 +/- 7.6 U/L; P < 0.01) and more frequent signs of chronic active hepatitis (10 of 13 [76.9%] vs. 10 of 22 [45.5%]) than patients with HCV without in vitro anti-GOR response.nnnCONCLUSIONSnThe humoral anti-GOR response in vitro is closely related to HCV infection and disease activity. Anti-GOR and anti-HCV core antibodies are regulated independently. It is likely that anti-GOR may reflect an HCV-associated autoimmune phenomenon.

Hepatitis C virus antibody secretion in vitro by peripheral blood lymphocytes

A recombinant polypeptide corresponding to a virus-specific cDNA clone (c100-3) serves as the antigen for a hepatitis C virus (HCV) antibody assay. Previous investigations have shown an 80% prevalence of HCV antibodies in sera of patients suffering from post-transfusional chronic hepatitis non-A, non-B, but positive results were also obtained for 30 to 70% of sera from patients with chronic hepatitis B or autoimmune hepatitis. In this study we show that HCV antibodies are secreted by peripheral blood lymphocytes (PBL) in vitro. PBL from 12/35 patients with chronic non-A, non-B hepatitis and 1/6 patients with chronic active hepatitis B spontaneously secreted HCV antibodies in cell culture supernatants. The results were confirmed by neutralisation assay and ELISAs using recombinant and synthetic polypeptides derived from the c100-3 antigen and from the HCV core antigen. Two patients suffering from non-A, non-B hepatitis were negative for HCV antibodies in serum, but their PBL produced HCV c100-3 antibodies in vitro. PBL from patients suffering from autoimmune chronic hepatitis, primary biliary cirrhosis, toxic-liver injury and healthy blood donors did not produce antibodies to HCV c100 antigen irrespective of HCV antibody test results in their sera. Polyclonal B cell activation or mitogenic stimulation of T helper cells led to increased immunoglobulin synthesis by PBL in vitro, but did not lead to enhancement of specific HCV antibody production. In addition, HCV antibody production was not induced by these stimulation procedures in control lymphocytes. This spontaneous HCV antibody production in vitro suggests persistent antigenic stimulation of the B cells in vivo.

Lack of monomeric IgM anti-hepatitis C virus (HCV) core antibodies in patients with chronic HCV infection

Antibodies of the IgM class against the hepatitis C virus core antigen are found in up to 70% of patients with either acute or chronic hepatitis C. The sedimentation rate of such IgM was analyzed by rate-zonal centrifugation of nine sera taken from seven patients, two acutely and five persistently infected with hepatitis C virus. All patients had circulating high-molecular weight (i.e. pentameric) IgM, indicating that the production of low molecular weight IgM, commonly observed in other persistent viral infections, does not apply to hepatitis C virus and cannot be used to distinguish acute from chronic hepatitis C virus infection.

Demonstration of specific detection of anti-HCV IgM core antibodies.

The specificity of IgM isotype response directed against the putative core of hepatitis C virus (HCV core IgM) was demonstrated in HCV IgM EIA reactive samples. No interference was noted when samples with increasing levels of rheumatoid factor (RF) alone, or in combination with graded concentrations of anti-HCV IgG (HCV IgG), were tested. No deterioration in assay specificity was seen in 30 sera from patients wih monoclonal gammapathies (all isotypes). With Protein G affinity chromatography, RF/HCV IgG immune complexes and HCV core IgM antibodies displayed different binding characteristics, HCV core IgM appeared in the buffer eluate while HCV IgG/RF remained bound. With sucrose density gradient centrifugation HCV core IgM sedimented at 17-19S.