Clinical and biologic importance of F-actin autoantibodies in HCV monoinfected and HCV-HIV coinfected patients

Easy recognition and high autoimmune hepatitis specificity of smooth muscle antibodies giving an actin microfilament immunofluorescent pattern on embryonal vascular smooth muscle cells

Smooth muscle antibodies (SMA) with anti-microfilament actin (MF-SMA) specificity are regarded as highly specific markers of type 1 autoimmune hepatitis (AIH-1) but their recognition relying on immunofluorescence of vessel, glomeruli, and tubules (SMA-VGT pattern) in rodent kidney tissue, is restricted by operator-dependent interpretation. A gold standard method for their identification is not available. We assessed and compared the diagnostic accuracy for AIH-1 of an embryonal aorta vascular smooth muscle (VSM) cell line-based assay with those of the rodent tissue-based assay for the detection of MF-SMA pattern in AIH-1 patients and controls. Sera from 138 AIH-1 patients and 295 controls (105 primary biliary cholangitis, 40 primary sclerosing cholangitis, 50 chronic viral hepatitis, 20 alcohol-related liver disease, 40 steatotic liver disease, and 40 healthy controls) were assayed for MF-SMA and SMA-VGT using VSM-based and rodent tissue-based assays, respectively. MF-SMA and SMA-VGT were found in 96 (70%) and 87 (63%) AIH-1 patients, and 2 controls (P < 0.0001). Compared with SMA-VGT, MF-SMA showed similar specificity (99%), higher sensitivity (70% vs 63%, P = ns) and likelihood ratio for a positive test (70 vs 65). Nine (7%) AIH-1 patients were MF-SMA positive despite being SMA-VGT negative. Overall agreement between SMA-VGT and MF-SMA was 87% (kappa coefficient 0.870, [0.789-0.952]). MF-SMA were associated with higher serum γ-globulin [26 (12-55) vs 20 g/l (13-34), P < 0.005] and immunoglobulin G (IgG) levels [3155 (1296-7344) vs 2050 mg/dl (1377-3357), P < 0.002]. The easily recognizable IFL MF-SMA pattern on VSM cells strongly correlated with SMA-VGT and has an equally high specificity for AIH-1. Confirmation of these results in other laboratories would support the clinical application of the VSM cell-based assay for reliable detection of AIH-specific SMA.

Extracellular Actin in Health and Disease

This review considers the functions of extracellular actin - cell surface bound, associated with extracellular matrix, or freely circulating. The role of this protein in different pathological processes is analyzed: its toxic effects and involvement in autoimmune diseases as an autoantigen. The extracellular actin clearance system and its role in protection against the negative effects of actin are characterized. Levels of free-circulating actin, anti-actin immunoglobulins, and components of the actin clearance system as prognostic biomarkers for different diseases are reviewed. Experimental approaches to protection against excessive amounts of free-circulating F-actin are discussed.

The occurrence of autoantibodies in patients with chronic HCV infection, including patients dialyzed and after kidney transplantation

Introduction

There are reports suggesting that hepatitis C virus (HCV) may stimulate the autoimmune process. Studies have been undertaken to evaluate the occurrence and type of autoantibodies in HCV-infected patients with and without immunosuppression. Results were analyzed according to HCV genotype, intensity of inflammation and liver fibrosis stage.

Material and methods

The study included 105 patients chronically infected with HCV, including 25 with immunological suppression administered for kidney disease or kidney transplantation. Blood samples were tested by immunoblotting for the presence of AMA-M2, SLA/LP, LKM-1, LC1, anti-F-actin, anti-desmin, anti-myosin, anti-gp210 and anti-sp100 autoantibodies, and ANA. All the patients were scored for autoimmune hepatitis.

Results

Autoantibodies were detected in 32.5% of patients without immunosuppression and in 16% with immunosuppression. Single types of autoantibodies were identified in 26% of patients. The most frequent ones were ANA (19%) and AMA-M2 (5.7%). The presence of antibodies in patients with genotype 1 was significantly higher in comparison to their occurrence in genotype 3. Autoimmune hepatitis was not diagnosed in any of the patients. Immunoglobulin G level was significantly higher in patients with detectable autoantibodies, compared to patients without antibodies (1.89 vs. 1.28 g/dl, p < 0.001). No correlation between fibrosis stage or intensity of inflammatory state and the frequency of antibodies was found.

Conclusions

The antibodies are significantly more frequent in patients without immunosuppression and in patients infected with genotype 1 than genotype 3. The presence of these autoantibodies is not associated with the development of autoimmune hepatitis. Higher level of immunoglobulin G in the serum correlates with the presence of autoantibodies.

Hepatitis C virus infection and autoimmunity

According to the WHO estimates, the rate of hepatitis C virus (HCV) infection is approximately 3% in the world, and approximately 170 million people are infected with HCV. About 3.15 million new cases of HCV infection are diagnosed each year. Multiple autoantibodies can often be detected in patients with chronic HCV infection. Elucidation of the relationship between HCV infection and autoimmunity will open new perspectives for understanding the pathogenesis of HCV infection and the natural history of hepatitis C.