Immunhistochemical identification of HCV target antigen in paraffin embedded liver tissue using the Tar DJI-22 monoclonal antibody: reproduciblity and staining patterns

ABSTRACT

Many of anti-HCV antibody-positive patients who are seronegative for HCV RNA were found positive by RT-PCR within the liver biopsy. In situ PCR, while sensitive, is technically difficult and expensive. So, there is a need for a simple, specific and reproducible method to identify HCV target antigens in liver biopsy specimens, which will help in more accurate diagnosis. Immunohistochemical staining has been applied successfully to detect HCV antigen in fresh frozen tissue. In paraffin-embedded tissues, however, minimal trials with conflicting results have been reported. The present study is a trial to evaluate the identification of HCV antigen in paraffin embedded liver biopsies using the anti HCV monoclonal antibody TORDJI-22 and to correlate the results with clinical and histopathological severity in chronic hepatitis C patients. Methods: We applied immunohistochemicl staining for HCV in 66 paraffin-embedded liver biopsy specimens. 46 from patients seropositive for HCV -RNA and twenty control liver biopsy specimens [5 HBV patients and negative for HCV, 5 metabolic liver diseases, 5 auto-immune chronic hepatitis and 5 extrahepatic biliary atresia]. The TORDJI-22 monoclonal antibody was applied in dilution 140, with overnight incubation. HBsAg and HBcAg immunohistochemistry were applied routinely. Results: Reproducible staining patterns of HCV antigen in tissues were identified among the majority [.42/46 - 91%] of HCV RNA seropositive cases. The staining pattern was cytoplasmic of hepatocytes, with occasional nuclear hue. It is mainly coarse granular with microvesicular pattern. Three staining patterns were identified A diffuse or membranous, B; patchy, and C;occasional paranuclear.Non of the control samples showed a similar staining pattern. Conclusion: Immunohistochemical identification of HCV antigen is easy to apply in paraffin embedded liver biopsy specimens when the optimal detection techniques were applied. HCV target proteins in liver tissues could be markers of progressive damage. Also, accumulation of these proteins may be involved in the pathogenesis of hepatocyte injury in chronic hepatitis C