Background: The identification of native HCV antigens may prove very useful in the diagnosis and early treatment of HCV infection. Here, we aimed to identify and partially characterize a native HCV-NS4 antigen.
Methods: The western blot, ELISA and immunohistochemical staining were used to identify the native antigen in sera and liver biopsies of HCV serotype 4 infected patients.
Results: The native NS4 antigen was identified in serum at 27-kDa molecular weight, in addition to a lower approximately 21-kDa antigen. The purified HCV antigen showed a polypeptide band at 27-kDa when analyzed by silver stained SDS-PAGE and a single peak at 7.6 min by capillary zone electrophoresis. The immunostaining pattern of hepatocytes was cytoplasmic with mainly coarse granular and diffuse pattern based on specific rabbit antisera to the native HCV antigen. A highly significant correlation (r=0.797, p<0.0001) was shown between serum concentrations of the HCV-NS4 antigen and HCV-RNA. Also, antigen detection rates were increased (p<0.05) with the progression of liver disease.
Conclusion: A native HCV-NS4 antigen was identified and partially characterized as 27-kDa protein and the NS4 antigenemia based ELISA test can serve as a useful addition to HCV diagnostic methods, especially under field condition.