Seroepidemiological studies on a non-A, non-B hepatitis specific antigen/antibody system (SO-antigen/anti-SO)

The patients and staff members of a haemodialysis unit were examined for their serological responses to SO-antigen, which was isolated from the urine of epidemic type non-A, non-B hepatitis patients at Tohoku University Hospital. To understand how SO-antigen or SO-antigen-related aetiology can be incriminated for the hepatitis found in the haemodialysis unit, the prevalence of SO-antigen/anti-SO system and hepatitis A and B virus-related antibodies was compared in the sera of patients and staff members. Although the SO-antigen was rarely detected in the serum, anti-SO antibody was frequently detected in the sera of patients and staff. A significantly higher prevalence was found in the serum of patients (15%, 54 out of 361) than staff members (7.1%, 13 out of 184) and volunteer blood donors (1%, 3 out of 305). The same prevalence percentages of HBV-related antibodies (either positive for anti-HBs or anti-HBc) and anti-HAV were observed among the patients, staff, and volunteer blood donors, irrespective of whether the sera were anti-SO positive or negative. Among the staff, anti-SO antibody was more frequently found in those with a history of acute hepatitis (16.7%, 3 out of 18) than in those without (6%, 10 out of 166). These prevalence ratios conformed with those of HBV-related antibodies, but the same prevalence ratios of antibody to HAV were observed between the staff with and without a history of acute hepatitis. These results indicate that the SO-antigen/anti-SO system or entity related to this immune system is distinct from HBV or HAV, and this immune system was found widely in the haemodialysis unit where type B and non-A, non-B hepatitis were also found frequently.