Hepatitis B surface antigen particles of subtypes <i>adw</i> and <i>adr</i>, and compound subtype (<i>adwr</i>) in symptom‐free carriers in Japan

Abstract

Of sera from 1,878 Japanese blood donors who carried hepatitis B surface antigen (HBsAg), 420 were subtyped as adw (22.4%) and 1,443 as adr (76.8%); only 15 (0.8%) contained HBsAg of subtype ayw or ayr. Sera with HBsAg/adr had higher HBsAg titres than those with HBsAg/adw (geometric mean of haemagglutination titre: 10.1 +/- 2.4 vs. 9.7 +/- 2.4, p less than 0.01), and a higher prevalence of hepatitis B e antigen (24% vs. 13%, p less than 0.001). Carriers of HBsAg/adr progressively predominated over those of HBsAg/adw with increasing age. Of sera from 1,863 carriers of HBsAg/adw or HBsAg/adr, 182 (9.8%) contained HBsAg particles with both subtypic determinants in the w/r allele. The presence of w and r determinants on the same particles was ascertained by sandwiching them between monoclonal antibody with the specificity for w and that with the specificity for r. HBsAg particles of compound subtype (adwr) were found more often in sera with hepatitis B e antigen than those without it (145/403 [36.0%] vs. 37/1,460 [2.5%], p less than 0.001). Sera with HBsAg/adwr particles had HBsAg titres higher than those without them (12.4 +/- 1.9 vs. 9.7 +/- 2.3, p less than 0.001). HBsAg/adwr particles arise from phenotypic mixing of the S-gene product of wild-type virus and that of mutants with point mutations for subtypic changes. The results obtained indicated that HBV strains of subtype adr have a higher replicative activity than those of adw, and suggested that mutations in the S gene for subtypic changes would be associated with an active replication of hepatitis B virus.