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 <0.01), and a higher prevalence of hepatitis B e antigen (24% vs. 13%, p <0.001). Carriers of HBsAg/awr 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 wir allele. The presence of wand __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 <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 <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. © 1992 Wiley‐Liss, Inc.