POLYMERASE CHAIN-REACTION CAN RESOLVE SOME UNDEFINED CASES OF HEPATITIS-B VIRUS ANTIGENIC SUBTYPING

HBsAg subtypes were defined by means of adsorbed polyclonal antisera; however, HBsAg subtyping is currently usually carried out with monoclo nal antibodies (Mab). We developed a complementary subtyping method ba sed on the polymerase chain reaction. Reference samples belonging to a ll known HBsAg subtypes could be detected and grouped into four differ ent categories (ayw1/ayw4/ayr, ayw2/ayw3, adw2/adrq+/adrq-, adw4). Thi rteen HBsAg-positive serum samples previously subtyped as ad by means of monoclonal antibodies fell into the adw2/adrq+/adrq- group, as well as 13 ay samples into the ayw2/ayw3 group. These results could be con firmed by means of reference polyclonal antisera in nine ad cases (all adw2) and in seven ay cases (all ayw3); the remaining seven were belo w the detection limit of the polyclonal assay. Four samples which were not recognized by any of the d/y subtype-specific Mab were shown to c ontain ayw2/ayw3 sequences. Only one contained sufficient HBsAg to be confirmed as ayw3 by means of reference antisera. Th ree of five sera showing simultaneous reactivity both for d and y-specific Mab were cla ssified as adw4 by PCR, as was one by reference polyclonal antisera. T he y-specific monoclonal antibody cross-reacted with the adw4 subtype. Single adw2 sequences were amplified in one of the remaining two case s, as well as single ayw2/ayw3 sequences in the other, suggesting that they showed true coexistence of two strains of different subtype, onl y one of which was in active replication state. It is concluded that t he method described is useful in the solution of some undefined cases obtained with the monoclonal-based assays. (C) 1994 Wiley-Liss, Inc.