Determination of hepatitis B virus subtypes by an enzyme immunoassay method using monoclonal antibodies to type-specific epitopes of HBsAg

We described a Hepatitis B surface antigen (HBsAg) subtyping method based o n a commercial enzyme immunoassay (EIA) for detection of HBsAg in which the procedure was modified to include the use of monoclonal antibodies with re stricted anti-BBs specificities. This method, which was able to classify HB sAg as: ayw1, ayw2, ayw3, ayw3* (intermediate between ayw3 and ayw4), ayw4, ayr, adw2 adw4 and adr, was compared to counter electrophoresis procedure (CEP) by testing HBsAg positive sera from blood donors included in a prospe ctive national epidemiological survey, Among the 256 HBsAg positive samples tested with both techniques, 111 (43.3%) could not be subtyped with CEP vs 10 (3.9%) with our modified EIA. This difference was related to the serum HBsAg concentration which must be greater than 3000 ng/mL and 100 ng/mL for CEP and EIA, respectively. The results obtained from 145 sera with both me thods were concordant. Seventeen out of 18 samples partially classified as ay with CEP were completely determined with FIA. This reliable procedure, derived from commercially available reagents, can be easily used in several applications such as large epidemiologic studies and as a substitute for nucleotide. sequencing genotyping which is not adap ted for large-scale screening and not applicable on samples from nonviremic hepatitis B virus (HBV) carriers.