Distribution of Hepatitis B Virus Genotypes among American Blood Donors Determined with a PreS2 Epitope Enzyme-Linked Immunosorbent Assay Kit

Abstract

ABSTRACT We genotyped 418 sera from volunteer blood donors from two large, regional blood centers in the United States who were HBsAg positive by an enzyme-linked immunosorbent assay (ELISA). The HBV genotypes were determined by a serological method using a preS2 epitope ELISA kit (Institute of Immunology, Tokyo, Japan) with monoclonal antibodies. Of the 418 samples, the genotypes of 320 could be determined (76.6%). One hundred forty-three (34.2%) were genotyped as A (preS2 subtype su), 31 (7.4%) were genotyped as B (subtype m), 59 (14.1%) were genotyped as C (subtype ks), 83 (19.9%) were genotyped as D or E (subtype ksu), and 4 (1.0%) were genotyped as F (subtype k). This kit cannot differentiate genotypes D and E. For 98 (23.4%) of the 418 samples, the genotype could not be determined; 11 of these 98 samples were positive for at least one of the preS2 genotype-specific epitopes (m, k, s, and u), but the combinations of positive epitopes were different from those of samples that could be genotyped; 45 had only the common epitope (b). In the group with a high signal-to-cutoff (S/C) ratio, the HBV genotype could be determined for 199 (84%) of 237 samples; in contrast, in the low-S/C-ratio group, only 10 (20%) of 51 samples could be genotyped ( P < 0.001). These findings may indicate the limitation of genotyping samples with low S/C ratios for HBsAg by ELISA or the existence of genotype G or other new HBV genotypes in HBsAg-positive blood donors in the United States. Of the genotyped samples, 201 were assayed for HBeAg; only 9 (4.5%) were positive for HBeAg. The frequency of genotype C in HBeAg-positive donor samples (5 of 9 or 56%) was higher than that in HBeAg-negative donor samples (33 of 192, or 17%) ( P = 0.022).