Analysis of fitness differences of hepatitis B virus genotypes D and F using a cotransfection assay

Abstract

Hepatitis B virus (HBV) circulates as a collection of genetically related variants that evolve throughout the chronic infection. Those viral variants that have the greatest ftness are fxed. We recently showed diferent ftness for HBV variants involved in two epidemiological situations. To understand these ftness diferences better, we determined the levels of extracellular HBV DNA, the synthesis of HBV DNA intermediates, and the expression of HBeAg and HBsAg in transfection and cotransfection assays. Our results show that for the subgenotype (sgt) D1, which has an 8-nucleotide deletion (sgtD1del) and exhibits lower ftness, the levels of extracellular DNA and intracellular replicative intermediates were much lower than with sgtD1wt or sgtD1mut (G1896A), which had higher ftness. In addition, in the cotransfection assay, sgtD1del inhibited sgtD1mut but not sgtD1wt replication. We also found that sgtF1b, which exhibits higher ftness, produces signifcantly higher levels of both extracellular DNA and intracellular replicative intermediates than does the lower-ftness sgtF4. These results demonstrate a relationship between ftness and the replicative ability of the HBV genome in the transfection assay. In addition, the data obtained by cotransfecting cells with sgtD1del and sgtD1mut provide new information about the impact of simultaneous replication of two viral variants in the same cell system on HBV replication.