IN-VIVO SELECTION OF A HEPATITIS-B VIRUS MUTANT WITH ABNORMAL VIRAL PROTEIN EXPRESSION

We have investigated the molecular basis for the in vivo selective adv antage of a hepatitis B virus (HBV) mutant. We have determined the com plete nucleotide sequences of the major HBV forms identified at the be ginning (B1-83) and end (B1-89) of a 6 year follow-up of a chronically infected patient. The B1-89 sequence showed marked nucleotide rearran gements (a nucleotide divergence of 11.3 % compared with the adw2 subt ype), but sequence comparison showed that both viral molecules were of common origin (62/138 mutations were found on both molecules, compare d to adw2). In vitro transfection of Huh7 cells showed important modif ications in B1-89 viral protein expression. We observed a decrease in B1-89 envelope protein expression associated with a modification of th e migration pattern of the large envelope protein. For the B1-89 capsi d protein, an insertion of 36 nucleotides at the 5' end of the C gene resulted in increased expression of a core-specific protein of abnorma l size (24 kDa versus 22 kDa). Finally, our data also suggest an incre ase in the trans-complementation efficiency of the mutated B1-89 polym erase protein. Thus, we were able to demonstrate distinct intrinsic pr operties of HBV DNA molecules isolated from a chronic carrier with vir us multiplication at different times during infection. Modifications o f viral protein expression in the mutated form illustrate strategies u sed by the virus to prevent clearance and to contribute to viral persi stence.