Residual integrated viral DNA after hepadnavirus clearance by nucleoside analog therapy

Abstract

We determined the frequency of integrated viral DNA in the livers of three woodchucks chronically infected with the woodchuck hepatitis virus before and during 30 weeks of therapy with the nucleoside analog L-FMAU [1-(2-fluoro-5-methyl-beta, L-arabinofuranosyl)uracil, clevudine]. We found that although viral covalently closed circular DNA declined 20- to 100-fold, integrated viral DNA showed no discernable decrease over the course of treatment. Thus, chemotherapeutic clearance of covalently closed circular DNA did not involve the replacement of the infected hepatocyte population with uninfected progenitors, but rather, uninfected hepatocytes in the treated liver were derived from the infected hepatocyte population. The frequency of integrated DNA in chronically infected woodchucks was found to be 1 or 2 orders of magnitude higher than that in transiently infected woodchucks, implying that integration and other genomic damage accumulate over the duration of infection. Our results indicate that genetic changes from this damage remain in the liver even while virus infection is cleared and argue for early antiviral intervention in chronic hepatitis.

Fig. 1.

Cumulative distribution of viral recombination sites of 95 left-end viral-cell junctions. Symbols indicate the cumulative frequency of recombination sites as a function of their positions on the WHV genome, from right to left. The numbered arrows mark the positions on the genome of the following: 1, the sequencing primer (3′ end at nucleotide 2145); 2, the left end of in situ primed linear DNA (nucleotide 1935); 3, the 3′ end of DR2 (nucleotide 1729). Ninety-eight percent of all viral recombination sites are to the right (downstream) of nucleotide 1729 (arrow 3).