Integration of hepadnavirus DNA in infected liver: Evidence for a linear precursor

DNA of the avian hepadnavirus, duck hepatitis B virus, was found to be inte grated at low abundance into the cellular DNA extracted from the livers of infected ducklings. The frequency of integration was estimated to be at lea st one viral genome per 10(3) to 10(4) cells by 6 days postinfection. The s tructures of virus-cell junctions determined by sequencing were compared wi th those of virus-virus junctions formed by nonhomologous recombination bet ween the ends of linear viral DNA forms. This comparison allowed us to conc lude that linear viral DNA was the preferential form used as an integration substrate. Potential factors promoting viral DNA integration during chroni c infection are discussed.