Appearance of viral RNA transcripts in the early stage of duck hepatitis B virus infection

Sequential analysis of duck hepatitis B virus (DHBV) DNA and RNA transcripts in the liver of the early stage of infection was carried out using 1-day-old ducklings inoculated with DHBV-positive serum. Using Southern blot analysis, a band of supercoiled DHBV DNA was detectable at 6 hr, when DHBV-specific poly[A]+RNA was also observed by Northern blot analysis as a faint smear below 3-kb. Bands of RNA at 3.5, 2.7, and 2.5 kb were detected at 12 hr, just before single-stranded viral DNA was detected. A prominent increase in the amount of viral RNA was demonstrated (between 12 hr and 3 days) prior to the increase of DHBV DNA (between 3 and 6 days). Our results suggest that 3.5-kb DHBV-specific RNA synthesized from supercoiled DNA may act as a template of reverse transcription, and that all steps of the replication pathway proposed by Summers and Mason (1982, Cell, 29, 403-415) are completed during 3 days.