The pregenome/C RNA of duck hepatitis B virus is not used for translation of core protein during the early phase of infection in vitro

Over the course of duck hepatitis B virus (DHBV) replication, one type of RNA (pregenome/C RNA, 3.5 kb) that corresponds to the whole genome of DHBV is generated from the transcription of viral cccDNA. Previous work has proposed three functions for the pregenome/C RNA: it can serve as the pregenome and be packaged into the core protein during the process of replication, and it encodes the mRNA for both the capsid protein and the viral polymerase. However, little is known about the timing of these functions during the different stages of viral infection. In this study, a reverse transcription quantitative real-time PCR assay was developed to analyze the dynamic transcription process of the pregenome/C RNA. The dynamic expression of the core protein was investigated using an indirect immunofluorescence assay (IFA) and by western blot analysis. The generation of pregenome/C RNA began at 12 h post infection and peaked at 20 h post infection; however, the core protein was not detectable until 24 h post infection. These results demonstrate that the core protein appeared approximately 12 h later than the pregenome/C RNA. These results suggest that the DHBV pregenome/C RNA is not used for the translation of the viral core protein during the early stages of infection.