Adenovirus 41 Replication: Cell-related Differences in Viral Gene Transcription

Adenovirus 41 infection of human embryo fibroblasts (HEF cells) leads to an abortive replication cycle whereas semi-permissive infection of Chang cells and permissive infection of 293 cells leads to the production of infectious particles. The aim of this study was to delineate where in the viral life cycle the block in replication occurs in non-permissive cells. DNA replication marks the onset of the late stage of the replication cycle but synthesis of DNA could only be detected when cultures were co-infected with Ad2, suggesting an early block in Ad41 replication. In order to map Ad41-specific transcripts produced following infection of HEF, Chang and 293 cells, tentative transcription units (determined by alignment with the Ad2 and Ad40 transcription maps) were first assigned to various plasmids carrying Pstl fragments. These plasmids were used as probes to detect Ad41 transcripts that map to these regions. Only transcripts mapping to the region between 0 and 12 map units were detected in Ad41 infected HEF cells. The level of late transcription was found to be low even in Chang and 293 cells and we therefore employed a more sensitive method to detect major late transcripts in Ad41 infected HEF cells. Transcripts carrying 59 kDa-fibre gene-specific sequences could be detected using RT-PCR at earlier times in 293 cells when compared to Chang cells but were present over a much longer time period in the latter cells, and could not be detected in HEF cells. These results are in agreement with the results from DNA synthesis in Ad41 infected HEF cells and mapping of transcripts to specific regions of the Ad41 genome, confirming that the Ad41 block in replication occurs within the early phase of the infectious cycle.