Insufficient accumulation of viral late mRNAs restricts the replicative cycle of human adenovirus type 37 in A549 cells.

Most serotypes of human adenoviruses, except subgroup C viruses such as serotype 2 (Ad2) and Ad5, can grow only to low titers in vitro in human cell lines. To analyze the properties of the replicative cycles of poorly growing Ad serotypes, we compared Ad37 and Ad5 in human A549 cells. In comparison with Ad5, Ad37 showed a slower development of viral-induced cytopathic effects and prolonged cell viability. Furthermore, the maximum yields of progeny viruses were reduced by almost 100-fold. Although the amount of viral DNA and E1A mRNA in infected cells reached comparable levels between these two serotypes, the accumulation of viral late mRNAs and structural proteins in Ad37-infected cells was severely reduced. Overall, our study explains critical steps in the replicative cycle of Ad, which cause serotype-specific restrictions in permissive human cell lines.