Understanding Adenovirus maturation: A nanomechanics approach

The ability of adenoviruses to infect a broad range of species and tissues has led to a widespread interest in their biological functioning. However, there remains a big gap in our understanding of their assembly and maturation pathways. Here, we present AFM (Atomic Force Microscopy) nanoindentation and fatigue studies1,2 of adenovirus capsids3 at different stages of maturation. Surprisingly, we find that the intermediate (no DNA) immature capsid is mechanically indistinguishable as compared with the mature (DNA filled), suggesting a major stabilizing role of the scaffold protein.3 However, these capsids have distinctly different disassembly pathways, as indicated by a mechanically-induced fatigue analysis. Additionally, we observed that mutation of the protease cleavage site of the precursor protein VI yields a maturation-intermediate capsid, G33A, which has reduced infectivity and releases half as many pentons as the WT capsid. The presented results strongly indicate that the reduced infectivity results from a reduction in protein VI exposure, partially inhibiting lysis of the endosome and leading to abortive infection.