Edited by Urs GreberIncoming adenoviruses seize control of cytosolic transport mechanisms to relocate their genome from the cell periphery to specialized sites in the nucleoplasm. The nucleus is the site for viral gene expression, genome replication, and the production of progeny for the next round of infection. By taking control of the cell, adenoviruses also suppress cell-autonomous immunity responses. To succeed in their production cycle, adenoviruses rely on wellcoordinated steps, facilitated by interactions between viral proteins and cellular factors. Interactions between virus and host can impose remarkable morphological changes in the infected cell. Imaging adenoviruses has tremendously influenced how we delineate individual steps in the viral life cycle, because it allowed the development of specific optical markers to label these morphological changes in space and time. As technology advances, innovative imaging techniques and novel tools for specimen labeling keep uncovering previously unseen facets of adenovirus biology emphasizing why imaging adenoviruses is as attractive today as it was in the past. This review will summarize past achievements and present developments in adenovirus imaging centered on fluorescence microscopy approaches.Adenoviruses (Ads) are nonenveloped icosahedral viruses with a diameter of~90 nm with slight structural differences between genotypes. The majority of the Ad capsid shell is composed of 240 hexon trimers, and each of the 12 vertices of the icosahedron is occupied by a penton. Pentons are involved in cell attachment and receptor recognition and are composed of the pentameric penton base from which the trimeric fiber molecule extends. Minor capsid proteins IIIa, VI, VIII, and IX are embedded in the capsid and contribute to capsid stability. Protein VI is located at the inner surface of the capsid, and biochemical data suggest that it may connect the capsid to the core containing the viral genome via protein V. The genome is ã 36-kb double-stranded linear DNA molecule with the terminal protein (TP) covalently bound to each 5 0end. Adenovirus genomes are highly condensed and organized into chromatin by several hundred copies of Abbreviations ADP, adenovirus death protein

Adenovirus vector-based genetic vaccines have emerged as a powerful strategy against the SARS-CoV-2 health crisis. This success is not unexpected because adenoviruses combine many desirable features of a genetic vaccine. They are highly immunogenic and have a low and well characterized pathogenic profile paired with technological approachability. Ongoing efforts to improve adenovirus-vaccine vectors include the use of rare serotypes and non-human adenoviruses. In this review, we focus on the viral capsid and how the choice of genotypes influences the uptake and subsequent subcellular sorting. We describe how understanding capsid properties, such as stability during the entry process, can change the fate of the entering particles and how this translates into differences in immunity outcomes. We discuss in detail how mutating the membrane lytic capsid protein VI affects species C viruses’ post-entry sorting and briefly discuss if such approaches could have a wider implication in vaccine and/or vector development.