Human Adenovirus 5 is a species C adenovirus within the genus *Mastadenovirus*. It is a non‑enveloped icosahedral virus containing a linear double‑stranded DNA genome and is one of the most studied adenoviruses due to its use as a vector in gene therapy and vaccine platforms.
Structure and Biology
Adenovirus 5 virions measure about 90 nm and consist of a protein capsid composed of hexon, penton base and fiber proteins surrounding the viral genome. The fiber knob binds to the coxsackie‑adenovirus receptor (CAR) on host cells, while the penton base engages integrins to facilitate endocytosis. Following uncoating, the viral genome is delivered to the nucleus where early genes modulate host cell functions and initiate viral DNA replication. Late genes encode structural proteins that assemble into new virions. Infection primarily involves epithelial cells of the respiratory and ocular mucosa, and newly formed virions are released upon cell lysis.
Clinical and Biotechnological Significance
Human adenovirus 5 typically causes mild respiratory illness, conjunctivitis or gastroenteritis in children, though most infections are asymptomatic. Immunocompromised patients may experience severe disease. Species C adenoviruses, including types 1, 2 and 5, establish persistent infections in tonsils and adenoids. Type 5 has gained prominence as a backbone for recombinant adenoviral vectors used in gene therapy and vaccination because it efficiently infects dividing and non‑dividing cells and induces robust immune responses. Examples include experimental therapies for cystic fibrosis, cancer, and licensed vaccines such as some COVID‑19 vaccines. Pre‑existing immunity to adenovirus 5 in the human population can reduce vector efficacy, prompting development of rare serotype vectors. Human adenovirus 5 illustrates how a common respiratory virus has been harnessed for biomedical applications while still contributing to seasonal infections. Understanding its biology and immunogenicity informs both clinical management and vector design. Related Terms: human adenovirus 2, adenoviral vector, gene therapy, coxsackie‑adenovirus receptor, respiratory infection