Human adenovirus 5 is a double‑stranded DNA virus belonging to species C. Its icosahedral virion, approximately 70–90 nm in diameter, contains a linear genome associated with core proteins and a terminal protein at each 5′ end. This ubiquitous type infects epithelial cells of the upper respiratory tract and can cause mild febrile illness, particularly in children.
Biology and pathogenesis
More than a hundred human adenovirus types have been described. HAdV‑5 shares many features with types 1 and 2: transmission via respiratory droplets, replication in the cell nucleus, and the ability to establish latent infection in lymphoid tissue. After attachment to the host cell, the virus enters by endocytosis and uncoats in the cytoplasm. Its DNA genome enters the nucleus where replication and virion assembly occur, leading to lysis of the cell and release of progeny virions. Host immunity is mediated by neutralising antibodies and cytotoxic T cells. Because type 5 provokes strong innate and adaptive responses and can infect both dividing and non‑dividing cells, it has been adapted into replication‑deficient vectors for gene therapy and vaccine development.
Clinical features and notable facts
Natural infection with HAdV‑5 usually presents as self‑limited pharyngitis, fever, cough and sometimes gastroenteritis. Compared with type 7 or type 14, which are associated with severe respiratory disease, type 5 rarely causes pneumonia. It is not among the adenoviruses that commonly cause epidemic keratoconjunctivitis or paediatric diarrhoea. However, HAdV‑5 is the most widely studied adenovirus in molecular biology. Its genome has been mapped and manipulated to remove early region genes, producing vectors that deliver therapeutic genes or vaccine antigens without replication. Several adenoviral vector vaccines against infectious diseases use a modified type 5 backbone. HAdV‑5 infection is ubiquitous and most adults have antibodies indicating past exposure. Clinically, it is an exemplar of adenovirus biology: mild disease, latent persistence in lymphoid tissues, and high immunogenicity. These characteristics have underpinned its adoption as a platform for vaccine and gene‑delivery research. Related Terms: Human Adenovirus 2, Human Adenovirus 1, Adenovirus vector, Vaccine vector