Wild-Type Human Adenovirus (Serotype 1)

Wild-type human adenovirus serotype 1 (HAdV-1) is a nonenveloped, double-stranded DNA virus belonging to the Adenoviridae family. It is primarily transmitted through respiratory droplets, direct contact with infected individuals, or fomites, and is highly contagious in crowded environments such as schools and daycare centers. HAdV-1 typically causes mild to moderate respiratory infections, including pharyngitis, conjunctivitis, and pneumonia, particularly in children and immunocompromised individuals. The virus initially infects upper respiratory epithelial cells and binds to cellular receptors, such as the coxsackievirus and adenovirus receptor (CAR) or CD46. Following internalization, the virus disrupts the host cell replication machinery, leading to cell lysis and subsequent viral shedding. In rare cases, the virus may disseminate systemically, causing severe consequences such as hepatitis or meningoencephalitis, particularly in vulnerable populations.

The HAdV-1 capsid is icosahedral, approximately 90 nanometers in diameter, and is composed of 252 capsomeres, consisting of 240 hexons and 12 pentons at the vertices. Pentons are attached to their surface by fiber proteins, which facilitate viral attachment to host cells. Enclosed within the capsid is a linear, double-stranded DNA genome of approximately 36 kilobase pairs (kbp), encoding approximately 30-40 genes. The genome is divided into early (E1-E4), intermediate, and late (L1-L5) transcriptional regions, which regulate viral replication, host immune evasion, and capsid assembly, respectively. Early genes (such as E1A) regulate the cell cycle, while late genes produce structural proteins. The genome also contains inverted terminal repeats (ITRs) essential for replication and virus-associated RNA (VA RNA), which suppresses the host interferon response.