AdenoviridaeEdit
Adenoviridae is a family of non-enveloped, icosahedral viruses with linear double-stranded DNA genomes that infect a broad range of vertebrates, including humans. These viruses are common causes of respiratory infections, conjunctivitis, and gastroenteritis, especially in children and in settings with close person-to-person contact. Beyond their role as pathogens, adenoviruses are also widely used as tools in biotechnology and medicine, notably as vectors for gene delivery and vaccine development. The family encompasses a number of genera that reflect differences in host range and biology, with human infections most frequently arising from members of the genus Mastadenovirus.
The taxonomy of Adenoviridae comprises several genera that infect diverse hosts. The best-known genera for human and mammalian infections are Mastadenovirus (mammals, including humans) and Aviadenovirus (birds). Other genera include Atadenovirus, Siadenovirus, and Ichtadenovirus, which together reflect the broad ecological footprint of this viral family. The diversity within the family helps explain why adenoviruses are capable of causing a variety of clinical syndromes and why they have become versatile platforms for laboratory research and biomedical applications.
Structure and genome
Adenoviruses are non-enveloped particles with an icosahedral capsid built from major structural proteins such as hexons and penton bases, plus fiber proteins that extend from the capsid and mediate receptor interactions. The genome is a linear double-stranded DNA molecule, typically in the range of about 26 to 45 kilobases, with ends containing terminal repeats that participate in genome replication and packaging. Early genes (including E1A, E1B, E2, E3, and E4) regulate viral transcription and host interactions, while late genes encode structural components required for virion assembly. Viral replication occurs in the host cell nucleus and relies on the host cell’s DNA polymerase and associated replication machinery, rather than a dedicated viral polymerase.
Key features that affect biology and pathogenicity include the use of fiber knobs to engage cellular receptors, the presence of immune-modulating genes, and the capacity to establish lytic infection in permissive cells. Because the capsid and genome can be manipulated in the laboratory, adenoviruses have become prominent tools in basic virology and biotechnology.
Life cycle and cell entry
Adenoviruses initiate infection by attaching to specific cellular receptors, with different serotypes showing preferences for receptors such as the Coxsackievirus and adenovirus receptor (Coxsackievirus receptor or CAR) and, in some cases, other surface molecules like CD46. Following attachment, the virion is internalized via endocytosis and trafficked to the nucleus, where the genome is released and transcription of early genes begins. The early phase sets up the replication program and counteracts host defenses, after which late gene expression produces structural proteins that assemble into new virions in the nucleus. Mature virions are released from the cell through lysis or non-lytic pathways, contributing to the spread of infection.
Hosts, diseases, and clinical relevance
Humans and a wide range of animals serve as hosts for various adenovirus species. In people, infections most commonly manifest as acute respiratory illness, pharyngitis, or conjunctivitis, but they can also cause gastroenteritis, cystitis, and, in immunocompromised individuals (such as organ transplant recipients or patients with congenital immunodeficiencies), more severe disease including pneumonia or disseminated infection. In animals, adenoviruses can cause ocular disease, hepatitis, enteritis, or other organ-specific syndromes depending on the host and viral genus (for example, aviadenoviruses in birds can contribute to inclusion body disease and related syndromes).
Diagnostic approaches for suspected adenovirus infections include molecular methods (such as polymerase chain reaction testing for viral DNA in respiratory or other specimens), antigen detection, and viral culture in specialized settings. Treatment is generally supportive; antiviral options are limited and depend on the clinical context. In certain immunocompromised patients, antiviral agents such as cidofovir have been used off-label with varying success, while prevention and infection-control measures are important to reduce transmission. Vaccines targeting adenoviruses have been developed for specific high-risk groups, notably military recruits, where vaccines against certain Ad serotypes (such as Ad4 and Ad7) are used to reduce disease burden.
## Uses in biotechnology and medicine
Adenoviruses have become valuable vectors for gene delivery in research and therapeutic contexts. First-generation adenoviral vectors, which are engineered to be replication-deficient, can efficiently transduce a wide range of cell types and achieve high levels of transgene expression. Their remains-on-chassis biology—non-integration into the host genome and robust expression—make them useful for vaccines and gene therapy trials, though pre-existing vector immunity and inflammatory responses present challenges that researchers continually address. Ongoing work explores improved vector designs, targeted delivery, and safer immunogenic profiles to expand their clinical utility.
In addition to human medicine, adenoviral vectors are used in biotechnology for functional genomics studies, vaccine development, and cancer research. The ability to package sizable genetic payloads and to produce high-tidelity transgene expression supports a broad array of experimental and therapeutic applications, while regulatory and ethical considerations guide their deployment in clinical settings.
History and epidemiology
Adenoviruses were first characterized in the 1950s after being isolated from adenoids or other respiratory tissues, which gave rise to the name. Their ubiquity across vertebrate species and their capacity to cause outbreaks in crowded settings—military barracks, schools, and similar environments—underscore their public health relevance. Although most infections are mild, severe disease can occur in susceptible individuals, which informs ongoing surveillance, diagnostic readiness, and vaccine development strategies. The diversity of serotypes and host species continues to shape how adenoviruses are studied in both clinical and research contexts.