Adeno Viruses Introduction History and Its TYPES
- 1. Adeno Viruses Syed Shah Raza MLT120212004
- 2. Introduction • Adenoviridae are medium-sized (80–100 nm). • These are nonenveloped (without an outer lipid bilayer) viruses with an icosahedral nucleocapsid. • It contains a double-stranded DNA genome. • Their name derives from their initial isolation from human adenoids in 1953.
- 3. Continue… They have a broad range of vertebrate hosts; • In humans, more than 50 distinct adenoviral serotypes have been found to cause a wide range of illnesses. • From mild respiratory infections in young children (known as the common cold) to life-threatening multi-organ disease in people with a weakened immune system.
- 4. Family of Adenoviradae This family of the Adenoviradae contains the following genera; • Atadenovirus • Aviadenovirus • Ichtadenovirus • Mastadenovirus (including all human adenoviruses) • Siadenovirus • Testadenovirus In humans, currently there are 88 human adenoviruses (HAdVs) in seven species (Human adenovirus A to G)
- 5. Structure • Icosahedral, about 80-110 nm diameter • 252 capsomeres • Fibre projects from each of 12 pentons base • 240 are called as hexons • Resemble a space ship • Genome is dsDNA • Replicates in nucleus
- 6. Mode of Replication • Adenoviruses attach to surface of the cells by their fibers, then penetrate the cell, and once inside the cell, uncoat the viral DNA. • The viral DNA is then transported into the nucleus of the cell and initiates replication cycle. • Host cell DNA-dependent RNA polymerase transcribes the early genes leading to formation of functional mRNA.
- 7. Continue… • Then in the cytoplasm, the early mRNA is translated into nonstructural proteins. • In the nucleus, after viral DNA replication, late mRNA is transcribed and then translated into structural virion proteins. • This is followed by assembly of virions in the nucleus and release of virions by lysis of the cells, but not by budding.
- 8. Transmission
- 9. Pathophysiology • Adenoviruses are transmitted mainly by respiratory or oral-fecal contact from humans. • They infect the conjunctiva or the nasal mucosa. • They may multiply in conjunctiva, pharynx, or small intestine, and then spread to cervical and mesenteric lymph nodes, where epithelial cells are infected.
- 10. Continue… Adenoviruses may cause three different types of interaction with the infected cells. These are • Lytic infection. • Latent infection. • Oncogenic infection.
- 11. Lytic Infection • Adenoviruses infect mucoepithelial cells in the respiratory tract, gastrointestinal tract, and conjunctiva or cornea, causing damage of these cells directly. • After local replication of the virus, viremia follows with subsequent spread to visceral organs. • Dissemination occurs more commonly in immunocompromised patients than in the immunocompetent individuals.
- 12. Latent Infection • The adenovirus has a unique ability to become latent in lymphoid and other tissues such as adenoids, tonsils, and Payer’s patches. • The exact mechanism of latency of adenoviruses in these tissues is not known. • These latent infections can be reactivated in patients infected with other agents or in the patients who are immunocompromised.
- 13. Oncogenic Infection • Some adenoviruses belonging to groups A and B have the property for oncogenic transformation in stem cells. • During oncogenesis the multiplication of adenovirus is inhibited followed by integration of viral DNA into the host DNA. • After integration adenoviruses produce E1A proteins which target stem cells by altering cellular transcription, finally leading to transformation of stem cells. • However, oncogenesis of human cells has not been demonstrated.
- 14. Clinical Syndromes • Adenoviruses primary infect children. • Adults are also infected. • More than one serotypes of virus may produce the same clinical syndrome and one serotype of virus may cause clinically different diseases. • Adenoviruses 1-7 are the common serotypes worldwide and are responsible for most cases of adenovirus-associated infections. • Incubation period varies from 5 to 8 days.
- 15. Pink Eyes Infection • This disease is caused by adenovirus serotypes 8, 11, 19, 37. • Redness and itchiness in one or both eyes. • Inflammation of the conjunctiva may persist for a week, accompanied with residual scarring and visual impairment. • A gritty feeling in one or both eyes. • A discharge in one or both eyes that forms a crust during the night that may prevent your eyes from opening in the morning. • Tearing. • Sensitivity to light.
- 16. Acute Respiratory Diseases • This disease is caused by adenovirus serotypes 4 and 7. • Fever, cough, and sore throat are the typical symptoms which last for 3-5 days. • This syndrome most often affects military recruits living in crowded conditions.
- 17. Gastroenteritis and Diarrhea • These conditions are most commonly associated with serotypes 40 and 41, but other serotypes may also be involved. • The enteric adenovirus infection is a common cause of infantile diarrhea. • The condition manifests as fever and watery diarrhea, which resolves within 1-2 weeks.
- 18. Laboratory Diagnosis • Specimens : from throat, urine, feces. • Isolation of virus: • Inoculation into cell cultures. • Serology : rise in concentration of antibodies in serum. • Electron Microscopy : for stool to see virus. • Immunofluorescence : antigen detection in Nasopharyngeal /occular specimens
- 19. Serology • These tests utilize measures to assess the levels of the antibodies that have been generated against an active infection with adenovirus. • Anti-AdV IgG antibodies are detected in the infection of adenoviruses.
- 20. Thank You!
Editor's Notes
- #10: Cervical: Neck region of backbone Mesentric lymphnode: The mesenteric lymph node is the “first pass” organ for nutrients and microbial substances entering the lymph fluid.
- #12: Visceral Organs: The soft interior organs of the body, such as the heart and lungs, and those in the abdomen, such as the liver, pancreas, and intestines.
- #13: Payer patches: Small clusters of lymphatic tissue found in the wall of the small intestine
- #16: Greet feeling: your eyes feel scratchy or rough.
- #18: 1) Diarrhea occurring in infants from newborn to 24-months old