microbiology of ADENOVIRUS and diseases caused.pptx

microbiology of the adenoviruses

1. ADENOVIRUS

2. Adenoviruses are a group of medium sized, nonenveloped, double stranded DNA viruses that share a common complement fixing antigen • Adenovirus have been divided into seven groups (A-G) on the basis of their genetic, physical, chemical and biological properties. • They are divided into serotypes on the basis of type specific antigens on penton bases and fibers

3. . medium-sized (80 nm) N onenveloped icosahedral viruses composed of a nucleocapsid and a double-stranded linear DNA genome There are over 52 different serotypes in humans, which are responsible for 5–10% of upper respiratory infections in children, and many infections in adults as well

4. MORPHOLOGY Adenovirus are 80 nm in size • No envelope • The capsid contains 252 capsomers arranged as icosahedrons with 20 triangular facets and 12 vertices. Each penton unit consists of penton base anchored in the capsid and projection or fibre consists of a rode like portion with a knob attached at the distal end • The virus appears like a space vehicle GENOME The genome is linear, nonsegmented double stranded (ds) DNA which is around 30–38 Kbp . • This allows the virus to theoretically carry 30 to 40 genes.

5. REPLICATION  Entry of adenoviruses into the host cell involves two sets of interactions between the virus and the host cell. • Entry into the host cell is initiated by the knob domain of the fiber protein binding to the receptor. • The two currently established receptors are: CD46 for group B human adenovirus serotypes and the coxsackievirus adenovirus receptor (CAR) for all other serotypes.  Once the virus has successfully gained entry into the host cell, the endosome acidifies, which alters virus topology by causing capsid components to disassociate. • These changes as well as the toxic nature of the pentons result in the release of the virion into the cytoplasm. • With the help of cellular microtubules, the virus is transported to the nuclear pore complex, whereby the adenovirus particle disassembles. • Viral DNA is subsequently released, which can enter the nucleus via the nuclear pore. • After this the DNA associates with histone molecules. • Thus, viral gene expression can occur and new virus particles can be generated

6. PATHOGENESIS   The recognized diseases of Adenoviruses predominantly involve the respiratory tract, Gastrointestinal tract and eye. • Virus may be introduced through contact, respiratory droplets or ingestion. After recovery of illness, adenoviruses may maintain latent persistent infections in the tonsils, adenoids and other lymphoid tissues • Infect and replicate in epithelial cells of respiratory tract, gastrointestinal tract, urinary tract and the eye. • Do not spread beyond regional lymph nodes. • Group C persists as latent infections for years in adenoids and tonsils and are shed in feces for many months after initial infection. • Most adenovirus replicate in intestinal epithelium after ingestion but usually produce sub clinical infection than overt symptoms. • Adenoviruses 1-7 are more common types worldwide and account for most instances of adenovirus associated illness. • Responsible for 5% of respiratory diseases in young children but account for much less in adults. • Most infections are mild and self limited. • Occasionally case disease in other organs particularly eye and gastrointestinal tract.

7. CLINICAL MANIFESTATIONS A. Respiratory diseases: B. Eye infections: C. Gastrointestinal disease D. Other diseases E. Adenoviral infections of the immune compromised host

8.   Respiratory Diseases: Typical symptoms: cough, nasal congestion, fever and sore throat. Symptoms most commonly manifested in infants and children and usually involves group C viruses. • Adenoviruses particularly 3, 7 and 21 are thought to be responsible for about 10-20% pneumonias in childhood. • Mortality rate of pneumonia 8-10% in very young. • Also are cause of acute respiratory disease syndrome among military recruits. Characterised by fever, sorethroat , nasal congestion, cough and malaise; sometimes leading to pneumonia

9.   EYE INFECTIONS: • Mild occular   involvement may be part of respiratory pharyngeal syndrome. • Pharyngoconjunctival fever occurs as outbreak such as in children’s summer camps (swimming pool conjunctivitis) and caused by type 3 and 7. • Duration 1-2 weeks and complete recovery with no lasting sequela is common outcome. • Epidemic keratoconjunctivitis more serious disease; occurs mainly in adults and is highly contagious. • Source of infection: sinks and hand towel. • Disease is characterised by acute conjunctivitis followed by keratitis (inflammation of the cornea) that usually resolves in two weeks but may leave subepithelial opacities in the cornea for up to two years. • Caused by serotypes 8, 19 and 37

10. Keratoconjunctivitis is  inflammation of the cornea and conjunctiva. • When only the cornea is inflamed, it is called keratitis • when only the conjunctiva is inflamed, it is called conjunctivitis • Pharyngoconjunctival Pharyngoconjunctival fever is a condition characterized by a fever, sore throat, and follicular conjunctivitis.   Gastrointestinal disease: • Can  often been isolated from feces but their relation to intestinal disease has not been conclusively established. • However two serotypes (types 40 and 41) have been etiologically associated with infantile gastroenteritis • May account for 5-15% cases of viral gastroenteritis in young children. Adenoviruses 40 and 41 are abundantly present in diarrhoeal stools. 

11.   ADENOVIRUS TREATMENT Antivirals against AdV : Potential   targets: AdV DNA polymerase , AdV cysteine protease , receptors for binding host cells . Antivirals in use: Ribavirin , Cidofovir ,Ganciclovir (Vidarabine) •PREVENTION OF ADENOVIRAL INFECTIONS • Vaccines were developed for adenovirus serotypes 4 and 7, but were available only for preventing among military recruits. • Strict attention to good infection-control practices is effective for stopping nosocomial outbreaks of adenovirus-associated disease, such as epidemic keratoconjunctivitis. • Maintaining adequate levels of chlorination is necessary for preventing swimming pool associated outbreaks of adenovirus conjunctivitis

12. .  PREVENTION AND CONTROL Careful hand  washing is the easiest way to prevent infection. Disinfection of Environmental surfaces with hypochlorite's. The risk of water borne outbreaks of conjunctivitis can be minimized by chlorination of swimming pools. Epidemic keratoconjunctivitis can be controlled by strict asepsis during eye examination