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ADENOVIRUSES
ADENOVIRUS- Classification
- DNA viruses first isolated from adenoidal tissue in 1953
- approximately 100 serotypes have been recognized, at least 47 of which
infect humans.
• Subdivided into 6 subgroups based on hemagglutination (A-F)
• Human pathogens belong to 49 serotypes
• Common serotypes:- 1-8, 11, 21, 35, 37, 40
• Enteric Adenoviruses belong to subgroup F
- Molecular biology research : splicing……
- Gene therapy : cystic fibrosis………..
Table 52-1. Illnesses Associated with Adenoviruses
Disease
Patient Population
Respiratory Diseases
Febrile, undifferentiated upper
respiratory tract infection
Infants, young children
Pharyngoconjunctival fever
Children, adults
Acute respiratory disease
Military recruits (serotype 4, 7)
Pertussis-like syndrome
Infants, young children
Pneumonia
Infants, young children; military recruits;
immunocompromised patients
Other Diseases
Acute hemorrhagic cystitis
Children; bone marrow transplant recipients
Epidemic keratoconjunctivitis
Any age; renal transplant recipients
Gastroenteritis
Infants, young children
Hepatitis
Liver transplant recipients; other
immunocompromised patients
Meningoencephalitis
Children; immunocompromised patients
ADENOVIRUS - Structure
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Non-enveloped DNA virus
Icosadeltahedrons (20면체)
70-90 nm in size
Linear ds DNA genome (36kb) with a
terminal protein (molecular mass, 55 kDa)
- capsid comprises 240 capsomeres, which consist of hexons and pentons.
-12 pentons : have a penton base and a fiber.
- fiber : viral attachment proteins
can act as a hemagglutinin.
-penton base and fiber are : toxic to cells, carry type-specific antigens.
BOX 52-1. Unique Features of Adenovirus
•Naked icosadeltahedral capsid has fibers (viral attachment proteins) at vertices.
•Linear double-stranded genome has 5' terminal proteins.
•Synthesis of viral DNA polymerase activates switch from early to late genes.
•Virus encodes proteins to promote messenger RNA and DNA synthesis, including its own DNA
polymerase.
•Human adenoviruses are grouped A through F by DNA homologies and by serotype (more than 42
types).
•Serotype is mainly a result of differences in the penton base and fiber protein, which determine the
nature of tissue tropism and disease.
•Virus causes lytic, persistent, and latent infections in humans, and some strains can
immortalize certain animal cells.
Simplified genome map of adenovirus type 2
-Transcription : both strand
- Early transcription – early protein : E1A, E1B, E2A, E2B, E3, E4
-Late transcription –late protein
- 11 polypeptide : 9 – structural protein (capsid)
2 – core (DNA-binding protein)
Gene
Number
M.W
(kDa2)
E1A*
Function
Activates viral gene transcription
Binds cellular growth suppressor: p105RB promotes transformation
Deregulates cell growth
Inhibits activation of interferon response elements
E1B
Binds cellular growth suppressor: p53 promotes transformation
Blocks apoptosis
E2
Activates some promoters
Terminal protein on DNA
DNA polymerase
E3
Prevents tumor necrosis factor-α (TFN-α) inflammation
E4
Limits viral cytopathologic effect
VA RNAs
Inhibit interferon response
Capsid
II
120
Contains family antigen and some serotyping antigens
III
85
Penton base protein
Toxic to tissue culture cells
IV
62
Fiber
Responsible for attachment and hemagglutination; contains some serotyping antigens
VI
24
Hexon-associated proteins
VIII
13
Penton-associated proteins
IX
12
IIIa
66
V
48
Core protein 1: DNA-binding protein
VII
18
Core protein 2: DNA-binding protein
Core
Entry and replication
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Fiber protein determines target cell specificity and attachment
Viral DNA enters host cell nucleus
Virus replicates in nucleus
- Fiber receptor : Ig superfamily
Coxsackie B viruses 도 이용
- Coxsackie adenovirus receptor
- MHC I 도 이용
- Penton base interact with av integrin
- receptor-mediated endocytosis
(clathrin-coated vesicles)
- Capsid delivers the DNA genome
to the nucleus
- Early transcription
- Replication
- Late gene transcription
: capsid proteins in cytoplasm 
nucleus  viral assembly
Pathogenesis and Immunity
-Lytic (용해감염) : mucoepithelial cells (점막상피세포)
-Latent (잠복감염) : lymphoid and adenoid cells
-Transforming (형질전환) : hamster, not human
BOX 53-2. Disease Mechanisms of Adenoviruses
•Virus is spread by aerosol, close contact, or fecal-oral means to establish
pharyngeal infection. Fingers spread virus to eyes.
•Virus infects mucoepithelial cells in the respiratory tract, gastrointestinal tract,
and conjunctiva or cornea, causing cell damage directly.
•Disease is determined by the tissue tropism of the specific group or serotype of the
virus strain.
•Virus persists in lymphoid tissue (e.g., tonsils, adenoids, Peyer's patches).
•Antibody is important for prophylaxis and resolution.
• viral fiber proteins determine the target cell specificity.
• toxic activity of the penton base protein can result in inhibition of
cellular mRNA transport and protein synthesis, cell rounding,
and tissue damage.
ADENOVIRAL INCLUSION BODIES
Histologic appearance of adenovirus-infected cells.
Inefficient assembly of virions yields dark basophilic
nuclear inclusion bodies containing DNA, proteins, and
capsids
The histologic hallmark of adenovirus infection is a dense, central
intranuclear inclusion within an infected epithelial cell that consists of viral
DNA and protein (Figure 52-3).
These inclusions may resemble those seen in cells infected with
cytomegalovirus, but adenovirus does not cause cellular enlargement
(cytomegaly).
Mononuclear cell infiltrates and epithelial cell necrosis are seen at the site of
infection.
• Viremia : immunocompromised
patients
• latent and persist in lymphoid and
other tissue, such as adenoids,
tonsils, and Peyer's patches
- Antibody : important for resolving lytic adenovirus infections and protects the
person from reinfection with the same serotype
- Cell-mediated immunity is important in limiting virus outgrowth, as borne out by the
fact that immunosuppressed people suffer more serious and recurrent disease.
- host defenses evasion
(1) encode small virus-associated RNAs (VA RNA) : prevent the activation of the
interferon-induced protein kinase R mediated inhibition of viral protein synthesis.
(2) viral E3 and E1A proteins block apoptosis induced by cellular responses to the
virus or by T cell or cytokine (e.g., TNF-α) actions.
(3) adenoviruses can inhibit CD8(+) cytotoxic T-cell action by preventing proper
expression of MHC I molecules and therefore antigen presentation.
Epidemiology
BOX 53-3. Epidemiology of Adenoviruses
Disease/Viral Factors
•Capsid virus is resistant to inactivation by gastrointestinal tract and drying.
•Disease symptoms may resemble those of other respiratory virus infections.
•Virus may cause asymptomatic shedding.
Transmission
•Direct contact via respiratory droplets and fecal matter, on hands, on fomites (e.g.,
towels, contaminated medical instruments), close contact, and inadequately
chlorinated swimming pools.
Who Is at Risk?
•Children younger than 14 years of age.
•People in crowded areas (e.g., daycare centers, military training camps, swimming
clubs).
Geography/Season
•Virus is found worldwide.
•There is no seasonal incidence.
Modes of Control
•Live vaccine for serotypes 4 and 7 is available for military use.
Clinical syndromes
Adenoviruses primarily infect children and less commonly infect adults.
Disease from reactivated virus occurs in immunocompromised children and adults.
BOX 52-4. Clinical Summaries
•Pharyngoconjunctival fever
(인두결막염) : A 7-year-old student
develops sudden onset of red eyes, sore
throat, and a fever of 38.9°C (102°F).
Several children in the local elementary
school have similar symptoms.
•Gastroenteritis: An infant has diarrhea
and is vomiting. Adenovirus serotype 41
was identified by polymerase chain
reaction analysis of stool for
epidemiologic reasons.
ACUTE FEBRILE PHARYNGITIS (급성 열성 인두염)
AND PHARYNGOCONJUNCTIVAL FEVER (인두 결막염)
- pharyngitis, which is often accompanied by conjunctivitis (pinkeye) and
pharyngoconjunctival fever.
- young children
- mild, flulike symptoms (including nasal congestion, cough, coryza, malaise, fever, chills,
myalgia, and headache) that may last 3 to 5 days.
- Pharyngoconjunctival fever occurs more often in outbreaks involving older children.
ACUTE RESPIRATORY DISEASE (급성 호흡기 질환)
-fever, cough, pharyngitis, and cervical adenitis.
-adenovirus serotypes 4 and 7.
-military recruits stimulated the development and use of a vaccine for these serotypes.
OTHER RESPIRATORY TRACT DISEASES
- coldlike symptoms, laryngitis, croup, and bronchiolitis.
- pertussis-like illness, viral pneumonia.
CONJUNCTIVITIS AND EPIDEMIC KERATOCONJUNCTIVITIS (유행성 결막염)
- follicular conjunctivitis : (Figure 52-6).
- Swimming pool conjunctivitis
- Epidemic keratoconjunctivitis may be an occupational hazard
- for industrial workers.
GASTROENTERITIS AND DIARRHEA
- major cause of acute viral gastroenteritis;
- Adenovirus serotypes 40 to 42 have been grouped as
enteric adenoviruses (group F)
Laboratory Diagnosis
- Immunoassays, including fluorescent antibody and enzyme-linked immunosorbent assays
- genome assays, PCR to detect, type, -must be used for enteric adenovirus serotypes 40 to 42, which
do not grow readily in available cell cultures.
Prevention
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Good handwashing
Contact precautions
Chlorination of water
Disinfection or sterilization of
ophthalmologic equipment
Use of single dose vials
Oral vaccine- restricted use
Gene therapy
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Used as VECTORS to transfer desired genetic material into cells
Viral genome is relatively easily manipulated in vitro
Efficient expression of inserted DNA in recipient cell
Gene Therapy
The transfer of selected genes into a host
with the hope of ameliorating or curing a disease state
Human many diseases
absence or inappropriate presence of a protein
Isolate and produce these natural proteins
genetic engineering and recombinant technology
Protein delivery
Sustained drug delivery
Gene therapy
Ultimate method of protein delivery
Body’s cells
Small factories
produce a therapeutic protein
for a specific disease over a prolonged period
Gene Transfer Technology
Viral Vectors for Gene Transfer
Retroviral Vectors
HIV
MMLV
Adenoviral Vector
Adeno-Associatedviral Vector
Herpes Simplex Viral Vector
Nonviral Techniques
Naked DNA
Liposome
Molecular conjugates
Antisense Technology
Non-catalytic antisense
Catalytic antisense molecules
Ribozymes: hammerhead or hairpin
Retrovirus Vectors
Advantages
High transduction efficiency
Insert size up to 8kB
Integrates into host genome resulting
in sustained expression of vector
Extremely well studied system
Vector proteins not expressed in host
Disadvantages
Requires dividing cells for infectivity
Low titers(106-107)
Integration is random
In vivo delivery remains poor.
Effective only when infecting helper
cell lines
Adenovirus vectors
Advantages
High transduction efficiency
Insert size up to 8kb
High viral titer (1010-1013)
Infects both replicating and
differentiated cells
Disadvantages
Expression is transient
(viral DNA does not integrate)
Viral proteins can be expressed in
host following vector administration
In vivo delivery hampered by host
immune response
Herpes simplex virus
Advantages
Large insert size
Could provide long-term CNS
gene expression
High titer
Disadvantages
System currently under development
Current vectors provide transient expression
Low transduction efficiency
AAV : Useful for a vector for gene therapy
-Lack of association with disease
-The ability to latently infect a high fraction of
exposed cells
-A minimal number of viral antigens to induce a host
immune response
-The possible ability to latently infect
non-dividing cells
-The possible advantage of site-specific integration
-The ability to latently infect a broad range of
human cell types
Delivery System Requirements
A practical gene delivery system must meet five demanding
requirements. It must be:
Efficient
•Capable of achieving the duration of expression of protein
from the gene required by the applicable medical situation
•Flexible with respect to the tissues it can deliver to
•Able to handle a wide range of therapeutic genes
•Able to demonstrate a dose-response relationship
•Efficient delivery of genes to both dividing and non-dividing target cells
•Absence of viral genes that may be responsible for causing an
undesirable immune response
•In vivo administration to patients
•High levels of gene expression
•Excellent stability allowing AAV vectors to be manufactured, stored and
handled like more traditional pharmaceutical products.
Structure of wild type and vector AAV genome
AAV Vector Delivery System
AAV Virus Particles
Structure of AAV Virus Genomic DNA
Structure of AAV Vector DNA
Adenovirus-dependent and Adenovirus-free production of rAAV
Gene Therapy