Upper respiratory tract infections

MODULE 93.MEDICAL VIROLOGY

Dr. Kaveh Haratian

Assistant professor

Department of Microbiology and immunology.

Faculty of Medicine

Alborz University of Medical Sciences

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UPPER RESPIRATORY TRACT

INFECTIONS

Adenoviruses, Coronaviruses and Rhinoviruses2

ADENOVIRUSES

Why so called?

First isolated from human adenoids.

They cause disease of :

Respiratory tract

Eyes

Digestive tract

Urinary tract

They give rise to an estimated :

5-10% of respiratory viral infections.

Main achievement of their study :

Discovery of mRNA splicing.3

PROPERTIES OF THE VIRUS

Icosahedral, non-enveloped, DNA viruses .

80 nm in diameter .

Isolated only from vertebrates .

Recognized genera :

Mastadenovirus : from mammals(humans)

Aviadenivirus : from birds

Atadenovirus : from birds, mammals , reptiles and

a marsupial

Siadenovirus : from reptiles and birds

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PROPERTIES OF THE VIRUS

51 serotypes of human adenoviruses are now

known ;fall into groups A – F .

Disease Predominant

serotypes

Infantile gastroenteritis 40 , 41

Upper respiratory tract infections 1,2,3,5,7,11

Lower respiratory tract infections 3,4,7,21

Pharyngoconjunctival fever 3,4,7

Epidemic keratoconjunctivitis 8,9,37

Acute haemorrhagic conjunctivitis 11

Acute haemorrhagic cyctitis 7,11,21,35

Genital ulcers, urethritis 2,19,37

Gastroenteritis and pneumonia 40, 41

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REMEMBER SOME AVIAN

The only reason for that is , they may

inadvertently found in eggs used for viral

vaccine production :

CELO : chick embryo lethal orphan virus

May cause cancer in animals

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MORPHOLOGY

Capsid formed from 252 capsomers,Icosahedral

Fiber projecting from each of 12 vertices.

Pentons and Hexons

Linear dsDNA, 36-38kbp(Baltimore class 1)

Inverted terminal repeats

A protein primer at each 5` terminus.

5 early transcription units(E1A,E1B,E2-E4)

3 delayed early(IX, IVa2, E2 late)

1 late that results to L1 – L5 mRNAs.

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ADENOVIRUS PARTICLE

8

9

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REPLICATION CYCLE

Divided into 2 phases

Binding to cell via fibers

Main receptor is CAR(Coxackievirus B and

Adenovirus receptor).

Binding the penton base to integrins on the cell

surface.

Fiberless virions entry by endocytosis.

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CLINICAL AND PATHOLOGICAL ASPECTS

Endemic respiratory infections in children

Most children, early in life

Stuffy nose, cough

Older children : pharyngitis

Mainly type 2

In colder area: type 3, 7

Pneumonia in younger than 2 years

Mainly transmit via fecal – oral(cups , utensils)

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CLINICAL AND PATHOLOGICAL ASPECTS

Epidemic disease in military recruits

Upper and lower respiratory tracts

Type 4, 7

Because of crowding and stress

Lasts about 10 days

Pneumonitis is common.

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CLINICAL AND PATHOLOGICAL ASPECTS

Pharyngoconjunctival fever

Pharyngitis and conjunctivitis

Mainly in children and young adults

May associated with swimming pool(after 1

week)

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CLINICAL AND PATHOLOGICAL ASPECTS

Epidemic keratoconjunctivitis (shipyard

eye)

Type 8

Permanent corneal scars and impaired sight

Transmitted by medical staff using infected

solution or inadequately sterilized instruments:

tonometer

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CLINICAL AND PATHOLOGICAL ASPECTS

Gastrointestinal infections

Mainly in infants

Types 40, 41

Don’t grow in cell culture

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CLINICAL AND PATHOLOGICAL ASPECTS

Other syndroms

Intussusception in infants

Necrotizing enterocolitis

Haemorrhagic cystitis

Meningoencephalitis

Immunosuppressed patients(AIDS,

transplantation) :

Pneumonitis

Encephalitis

Fulminant hepatitis

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PROPHYLAXIS

Live vaccine from type 4, 7

Just for American military crew

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CORONAVIRUSES

Infects human, birds, other animals

Mainly affects :

Ciliary epithelium of trachea

Nasal mucosa

Alveolar cells of lungs

Severe Acute Respiratory Syndrome(SARS)

Middle-East Respiratory Syndrome(MERS)

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PROPERTIES OF THE CORONAVIRUSES

Order : Nidovirals, Family: Coronaviridae

3 genera :

Coronavirus

Torovirus

Arterivirus

3 serotypes of human Coronaviruses

15 serotypes of birds and animals

Pleomorphic , 100 – 160 nm

Club-shaped glycoprotein surface spikes(20 nm) :

Crown

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PROPERTIES OF THE CORONAVIRUSES

Helical nucleocapsid

3 envelope proteins:

Matrix(gp)

Protein S : spikes, neutralizan, receptor binding,

membrane fusion, HA activity

HE: role in virus exit(neuraminidase)

Genome : largest of all RNA viruses of human.

ssRNA+, 27-30 kb, infectious

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CLINICAL AND PATHOLOGICAL ASPECTS

2-10% of common cold(OC43, 229E)

Wheezing in asthmatic and chronic bronchitis in

adults

Incubation period : 3 days

Followed by :

Nasal discharge and malaise

Excretion of virus (1 week)

Little / no fever

Cough and sore throat is not common

Toroviruses : in diarrhea samples, cause

gastroenteritis 25

EPIDEMIOLOGY AND PATHOGENESIS

Occur in colder months

Re-infection is common

Poor immune response

Antigenic mutations

Epithelium in the upper respiratory tract

Inflammation , edema, exudation (for several

days)

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RHINOVIRUSES

Family : Picornaviridae

Small, non-enveloped, ssRNA+, 18-30nm

Icosahedral symmetry

More the 150 serotypes

Labil to acid conditions

Low temperature for growth(33 ◦C)

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CLINICAL AND EPIDEMIOLOGICAL

ASPECTS

Upper respiratory tracts

Spread by aerosol/hand contact/surface of cups

and plates

Incubation period: 2-3 days

Nasal congestion, sneezing, sore throat,

headache, cough

Fever is rare

Serious sequel in chronic bronchitis and

asthmatics

Children are more susceptible than adults.

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