paramyxoviridae edited

8/14/2019 Paramyxoviridae Edited

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ParamyxoviridaeParamyxoviridaeParamyxoviridaeParamyxoviridae-All members initiate infection in RTAll members initiate infection in RT

-Parainfluenza & RSV Remain limited to respiratoryParainfluenza & RSV Remain limited to respiratory

epitheliumepithelium

- Mumps & measles become disseminated throughoutMumps & measles become disseminated throughoutthe body and produce generalized diseasethe body and produce generalized disease


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PARAMYXOVIRIDAE


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Paramyxovirinae

Pneumovirinae

PARAMYXOVIRIDAE

Two sub- families


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The Paramyxovirinae subfamily isdivided into 4 genera, 3 of which are

important:

1. Genus respirovirus: which include parainfluenza viruses 1 & 3 viruses

2. Genus Rubulavirus which include parainfluenza virus 2 &4 as well asmumps virus

3. Genus morbillivirus which include the measles (rubeola) virus


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The Pneumovirinae subfamily is

divided into two genera:1. Genus pneumovirus which includerespiratory syncytial virus RSV

2. Genus metapneumovirus whichinclude: human metapneumovirus


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Human MetapneumovirusThe human metapneumovirus which is a respiratorypathogen first described in 2001.It appears to be widespread in young adults & olderpersons.

Human metapneumovirus is able to cause a widerange of respiratory illnesses from MILD UR TO SEVERE LRT

DISEASE


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The paramyxoviruses are envelopedparticles,

Large (150-300 nm in diameter).

The viral genome is composed of: a negative sense

linear single stranded,

non segmented RNA molecule.

MORPHOLOGY


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Structural proteins are complexedwith RNA to form the nucleocapsid.

The nucleocapsid is surrounded by alipid envelope that is superimposedwith spikes (glycoprotein in nature).

MORPHOLOGY


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These spikes differentiated into twotypes:

- haemagglutinin-neuraminidasespike (HN)

- fusion (F) spike.

MORPHOLOGY


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HN and F spikes are bothantigenic, They are responsible for:

- host cell attachment,

- mediation of membrane fusion,

- haemolysin activity

The are key factors in infection andpathogenesis.

MORPHOLOGY

h f h h


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Characteristics of the genera in thesubfamilies of the family

Paramyxoviridae

Property Paramyxovirinae Pneumovirinae

Respiro Rubula Morbilli Pneumo metapneumo

Human

viruses

Parainfluenza

1,3Mumps,

parainfluenza

2,4a,4b

Measles RSV Humanmetapneumo

virusSerotypes 1 each 1 each 1 2 ??

F Prot

_______Haemolysin

+ + + + +

+ + + NO HAEMOLYINNO HA

NO NA

HA

+2 +2 +3

N

+2 +2 NO NA


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The activities of the

surface glycoprotein F glycoprotein . Also carries Hemolysin activity

HN glycoprotein .Hemagglutination andneuraminidase activities

Hemagglutination of erythrocytes is moreefficient by H glycoprotein that lacksneuraminidase activity


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The difference between theorthomyxo & paramyxoviruses

Orthomyxoviruses Paramyxoviruses

Diseases caused in

humans

Influenza types A, B and C Parainfluenza 1-4

infections, RSV diseaes,

mumps and measles

genome ssRNA8 segmented,

-ve sense

ssRNAnonsegmented

ve senseFusion of virus

with cell

Endosome Plasma membrane

Transcription ofviral RNA

HOST CELL NUCLEUS Host cell cytoplasm

Genetic

reassortment

frequent Rare

Rate of antigentic

change

high low


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Parainfluenza Viruses

Parainfluenza viruses are ubiquitous and

cause common respiratory illness ofvarying severity in all age groups

Transmission: droplet


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Parainfluenza Viruses

TYPE 1,2,& 3are particularly considered major pathogens ofsevere respiratory tract disease in infants & youngchildren

Type 4 does not cause severe disease even on primaryinfection.


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Croup : stridor

Caused mainly by serotype 1 & 2

age 6 -18 month

incubation period 2 to 6 days

subglottal sweling, which endangers the airway.

The principal differential diagnosis is epiglottitiscaused by Haemophilus influenza.

MOST IMPORTANTAcute laryngeo-tracheobronchitis


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PARAMYXOVIRIDAETwo sub- families

Paramyxovirinae Genus respirovirus: Parainfluenza 1 &3 Genus Rubulavirus Parainfluenza 2 & 4 and mumps virus Genus morbillivirus measles virus

Pneumovirinae Pneumovirus

RSV Metapneumovirus

metapneumovirus


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Pneumovirinae1. Genus pneumovirus which includerespiratory syncytial virus RSV

2. Genus metapneumovirus whichinclude: human metapneumovirus


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Respiratory syncytial virus


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RSV is a paramyxovirus that lacks: haemagglutinin

& neuraminidase activity.

The F peplomer as well lacks haemolysin activity.


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RSV is transmitted via dropletinfection.

Viral replication occurs in theepithelial cells of the nasopharynx.

Viraemia has not been detected.


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Alarming!!!!!! RSV is the most important cause of LRT illnessin infants and young children.

It is the main cause of: Bronhiolitis (about 50%)

Pneumonia (25%)

under one year of age.


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Pathogenesis of Respiratorysyncytial virus

Involvement of the:

immune responsein

the pathogenesis of some RSV

respiratory symptomsespecially bronchiolitis has been the

subject for much speculation.


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Laboratory diagnosis ofparainfluenza & RSV s

1. Detection of viral antigen & \ or viral nucleicacid:

Antigen detection:

- Clinical specimens (exfoliatednasopharyngeal cells, nasopharyngealsecretions, aspirates or washes) by:

- IF or ELISA techniques

- N.A detection from the same specimenscould be done using PCR


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Laboratory diagnosis ofrespiratory tract infections

(parainfluenza & RSV )2. Isolation & identification of the virus :

The virus grow readily on T.C.C. identification is by:

- the C.P.E;

- I.F ( to detected V.AG.) &- or PCR (to detect V.N.A.) .

In parainfluenza viruses:

haemadsorption

&

haemagglutination

may be used for specific identification.


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Laboratory diagnosis of respiratorytract infections parainfluenza & RSV

3. Serology :

Virus specific IgA are protective but

disappear within few months.


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Treatment of parainfluenza & RSVinfection

Treatment is mainly symptomatic and include

neubulized cold or hot steam with careful

monitoring of the upper airway.

Ribavirin delivered in the form of small particle

aerosal may be effective in life threatening

infections.


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Immunity to Parainfluenza

& RSVs It is apparent that serum neutralizing

antibodies are only partially protective.

Reinfections are common and can occur

in presence of viral antibodies but the

severity of the disease is lowered.

paramyxoviridae edited

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