Medical Microbiology

RNAviruses 465

&Paramyxovirinaewiththegenera:

— Paramyxoviruswiththehumanpathogenspeciesparainfluenzavirus

types 1 and3.

— Rubulaviruswiththemumpsvirusandparainfluenzavirustypes 2 and4.

— Morbilliviruswiththehumanpathogenmeaslesvirusandseveralzoo-

pathicspeciesthatcausesevererespiratoryinfectionsinvariousanimal

species(dogs[caninedistemper],cats,cattle,seals,dolphins,turtles).

— Thenonclassified,closelyrelatedzoopathicandhumanpathogenHendra

andNipahviruses.

&Pneumovirinae,genusPneumovirus,probablywithseveraltypesofRS

virus(respiratorysyncytialvirus).

StructureoftheParamyxoviruses

Allparamyxoviruseshaveasimilarstructure(Fig.8. 16 ).Theyarepleomorphic.The

smallestformsare 120 – 150 nminsize(withtheexceptionofthesomewhat

smallerRSvirus).Theyalsopossessanenvelopethatenclosesthenucleocapsid.

Thegenomeconsistsofacontinuous,single-strandedantisenseRNA.Theenvelope

isderivedfromthecellmembrane.Variousviralproteinsareintegratedinthe

envelope,visibleintheformofspikes.Thegenerictaxonsarebasedonthese

spikes:parainfluenzaandmumpsviruseshavetwotypesofspikes,onecontaining

the hemagglutinin(i.e., possessinghemagglutinationactivity)coupled with

neuraminidase(HNprotein),andtheothertheso-calledfusion(F)protein,respon-

sibleforfusionoftheenvelopewiththecellmembrane.Measlesvirusescontainno

neuraminidaseandpneumovirusespossessonlytheFprotein.

ParainfluenzaVirus

200 nm

NP

NC

Fig.8. 16 The envelope

hereistornopen,allowing

the helical nucleocapsid

(NC)toescape.NP:primary

nucleoproteinhelix(TEM).

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Kayser, Medical Microbiology © 2005 Thieme