Medical Microbiology

DNAViruses 415

Polyomaviruses

&Amedicallyimportantpolyomavirus,theJCvirus,causesprogressive

multifocalleukoencephalopathy(PML),ademyelinatingdiseasethathas

becomemorefrequentasasequeltoHIVinfections,butisotherwiserare.

ThesameappliestotheBKvirus,whichaffectsbonemarrowtransplantation

patients.ElectronmicroscopyorPCRarethemaindiagnostictools. &

Pathogens.Thepolyomavirusescanbedividedintotwogroups:inonegroup

aretheSV 40 andSV40-likeviruses(Fig.8. 2 )suchashumanpathogenJCand

BKviruses.Intheotherarethetruepolyomavirusessuchasthecarcinogenic

murinepolyomavirus.ThedesignationsJCandBKaretheinitialsofthefirst

patientsinwhomtheseviraltypeswereidentified.Therearealsoanumberof

otherzoopathiconcogenicpolyomaviruses.Thenamepolyomareferstothe

abilityofthisorganismtoproducetumorsinmanydifferentorgans.

Pathogenesisandclinicalpicture.TheJCandBKvirusesarewidespread:

over 80 %oftheadultpopulationshowantibodiestothem,despitewhich,

clinicalmanifestationslikePMLareveryrare.Thevirusescanbereactivated

byaweakeningoftheimmunedefensesystem.TheJCvirusattacksthe

macroglia,especiallyin AIDSpatients, tocauseprogressive multifocal

PML,ademyelinatingprocessinthebrainwithdisseminatedfocithatisfatal

Polyomaviruses(SV40)

500 nm

Fig.8. 2 Section through

viral conglomerations in

the nucleus ofthe host

cell(TEM).

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Kayser, Medical Microbiology © 2005 Thieme