Medical Microbiology

414 8 VirusesasHumanPathogen

Pathogenesisandclinicalpicture.Papillomavirusesinfectcellsintheouter

layersoftheskinandmucosaandcausevarioustypesofwartsbymeansof

localcellproliferation(Fig.8. 1 ).Specificvirustypescorrelatewithspecific

pathohistologicalwarttypes.Plantarandvulgarwarts,flatjuvenilewarts,

andjuvenilelaryngealpapillomasapparentlyalwaysremainbenign.Bycon-

trast,thegenitalwartscausedbytypes 6 and 11 (condylomataacuminata)

canshowcarcinomatouschanges.Ofallpapillomavirus-causedcervicaldys-

plasias, 50 %containhumanpapillomavirus(HPV) 16 and 20 %HPV 1 8.

Allwartvirusesinduceprimaryproliferationoftheaffectedcellswith

largenumbersofvirusesfoundinthecellnuclei.Whetheramalignantde-

generationwilltakeplacedependsonthecellandvirustypeinvolved,but

likelyonthepresenceofcocarcinogensaswell.Incarcinomas,theviralDNAis

foundinintegratedformwithinthehost-cellgenome,whereasinpremalig-

nantchangestheviralgenomesarefoundintheepisomalstate.Papilloma-

virusespossessoncogenes(E5,E6,andE7genes)thatbindtheproductsof

tumorsuppressorgenes:E6bindsthep53geneproduct,E7theRbgenepro-

duct(seep.396f.).

Diagnosis.Humanpapillomavirusescannotbecultivatedinvitro.Theyare

detectedandidentifiedbymeansofhistologicalanalysisand,inmalignancies

inparticular,bymeansofin-situhybridization.Antibodyassayresultshavea

lowsignificancelevelandtheseproceduresarenotstandardroutine.

Epidemiologyandprevention.Sincevirusesareproducedandaccumulatein

warttissues,papillomavirusesaretransmissiblebydirectcontact.Wartscan

alsospreadfromonepartofthebodytoanother(autoinoculation).Acertain

levelofprophylacticprotectioncanbeachievedwithhygienicmeasures.

WartsCausedbyPapillomaviruses

Fig.8. 1

8

Kayser, Medical Microbiology © 2005 Thieme