EnzymeimmunoassayforthequantitativedeterminationofIgAclassantibodiesagainstBordetellapertussisinhumanserumorplasma(citrate).Bordetellapertussisisarespiratorypathogenthatcausespertussis,commonlyknownaswhoopingcough,alocalizedinfectionoftheciliatedepitheliumofthebronchialtree.Pertussisischaracterizedbyaprolongedparoxysmalcoughoftenaccompaniedbyaninspiratorywhoop.Thediseaseaffectsmainlychildren,butadultshavealsobeenincreasinglyreportedtobeaffected.Thepathogenproducestoxinswhichcauselocaldamagetotheciliaofepithelialcells,whichleadstoprolongedillnessandpertussis.Diseasepresentationvarieswithageandhistoryofpreviousexposureorvaccination.Severediseaseisinfrequentinhealthy,vaccinatedpersons.Infants,particularlythosewhohavenotreceivedtheprimaryvaccinationseriesagainstpertussis,areatriskforcomplicationsandmortality.InadditiontoB.pertussis,threeotherBordetellaspeciescancausediseaseinhumans:B.parapertussis,B.holmesii,andB.bronchiseptica.B.parapertussiscausesapertussis-likeillnessthatisgenerallymilderthanpertussisbecausethebacteriadonotproducepertussistoxin.Co-infectionofB.pertussisandB.parapertussisisnotunusual.B.pertussisisofworldwideprevalence.Globally,20-40millioncasesofpertussisoccureachyear,90%ofwhichareindevelopingcountries,andthereareupto400,000fatalitieseachyear,mostlyinyounginfants.TransmissionofB.pertussisoccursprimarilyviaclosedirectcontactwithaninfectedpersonorinhalationofairbornedroplets.Symptomsdevelopfollowinginhalationoftheairbornepathogen.Theorganismishighlycontagious,withupto90%ofhouseholdcontactsdevelopingthedisease.Infectedpersonsaremostcontagiousinthecatarrhalandtheparoxysmalstages.Theincubationperiodisusuallysevento10days,witharangeof4-21days.Typicalpertussissymptomsoccurinthreedifferentstages:catarrhal,paroxysmal,andconvalescent.Thecatarrhalstagelastsforabout1-2weeks,andischaracterizedbynon-specificsymptomssuchasrhinorrhea,sneezing,low-gradefeverandcough.Thesecondstageistheparoxysmalstage,lastingforabout4-6weeks,andischaracterizedbyvariouspathognomonicsymptomsofpertussissuchasepisodesofparoxysmalcoughwithacharacteristicwhoopingsound.Thefinalstageistheconvalescentstage.Duringthisstage,therespiratorysymptomsgraduallydecreasealthoughcoughcancontinueformonths.Manyfactorscanaltertheusualcourseofpertussis,causinganatypicalpresentation.Previouslyvaccinatedadolescentsandadultsmayhavelesssevereparoxysmalsymptoms.ThequantitativeimmunoenzymaticdeterminationofIgA-classantibodiesagainstB.pertussistoxin(PT)isbasedontheELISA(Enzyme-linkedImmunosorbentAssay)technique.MicrotiterstripwellsarecoatedwithB.pertussistoxin(PT)antigenstobindcorrespondingantibodiesofthespecimen.AfterwashingthewellstoremoveallunboundsamplematerialhorserADIshperoxidase(HRP)labelledanti-humanIgAconjugateisadded.ThisconjugatebindstothecapturedB.pertussistoxin(PT)-specificantibodies.TheimmunecomplexformedbytheboundconjugateisvisualizedbyaddingTetramethylbenzidine(TMB)substratewhichgivesabluereactionproduct.TheintensityofthisproductisproportionaltotheamountofB.pertussistoxin(PT)-specificIgAantibodiesinthespecimen.Sulphuricacidisaddedtostopthereaction.Thisproducesayellowendpointcolour.Absorbanceat450nmisreadusinganELISAmicrowellplatereader.