HIV Virus, defination, morphology,types, lab diagnosis

HIV virus

1. HIV
(DrJagroopSinghSidhu)
1.INTRODUCTION
HIV(HumanImmunodeficiencyVirus)isaretrovirusthatcauses
AcquiredImmunodeficiencySyndrome(AIDS).
ItprimarilyinfectsanddestroysCD4+Tlymphocytes,whicharevital
forimmunedefence.
Thevirusleadstoagradualdeclineoftheimmunesystem,makingthe
bodyvulnerabletoopportunisticinfectionsandcertaincancers.
HIVinfectionisamajorglobalhealthconcern,especiallytransmitted
throughsexualcontact,bloodtransfusion,andmother-to-child
transmission.
2.Classification
HIVbelongstothefamilyRetroviridaeandgenusLentivirus.
TherearetwomaintypesofHIV:
TypeDescription GeographicDistribution
HIV-1MostcommonandvirulentstrainWorldwide
HIV-2Lesspathogenic,slowerprogressionWestAfrica
BothHIV-1andHIV-2causeAIDS,butHIV-1isresponsibleformostglobal
infections.
3.Morphology
A.SizeandShape
HIVisaspherical,envelopedvirus,measuring100–120nmindiameter.
B.Structure
HIVconsistsofthreemajorparts:
1.Envelope
Outercoveringderivedfromthehostcellmembrane.

2. Containsglycoproteinsgp120andgp41,whichhelpinattachmentand
fusionwithhostcells.
2.Core(Capsid)
Madeofp24protein,enclosingtheviralgenome.
Givesthevirusitscharacteristicconical(cone-shaped)structure.
3.Genome
Composedoftwoidenticalsingle-strandedRNAmolecules.
Containsgenesthatcodeforstructuralandregulatoryproteins:
ogag–codesforcoreproteins(p24,p17)
opol–codesforenzymes(reversetranscriptase,integrase,protease)
oenv–codesforenvelopeproteins(gp120,gp41)

3. 4.PathogenicityofHIV:
HIVcausesdiseasebyspecificallyinfectinganddestroyingCD4+T
lymphocytes,whichplayacentralroleincoordinatingtheimmuneresponse.
ThevirusentershostcellsbybindingtotheCD4receptorandaco-receptor
(CCR5orCXCR4),thenfuseswiththecellmembrane.Insidethecell,HIV
usesreversetranscriptasetoconvertitsRNAgenomeintoDNA,whichis
integratedintothehostgenomebyintegrase,formingaprovirus.Theinfected
cellthenproducesnewviralparticles,whichbudfromthecellsurfaceand
maturetoinfectothercells.Thiscontinuouscycleleadstoprogressive
depletionofCD4+Tcells,weakeningtheimmunesystem,impairingthe
body'sabilitytofightinfections,andmakingthehostsusceptibleto
opportunisticinfectionsandcertainmalignancies.Overtime,ifuntreated,
thisresultsinAcquiredImmunodeficiencySyndrome(AIDS).
C.EffectsontheImmuneSystem
ProgressivelossofCD4+Tcells.
Impairedimmuneresponse→increasedsusceptibilitytoopportunistic
infections.
Chronicimmuneactivation→immuneexhaustion.
D.StagesofHIVInfection
Stage Description KeyFindings
1.Acute
Phase
2–4weeksafter
infection
Flu-likeillness,highviralload,fallin
CD4count
2.Latent
Phase
Asymptomatic for
monthstoyears
Slowreplicationinlymphnodes
3.AIDSFinalstage CD4count<200cells/μL,severe
immunodeficiency, opportunistic
infections
5.LaboratoryDiagnosis
A.Specimen
Serumorplasma(forantibody/antigendetection)

4. Wholeblood(forCD4count,viralload)
B.ScreeningTests
UsedforinitialdetectionofHIVantibodiesorantigens:
1.ELISA(Enzyme-LinkedImmunosorbentAssay)–highlysensitive;
detectsantibodiesagainstHIV.
2.RapidTests/SpotTests–easytoperform;usefulforscreeninginblood
banks.
3.Combination(4thGeneration)Tests–detectbothp24antigenand
HIVantibodies,allowingearlydiagnosis.
C.ConfirmatoryTests
Usedtoconfirmreactivescreeningresults:
1.WesternBlotTest–detectsspecificviralproteins.
2.LineImmunoassay–advancedconfirmatorytest.
3.NucleicAcidTest(NAT)/PCR–detectsHIVRNAdirectly;usedfor
earlydetectionandmonitoringtherapy.
D.OtherInvestigations
CD4count:Monitorsimmunestatus(normal:500–1500cells/µL;AIDS:
<200cells/µL).
Viralloadtest:MeasuresamountofHIVRNAinblood,helpsassess
treatmentresponse.
6.PreventionandControl
A.GeneralPrecautions
Avoidunprotectedsexualcontact.
Usesterileneedlesandsyringes.
Screenallbloodandbloodproductsbeforetransfusion.
Usepersonalprotectiveequipment(PPE)inlaboratoriesandhospitals.
B.PreventionofMother-to-ChildTransmission
Antiretroviraltherapy(ART)duringpregnancy.

5. Avoidbreastfeedingifpossible.
Providesafedeliverypractices.
C.Post-ExposureProphylaxis(PEP)
Forhealthcareworkersafterneedle-stickinjuryorexposuretoHIV-
positiveblood.
PEPshouldbeginwithin2hoursofexposureandcontinuefor28days.
Regimenusuallyincludesa3-drugARTcombination.
D.HealthEducation
Publicawarenessprograms.
Safesexualpractices.
Counsellingandtestingcentres(ICTC).
7.Treatment(Overview)
AntiretroviralTherapy(ART)isthemainstayoftreatment.
Acombinationofatleastthreedrugsfromdifferentclassesisusedto
preventresistance.
CommonDrugClasses
1.NucleosideReverseTranscriptaseInhibitors(NRTIs)
2.Non-NucleosideReverseTranscriptaseInhibitors(NNRTIs)
3.ProteaseInhibitors(PIs)
4.IntegraseInhibitors
5.Entry/FusionInhibitors
GoalsofART
Reduceviralload.
Restoreandpreserveimmunefunction.
Improvequalityoflifeandsurvival.
Preventtransmission.