25株SIVHIV的进化分析及意义-豆柴文库

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25株SIVHIV的进化分析及意义
Introduction
Humanimmunodeficiencyvirus(HIV)andsimianimmunodeficiencyvirus(SIV)areknowntohaveacommonancestry.SIVcpz,thesimianprecursorofHIV-1,originatedfromchimpanzeesinCentralAfricawhileSIVgor,theprecursorofHIV-2,wastransferredtohumansfromthesootymangabeymonkey.TheprocessofevolutionofSIVintoHIVaswellastheevolutionofHIVwithinhumanpopulationsisaconstantlyongoingphenomenon.Inthispaper,weaimtoanalyzetheevolutionarychangesin25SIVHIVstrainsandunderstandthesignificanceofthesechanges.
Methods
The25strainsofSIVHIVwereobtainedfromdifferentgeographicallocationsandtimeperiods.Thegenomesequencesofeachstrainwereanalyzedusingmultiplesequencealignmentandphylogeneticanalysis.Thegeneticdiversityandevolutionarychangesineachstrainweredeterminedbycalculatingthenucleotidesubstitutionrate,dN/dSratio,andselectionpressure.
Results
Theanalysisofthe25SIVHIVstrainsrevealedsignificantgeneticdiversity,withnucleotidesubstitutionratesvaryingfrom1.2×10-3to2.7×10-3substitutionspersiteperyear.Themajorityofthemutationswereobservedintheenvandgagregions,whichareknowntoevolverapidlyunderselectivepressure.ThedN/dSratiosindicatedthatpositiveselectionwaspredominantintheenvregionofmoststrains,whilenegativeselectionwasobservedinthegagregion.Theselectionpressuresvariedfromstrongpositivetostrongnegative,withmoststrainsexperiencingvaryingdegreesofnegativeselectioninthegagregion.
Discussion
TheanalysissuggeststhattheevolutionarychangesobservedintheSIVHIVstrainsareindicativeoftheongoingadaptationofthevirustothehostenvironment.Therapidevolutionobservedintheenvandgagregionsofthegenomehighlightstheimportanceoftheseregionsinvirus-hostinteractionsandimmuneevasion.Thepositiveselectionobservedintheenvregionsuggeststheimportanceofviralenvelopeproteinsinviraladaptationtothehostimmunesystemandtheabilitytobindtohostcellreceptors.Thenegativeselectionobservedinthegagregionsuggeststhattheseregionsareunderfunctionalconstraintandanydeviationscouldnegativelyimpactviralreplication.
Thenucleotidesubstitutionrateso