8/12/2019 Intro to Virus

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Viral Replication

Determines host range/tropismi.Very specificii.

0-4C1)

Ionic interactions2)

No energy needediii.

VAP of virion recog Rs on host cellsa.Adsorption/AttachmentI.

@ plasma memi.Need energy for mem conformational changeii.Tm-depiii.

pH-independenta.

Taken up via endocytic pathwaysi.Reduced pH is neededii.

pH-dependentb.

Actin cytoskeleton is used to move V from endocytic pathway to other parts of the cell1)Clathrin-depi.Macropinocytosisii.Calveolariii.Clathrin & Caveolin Indepiv.Phagocytosisv.

Endocytosis Pathwaysc.

PenetrationII.

Sep genome/internal nucleocapsid from outer strct of viriona.

No capsid=No infectivityi.

Naked viruses are taken up via endocytosis into endosome and its capsid is degraded thereb.

No envelop=No infectivityi.Fusion mech: mem bending through HAIRPIN formationii.

Envelop of the env viruses fuse with endosome memc.

Doesn't mean it won't be infectious, it's just hidingi.The loss of infectivity="Eclipse period"d.

UncoatingIII.

Prot found in VIRION particlesStructural proteinsa.

Prot prod in infected cell but not in virioni.Nontructural proteinsb.

SynthesisIV.

If enveloped, wrap nucleocapsid in envelopei.Virions formed=pack genome in capsida.

Naked virus accum in cell-->released when cell diesb.

Matrix line up under viral glycoproteini.

Ionic interaction b/w matrix & capsid pulls matrix around capsid1)

Closing both ends2)

Nucleocapsid recog matrix & form cxnii.

Budding occurs at plasma mem/golgi/ER, nuclear memiii.Specific to each virusiv.

Env virus acquire env by BUDDING through cell memc.

AssemblyV.

As it buds, virions get releaseda.ReleaseVI.

Chlamydia vs. Virus

Both are obligate intracellular parasite-

Chlamydia (bacteria) has BOTH DNA & RNA-

Viruses have DNA OR RNA-

Biphasic intracellular growth cycle-

Infectious

Metabolically inert

Extracellular form

EB (elementary body)-

Metabolically active

With conventional bacteria-like propertie

RB (reticulate body)-

Chlamydia

DNA Polymerase (enz that makes polymefrom DNA)

a.

aka. Replicaseb.

DNA Syn/Replication1.

RNA Polymerasea.aka. Transcriptaseb.

RNA Syn/Transcription2.

Ribosome, tRNA, Protein factorsa.Protein Syn/Translation3.

Types of Infection

Temporary, virus cleared (genome clearea.Transient1.

Chronic=infection continuously presi.Latent=virus genome present in cellvirions (not infectious)

ii.

Recurrent=latent infection reactivainfectious virus before becoming lat

iii.

Virus not cleared; imm resp may still be factive

a.Persistent2.

Chronic persistent infection with prolongincubation period (mo to yr); Sx progressworsen to death

a.

Subacute sclerosing panencephalitis-ie. SSPE (Slow infection of measles)

Slow virus3.

Immune Response of Host

Neutralize virus ability to infecti.Block R binding (NEUTRALIZING Ab)a.

Prevent uncoatingb.

Remove coated (Ab coated) virusi.Phagocytosisc.

May need complement to neutralize somed.

Virus-specific Ab1.

Kill infected cell when recog Ag on MHC-1a.Virus-specific T2.

Fever

Myalgia

Malaise

Anorexia

Undifferentiated Sx of Viral infection

***Sx occur AFTER host imm resp; virus often no longer present***

Intro to VirusMonday, August 26, 2013

10:00 AM

Virology Page 1