General Characteristics General Characteristics of Virusesof Viruses

HIV ! HIV ! Avian Flu !Avian Flu !

SARS ! SARS ! Ebola !Ebola !

West Nile !West Nile ! Smallpox !Smallpox !

Hepatitis A,Hepatitis A,BB,,CC,,DD,,E E ! !

Polio !Polio ! HPV !HPV !

Viruses infect all living thingsViruses infect all living things

• Animal kingdomAnimal kingdom

• Plant kingdomPlant kingdom

• MicrobesMicrobes

•Specificity/selectivity for hostSpecificity/selectivity for host

Manifestations of Viral InfectionsManifestations of Viral Infections

• AsymptomaticAsymptomatic• Acute viral syndrome Acute viral syndrome (influenza, rhinovirus, etc)(influenza, rhinovirus, etc)

• Persistent viral syndrome Persistent viral syndrome (EBV)(EBV)

• Chronic infectionChronic infection– Reactivating (HSV-1/2, VZV (chicken pox/shingles))Reactivating (HSV-1/2, VZV (chicken pox/shingles))– Progressive (HBV, HCV, HIV)Progressive (HBV, HCV, HIV)

• Cancer Cancer (EBV, HPV-16, HBV, HCV, KSHV)(EBV, HPV-16, HBV, HCV, KSHV)

• Death Death (HIV, et al)(HIV, et al)

• Acute death Acute death (smallpox, Ebola, SARS)(smallpox, Ebola, SARS)

Viral pathogenesis --- diseaseViral pathogenesis --- disease

• Virus replicationVirus replication

• Targeted cellsTargeted cells

• Host responseHost response

What is a virus?What is a virus?

What are the essential characteristics What are the essential characteristics of a virus?of a virus?

• PhysicalPhysical

• BiologicalBiological

What is a virus?What is a virus?• Physical CharacteristicsPhysical Characteristics

– Genetic MaterialGenetic Material• Nucleic acid Nucleic acid

– RNA (ssRNA, dsRNA, segmented)RNA (ssRNA, dsRNA, segmented)– DNA (ssDNA, dsDNA)DNA (ssDNA, dsDNA)

– Protein coat (subunit structure)Protein coat (subunit structure)• NucleoproteinNucleoprotein• CapsidCapsid

– Capsomeres, Geometrical constraintsCapsomeres, Geometrical constraints

– Envelope (some)Envelope (some)

HIV-1, SIV and Other RetrovirusesHIV-1, SIV and Other Retroviruses AdenovirusesAdenoviruses

Rhabdoviruses (rabies)Rhabdoviruses (rabies)

Size of VirusesSize of Viruses

What is a virus?What is a virus?• Genetic material limitedGenetic material limited

• 10^3 to 10^5 bases long10^3 to 10^5 bases long– Codes for unique proteinsCodes for unique proteins

• Polymerases – RNA replicationPolymerases – RNA replication• KinasesKinases• ProteasesProteases• Structural proteinsStructural proteins• Accessory proteinsAccessory proteins

Targets for antiviral agents - limitedTargets for antiviral agents - limited

What is a virus?What is a virus?Biological CharateristicsBiological Charateristics

• Viruses as parasitesViruses as parasites

• ParasitesParasites

– Not capable of independently Not capable of independently completing a full replication cycle completing a full replication cycle

– Cellular parasitesCellular parasites

– Subcellular “parasites”Subcellular “parasites”

• VirusesViruses

• ViroidsViroids

• PrionsPrions

What is a virus?What is a virus?

• Are viruses alive?Are viruses alive?

• Characteristics of living organisms?Characteristics of living organisms?

What is a virus?What is a virus?Biological CharacteristicsBiological Characteristics• Viral replication strategiesViral replication strategies• Viral replication cyclesViral replication cycles

– Binding/entryBinding/entry– UncoatingUncoating– Genome replication (w/wo integration)Genome replication (w/wo integration)– Protein productionProtein production– Assembly Assembly – BuddingBudding

• Host cell tropism (receptors)Host cell tropism (receptors)• Lytic vs. non-lytic infectionLytic vs. non-lytic infection

VacciniaPoliovirus

AdenovirusHerpesvirus

Morphological AssaysMorphological Assays

• Electron microscopyElectron microscopy

• Isolated virus or Isolated virus or infected cellsinfected cells

• Nonenveloped or Nonenveloped or enveloped (alternate enveloped (alternate method to determine if method to determine if an envelope is an envelope is present?)present?)

• Core structureCore structure

EpidemiologyEpidemiology• Tracking prevalence of viruses in host Tracking prevalence of viruses in host

populationspopulationsBlood components and tissue samplesBlood components and tissue samples– Virus cultureVirus culture

• In vitro (tissue culture)In vitro (tissue culture)• In vivo (susceptible animal model)In vivo (susceptible animal model)

– Molecular testingMolecular testing• PCR methodsPCR methods• Southern blotSouthern blot

– ELISA (enzyme linked immunosorbent assay)ELISA (enzyme linked immunosorbent assay)• Assay for antigen (viral protein)Assay for antigen (viral protein)• Assay for antibody directed against virusAssay for antibody directed against virus