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General Characteristics of Viruses

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Presentation on theme: "General Characteristics of Viruses"— Presentation transcript:

1 General Characteristics of Viruses

2 HIV ! Avian Flu ! SARS ! Ebola ! West Nile ! Smallpox ! Hepatitis A,B,C,D,E ! Polio ! HPV !

3 Viruses infect all living things
Animal kingdom Plant kingdom Microbes Specificity/selectivity for host

4 Manifestations of Viral Infections
Asymptomatic Acute viral syndrome (influenza, rhinovirus, etc) Persistent viral syndrome (EBV) Chronic infection Reactivating (HSV-1/2, VZV (chicken pox/shingles)) Progressive (HBV, HCV, HIV) Cancer (EBV, HPV-16, HBV, HCV, KSHV) Death (HIV, et al) Acute death (smallpox, Ebola, SARS)

5 Viral pathogenesis --- disease
Virus replication Targeted cells Host response

6 What is a virus? What are the essential characteristics of a virus?
Physical Biological

7 What is a virus? Physical Characteristics Genetic Material
Nucleic acid RNA (ssRNA, dsRNA, segmented) DNA (ssDNA, dsDNA) Protein coat (subunit structure) Nucleoprotein Capsid Capsomeres, Geometrical constraints Envelope (some)

8 HIV-1, SIV and Other Retroviruses
Adenoviruses Rhabdoviruses (rabies)

9 Size of Viruses

10 What is a virus? Genetic material limited 10^3 to 10^5 bases long
Codes for unique proteins Polymerases – RNA replication Kinases Proteases Structural proteins Accessory proteins Targets for antiviral agents - limited

11 What is a virus? Biological Charateristics Viruses as parasites
Not capable of independently completing a full replication cycle Cellular parasites Subcellular “parasites” Viruses Viroids Prions

12 What is a virus? Are viruses alive?
Characteristics of living organisms?

13 What is a virus? Biological Characteristics
Viral replication strategies Viral replication cycles Binding/entry Uncoating Genome replication (w/wo integration) Protein production Assembly Budding Host cell tropism (receptors) Lytic vs. non-lytic infection

14 Vaccinia Poliovirus Adenovirus Herpesvirus

15 Morphological Assays Electron microscopy
Isolated virus or infected cells Nonenveloped or enveloped (alternate method to determine if an envelope is present?) Core structure

16

17 Epidemiology Tracking prevalence of viruses in host populations
Blood components and tissue samples Virus culture In vitro (tissue culture) In vivo (susceptible animal model) Molecular testing PCR methods Southern blot ELISA (enzyme linked immunosorbent assay) Assay for antigen (viral protein) Assay for antibody directed against virus

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