Viruses

• Individual Viruses =

Virion• Not cells – nonliving• Size 0.02 -0.3 μm• Bacterial Viruses =

Bacteriophage

T 4

Viral Genome

• Double Strand or Single Strand

• DNA or RNA

• Most Genomes Linear

• Overlapping genes

Human Papillomavirus

Protein Coat

• Capsid, Coat, Shell• Capsomer -

Individual Proteins• Self Assembly• Nucleocapsid

Viral Symmetry

• Icosahedral •Helical

20 faces, 12 vertices

Icosahedral Subunits

Tobacco Mosaic VirusHerpes Simplex Virus

Enveloped Virus

Complex Virus

T 4 Bacteriophage

Enzymes in Viruses

• Reverse Transcriptase

• Lysozyme• RNA Polymerase• Neuraminidase

Viral Host

• Living Cells• Animal Host• Cell Culture• Tissue Culture• Monolayer

Cell Line

•Primary Culture Line•Transformation

–Viruses

–Mutagen

•Permanent Cell line•HELA –Henrietta Lacks

Quantification of Viruses

• Plaque Assay – Bacteria

• Efficiency of Plating• Animal Infectivity

Methods• End Point Dilution

Bacteriophage Plaques

Plaques in Tissue Culture Monolayer

Viral Replication

• Attachment

• Penetration

Synthesis

1. Production of Early Proteins

Replication of Nucleic Acids

2. Production of Late Proteins

Viral Coat

• Assembly

• Release

One-step Growth Curve

Latent Period

•Some Host Cells Use Restriction Enzymes to Destroy DNA Viruses

•Some Viruses Can Modify Their Genome’s Restriction Sites for Protection

Baltimore Classification Scheme

David Baltimore, Howard Temin, Renato Dulbecco 1975

Reverse transciptase Retro virus

6 Classes based on DNA→RNA→Protein7th Class Hepadnaviruses added

+/- SS RNA Viruses

SS DNA Viruses

DS Intermediates

Reverse Transcriptase

Virulent Bacteriophage

• Lytic T Phages• T4, T7 DS DNA• Head, Tail, Spikes

Base Plate, Tail Fibers, Contractile Sheath

• Hydroxymethyl-cytosine

Lambda

• Best Known Virus?

• Can be Virulent or Temperate

• Lysis or Lysogeny

• Becomes Prophage (Provirus)

• Gives Immunity to Host

• Specific Insertion Site

Maintenance of Lysogeny

• Lambda Repressor -Lysogeny

• CRO Protein - Lysis

• Induction

Animal VirusesDNA Viruses RNA Viruses

Eukaryotic Host

Types of Infections:

Lytic

Persistent

Latent

Hepatitis A

Herpes

Cancer Viruses

• Transformation• Neoplasm• Benign

• Malignant• Metastasis• Oncogene

Retrovirus

• RNA Genome

• Reverse Transcriptase

• DNA Copy Insert into Host Genome

• AIDS

• Acquired Immunodeficiency Syndrome

• HIV – Human Immunodeficiency Virus

HIV

Subviral Entities

• Defective Viruses

• Parasitic?

• Helper Viruses

• Satellite Viruses

• AAV – Adenovirus Associated Virus

• Specific Insertion Sites

Viroids

• Naked Circles

• SS RNA

• 246-375 Nucleotides

• Plant Diseases

• Regulatory RNA

• -sRNA

Prions

• Infectious Proteins?

• Chaperone Protein

• Kuru

• Mad Cow Disease

• Scrapies

• Creutzfeldt-

Jakob Disease04/20/23

Prion Infectious Cycle

• PrPc → PrPsc

• Infectious,

• Sporadic, or

• Inherited Prion Disease

• Mice with no PrPc are Normal?

Viruses Word ListVirion

Bacteriophage

28 –200 nm (0.2 μm)

Genome

SS/DS RNA/DNA

Capsid, Coat, Shell

Capsomer

Self-Assembly

Nucleocapsid

Viral Symmetry

Helical

Icosahedral

Enveloped

Viruses

Complex Viruses

Enzymes in Virion

Reverse

Transcriptase

Lysozyme

Viral Host

Living

Organisms

Cell (Tissue)

Culture

Monolayer

Primary

Culture Line

Viruses 2

Transformation

Permanent Cell Line

Quantification

of Viruses

Plaque Assay

Efficiency of

Plating

Animal

Infectivity Methods

End Point

Dilution

Viral

Reproduction

Attachment

Penetration

Early Steps (Early Proteins)

Replication of

Nucleic Acids

Synthesis of

Proteins (Late)

Assembly

Release

Viruses 3One-step Growth Curve

Latent Period

Restriction/ Modification

Restriction Enzymes

Modification

+/- SS RNA Viruses

SS DNA Viruses

DS Intermediates

Reverse Transcriptase

 

BACTERIAL VIRUSES

Model Viruses

Genetic Engineering

RNA Bacteriophage

+SS RNA Viruses

MS2

“Male” Specific Phage

Viruses 4

4 Proteins4 Proteins

Maturation, Coat, Lysis

& RNA Replicase

Overlapping Genes

SS DNA Icosahedral Phage

ФX 174

DS DNA Phage – Lytic

T7, T4

Head, Tail, Base Plate,

Spikes, Tail

Fibers, Contractile Sheath

Hydoxymethylcytosine

Temperate Bacteriophage

Lambda

Viruses 5

Virulent – Temperate

Lysogeny

Prophage – Provirus

Immunity

Lambda Repressor

Cro protein

Transposable Phage

Insertion Elements

Transposon

Mu Phage – Mutator

Animal Viruses

Eukaryotic Hosts

Lytic Infections

Persistent Infections

Latent Infections

Viruses 6

Cancer

Transformation Neoplasm

Benign

Malignant

Metastasis

Oncogene

+SS RNA Viruses

Rhinovirus

Foot-and-Mouth Virus

Poliovirus

Polyprotein

Viral Protease

-SS RNA Virus

Rhabdovirus

RNA Dep. RNA Polymerase

Influenza

Segmented Genome

DS RNA Virus

Reovirus

Rotavirus

Viruses 7

DNA Virus

Papovavirus

SV 40

Herpesviruses

Herpes simplex, Chickenpox,

Shingles, Epstein-Barr,

Burkitt’s Lymphoma

Pox Virus

Smallpox

Adenovirus

Retrovirus

Reverse Transcriptase

Acquired Immuno

deficiency

Syndrome – AIDS

 

Viroids

SS RNA Circles

Viruses 8

Prions

“Mad Cow Disease”

Kuru

Scrapies

Creutzfeldt-Jakob Disease