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