-
What are some General characteristics of Viruses?
- -Obligatory intracellular parasites
- -Contain DNA or RNA
- -Contain a protein coat
- -Some are enclosed by an envelope
- -some viruses have spikes
- -most viruses infect only specific types of cells in one host
- -Host range is deteremined by speficif host attachement sites and cellular factors.
-
What are some Virion structures?
- -Nucleic acid -----DNA or RNA
- -Capsid-----Capsomeres
- -Envelope
- -Spikes
-
Taxonomy of Viruses
What do family names end in?
-viridae
-
Taxonomy of Viruses
What do Genus names end in?
-virus
-
What are viral species?
A group of viruses sharing the same genetic information and ecological niche(host). Comon names are used for species
Subspecies are designated by a number.
-
Taxonomy of Viruses
Examples:
- * Herpesviridae
- * Retroviridae
-Human herpes virus-- HHV-1, HHV-2, HHV-3
- -Human immunodeficiency virus HIV-1, HIV2
-
-
Growing Viruses
Viruses must be grown in living cells
Bacteriophages form plaques on a lawn of bacteria
-
Growing viruses
Animal viruse may be grown in living animals or in embryonated eggs
-
Animal and plant viruses may be grown in cell culture
continuouss cell lines may be maintained indefinitely
-
Virus Identification
-Cytopathic effects
-serological tests
-Nucleic acids
- serological tests
- -detect antibodies against viruses in a patient
- -uses antibodies to identify viruses in netralization tests, viral hemagglutination, and Western blot
-
-
What is the Lytic Cycle
- -Attachment
- -Penetration
- -Biosynthesis
- -Maturation
- -Release
-
-
Lytic Cyle
Attachment
Phage attaches by tail fibers to host cell
-
Lytic Cycle
Penetration
Phage lysozyme opens cell wall, tail sheath contracts to force tail core and DNA into cell
-
Lytic cycle
Biosynthesis
Production of phage DNA and proteins
-
Lytic Cycle
Maturation
Assembly of phage particles
-
Lytic cycle
Release
Phage lysozyme breaks cell wall
-
Results of Multiplication of Bacteriophages
Lytic Cycle
Phages causes lysis and death of host cell
-
Results of Multiplication of Bacteriophages
Lysogenic Cycle
- -Prophage DNA incoporated in host DNA
- -Phage conversion
- -Specialized transduction
-
-
What are Lysogenic Cells
- -Latent cells
- -possible prophage (insertion into bacterial chromosome)
- -three results of lysogeny:
- *immune to reinfection
- *phage conversion
- *specialized transduction
-
Multiplication of Animal Viruses
-What is the extra step
- -Attachment: viruses attach to cell membrane
- -Penetration: by endocytosis or fusion
- -Uncoating: by viral or host enzymes
- -biosynthesis:production of nucleic acid and proteins
- -Maturation: nucleic acid and capsid proteins assemble
- -Release: by budding (enveloped viruses) or rupture
-
Attachment, Penetration, Uncoating
Happens by pinocytosis
-
Attachment, Penetration, Uncoating
By Fusion
-
Cancer
- -Activated oncogenes transform normal cells into cancerous cells
- -Transformed cells have increased growth, loss of contact inhibition, tumor-specific transplant antigens, and T antigens
- -The genetic material of oncogenic viruses becomes integrated into the host cell's DNA
-
What are Oncogenic DNA Viruses?
- -Adenoviridae
- -Herpesviridae
- -Poxviridae
- -Papovaviridae
- -Hepadnaviridae
-
-
What are Oncogenic RNA viruses?
- -Retroviridae
- -Viral RNA is transcribed to DNA, which can integrate into host DNA
- -HTLV-1
- -HTLV-2
-
What happens during Latent viral infections
Virus remains in asympotmatic host cell for long periods
-COld sores, shingles
-
What happens in Persistent viral infections?
- -Disease processes occurs over a long period; generally is fatal
- *subacute sclerosing panencephalitis (measles virus)
-
What are prions?
A prion is a protein.
- -Proteinaceous infection particle
- -Inherited and transmissible by ingestion, transplant, and surgical instruments
- -spongiform encephalopathies: sheep scrapie, Creutzfeldt-Jakob disease, Gerstmann-Straussler-Scheinker syndrome, fatal familial insomnia, mad cow disease
**Must come in contact with brain to be infected with any prion disease
-
Prions
PrPc: Normal cellular prion protein, on cell surface
PrPsc: Scrapie protein; accumulates in brain cells, forming plaques
-
What are plant viruses?
Enter through wounds or via insects
-
What are viroids?
Infectious RNA
-potato spindle tuber disease
**only found to infect plants. Very specific, can only infect plants
-
How can a protein become infectious?
Become plaque or build up of proteins
-
What is orthomyxovirdae?
- -Single-stranded RNA,
- -each strand, has multiple RNA strands
- -enveloped spikes can agglutinate RBCs
- -Influenzavirus (influenza viruses A and B)
- -Influenza C virus
|
|