Chapter 4 - V Flashcards
Lytic infections
Virus: Naked DNA or RNA genome
Fate of cell: lysed when replication is complete
Fate of person: if cell is routinely replaced, no permanent damage
if cell is not routinely replaces, permanent damage may result
Persistent infection
Virus: Enveloped DNA or RNA genome
Fate of cell: progeny slowly buds out , cells dies after weeks- months
Fate of person:
Virus evades host immune system but continuously stimulates it - inflammation contributes to long term damage
Latent Infections
Virus: DNA or retrovirus
viral genome persist in cells for years- usually integrates into host cell DNA
Fate of cell: inefficient or absent viral gene expression - viral production may resume after prolonged period
Fate of person: depends on cell type that is infected
Oncogenic Infections
Virus: DNA or retrovirus
DNA integrate into host cell DNA
Fate of cell: viral genes are expressed resulting in loss of growth control of the cell
Fate of person: development of cancer
What does virus need to be successful
A cells infection with a virus may not result in death of the cell
Evolution has led to a symbiosis between the virus and host organism
Cells can respond to a viral infection in various ways
- no apparent change
- cytopathic effect - cell injury, formation of inclusion bodies, fusion of cells
- loss of growth control (transformation, tumor cells)
Pathogenesis of viral infection
Normal cells in culture have a distinct appearance
infection of the virus may cause rounding of cell = dead or dying then lysis
or
Formation of inclusion bodies (aggregates of viral particles) in the cytoplasm or nucelus
Pathogenesis of viral infection
Neoplastic transformation
formation of multi nucleotide - giant cell
Cultivation of viruses in the lab
viruses don’t grow like bacteria or cell lines
viruses assemble from individual components (protein, Nucleic acid)
Need to grow in host cell
there are many methods for cultivating viruses
- some methods are better for some virus species than other
Primary cell culture
- sufficient for initial isolation
Continuous cell culture and Embryonated egg
- good for vaccine production
Animals:
- may be required for initial isolation
- used when other options fail
- Least desirable option
Primary cell culture
Take an organ or part of mouse
To obtain a single cell suspension from primary tissue (eg muscle biopsy)is by mechanical teasing a treatment protease enzyme such as trypsin to disperse cells
The cells are then incubated in a tissue culture dish with nutrient-rich growth media enriched with blood
Normal primary cells will divide a limited number of times and drow as a monolayer
Transformed cell line can indefinitely grow in vitro
-Convenient to cultivate more viruses
Virus cultivation
Embryonated Chicken egg can be used to cultivate many different virus species using different site of inoculated
Require a lot of eggs to make enough influenza vaccine for the world
Take time
- chicken must lay egg
- egg must develop to certain stage
- 7 days incubation after inoculation
- takes space and time
