Virology Chapter 4: Virus Cultivation – Outcomes of Infection Flashcards
Unlike bacteria, what can’t eukaryotic cells growth without?
growth factors – signalling/stimulating molecules
In what conditions are eukaryotic cells grown in cell culture?
- culture medium includes: sugars, amino acids, vitamins, minerals, growth factors
- in incubators with CO2 – cells are very sensitive to pH changes
How do viruses grow in primary cultures?
individual cells isolated from tissue grow attached to the surface of the culture container in a monolayer
- contact inhibition slows growth of cells once they become too dense and begin touching each other
- at this point, growth can only be sustained by making a secondary structure
What are tumour/transformed cell lines (continuous cell culture)?
transformed cells or individual cells isolated from a tumour grow in a monolayer, and beyond
not affected by contact inhibition – grow indefinitely because they are transformed and no longer sensitive to constraints of primary cells
What are the two types of cell cultures?
- primary
- tumour/transformed
What type of abnormalities may be observed in cells infected by a virus?
- rounding of cells
- formation of inclusion bodies in cytoplasm or nucleus
- formation of synctia
- complete cell lysis
- uncontrolled growth
- detachment from surfaces of the culture vessel
- shrinkage of nucleus
- appearance of vacuoles in cytoplasm
- increase in membrane permeability
- some viruses do not immediately kill the host cell
What are cytopathic effects (or cell injuries)?
morphological changes exhibited by animal cells infected with viruses – either directly or indirectly induced by virus
What are synctia?
masses of fused cells containing more than one nucleus
What are inclusion bodies?
aggregates of viral protein that appear as granules within the cell
What are two components to consider when considering diseases caused by viruses?
- effects of virus’ replication cycle
- effects of immune response to infection
What can viral disease be caused by?
- replication of the virus
- host’s immune response to the virus (ie. inflammatory responses are triggered by cytokines released by cells of the immune system after the recognition of the pathogen)
Where do viruses enter the host organism?
- respiratory system
- GI system
- genitourinary system
- abrasions in skin
- direct inoculation (ie. needles, insect bites)
Where must a virus go after infection the host organism?
must reach a site where it undergoes primary replication – usually close to portal of entry
In many cases, where is the virus shed?
- respiratory secretions (ie. coughs or sneezes)
- enteric or genitourinary secretions
- ingestion of blood meal from viremic host by insects
How can viruses be transmitted?
- transfusion of blood, blood products
- organ transplant
- direct skin-to-skin contact
- insect bites
What are the 4 possible outcomes of viral infection in eukaryotic cells?
- lytic/acute infection
- persistent/chronic infection
- latent infection
- oncogenic infection
What is lytic/acute infection?
host cell is killed, usually during release of progeny virus particles
What is persistent/chronic infection?
slow release of virus over a long period of time, with only the death of a few infected cells
What is a latent infection?
extreme case of persistent/chronic infection
virus genome remains present in the cell, but is not replicated and the virus does not harm the cell
- provirus may express some genes to ensure survival of the genome and allow for reactivation of replication cycle
- provirus can be reactivated and result in production of virus particles at some later time
- no symptoms
- no free viruses detected in body
What is an oncogenic infection?
integration of viral genome into host chromosome
- viral genome is replicated along with host DNA, and passed onto progeny cells
- some viral genes are expressed, and often alter cells and cause them to become tumour cells – transformation
