Effects of Viruses on Host Cells Flashcards
What effects can viruses have on host cells?
- Cytocidal (cell death)
- Non cytocidal (persistant infection)
- Cell transformation (tumor cells)
What are inclusion bodies?
abnormal structure in a cell nucleus or cytoplasm or both, such as aggregates of proteins
has a characteristic staining property associated with a certain viral infection
- helps to ID certain viruses
What are examples of ways inclusion bodies can be formed?
- Accumulation of viral components
- Result from degenerative changes in the cell
- crystalline aggregates of virions
How are inclusion bodies described?
- location - intracytoplasmic vs intranuclear
- Staining property - basophilic or eosinophilic
In tissue culture, visible morphological changes/damages to monolayer cells resulting from virus infection is also known as _________
Cytopathic effect
What are ways viruses can cause cell injury and death?
- Inhibition of nucleic acid synthesis
- Inhibition of mRNA transcription
- Inhibition of protein synthesis
- Release of lysosomes by virus which destroy host cell
- Interference with cell membrane fusion
How is apoptosis different from lysis?
Apoptosis is programmed cell death - death of host cell to prevent viral release of progeny
Lysis is when the virus destroys the host cell and releases new virions
_________ are responsible for degradation of the cells own DNA and proteins during apoptosis
Caspases
How is the intrinsic pathway activated?
viruses cause cell injury which results in increased permeability and activation of intrinsic/mitochondrial apoptotic pathway
How is the extrinsic pathway activated?
by engagement of specific cell membrane receptors (TNF family)
binding of the cytokine TNF to its cell receptor triggers apoptosis
What is another apoptotic pathway other than intrinsic and extrinsic?
CD8+ T cells use perforin and granzymes that directly activate caspases in the target cell
How do viruses activate ADCC?
enveloped viruses enter host cell via membrane fusion and leave viral glycoproteins on the surface of host cell
these are antigenic and detected by Ab which calls NK cell over to kill infected host cell
What is metastasis?
spread of cancer from the part of the body that it started to other places
What is a proto-oncogene?
Encodes proteins that function in normal cell growth and differentiation
What does a tumor suppressor gene do?
Encodes proteins that regulate and inhibit uncontrolled growth
keeps cell division in check
Important tumor suppressor genes:
Rb and p53
What is an oncogene?
Mutated form of a prot-oncogene or aberrantly expressed proto-oncogene
What does Rb stand for and what does it do?
Retinoblastoma protein
tumor suppressor gene that blocks E2F from abnormal / uncontrolled cell division
What does p53 do?
tumor suppressor gene that prevents cells with damaged DNA from dividing
tries to repair damaged DNA and if it can’t it mediates apoptosis
What oncogenic virus generates a DNA provirus after infection?
Retroviruses (RNA virus)
How can oncogenic DNA viruses develop into cancer?
If it infects a non permissive cell
- virus cant replicate so it integrates viral DNA into host DNA OR DNA remains episomal (plasmid) and results in cancer
What is the result of an oncogenic DNA virus infecting a permissive cell?
Does not cause cancer
virus is able to replicate resulting in cell lysis + release of virus into body
What is the result of an oncogenic DNA virus infecting a non- permissive cell?
Causes cancer!!
virus cant replicate so it integrates viral DNA into host DNA OR DNA remains episomal (plasmid) and results in cancer
**virus transforms without completing replication cycle
Two ways oncogenic RNA viruses can occur?
- Acute transforming retroviruses
- Slow/Chronic transforming retroviruses
How do acute transforming retroviruses result in oncogenic RNA viruses?
virus steals proto-oncogene from infected host cell DNA + converts it into the oncogene = cancer
How do slow/chronic transforming retroviruses result in oncogenic RNA viruses?
virus genome integrates into REGULATORY gene of host DNA
as a result regulatory gene can’t act on proto-oncogene, allowing the proto-oncogene to excessively divide = cancer
What are tumor antigens?
New Ag that appear on the surface of a tumor cell that can provoke immune response
Ex: FOCMA - feline oncoronavirus membrane associated antigen
Which virus has high neuroinvasiveness and high neurovirulence?
Rabies virus
Which virus has low neuroinvasiveness and high neurovirulence?
Herpes virus
