Virus-cell interactions (Oncogenes) Flashcards
The virus’ survival against the cell is hindered by which factors?
- Resistance
- Interferon production
- Latency
- Persistent infection
- Oncogenicity
- Cytopathic effects
Abortive infection
No virus release
Productive infection
Virus release and shedding
Resistance
No surface receptor for vital attachment
- Not susceptible - host spectrum
Interferon (IFN) production
- IFN: Cell-coded mediator protein - Cell defence mechanism
- Interferon inducer: dsRNA, RI forms → cascade - IFN release
- IFN effects on neighbouring cells:
- Structural changes on the cytoplasmic membrane
- Penetration
- L-RNase: mRNA degradation
- Proteinkinase: protein production inhibited
- Structural changes on the cytoplasmic membrane
Give the types of IFN
- IFN-α (epithelial, leucocytes)
- IFN-β (fibroblast)
- IFN-γ (lymphocyte)
IFN efficacy is at what dose?
10-9 mg
IFN production time
- 2-4 hours after infection
- Maximum after 12 hours
- Clearance after 24 hours
Describe the specificity of IFNs
- Not virus specific
- Host specific
Problems with IFN therapy
- Expensive
- Parenteral use, short-term efficiency
- The inducers are toxic
- Toxic side effects
Latency
- After infection of the virus, no more multiplication
- Only NA + proteins are present
- Episome
- Integration
- No virus shedding/clinical signs
- Carrier
- Reactivation
- Immunosuppression
Persistent infection
- Virus production, but not severe cell damage
- Continuous shedding
- In vitro cell cultures: diagnostic problems
Viral oncogenicity effect
- Cell proliferation
- Less differentiated cell forms
- Less effective cell forms
- Usually not able to function effectively
- Tumours
Cellular oncogenesis
- Oncogenes: Genes necessary for cell division + maturation
- Active cell: Supressed proto-oncogenes (c-onc)
- Activation - oncogenesis
Oncogenic virus examples
- DNA viruses: Papilloma-, Polyoma-
- RNA viruses: Retroviridae
Types of tumours
- Benignant: Limited/less destructive
- Malignant: Invasive/ destructive
Mechanism of viral oncogenesis: Activation of cellular oncogenes
- DNA integration into cellular genome
- Retroviral LTR regions → Intensive promoter → translation
- c-onc activated
- Oncoprotein expression → Cell proliferation
- Development of lymphatic tumours
Mechanism of viral oncogenesis: Expression of viral oncogenes
- Recombination between and proviral genome
- c-onc gene transposed into virus genome → v-__onc
- Oncogene carried by the virion
- Oncoprotein production
- Development of malignant tumours
- Replacing essential genes
The v-**onc gene isn’t essential for the virus
Mechanism of viral oncogenesis: Viral proteins with consequent oncogenic effect
- Oncogenic DNA viruses
- Viral modulator proteins control cell machinery
- Inactivation of cellular anti-oncogenic proteins
- Inhibition of apoptosis
Usually benignant tumours
In vitro cell cultures lead to
Malignant transformation
