8.2 Tumour Viruses

Question 1

Cell transformation is characterised by… (3)

Answer 1

• Unregulated cell growth
• Loss of contact inhibition
• Altered cell morphology

Question 2

What is an oncogene?

Answer 2

A gene coding for proteins that can transform a cell

Question 3

Describe Papillomaviruses

Answer 3

DS DNA virus
Non-enveloped
Resistant to diverse environment
Species specific

Question 4

Describe papillomavirus pathogenesis

Answer 4

• Entry via lesion in epithelium
• Infection of (dividing) basal cells
• Expression of early proteins = proliferation
• Structural proteins and viral particles only produced in upper layers of epithelium
• Transmission via exfoliated cells

Question 5

What is Bovine Papillomavirus

Answer 5

Benign skin tumours on head, neck, shoulder, udder
Calves and yearlings
Tumours usually regress spontangeously ~6mnth

Question 6

How does BPV survive in host?

Answer 6

• viral protein E5 binds receptor PDGF = cell proliferation
• E5 inhibits formation of gap junctions = reduced communication = lack of growth inhibitory signals
• E5 downregulates MHC1 expression = evades host immunosurveillance

Question 7

Describe canine papillomavirus

Answer 7

Benign tumours on lips, tongue, palate
Spontaneous regression

Question 8

Describe equine papillomavirus

Answer 8

Benign skin tumours
Self-limiting
Cases equine sarcoid (locally invasive skin tumours)

Question 9

Describe Retroviruses

Answer 9

RNA viruses
Enveloped
Reverse transcriptase enzymes (RNA>DNA)

Question 10

Retroviral replication

Answer 10

Adsorption to receptors
Membrane fusion
Penetration and uncoating
Reverse transcriptase
Integration (provirus)
Transcription
Translation
Capsid assembly
Budding
Maturation

Question 11

Organisation of retroviral genome

Answer 11

LTRs (long terminal repeats) at each end to regulate gene expression

GAG (Group specific Antigen) cides for capsid

POL (Codes for polymerase) Reverse transcriptase

ENV (COdes for envelope proteins)

Question 12

Cell transformation by retrovirus

Answer 12

• Some carry oncogenes (v-onc) in viral genome
• May activate cellular proto-oncogenes
• May inactivate tumour supressor gene

Question 13

Jaagsiekte (JSRV) = ‘driving sickness’

Answer 13

Invades type II pneumocytes, ↑ proliferation = solid tumous = no breathing

Progenitor cells produce surfactant = mucous production

Wheelbarrow test

Question 14

Bovine Leukemia Virus

Answer 14

Causes Enzootic Bovine Leukosis (EBL)
- Infects B lymphocytes
- Polyclonal expansion = viral spread
- Notifiable disease
- Sitting cows

Question 15

Cell transformation by retrovirus

Answer 15

• carry oncogenes (v-onc) in genome
• may activate cellular proto-oncogene
• may inactivate tumour suppressor gene

Retroviruses that dont carry oncogenes = insertional mutagenesis

Question 16

FeLV pathogenesis

Answer 16

Mutation by insertion of viral genome
at C-myc gene (encodes protein that regulates transcription)
Mutation = uncontrolled proliferation

Question 17

FeLV prevalence

Answer 17

Transmitted oronasally in saliva
Causes tumours of lymphocytes = lymphoma