Oncology: Viruses Flashcards
Name 4 retroviridae (RNA viruses) that cause cancer
Avian leukosis
Feline retroviruses
Jaagsiekte sheep retrovirus
Bovine leukosis
What type of tumours does Avian leukosis cause?
Avian leukosis – lymphoid, myeloid tumours, sarcomas
What type of tumours do Feline retroviruses cause?
Feline retroviruses – lymphoid tumours
What type of tumours does Jaagsiekte sheep retrovirus cause?
Jaagsiekte sheep retrovirus – lung adenocarcinoma
What type of tumours does Bovine leukosis cause?
Bovine leukosis – lymphoma
Name a herpesviridae (DNA virus) that causes cancer
Marek’s disease virus – lymphoid tumours
Name a papillomaviridae (DNA virus) that cause cancer
Bovine, equine, canine papilloma viruses - skin, mucosal
Viral transduction can result in….
…overproduction of protein homologous to cellular oncogene (v-onc)
Viral insertion can also….
….upregulate production of a cellular oncogene
Where do chickens get avian leucosis form?
Transmitte d from the hen to the gee, leads to persistently infected chicks which are immunotolerant to viral antigens
How long is the incubation period until tumour development for avian leucosis?
Over 4 months
What are the three most important avian leucosis virus subgroups?
ALV subgroups A and B (‘conventional’) - B lymphocyte tumours in some birds
ALV subgroup J (emerging virus) - Myeloid tumours
How is ALV controlled?
Control by eradication in breeder flocks: Select virus-free hens by screening eggs
Check eggs over 14-day period for ALV antigen in albumen by ELISA
Hatch chicks and rear in isolation
Test for ALV antigen in blood
What type of retrovirus is bovine leukaemia virus and what does it cause?
(δ retrovirus)
Causes enzootic bovine leukosis
Where does BLV infect?
Virus infects B lymphocytes and becomes latent so no free virus in blood
Antiviral antibodies in persistently infected cattle
How is BLV transmitted?
Transmission via infected cells e.g. milk, blood.
Can be transmitted vertically or horizontally
Is BLV notifiable?
Yes
How does BLV cause tumours?
The viral Tax protein transactivates cellular genes
Products of transactivated cellular genes may be oncogenic
Lymphocytosis, lymphoma formation in older cattle
What type of retroviridae is Jaagsiekte sheep retrovirus ?
(β retrovirus)
How does JSRV cause tumours?
JSRV replicates only in type II pneumocytes and Clara cells
Replication leads to transformation of every cell
Viral Env protein switches on signals for cell division – activates cellular signalling pathways
How does JSRV cause tumours?
JSRV replicates only in type II pneumocytes and Clara cells
Replication leads to transformation of every cell
Viral Env protein switches on signals for cell division – activates cellular signalling pathways
What are the clinical signs of JSRV?
Wheelbarrow test- produces lots of surfactant fluid from lungs
Respiratory secretions are infectious
How is JSRV transmitted and treated?
Requires close contact - More common in housed sheep
Can eliminate the disease by rapid isolation and culling of diseased animals
How is JSRV diagnosed?
Diagnosis by histopathology/RT-PCR
How do cows contract bovine papillomatosis?
When cows eat bracken they are exposed to a number of immunosupressive and mutagenic chemicals
e.g. quercetin and ptaquiloside and when exposed to the BPV they can develop tumours
What are the types of bovine papillomatosis?
BPV-2: bladder carcinomas (enzootic haematuria)
BPV-4: alimentary carcinomas (oesophageal, rumen, reticulum)
What is marek disease virus?
Oncogenic herpesvirus
Tumours derived from T lymphocytes
Field strains show variable virulence but commonly affects birds aged 12-24 wk.
Birds go off their legs due to neoplastic lymphoid cells blocking the nerve roots
