63+66 Retroviruses Flashcards
How do retroviruses replicate?
They use reverse transcriptase to convert their gRNA back into DNA, which then gets transcribed into mRNA to make proteins
Are retroviruses environmentally hardy?
Nope; enveloped
Retroviruses are _____ (large/small)
Small - aprox 10k base pairs
Describe the mechanism of retroviral replication starting at entry into the cell.
Virus binds host cell receptor to initiate membrane fusion; releases viral capsid into cytosol. Reverse transcription of viral RNA into proviral DNA, which then travels into nuclear envelope and integrates into host genome. Eventually gets transcribed into mRNA
What are endogenous retroviruses?
Permanently encoded viral genes that are passed vertically from parent to offspring. Usually don’t cause disease and are replication incompetent
Clinically, what are 3 things associated with retroviruses?
Tumors
Chronic inflammation
Immunodeficiency
What is a protooncogene?
A non-pathogenic gene that if it becomes unregulated turns into an oncogene
List and describe the 3 mechanisms of retroviral oncogenesis.
-Insertional mutagenesis: virus randomly inserts into genome upstream of a protooncogene; causes dysregulation
-Oncogene capture: virus selectively takes an oncogene from the host and expresses it in an unregulated manner. Virus may not be able to replicate alone afterwards if they got rid of a replication gene to make room for the oncogene
-Oncogenic viral protein: The virus just so happens to naturally encode an oncogene
What are two important diseases caused by Alpharetrovirus spp?
Avian leucosis virus and rous sarcoma virus
How does rous sarcoma virus (RSV) cause tumors?
Host-captured oncogene
How is avian leucosis virus transmitted, and which mechanism is the most important?
Horizontal transmission, vertical transmission, and congenital transmission (most important because chicks are born tolerant to virus)
What type of neoplasia does ALV (avian leucosis virus) cause?
B cell lymphoma
What are two important diseases caused by Betaretrovirus spp?
Jaagsiekte disease (JSRV); enzootic nasal tumors (ENTV)
For both Jaagsiekte and enzootic nasal tumor viruses, which part of the virus is oncogenic?
The envelope
What species are affected by Jaagsiekte and enzootic nasal tumors?
Sheep»_space;> goats
What type of neoplasia does ENTV cause?
Nasal adenocarcinoma
What type of tumor does JSRV cause?
Pulmonary adenocarcinoma
What does JSRV do to the lung?
Makes it produce excess surfactant; can hold up hind end of animal and it will come out the nares
What is an important deltaretrovirus in vet med?
Bovine leukosis virus (BLV)
T or F: BLV is always symptomatic
F; often asymptomatic and is endemic
What cells do BLV target?
Macrophages and B cells
How is BLV transmitted and why is this important for production animals?
Horizontally transmitted; shed in colostrum. BLV infected milk is NOT zoonotic
What is a common clinical sign associated with healthy BLV infected cattle?
Persistent lymphocytosis
T or F: BLV can cause neoplasia in young animals.
F; only in adults
What type of neoplasia does BLV cause?
Lymphoma
What is an important gammaretrovirus in vet med?
FeLV
Does FeLV cause viremia?
Yes
What are the mechanisms of oncogenesis for FeLV?
Insertional mutagenesis and oncogene capture
What cells do FeLV target?
Macrophages, T cells, hematopoietic progenitor cells
How is FeLV transmitted?
Saliva and milk
The FeLV snap test is an ____(antigen/antibody) test.
Antigen
What are important viruses from the genus Lentivirus?
Small ruminant lentivirus (SRLV), equine infectious anemia (EIA), FIV
What diseases do small ruminant lentivirus cause and in what species?
-Caprine arthritis encephalitis virus; goats»sheep
-Maedi vista virus; sheep»goats
What is the target cell of SRLV?
Macrophages
What tissue types are affected by SRLV?
Joints, CNS, lung, mammary
How is SRLV controlled?
Colostrum administration and segregation of infected adults
What kind of synovitis and mastitis do SRLV cause?
Fibrinous synovitis and “hard bag” fibrosing mastitis
What cells are targeted by EIA?
Macrophages
Describe the clinical signs of EIA.
Cyclic viremia, anemia, thrombocytopenia, fever, edema, and wasting
What is the vector for EIA?
Arthropods/biting flies
What test is used for EIA?
Coggins test
What is the primary leukocyte affected by FIV?
CD4 T cells (central to the adaptive immune system)
What does FIV progressively do to the immune system?
Drops in B and T cell numbers; lymphoid atrophy; eventual FAIDS
Why is or isn’t FIV directly oncogenic?
Not directly oncogenic–shuts down the immune system and the immune system kills neoplastic cells
Does FIV cause viremia?
Not a prolonged viremia
The FIV snap test is an ____(antigen/antibody) test.
Antibody
