63+66 Retroviruses

Question 1

How do retroviruses replicate?

Answer 1

They use reverse transcriptase to convert their gRNA back into DNA, which then gets transcribed into mRNA to make proteins

Question 2

Are retroviruses environmentally hardy?

Answer 2

Nope; enveloped

Question 3

Retroviruses are _____ (large/small)

Answer 3

Small - aprox 10k base pairs

Question 4

Describe the mechanism of retroviral replication starting at entry into the cell.

Answer 4

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

Question 5

What are endogenous retroviruses?

Answer 5

Permanently encoded viral genes that are passed vertically from parent to offspring. Usually don’t cause disease and are replication incompetent

Question 6

Clinically, what are 3 things associated with retroviruses?

Answer 6

Tumors
Chronic inflammation
Immunodeficiency

Question 7

What is a protooncogene?

Answer 7

A non-pathogenic gene that if it becomes unregulated turns into an oncogene

Question 8

List and describe the 3 mechanisms of retroviral oncogenesis.

Answer 8

-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

Question 9

What are two important diseases caused by Alpharetrovirus spp?

Answer 9

Avian leucosis virus and rous sarcoma virus

Question 10

How does rous sarcoma virus (RSV) cause tumors?

Answer 10

Host-captured oncogene

Question 11

How is avian leucosis virus transmitted, and which mechanism is the most important?

Answer 11

Horizontal transmission, vertical transmission, and congenital transmission (most important because chicks are born tolerant to virus)

Question 12

What type of neoplasia does ALV (avian leucosis virus) cause?

Answer 12

B cell lymphoma

Question 13

What are two important diseases caused by Betaretrovirus spp?

Answer 13

Jaagsiekte disease (JSRV); enzootic nasal tumors (ENTV)

Question 14

For both Jaagsiekte and enzootic nasal tumor viruses, which part of the virus is oncogenic?

Answer 14

The envelope

Question 15

What species are affected by Jaagsiekte and enzootic nasal tumors?

Answer 15

Sheep&raquo_space;> goats

Question 16

What type of neoplasia does ENTV cause?

Answer 16

Nasal adenocarcinoma

Question 17

What type of tumor does JSRV cause?

Answer 17

Pulmonary adenocarcinoma

Question 18

What does JSRV do to the lung?

Answer 18

Makes it produce excess surfactant; can hold up hind end of animal and it will come out the nares

Question 19

What is an important deltaretrovirus in vet med?

Answer 19

Bovine leukosis virus (BLV)

Question 20

T or F: BLV is always symptomatic

Answer 20

F; often asymptomatic and is endemic

Question 21

What cells do BLV target?

Answer 21

Macrophages and B cells

Question 22

How is BLV transmitted and why is this important for production animals?

Answer 22

Horizontally transmitted; shed in colostrum. BLV infected milk is NOT zoonotic

Question 23

What is a common clinical sign associated with healthy BLV infected cattle?

Answer 23

Persistent lymphocytosis

Question 24

T or F: BLV can cause neoplasia in young animals.

Answer 24

F; only in adults

Question 25

What type of neoplasia does BLV cause?

Answer 25

Lymphoma

Question 26

What is an important gammaretrovirus in vet med?

Answer 26

FeLV

Question 27

Does FeLV cause viremia?

Answer 27

Yes

Question 28

What are the mechanisms of oncogenesis for FeLV?

Answer 28

Insertional mutagenesis and oncogene capture

Question 29

What cells do FeLV target?

Answer 29

Macrophages, T cells, hematopoietic progenitor cells

Question 30

How is FeLV transmitted?

Answer 30

Saliva and milk

Question 31

The FeLV snap test is an ____(antigen/antibody) test.

Answer 31

Antigen

Question 32

What are important viruses from the genus Lentivirus?

Answer 32

Small ruminant lentivirus (SRLV), equine infectious anemia (EIA), FIV

Question 33

What diseases do small ruminant lentivirus cause and in what species?

Answer 33

-Caprine arthritis encephalitis virus; goats»sheep
-Maedi vista virus; sheep»goats

Question 34

What is the target cell of SRLV?

Answer 34

Macrophages

Question 35

What tissue types are affected by SRLV?

Answer 35

Joints, CNS, lung, mammary

Question 36

How is SRLV controlled?

Answer 36

Colostrum administration and segregation of infected adults

Question 37

What kind of synovitis and mastitis do SRLV cause?

Answer 37

Fibrinous synovitis and “hard bag” fibrosing mastitis

Question 38

What cells are targeted by EIA?

Answer 38

Macrophages

Question 39

Describe the clinical signs of EIA.

Answer 39

Cyclic viremia, anemia, thrombocytopenia, fever, edema, and wasting

Question 40

What is the vector for EIA?

Answer 40

Arthropods/biting flies

Question 41

What test is used for EIA?

Answer 41

Coggins test

Question 42

What is the primary leukocyte affected by FIV?

Answer 42

CD4 T cells (central to the adaptive immune system)

Question 43

What does FIV progressively do to the immune system?

Answer 43

Drops in B and T cell numbers; lymphoid atrophy; eventual FAIDS

Question 44

Why is or isn’t FIV directly oncogenic?

Answer 44

Not directly oncogenic–shuts down the immune system and the immune system kills neoplastic cells

Question 45

Does FIV cause viremia?

Answer 45

Not a prolonged viremia

Question 46

The FIV snap test is an ____(antigen/antibody) test.

Answer 46

Antibody