Retroviridae (Final)

Question 1

What are Retroviruses causative agents of?

Answer 1

cancer
immunosuppression
immunodeficiency diseases

Question 2

Describe the enzyme encoded by Retroviridae

Answer 2

Reverse Transcriptase

• an RNA-dependent DNA polymerase
• needed to replicate

Question 3

General Features of Retroviridae

• structure
• genome

Answer 3

• enveloped, spherical
• studded with glycoproteins
• matrix layer
• diploid genome with 2 copies of single stranded pos sense RNA

Question 4

What are the 4 important genes in Retroviridae?

What do they each encode?

Answer 4

• gag gene: encodes virus core proteins
• pol gene: encodes reverse transcriptase and integrase
• env gene: encodes envelope proteins, surface, and transmembrane
• pro gene: encodes protease

Question 5

What diseases are caused by Alpharetroviruses?

Answer 5

Viruses of Chickens

• avian luecosis virus
• avian sarcoma virus
• avian myeloblastosis virus
• rous sarcoma virus

Question 6

What diseases are caused by Betaretroviruses?

Answer 6

• Mouse mammary tumor virus
• Mason-Pfizer monkey virus
• Jaagsiekte of sheep

Question 7

What diseases are caused by Gammaretroviruses?

Answer 7

Viruses of Reptiles and Mammals

• feline leukemia virus
• feline sarcomavirus
• avian reticuloendotheliosis virus

Question 8

Alpharetroviruses

• simple or complex?
• genes contained
• type of virion morphology
• endo, exo, or both?

Answer 8

• simple retrovirus
• gag, pol, pro, and env genes
• type C virion morphology
• endogenous and exogenous viruses

Question 9

Betaretroviruses

• genes contained
• endo, exo, or both?

Answer 9

• gag, pro, pol, env
• MMTV also contains sag gene which encodes the superantigen
• endogenous and exogenous viruses

Question 10

Gammaretrovirus

• simple or complex?
• genes contained
• type of virion morphology
• endo, exo, or both?

Answer 10

• simple retrovirus
• gag, pro, pol, env
• type C virion morphology
• endogenous and exogenous viruses

Question 11

Deltaretroviruses

• simple or complex?
• type of virion morphology
• genes contained
• endo, exo, or both?

Answer 11

• complex retrovirus
• type C virion morphology
• gag, pro, pol, env, and regulatory genes rex and tax
• rex and tax control synthesis and processing of viral RNA
• only exogenous

Question 12

What diseases are caused by Deltaretroviruses?

Answer 12

• Human T-lymphotrophic virus

- Bovine leukemia virus

Question 13

Epsilonretroviruses

• single or complex?
• type of virion morphology
• genes contained
• endo, exo, or both?

Answer 13

• complex retrovirus
• type C virion morphology
• gag, pro, pol, env, ORF A, B and C
• only endogenous

Question 14

What diseases are caused by Epsilonretroviruses?

Answer 14

Viruses of Fish and Reptiles

- Walleye dermal sarcoma virus

Question 15

Lentiviruses

• simple or complex?
• morphology
• genes contained
• endo, exo, or both

Answer 15

• complex viruses
• cylindrical or conical shaped core
• gag, pol, pro, env, and accessory genes
• exogenous in many mammals

Question 16

Functions of the 4 accessory genes found in Lentiviruses

Answer 16

• tat gene: encodes a transactivator that enhances RNA polymerase
• rev gene: encodes protein that facilitates transport of non-spliced viral RNA from nucleus to cytoplasm
• nef gene: encodes nef protein that is needed for replication, and down regulates CD4 molecule
• vif gene: encodes vif protein that enhances replication in lymphocytes

Question 17

What diseases are caused by Lentiviruses?

Answer 17

• human immunodeficiency virus (HIV)
• caprine arthritis encephalitis virus
• meadi-visna virus

Question 18

Spumaviruses

• simple or complex?
• morphology
• genes contained
• endo, exo, or both
• main disease caused

Answer 18

• complex virus
• spikes on surface, uncondensed core
• gag, pro, pol, env, tas/bel-1, bet
• exogenous viruses in mammals
• Human foamy virus

Question 19

How retroviruses cause acute vs chronic transformation

Answer 19

• acute: viruses contain viral oncogenes

- chronic: insertion/mutation through random integration into host genome

Question 20

Feline Leukemia

• genus
• genes contained
• subtypes

Answer 20

• gammaretrovirus
• env, pol, gag
• A: in every infection
• B: recombination of FeLV A with enFeLV
• C: mutations in the env gene
• T: tropism for T lymphocytes

Question 21

Feline Leukemia transmission

Answer 21

• virus shed from saliva, nasal secretions, feces, and milk
• transmitted via bites and grooming
• risk: young, high population, poor hygiene
• embyronic death, stillbirth, or viremic kittens

Question 22

Pathogenesis of Feline Leukemia

Answer 22

• SU protein determines pathogenicity
• infection through oral or pharyngeal tissue
• spreads through monocytes and lymphocytes
• viremia develops
• tropism to lymphoid tissue
• defects in T cells
• wasting syndrome and thymus atrophy
• low or no cellular immunity

Question 23

Clinical signs of Feline Leukemia

Answer 23

• immunosuppression
• non-regenerative anemia caused by chronic inflammatory mechanisms
• myelodestruction, myelosuppression, myeloproliferative diseases
• lymphoma or leukemia

Question 24

Diagnosis of Feline Leukemia

Answer 24

• p27 ELISA
• immunofluorescence assay
• virus isolation in cell culture (best)
• RT-PCR
• reverse transcriptase PCR
• serology

Question 25

Feline Immunodeficiency Virus (FIV) - genus - general mechanism of disease - at risk animals

Answer 25

- Lentivirus - attacks immune system, so weakens immune response to infections and cancers - outdoor, free roaming cats, aggressive males

Question 26

Pathogenesis of FIV

Answer 26

- replicates in lymphocytes - binds to activates CD4 cells, reducing this cell type - reduction of IL-2 production - lymphopenia - activates Treg - increases IL-10 production - immunosuppression

Question 27

Transmission of FIV

Answer 27

- primarily through deep bite wounds and scratches - infected mother to kittens during passage through birth canal - in utero or through milk is rare

Question 28

Clinical signs of FIV

Answer 28

- poor coat condition, persistent fever - loss of appetite, lethargy - gingivitis, stomatitis - urinary bladder and upper resp infections - slow weight loss, severe wasting - cancer and blood diseases may develop - abortion

Question 29

Diagnosis of FIV

Answer 29

- ELISA - immunoblotting - PCR

Question 30

Which genus's infect chickens?

Answer 30

- Alpharetrovirus, Gammaretrovirus

Question 31

Thick Leg Syndrome - type of condition - cause by what? - effects/pathogenesis

Answer 31

- osteoporosis - caused by replication defective avian retrovirus - affects long bones of the legs - results in uniform or irregular diaphyseal and metaphyseal thickening of affected bones

Question 32

Erythroblastosis - caused by what? - target - signs

Answer 32

- cellular transformation of oncogenic virus - targets progenitor erythroblasts - liver and kidneys may be swollen - anemia - erythroblasts in blood

Question 33

Equine Infectious Anemia Virus - also called what? - genus

Answer 33

- Swamp fever | - lentivirus

Question 34

Equine Infectious Anemia Virus transmission

Answer 34

- blood - virus in all secretions - venereal, in-utero, milk, colostrum - transmitted by insects (if uninterupted, then no transmission)

Question 35

Equine Infectious Anemia Virus pathogenesis

Answer 35

- initially infects monocytes, but no replication - monocytes enter tissue and become macrophages, replication begins - virus spreads to lymphocytes - virus in blood is absorbed onto RBCs - antibodies mediate lysis of RBCs, resulting in anemia and thrombocytopenia

Question 36

Equine Infectious Anemia Virus clinical signs

Answer 36

- anemia, lethargy, weight loss, fever - enlarged spleen, swollen belly and legs - depression, decreased athletic performance