Retroviridae (Final) Flashcards
What are Retroviruses causative agents of?
cancer
immunosuppression
immunodeficiency diseases
Describe the enzyme encoded by Retroviridae
Reverse Transcriptase
- an RNA-dependent DNA polymerase
- needed to replicate
General Features of Retroviridae
- structure
- genome
- enveloped, spherical
- studded with glycoproteins
- matrix layer
- diploid genome with 2 copies of single stranded pos sense RNA
What are the 4 important genes in Retroviridae?
What do they each encode?
- 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
What diseases are caused by Alpharetroviruses?
Viruses of Chickens
- avian luecosis virus
- avian sarcoma virus
- avian myeloblastosis virus
- rous sarcoma virus
What diseases are caused by Betaretroviruses?
- Mouse mammary tumor virus
- Mason-Pfizer monkey virus
- Jaagsiekte of sheep
What diseases are caused by Gammaretroviruses?
Viruses of Reptiles and Mammals
- feline leukemia virus
- feline sarcomavirus
- avian reticuloendotheliosis virus
Alpharetroviruses
- simple or complex?
- genes contained
- type of virion morphology
- endo, exo, or both?
- simple retrovirus
- gag, pol, pro, and env genes
- type C virion morphology
- endogenous and exogenous viruses
Betaretroviruses
- genes contained
- endo, exo, or both?
- gag, pro, pol, env
- MMTV also contains sag gene which encodes the superantigen
- endogenous and exogenous viruses
Gammaretrovirus
- simple or complex?
- genes contained
- type of virion morphology
- endo, exo, or both?
- simple retrovirus
- gag, pro, pol, env
- type C virion morphology
- endogenous and exogenous viruses
Deltaretroviruses
- simple or complex?
- type of virion morphology
- genes contained
- endo, exo, or both?
- 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
What diseases are caused by Deltaretroviruses?
- Human T-lymphotrophic virus
- Bovine leukemia virus
Epsilonretroviruses
- single or complex?
- type of virion morphology
- genes contained
- endo, exo, or both?
- complex retrovirus
- type C virion morphology
- gag, pro, pol, env, ORF A, B and C
- only endogenous
What diseases are caused by Epsilonretroviruses?
Viruses of Fish and Reptiles
- Walleye dermal sarcoma virus
Lentiviruses
- simple or complex?
- morphology
- genes contained
- endo, exo, or both
- complex viruses
- cylindrical or conical shaped core
- gag, pol, pro, env, and accessory genes
- exogenous in many mammals
Functions of the 4 accessory genes found in Lentiviruses
- 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
What diseases are caused by Lentiviruses?
- human immunodeficiency virus (HIV)
- caprine arthritis encephalitis virus
- meadi-visna virus
Spumaviruses
- simple or complex?
- morphology
- genes contained
- endo, exo, or both
- main disease caused
- complex virus
- spikes on surface, uncondensed core
- gag, pro, pol, env, tas/bel-1, bet
- exogenous viruses in mammals
- Human foamy virus
How retroviruses cause acute vs chronic transformation
- acute: viruses contain viral oncogenes
- chronic: insertion/mutation through random integration into host genome
Feline Leukemia
- genus
- genes contained
- subtypes
- 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
Feline Leukemia transmission
- 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
Pathogenesis of Feline Leukemia
- 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
Clinical signs of Feline Leukemia
- immunosuppression
- non-regenerative anemia caused by chronic inflammatory mechanisms
- myelodestruction, myelosuppression, myeloproliferative diseases
- lymphoma or leukemia
Diagnosis of Feline Leukemia
- p27 ELISA
- immunofluorescence assay
- virus isolation in cell culture (best)
- RT-PCR
- reverse transcriptase PCR
- serology
Feline Immunodeficiency Virus (FIV)
- genus
- general mechanism of disease
- at risk animals
- Lentivirus
- attacks immune system, so weakens immune response to infections and cancers
- outdoor, free roaming cats, aggressive males
Pathogenesis of FIV
- 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
Transmission of FIV
- primarily through deep bite wounds and scratches
- infected mother to kittens during passage through birth canal
- in utero or through milk is rare
Clinical signs of FIV
- 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
Diagnosis of FIV
- ELISA
- immunoblotting
- PCR
Which genus’s infect chickens?
- Alpharetrovirus, Gammaretrovirus
Thick Leg Syndrome
- type of condition
- cause by what?
- effects/pathogenesis
- 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
Erythroblastosis
- caused by what?
- target
- signs
- cellular transformation of oncogenic virus
- targets progenitor erythroblasts
- liver and kidneys may be swollen
- anemia
- erythroblasts in blood
Equine Infectious Anemia Virus
- also called what?
- genus
- Swamp fever
- lentivirus
Equine Infectious Anemia Virus transmission
- blood
- virus in all secretions
- venereal, in-utero, milk, colostrum
- transmitted by insects (if uninterupted, then no transmission)
Equine Infectious Anemia Virus pathogenesis
- 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
Equine Infectious Anemia Virus clinical signs
- anemia, lethargy, weight loss, fever
- enlarged spleen, swollen belly and legs
- depression, decreased athletic performance
