Chapter 13 Flashcards
What are the key features of retrovirus replication?
- Entry via membrane fusion or receptor mediated endocytosis
- High error rate of reverse transcriptase
- Stable integration into host genome
- Release from cell via budding
What is a provirus?
A DNA copy of genomic RNA, which integrates into the hosts genome
What are the four main retroviral genes?
LTR, GAG, POL, and ENV
What does LTR do?
controls the expression of viral genes
What does GAG encode for?
Encodes core proteins
What does POL encode for?
Encodes polymerase and viral enzymes
What does ENV encode for?
Encodes envelope proteins
What are the 7 principle retroviral genera?
- Alpharetrovirus
- Betaretrovirus
- Gammaretrovirus
- Deltaretrovirus
- Episilonretrovirus
- Lentivirus
- Spumavirus
What are the three key features of retrovirus replication that contribute to transformation?
- Reverse transcription of (+) ssRNA into dsDNA
- Integration of dsDNA into host cell chromosome
- Transcriptional regulatory sequences in the viral long terminal repeat
What three genera of retroviruses can cause transduction of proto-oncogenes?
alpha, beta, and gamma
What is cis-activation in the context of retroviral oncogenesis?
- The retrovirus genome integrates near a cellular oncogene
- The transcriptional expression of proto-oncogene is under the control of the virus LTR and no longer the control of the cell
What is trans-activation in the context of retroviral oncogenesis?
- The retrovirus encodes a protein that activates expression of cellular proto-oncogene
What retrovirus genuses use cis-activation?
alpha, beta, and gamma
What retrovirus genuses use trans-activation?
delta
What are the two classes of avian alpharetroviruses and which is pathogenic?
Endogenous - non-pathogenic
Exogenous - pathogenic
What are the two forms of exogenous alpharetroviruses?
Replication competent and replication defective
Explain the concept of the helper virus.
Replication defective viruses have required an oncogene from a cellular oncogene so they are not able to replicate. Helper viruses are replication competent viruses. They aid replication defective viruses by providing the function of the missing gene.
What five disease forms does Avian Leukosis Virus cause?
- Erythroblastosis
- Myeloblastosis
- Myelocytomatosis
- Hemangioma
- Connective tissue tumors
What five clinical syndromes does Avian Leukosis Virus cause?
- Lymphoid leukosis
- Osteopetrosis
- Erythroblastosis
- Myeloblastosis
- Others: connective tissue tumors, hemangiomas, myelocytomatosis
What genus does Jaagsiekte sheep retrovirus belong in?
betaretrovirus
What does Jaagsiekte sheep retrovirus cause?
Ovine pulmonary adenomatosis
What clinical syndrome/disease does Ovine pulmonary adenomatosis cause?
bronchioalveolar carcinoma of sheep
What are the two broad groups gammaretroviruses and what species are involved?
Exogenous and endogenous viruses
cats
What are the exogenous gammaretroviruses?
Feline leukemia viruses
Feline Sarcoma virus
What are the endogenous gammaretroviruses?
Endogenous feline leukemia virus
What are the four subgroups of FeLV?
A, B, C, and T
Which FeLV subgroup is contagious and transmitted horizontally from cat to cat?
A
Which FeLV subgroup is a genetic variant of subgroup A?
T
How did FeLV subgroups B and C evolve?
They evolved de novo in FeLV-A infected cats by mutation and recombination between FeLV-A and cellular or endogenous retroviral sequences contained in normal feline DNA
Pathogenicity of subgroups _ and _ are higher than subgroup B.
B and C
Which FeLV subgroup is mainly associated with malignancies?
B
Which FeLV subgroup is mainly associated with non-regenerative anemia?
C
Which FeLV subgroup is found in all naturally infected cats?
A
Which FeLV subtype is the only subtype to be transmitted from cat to cat?
A
Subgroup B is found in __ % of naturally infected cats.
50
Subgroup C is found in _% of naturally infected cats.
1
Which FeLV subgroup is highly cytopathic and contains two different cell receptors?
T
Which FeLV subgroup is responsible for causing immunosuppression?
T
What are the 3 most clinically important antigens found in the virion of FeLV?
gp70, p15E, and p27
What is gp70?
The major antigen expressed in the viral envelope of FeLV, mediates cell-attachment, carries neutralizing determinants
How many subtypes does gp70 have and which is the most common?
3 -A
What is p15E?
Non-glycosylated envelope transmembrane protein; its role in immunosuppression is controversial
What is p27?
core protein
Which FeLV protein does ELISA and IFA detect?
p27
True or False: FOCMA is encoded by FeLV.
False: It is not encoded by a virus, but is expressed on cells transformed by FeLV
How is FeLV transmitted predominantly?
saliva
What are the possible outcomes to infection with FeLV?
- Immunity
- Persistent infection
- Sick - Neoplasia, degenerative disease, or immunosuppression
- Latent infection
What are the FeLV-related disorders?
Neoplasia, anemia, immune complexes, reproductive problems, enteritis, neuropathy, osteochondromatosis, fading kitten syndrome
What are the 4 diagnostic approaches to FeLV infection?
ELISA, IFA, PCR, FOCMA
What is the interaction between FeLV and FeSV?
FeSV is a replication defective virus and requires FeLV to function as a helper virus
What virus causes enzootic bovine leukosis?
Bovine leukemia virus
What type of retrovirus is bovine leukemia virus?
an exogenous deltaretrovirus
What cell type does bovine leukemia virus infect?
B lymphocytes
How is bovine leukemia virus transmitted horizontally?
via rectal palpation, dehorning, and close contact with a herd
What percentage of calves are born with bovine leukemia virus?
<10%
What inactivates bovine leukemia virus?
pasteurization
What three lentiviruses replicate in both monocytes and lymphocytes?
Human immunodeficiency virus (HIV)
Simian immunodeficiency virus
Feline immunodeficiency virus
What four lentiviruses replicate in monocytes and macrophages?
Visna/Maedi/OPP group
Caprine arthritis-encephalitis (CAE)
Equine Infectious anemia (EIA)
Bovine immunodeficiency virus (BIV)
What are the important features of Lentiviruses?
Lentivirus genomes contain a number of genes that mediate complex virus-host interactions and contribute to persistence and pathogenesis
Lentiviruses have a high rate of genetic variation
What cell types does FIV infect?
macrophages and lymphocytes
Where can FIV disseminate?
CNS system and lymphoid organs
What can result from FIV CNS dissemination?
alteration in neuronal metabolism, neuronal toxicity, and behavioral changes
What can result from FIV lymphoid dissemination?
Increased viremia
Infection may be contained by adequate immune response or there could be progressive immune dysfunction
What clinical syndromes are associated with FIV?
Chronic stomatitis, severe gingivitis, chronic upper respiratory tract disease, lymphadenopathy, mild pyrexia, depression, and leukopenia, wasting, anemia, chronic skin disease, chronic, diarrhea, neurological signs
How is FIV transmitted horizontally?
mainly bite and fight wounds
How is FIV transmitted vertically?
In utero or via milk
What are the three forms of equine infectious anemia (EIA)?
Acute, chronic, or inapparent
How would you characterize acute EIA?
High levels of virus replication, may result in death in 1-4 weeks post infection
How would you characterize chronic EIA?
Recurrent cycles of fever, viremia, and thrombocytopenia
Anemia, edema, glomerulonephritis
How would you characterize inapparent EIA?
seropositive, no clinical signs
What is the major impediment to development of effective vaccines for EIA?
Genetic mutations arise in genes encoding structural proteins and antigenic variation provides a periodic escape of virus from neutralizing antibody and CTL
How is EIA transmitted?
Biting flies and blood contaminated fomites
What diseases does Caprine arthritis-enecephalitis virus cause (CAEV)?
Arthritis, encephalitis, mastits, interstitial pneumonia
True or False: CAEV persists for line in the infected goat
true
What is the major route of transmission of CAEV?
major route of transmission is from does kid in colostrum and milk
What are the clinical prestentations of Ovine Progressive Pneumonia Virus (OPPV)?
Encephalitis, arthritis, and mastitis
What is Visna?
neurological manifestion of OPPV infection
What do we need to know about bovine immunodeficiency virus
there is a worldwide seroprevalence but the clinical significance is not clear
