3.8 (1) Retroviruses Flashcards
retroviruses:
- genome
- enveloped/nonenveloped
2 copies of ssRNA
enveloped
what type of cells do retroviruses infect
CD4+ lymphocytes
what is unique about replication machinery of retroviruses
they have reverse transcriptase (RNA -> DNA)
what is the role of reverse transcriptase
after infection, RT converts the RNA genome into dsDNA, which then integrates into the host genome
how are retrovirus genes transcribed and translated
from the genome integrated viral DNA
what does the following encode:
- gag
- pro
- env
- pol
gag: structural proteins
pro: proteases
env: envelope
pol: polymerase
what are the 3 functions of the polymerase of retroviruses
1) RNA-dependent DNA polymerase (reverse transcriptase)
2) DNA dependent DNA polymerase
3) RNAse
what are the 5 genera of retroviruses
alpharetrovirus, betaretrovirus, deltaretrovirus, gammaretrovirus, lentivirus
name an important alpharetrovirus
avian leukosis virus (ALV)
name an important deltaretrovirus
bovine leukemia virus (BLV)
name an important gammaretrovirus
feline leukemia virus (FeLV)
name an important lentivirus
feline immunodeficiency virus (FIV)
T/F lymphoma and lymphosarcoma are synonymous
T
leukosis is the basis of
leukemia
________ is the basis of leukemia
leukosis
what is leukosis
neoplastic proliferation of leukocyte-forming tissue
avian alpharetroviruses can be classified as (3)
exogenous replication competent, exogenous replication incompetent, endogenous avian leukosis viruses
describe exogenous replication competent viruses
- transmitted horizontally or congenitally
- usually slow tumor development because they do not have their own oncogenes
- tumors arise from insertion mutations
describe exogenous replication incompetent viruses
- have an oncogene but lose viral proteins
- require a helper virus for replication
- rarely transmitted
- rapidly transform because of the oncogene
describe endogenous avian leukosis viruses
- proviruses in somatic and germline genome
- transmitted genetically only
where is avian leukosis virus commonly seen and where is it rarely seen (what type of flocks)
commonly seen in backyard chickens, low occurence in commercial flocks
does avian leukosis virus have a fast or slow rate of tumor development
slow
what are the two syndromes seen in a chicken with avian leukosis virus
- enlarged long bones (wings, legs)
- tumors in liver, kidney, spleen
what is an important differential for a chicken that may have avian leukosis virus
mareks disease
avian leukosis virus:
- detection of viral antigen is via:
- detection of antibody in serum is via:
- detection of nucleic acid is via:
- ELISA
- ELISA
- PCR
it is important to distinguish if a chicken has Mareks or Avian Leukosis virus because
Marek’s has a vaccine but Avian Leukosis does not
what is the name of the disease caused by BLV
enzootic bovine leukosis
cow herds require to be free of what retrovirus for export
BLV
how many dairy cattle in the USA are infected with BLV; of these how many tend to develop clinical disease
25%; few
T/F BLV is highly transmissible
F
how is BLV transmitted
mainly by blood or tissue containing infected lymphocytes; rarely by insects as mechanical vectors
BLV infects primarily _________, which is mediated by the viral oncoprotein _______
B lymphocytes; Tax
what happens to animals infected with BLV
lymphosarcoma of B cell origin in a variety of tissues (lymph node, abomasum, heart, spleen, kidneys, uterus, meninges, brain)
what signs are seen in an animal with BLV…. what is seen on postmortem?
enlarged pre-femoral and retropharyngeal lymph nodes; tumors in uterus and on thoracic vertebrae
how is BLV diagnosed (2)
- ELISA
- PCR
what is the treatment for BLV
no treatment… animals are sent to slaughter
T/F there is a vaccine for BLV
F
what type of virus is FeLV
exogenous gammaretrovirus
what determines the pathogenicity of FeLV and what 4 antigenic types does it give rise to
pathogenicity is determined by envelope proteins
subtypes:
- A
- B
- C
- T
Describe the following:
- FeLV-B:
- FeLV-C:
- FeLV-T:
B: neoplasia
C: anemia
T: immunosuppression (destruction of T cells)
what 4 disorders does FeLV cause
1) neoplasia
2) neurologic disorders
3) immunosuppression
4) reproductive failure
how is FeLV transmitted
saliva and tears (friendly cat disease)
is FeLV usually an acute or chronic disease
chronic
there are multiple disease trajectories of FeLV, which are influenced by (5)
- age
- genetics (cat)
- environment
- virus
- concurrent infection
what are the 3 types of infection that can develop in a cat with FeLV
1) abortive
2) regressive
3) progressive
describe the following:
1) abortive FeLV
2) regressive FeLV
3) progressive FeLV
1) no viremia
2) viremia that is cleared
3) persistent viremia
how is FeLV diagnosed:
- antigen detection by_______
- nucleic acid detection by _______
ELISA; PCR
interpret the following FeLV test results:
1) ELISA - and PCR -
2) ELISA - and PCR +
3) ELISA + and PCR -
4) ELISA + and PCR +
1) abortive
2) and 3) regressive
4) progressive
interpret the following FeLV test results:
1) high levels of provirus DNA and antigen
2) low levels of provirus DNA and antigen
1) progressive infection
2) regressive infection
T/F antiretroviral compounds have high success at treating FeLV
F
what type of virus is FIV and what does this mean about the course of infection
lentivirus; slow infection for life
T/F FIV is endemic
T
how is FIV shed
saliva
what cats are the greatest risk of FIV
free-roaming, male, older cats
what is a common dual infection in cats
FIV and FeLV
what are the 3 stages of FIV
1) acute
2) subclinical
3) terminal
terminal FIV infection is characterized by
immunodeficiency due to a loss of CD4+ lymphocytes -> opportunistic bacterial and fungal infections
