Retroviruses Flashcards
What important enzyme is found in all retroviruses?
reverse transcriptase, RNA-dependent DNA polymerase
genome of retroviruses
two copies of ssRNA (+)
Which enzyme is responsible for integrating the retrovirus genome into the host genome?
integrase
two subfamiles of retroviridae
orthoretrovirinae and spumaretrovirinae
T/F Type B retroviruses have a round centrally positioned inner core
F: eccentrically positioned
T/F retro virions are resistant to UV or X rays
T
What does the gag gene encode
capsid, nucleocapsid, matrix
What does pol encode?
RT and IN
What does env gene encode?
surface and transmembrane envelope proteins
What does the pro gene encode?
protease
What is the role of Nef protein?
essential for replication in target hosts; may downregulate CD4 or alter activation status of target cells
What type of morphology do alpharetroviruses have?
Type C: concentric core
What virus represents alpharetroviruses?
avian leucosis and sarcoma virus (ALSV)
T/F exogenous retroviruses are those viruses included in the genome of most animals
F: endogenous
T/F exogenous retroviruses are transmitted vertically
F : horizontally
What morphology are betaretroviruses?
type B (eccentric core) or D (cylindrical core)
What is an important betaretrovirus?
mouse mammary tumor virus (MMTV)
What type of morphology do gammaretroviruses have?
C type
Important gammaretrovirus?
FLV
Morphology of deltaretroviruses?
type C
example of a deltaretrovirus?
bovine leukemia virus
Which retro genus has rex and tax regulatory genes?
deltaretroviruses -> control synthesis and processing of viral RNA
Are there any known endogenous deltaretroviruses?
no
What is an example of an epsilonretrovirus?
Walleye dermal sarcoma virus
Important lentiviruses?
HIV, caprine arthritis-encephalitis virus, visna virus
Important spumavirus?
human foamy virus
receptors for retroviruses
alpha: membrane anchored glycoprotein
beta: transferrin receptor tfr-1
gamma: GLVR1 or FeLIX
delta: AP-3 complex
lenti: CD4
Where does uncoating occur?
cytoplasm
Where does integration occur?
nucleus
Which end of virla dsDNA is processed by IN?
3’
Is integration site specific?
no, but transcriptionally active preferred
When is viral DNA called a provirus?
after integration into the host cell chromosome has completed
What happens to produced viral RNA?
spliced and transported to cytoplasm
What are the two pools of viral mRNA in cytoplasm of infected cell?
full length : packaged into virions as viral RAN
spliced: express structural proteins (gag, pol, env)
How are virions released?
budding from the cell membrane
Which genus causes cell death?
lentivirus -> formation of syncytium and apoptosis
What is necessary for acute transformation?
v-onc
How do retroviruses cause chronic transformation?
intertion/mutation through random integration into genome of host
Two forms of endogenous gammaretroviruses
enFeLV nad RD114 virus
T/F prevalence of FeLV in individually kept cats is high
false 1%
Where is FeLV shed in infected cats?
saliva, nasal secretions, feces, milk
How is FeLV transmitted?
bites and mutual grooming
T/F aged cats become resistant to FeLV infection
T
What is the main determinant of pathogenicity in FeLV?
SU protein
What tissue does FeLV have tropism to?
lymphoid tissue
What is the effect of FeLV on T cells?
reduced the number of CD4 cells
T/F Cats with FeLV have normal IgM levels
F: reduced IgM levels but normal IgG levels
symptoms of FeLV
immunosuppression, anemia, lymphoma and leukemia
Diagnosis of FeLV?
virus isolation in cell culture if the ultimate criterion (also p27 ELISA)
What causes FIV?
lentivirus
Why are lentiviruses called slow viruses?
long incubation period (up to 6 years)
In what cells does FIV replicate?
CD4 mostly, also B cells and macs
How is FIV transmitted?
deep bite wounds and scratches
Can FIV be transmitted from mother to kittens during passage through birth canal?
yes occasionally
clinical signs of FIV
poor coat, persistent fever, gingivitis, lethargy, upper resp infections
treatment for FIV?
treated symptomatically, can’t eliminate the virus
T/F If a cat has antibodies for FIV, it has the virus.
False - the vaccine will cause cats to be FIV antibody positive
