What do retroviruses cause?
immunosuppression, immune deficiency, cancer
What do all retroviruses need to replicate?
Reverse transcriptase
What three scientist discovered the importance of reverse transcriptase in retroviruses?
Baltimore, Dubelco, Temin
Reverse transcriptase is a
RNA dependent DNA polymerase (found in the virion of all retroviruses)
T/F: Retroviruses are enveloped
TRUE
T/F: Retroviruses have a triploid genome
FALSE.
Retroviruses have a DIPLOID genome: two single stranded copies of positive sense RNA
T/F: Since retroviruses have positive sense RNA, they directly synthesize proteins
FALSE.
Positive sense RNA is used as a template for DNA –> then makes RNA –> protein synthesis
What enzyme allows retroviruses integrate into the host cell genome?
INTEGRASE
What shape are retroviruses?
Spherical
T/F: Retroviruses are NOT easily inactivated by lipid solvents or heating.
FALSE
Easily inactivated by these due to envelope
T/F: Retroviruses are resistant to UV and X-rays
TRUE
What are the 4 most important genes retroviruses have, and what do they encode for?
gag - encodes for core proteins: capsid, nucleocapsid, matrix
pol - encodes for reverse transcriptase & integrase
env - encodes for surface and transmembrane proteins
pro - encodes for protease
What are the two subfamilies of retroviridae?
Supumaretrovirinae
Orthoretrovirinae
What are the genera of the subfamily Orthoretrovirinae?
alpharetrovirus betaretrovirus gammaretrovirus deltaretrovirus epsilonretrovirus lentiretrovirus
Which genera of the Orthoretrovirinae subfamily are simple retroviruses?
What is a simple retrovirus?
Alpha, beta, gamma
Simple retroviruses have only the core retrovirus genes: gag, pol, pro, env
They are BOTH Endogenous and Exogenous
To which genus does Mouse Mammary Tumor Virus (MMTV) belong?
What is the unique gene it encodes for?
What is the significance of this virus?
MMTV is a betaretrovirus. It is often and most commonly used as an experimental virus model. It encodes for the sag gene - super antigen.
Important for research
What does it mean if a virus is Exogenous?
It can be transmitted HORIZONTALLY.
rarely in-utero or germline
What does it mean if a virus is Endogenous?
The virus is included within the host genome.
What are some alpharetroviruses?
Avian leucosis virus
Avian Sarcoma virus
Avian myeloblastosis virus
Rous sarcoma virus
What are some gammaretroviruses?
Feline Leukemia virus
Feline sarcoma virus
Avian reticuloendotheliosis virus
Examples of deltaretroviruses?
Human T-lymphotropic virus (HTLV)
Bovine leukemia virus
What genus does Walleye dermal sarcoma virus belong to? Who does it infect?
Epsilonretrovirus
Fish
HIV is what kind of virus?
Lentivirus
Other viruses in the genus: Caprine arthritis-encephalitis virus and Meadi-visna virus
T/F: Epsilonretroviruses are endogenous only
TRUE
In fish and reptiles
T/F: Deltaretroviruses are endogenous only
FALSE:
Exogenous only
Are lentiretroviruses exogenous, endogenous, or both?
Exogenous
What is required for a retrovirus to enter a host cell?
Cell surface molecule receptor + envelope proteins on the virion surface
(Retrovirus cell receptors)
Each genus has a specific receptor(s)
When a retrovirus is actively lysing host cells, what stage of disease is present?
Acute disease
Insertion and or mutation through virus integration is describing what stage of disease?
Chronic
The process by which a retrovirus acquires a cellular oncogene and modifies it into a viral oncogene is what?
ONCOGENESIS
What two specific proteins does of FeLV env gene encode for?
gp70 - surface protein
p15E - transmembrane protein **BLOCKS T CELL reactivity
What specific protein does the FeLV gag gene encode for?
What is its importance?
p27 - Many diagnostic tests are based on this protein, including ELISA
T/F: FeLV survives well in the environment
FALSE
Does not survive well outside of the host. It is easily killed by disinfectants, soap, heating, and drying
What is the % prevalence of FeLV in a single cat house hold? Multi-cat house hold?
Single cat home - 1%
Multi-cat home - 20%
What cats spread FeLV and how?
Cats with viremia are the source of infection via: saliva, nasal secretions, feces, and milk
Mutual grooming and cat bites are most common modes of transmission
What factors will increase a cats potential of FeLV infection?
young age
high population density
poor hygiene
What are the two versions of the feline leukemia virus?
Endogenous FeLV (enFeLV) RD114 virus
What are the different Subtypes of FeLV
Subtype A, B, C, T
What occurs when a pregnant cat is FeLV positive?
Abortion
still birth
or viremic kittens are born (carriers)
What is the progression of FeLV? (Where does infection begin and spread)
Infection typically begins in the oral or pharyngeal tissue then progresses to the lymphoid tissue.
The virus will spread to peripheral tissue via Monocytes and lymphocytes
Viremia occurs within a few weeks - months
Where does the FeLV virus have a tropism for?
T-lymphocytes and lymphoid tissue
What receptors does the FeLV virus use to attack T-lymphocytes?
Pit1 (phosphorus transportation protein 1)
FeLIX (FeLV infectivity X-essory protein)
What is the cellular consequence of FeLV?
Decrease in CD4+Tcells = immunosuppression = highly susceptible to secondary infections
Wasting syndrome and atrophy of the thymus due to recurrent infections
T/F: When a patient has FeLV, they can fight off other infections with their cellular immunity
FALSE
FeLV ruins the cellular immune response
What is the GOLD STANDARD Dx test for FeLV?
Isolation of virus from cell culture is the BEST diagnostic (but it can be $$$$$ and not all labs perform this test)
ELISA and IFA are good dx
Real time PCR and Reverse transcriptase PCR (DNA confirms virus, RNA confirms live/active infection)
Is the FeLV vaccine 100% effective?
NO
T/F: You should recommend euthanasia if a cat tests positive for FeLV
FALSE
These cats can live a long life. They should be kept INDOOR ONLY to prevent further spread of the virus and secondary infections. These cats should be in a single cat home.
What is the most common mode of FIV transmission?
DEEP BITE WOUNDS
What age group is most susceptible to FIV infections?
ALL AGES
Outdoor cats and Feral cats are the most susceptible
What doctors discovered the FIV infection at UC Davis in 1986?
Yamato and Pederson
What percentage of cats are FIV positive in the United States?
25%
What genus is FIV in?
Lentivirus
What is the best dx test for FIV?
ELISA
What clinical signs may you seen in a cat with FIV?
Persistent fever and DHR Decreased appetite weight loss gingivitis and stomatitis recurrent skin infections, UTI, URIs
Sometimes cancer and blood dz
CNS signs = terminal phase
T/F: there is treatment to eliminate FIV
FALSE There is no tx to eliminate FIV - can only tx symptomatically AB for secondary infections Appetite stimulants Corticosteroids Immune modulators etc
T/F: A cat that is vaccinated for FIV, will always test positive in the future
TRUE
They will always be FIV antibody positive
What are the two types exogenous avian retroviruses?
Replication Competent: usually non pathogenic in most chickens
Replication Defective: virus goes immediately into DNA, acquires viral oncogene(s) and causes malignant tumors
What differs in the pathogenicity in chickens who get an avian retrovirus that is replication defective via horizontal transmission or via vertical transmission?
Horizontal: chickens are usually infected @ 5 days old, will have transient viremia and are unlikely to develop leukemia
Vertical: congenital or genetic infections - persistent viremia, tends to progress to leukemia
T/F: Chickens with lymphoid leukosis will produce large amounts of IgM
TRUE
T/F: Lymphoid leukosis is the most common form found in chickens 4-30wks of age
TRUE
If you run a Coggins test, what are you trying to diagnose and who is your patient?
Equine Infectious Anemia - Horse of course ;)
Where does equine infectious anemia replicate?
Infects monocytes - then replicates in macrophages
What kind of hypersensitivity is associated with equine infectious anemia?
Type II hypersensitivity
think blood!
What are some clinical signs of equine infectious anemia?
Anemia and Thrombopenia = petechial, edema, lethargy, fever, weight loss, splenomegaly, depression
T/F: Flies can transmit equine infections anemia
TRUE
When a fly is interrupted in feeding - it is more likely to bite again right away. This is when virus transmission is most likely
T/F: A horse with EIA will always be symptomatic
FALSE
there are asymptomatic carriers
T/F: Horses can pass EIA to their foals via milk and colostrum
TRUE
MOT: blood - via insects or instruments
Venereal, milk, colostrum
What avian diseases are caused by retroviruses?
lymphoid leukosis
osteoporosis “Thick leg syndrome”
Eythroblastosis
