VETS3010 Retroviruses單詞卡 | Quizlet

Describe some characteristics of retroviruses?

- enveloped

- single-stranded, positive-sense RNA (2 copies)

- fragile in environment

- transmission by close contact, transfer of body fluids

Describe retrovirus transmission?

Contains a reverse transcriptase (RT) enzyme which makes a DNA copy ("provirus") of the viral RNA genome

Provirus is inserted into the host cell's DNA

Provirus may remain transcriptionally silent for long periods, or produce viral DNA = new virus particles

Virion buds from plasma membrane, acquiring envelope as they exit

What are exogenous retroviruses?

Transmitted horizontally - contact etc

Non-self

What are endogenous retroviruses?

If the provirus is incorporated into germline DNA (sperm, ova, embryo), the virus is transmitted as an inherited element - "self"

Endogenous retroviruses are present in the DNA of every cell of every individual in a species

T/F

True - many are ancient, present for over 100 million years

Retroviruses can cause ?

1. neoplasia

2. slowly progressive disease w/ prolongued incubation period and immunosuppression

3. no disease

Overall, persistent, lifelong infections

Most retroviruses can be eliminated from the body with time

T/F

False!

Cannot be eliminated from the body by the immune system

The presence of ? indicates the present of retroviruses

Antibodies

=> persistent infection that cannot be eradicated

Oncogenic retroviruses produce tumours by 2 methods ?

1. virus affects cellular oncogene -> chronic transforming

2. virus possesses an oncogene (v-onc) -> acute transforming

Describe chronic transformation w/ oncogenic retroviruses?

1. provirus inserts near a cellular oncogene

2. increased gene expression

3. slow oncogenesis (requires a chance event to occur)

not every animal will develop neoplastic change

Describe acute transformation w/ a oncogenic retrovirus?

1. viruses are directly oncogenic

2. oncogenesis occurs in all infected individuals

3. v-onc has normally displaced another viral gene

4. virus is replication defective and requires helper virus to replicate

Describe avian lymphoid leucosis transmission and pathogenicity?

- transmitted horizontally & vertically

- if hatched from an infected egg, chick is persistently viremic

- if infected by contact, mounts immune response, clears virus

-> may become carries

A chick with vertically-transmitted avian lymphoid leucosis will be antibody positive

T/F

False - will be antibody negative as the viral proteins are seen as 'self'

Avian lymphoid leucosis infects ? cells

B

Avian lymphoid leucosis does not cause clinical signs

T/F

True

Describe the differences in pathogenicity of feline leukaemia virus in old vs. young cats?

Old:

- mount immune response

- clear virus

Young:

- ineffective immune response

- virus replication unchecked

- persistent viremia

Feline leukaemia virus only causes disease in ?

Persistently viremia cats

What does FLV cause?

- lymphoid and myeloid leukaemia

- lymphosarcoma

- bone marrow aplasia = anaemia

- immunosuppression

Describe the sub-groups of feline leukaemia virus?

4 subgroups

FeLV-A is the most common; all other subgroups are sourced from FeLV-A

FeLV-B is a recombination b/w FeLV-A and an endogenous retrovirus

FeLV_C and FeLV-T are mutations of FeLV-A

FeLV-B is associated w/ ?

Tumours

FeLV-C is associated w/ ?

Anaemia

FeLV-T is associated w/ ?

Immunodeficiency

FeLV is shed in ?

Saliva and other secretions/excretions

FeLV infection occurs through ?

Close, prolonged contact

- mutual grooming

- sharing feed bowls

- ingestion

How can you diagnose

FeLV?

Need to detect persistent viraemia - these are the cats that will develop disease

- FeLV antigens in blood (ELISA, RATs)

Antibody detection of FeLV is not useful

T/F

True - because all cats that have been exposed to the virus (viraemic and previously infected/clear) will be antibody positive

What is the FeLV vaccine?

A recombinant vaccine

Describe enzootic bovine leucosis?

- causes persistent lymphocytosis and lymphosarcoma

- spread by blood transfer b/w animals

Leucosis?

Leukaemia like virus that affects lymphocytes

How may enzootic bovine leucosis be spread?

Spread by blood transfer:

- dehorning

- rectal palpation

- reusing needles

- insect vectors

The bovine leucosis virus has a vaccine

T/F

False - no vaccine available

Feline sarcoma virus is a ?

Retrovirus - oncogenic

What do lentiviruses do?

Retroviruses!

Cause persistent, lifelong infection, & cause slowly progressive diseases

Transmitted by close contact

Why do lentiviruses cause persistent, lifelong infection?

The viral genome is integrated into the host cell's DNA, which is hidden from the immune system (seen as non-self)

The high mutation rate results in antigenic variation (if the immune system starts to overcome, virus mutates and changes, immune system has to 'start again')

Lentiviruses infect lymphocytes and monocytes leading to immune dysfunction (cell death, dysfunction)

Describe Maedi-visna virus?

- affects sheep and goats

- incubation period is 2-3 years

causes:

- slowly progressive pneumonia = dyspnoea and wasting = death

- slowly progressive demyelination = neurological signs = death

What is caprine arthritis encephalitis virus?

Infects goats - infects monocytes and macrophages, causing granulomatous formation

Transmitted via colostrum

Causes lesions in:

- joints

- brain

- lungs

- mammary glands

Control of caprine arthritis encephalitis virus is via ?

- removal of kids from infected dams before suckling

- culling removal of infected animals

- donor or heat-treated colostrum

Describe equine infectious anaemia?

A retrovirus!

Causes:

- fever

- anaemia

- abnormal iron metabolism

- increase Ig levels

- immunosuppression

Describe the Csx of equine infectious anaemia?

Horses may

- die acutely

- have recurrent episodes of disease over time w/ progressive debilitation

Equine infectious anaemia is transmitted by ?

Mechanical - biting insects

What is feline immunodeficiency virus?

Retrovirus!

Attacks CD4+ cells

Transmitted by biting and fighting (low conc. in saliva = requires direct entry)

Causes:

- immunosuppression

- opportunistic infections

What is the FIV vaccine?

A killed vaccine

FIV can be diagnosed by ?

Detection of antibodies in serum - a vaccinated cat will be +ve as well

Hence,

Test using PCR - if the WBCs contain DNA or RNA of FIV

FIV always results in immunosuppression

T/F

False - cats may have FIV and never become immunosuppressed (individual resistance)

A cat with FIV and FeLV is susceptible to ?

- leukaemia

- lymphosarcoma

- anaemia (FeLV)

- 2nd infections (respiratory etc)