Retroviruses Flashcards by Claire Evans

What is the classification of retroviruses?

RNA genome
Icosahedral capsids
Enveloped (inactivated by solvents, detergents and heat)
More resistant to UV

How well did you know this?

Not at all

Perfectly

Name 4 common characteristics of retroviruses

Infect wide range of mammals
Host adapted and rarely cross host barriers
Diseases induced by retroviruses are diverse and have distinct pathogenic mechanisms
They integrate into the host cell genome (activate specific genes)

How well did you know this?

Not at all

Perfectly

Name 4 characteristics of Alpharetroviruses

Tumour forming
Very well studied
Need to have an understanding of tumour cell biology
Oncogene discovery

How well did you know this?

Not at all

Perfectly

What is Jaagskiekte sheep retrovirus responsible for in sheep?

It is responsible for contagious lung tumours
(ovine pulmonary adenocarcinoma)

How well did you know this?

Not at all

Perfectly

How is Jaagskiekte transmissed?

Via aerosol spread

How well did you know this?

Not at all

Perfectly

What are the main symptoms of Jaagsiekte sheep retrovirus?

The symptoms are similiar to pneumonia
General loss of condition and breathing difficulties
* watery discharge from the nose

How well did you know this?

Not at all

Perfectly

What clinical sign is unique to OPA?

over-production of fluid in the lungs

How well did you know this?

Not at all

Perfectly

What are sheep affected by OPA invariably more susceptible to?

other types of pneumonia, particularly pasteurelliosis

How well did you know this?

Not at all

Perfectly

What cells does EBL target?

Targets B cells
* the clonal expansion and accumulation of B cells creates tumours

How well did you know this?

Not at all

Perfectly

How is EBL mainly transmissed?

Give 3 ways

mainly via milk to calves from dams
Can be iatrogenic
Mechanical transfer from biting insects

How well did you know this?

Not at all

Perfectly

What are the usual post mortem findings for EBL?

Abomsal tumours that may result in diffuse thickening of the mucosa and sub-mucosa with associated ulceration and haemorrhage

How well did you know this?

Not at all

Perfectly

What may you see in the EBL serology?

AGIDT on single sera.
ELISA on serum on single and pooled sera.
ELISA on single and bulk milk.

How well did you know this?

Not at all

Perfectly

What is equine infectious anaemia also known as

Swamp Fever

How well did you know this?

Not at all

Perfectly

Where does equine infectious anaemia have increased prevalence?

Warm humid environments

How well did you know this?

Not at all

Perfectly

How is EIA transmissed iatrogenically?

Re-using needles
Blood/ Plasma donation to young foals

How well did you know this?

Not at all

Perfectly

How is EIA transmissed mechanically?

Via biting insects, such as horseflies and deerflies

What does it mean when we say that retroviruses rarely cross host barriers?

Typically only affects one species or closely related species

Retroviruses typically affect mammals

What is the capsid shape of retroviruses?

Icosahedral

What sense is the RNA?

Positive sense
BUT contains reverse transcriptase
this means it can convert into DNA to integrate into the host cell

How many copies of the RNA genome are there?

two copies

What is the meaning of the retrovirus being enveloped?

Inactivated by solvents, detergents and heat
More resistant to UV

When provirus DNA enters the cell where is it integrated into the host genome?

In areas of active transcription

What is the function of Gag and Gag-Pol Polyproteins?

Polyproteins that are responsible for synthesising a new virus

What do sheep with OPA not respond to?

Antibiotics

How many sheep are invariably lost to OPA?

* Affected flocks may lose 1-5% sheep per annum * More than 20% in some cases

What should you do if you have a sheep flock with recurring pneumonia?

They should be investigated so you can determine if OPA is an underlying factor

What are the three main clinical signs of EBL?

1. Neurological manifestations 2. weakness/ general debility 3. inappetence/ weight loss

How much may the milk production reduce in a cow with EBL?

2.5%

What may you see in the serology of EBL?

* AGIDT in single sera * ELISA on serum in single and pooled sera * ELISA on single and bulk milk

What are lentiviruses characterised by?

Retroviruses that are characterised by their ability to evade the immune system and have long incubation periods

What are the clinical signs of acute EIA?

* lethargy, anaemia, pyrexia, thrombocytopenia, emaciation

What are the clinical signs of EIA when they are in the 'inapparanet carrier state'

* Asymptomatic due to strong immune control

How quickly may horses with acute EIA die?

may die within 2-3 weeks

What are the main clinical signs of chronic/ recurring EIA?

1. Fever- generally around 40.5 2. Depression- generally listless 3. Wasting away 4. Blood shows a marked drop in RBC count 5. Oedema- horses may show swelling under the skin in legs and chest

What do over 90% of EIA infected horses look like?

* No overt clinical abnormalities * they survive as reservoirs of infection * have dramatically lower concentrations of EIAV

What is considered to be the 'gold-standard' test for EIA?

the AGID test | uses serum to detect antibodies

Where do retroviruses replicate within the cell?

They begin replication in the cytoplasm,- then pro-virus integrates into the host genome and replication continues within the nucleus

How do the retroviruses replicate (simply)

1. Single stranded RNA enters the cytoplasm 2. Converted into DNA 3. DNA integrates into the host genome in the areas of active transcription 4. Provirus DNA is used to produce mRNA 5. mRNA enters the cytoplasm and is used as a template to produce proteins and virions

What are the four main methods of EIA transmission?

* Iatrogenic (needles) * Mechanical (flies) * Aersols * Vertical (in-utero/ milk)