RETROVIRIDAE

Question 1

Genus –

Answer 1

(Retro- reverse transcription i.e RNA  DNA)

1. Orthoretroviridae -
   - Alpha,
   - Beta,
   - Gamma,
   - Delta,
2. Epsilon-retrovirus,
3. Lentivirus
4. Spumaretrovirus
5. Spumavirus

Question 2

Morphology

Answer 2

Enveloped

Diploid +ssRNA genome

Helical + Icosahedral capsid

• many layered,
• released into cell through cytoplasmic membrane.
• After release  final maturation of virus

Question 3

Resistance

Answer 3

Very sensitive

Question 4

Biological properties

Answer 4

– Baltimore VI

– viral reverse transcriptase forms a pro-virus

• If cell divides, viral genome is also transmitted
  = a life-long infection

Question 5

Genetic structure

Answer 5

5’-LTR-gag-pro-env-pol-LTR-3’

+/- Oncogene substitution of mutants  a transforming/defective virus

• Oncogene kicks out the envelope gene- rather like a cuckoo! –
• i.e need helpers to multiply
  • Tumours (Oncogenic!!)

Question 6

Multiplication competent viruses –

Answer 6

Strong CPE (Giant cells – synsytia) + tumours

Question 7

Transmission

Answer 7

– Sensitive so need special methods of infection

1. “Vertical route” – sex, placenta, etc i.e protected

2- Virus adapts to host so lies dormant ”pseudo virus” –

- A part of genome but virus never develops
- Much of genome is “pseudo virus”

3. Cell associated
   – germ cells, colostrum, epithelium

Question 8

Antigenes –

Answer 8

Good antigens in theory

• Surface protein antigenes are hyper-variable
• But Iummunoglobins not effective vs integrated virus
• Destroys the immune system!
  
  • Virus often mutates within lymphocytes
    
    • the cells that suppress viruses

Question 9

Diagnosis

Answer 9

– Can use direct/indirect viruses together
1-Clinical signs – tumours (Leukemia)

2- Direct – ELISA, IF, PCR, NA hybridization

3-Indirect – ElISA, AGID (Coggin’s test – EIA)

Question 10

Ortheroretroviridae family –

Alpha-retrovirus

Answer 10

1- Avian Leucosis Virus
– Chicken – Leukemia, Lymph tumours
(with Marek disease – most destructive poultry virus)

2- Avian sarcoma
– Chicken – fast developing tumours

Question 11

Beta-retrovirus

Answer 11

1- Ovine pulmonary adenocarcinoma virus

– Sheep – “Jaagsiekte”

Question 12

Gamma-retrovirus

Answer 12

Feline Leukemia

– Sarcoma develop

Question 13

Delta-retrovirus

Answer 13

1. Bovine leukaemia virus – (BLV)
   – notifiable
   - Economic loss
   - Cattle – leucosis, slow developing lymph tumours
2. Human T-lymphotrophic virus 1-2 (HTLV) - Causes leukaemia
   - Sexually transitted – caribean
   - Human T-cell leukemia

Question 14

Epsilon-retrovirus

Answer 14

Fish virus – Walleye

Question 15

Lentivirus

Answer 15

(Lente – slow)
– rarely cause tumours Immuno suppressive

1. Equine infectious anaemia virus (EIA) 
– 	No vaccines against it
- Horses – anaemia, 
- wasting - lethal
- Arthropod transmitted – “Swamp fever”

2. Maedi-Visna virus – (Maedi –pneumonia – lungs; Visna encephalitis)
   - Leads to paralysis of hind leg

3- Caprine arthritis – encephalitis virus (CAE) - Goats – arthritis, lameness

4. Human Immunedeficiency Virus – HIV 1-2

• T-helper cell destruction - immunosuppression
• AIDS – acquired immune deficiency syndrome
• In parts – 80% of population – Africa
• Can have virus but show no symptoms – some resistance (low in Africa)

5. Feline immune deficiency virus (FIV)- Esp male cats – similar to humans
6. Bovine immune deficiency virus
7. Simian immune deficiency virus (SIV)

Question 16

Spumavirus

Answer 16

(Spuma – foamy)
1. Bovine foamy virus

• End of animal viruses!