Difference between revisions of "Retroviridae"

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=Introduction=
 +
Retroviruses are persistent, non-cytopathic, systemic viruses that give rise to secondary disease, such as tumors, immune-complex disease, or immunosuppression
 +
 +
=Morphology=
 +
*Fragile, enveloped RNA viruses with roughly spherical spike proteins
 +
*Genome has 3 genes:
 +
**''gag'': group-specific antigen coding gene, encodes capsid proteins
 +
**''pol'': encodes reverse transcriptase (RT) and integrase
 +
**''env'': encodes envelope spikes, and can be used in diagnosis and subunit vaccines
 +
*Both ends of genome show a promoter (LTR: long terminal repeat)
 +
 +
=Virulence and Pathogenesis=
 +
*Replication involves integrating into the host cell genome:
 +
**'''Uncoating''' to release RNA and RT
 +
**+RNA '''transcribed''' to -DNA by RT
 +
**-DNA becomes circular dsDNA and is '''integrated''' into host chromosome by integrase
 +
**DNA '''codes''' for viral proteins using cellular organelles and enzymes
 +
**Because of this technique, virus replication is much '''slower''', and retroviruses can remain '''latent'''
 +
*Tumor production takes 2 forms:
 +
**Viruses can carry oncogenes within their genome --> tumor production occurs quickly
 +
**Insertion of the viral LTR switches on proto-oncogenes in the host cell genome --> tumor production can take years
 +
 +
=Types and Subtypes=
 +
7 Genera, including these of veterinary relevance:
 +
#Mammalian Type C retrovirus
 +
#*[[Feline Leukemia Virus (FeLV]]
 +
#*Feline sarcoma virus (rare)
 +
#*Porcine type C oncovirus (rare)
 +
#Mammalian Type D retrovirus
 +
#*[[Sheep Pulmonary Adenomatosis]]
 +
#Avian Type C retrovirus
 +
#*[[Avian Leukosis Virus]]
 +
#Spumavirus
 +
#*Feline and bovine syncitial viruses (common, nonpathogenic)
 +
#BLV-HTLV retroviruses
 +
#*Bovine Leukosis Virus
 +
#Lentiviruses
 +
#*[[Feline Immunodeficiency Virus (FIV)]]
 +
#*Bovine Immunodeficiency Virus
 +
#*[[Visna-Maedi Virus of Sheep]]
 +
#*[[Caprine Arthrirtis Encephalitis Virus]]
 +
#*[[Equine Infectious Anemia]]
 +
#*Jembrana of Bali cattle
 +
#*Human Immunodeficiency Virus (HIV)
 +
 +
=Antigenicity=
 +
*Group-specific antigens (gag's) are shared by all isolates of each virus
 +
**This can be exploited by diagnostic tests
 +
*Lentiviruses show variation by mutation, making vaccination difficult
 +
 
===Retroviruses===
 
===Retroviruses===
  

Revision as of 16:29, 18 October 2008


 This article is still under construction.


Infectious agents and parasitesWikiBugs Banner.png
VIRUSES



Introduction

Retroviruses are persistent, non-cytopathic, systemic viruses that give rise to secondary disease, such as tumors, immune-complex disease, or immunosuppression

Morphology

  • Fragile, enveloped RNA viruses with roughly spherical spike proteins
  • Genome has 3 genes:
    • gag: group-specific antigen coding gene, encodes capsid proteins
    • pol: encodes reverse transcriptase (RT) and integrase
    • env: encodes envelope spikes, and can be used in diagnosis and subunit vaccines
  • Both ends of genome show a promoter (LTR: long terminal repeat)

Virulence and Pathogenesis

  • Replication involves integrating into the host cell genome:
    • Uncoating to release RNA and RT
    • +RNA transcribed to -DNA by RT
    • -DNA becomes circular dsDNA and is integrated into host chromosome by integrase
    • DNA codes for viral proteins using cellular organelles and enzymes
    • Because of this technique, virus replication is much slower, and retroviruses can remain latent
  • Tumor production takes 2 forms:
    • Viruses can carry oncogenes within their genome --> tumor production occurs quickly
    • Insertion of the viral LTR switches on proto-oncogenes in the host cell genome --> tumor production can take years

Types and Subtypes

7 Genera, including these of veterinary relevance:

  1. Mammalian Type C retrovirus
  2. Mammalian Type D retrovirus
  3. Avian Type C retrovirus
  4. Spumavirus
    • Feline and bovine syncitial viruses (common, nonpathogenic)
  5. BLV-HTLV retroviruses
    • Bovine Leukosis Virus
  6. Lentiviruses

Antigenicity

  • Group-specific antigens (gag's) are shared by all isolates of each virus
    • This can be exploited by diagnostic tests
  • Lentiviruses show variation by mutation, making vaccination difficult

Retroviruses


Lentiviruses

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