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