85. General characteristics and grouping of retroviruses.

Question 1

General info?

Answer 1

• (+) simple stranded RNA, diploid, helical/icosahedral capsid
• Enveloped from hosts cells membrane low resistance(wont survive long in the enviroment) virus is shed in infected cells
• Enzymes
• Reverse transcriptase: RNA -> cDNA
• Integrase: integration in the host cells, into different chromosome parts
• Protease: assemble virus
• Retroviruses: endogen retroviruses, exogen retroviruses
• 8-11 common core proteins: 2 surface glycoprotein (attachment, entrace, VN, penetrate into host cell)
• Strong species specificity
• Diploid (2 identical RNA threads)
• Tissue cultures: syncytium, cell lysis ʹ good for diagnosis
• Permanent infection, good antigen, frequent genetic changes - mistakes in transcription, recombinations

Question 2

Pathogenesis?

Answer 2

Pathogenesis:

• Infection with infected lymphoid cells (discharges)
• Reverse transcriptase RNA -> cDNA, integrate into genome (integrase) provirus enter germ cells
• (endogen provirus Æ vertical spread)
• Long infection
• Consequence of provirus: replicate or latent (which can become activated)
• Lifelong, cell bound carriage of virus
• Translation error (2 identical RNA threads)
• mutations, recombinations (translation from different
• thread, host cell, endogen provirus)
• defect/oncogenic virus can be produced (own gene for tumour
• formed if oncogenic type)
• Therefore, very variable clinical signs
• Endogen provirus (passed to the next generation)
• Silent - activation
• Consequences of a retrovirus infection:
• 1) Malignant transformation of the host cells:
• slow (years): integration of proviral cDNA close to cell oncogene
• fast tumor transformation (own oncogen)
• 2) Proliferation of the lymphoid cells, immunosuppression
• lysis and proliferation of lymphoid cells
• Frequent mutation and recombination

Question 3

Subfamilies, genera?

Answer 3

Subfamilies, genera:

• Orthoretrovirinae:
• Alpharetrovirus: avian leukosis-sarcoma virus, avian sarcoma, -myeloblastosis, -carcinoma viruses,
• Rous-sarcoma virus
• Betaretrovirus: ovine pulmonary adenomatosis virus, ovine enzootic nasal adenocarcinoma virus
• Gammaretrovirus: feline leukosis, feline sarcoma virus, reticuloendotheliosis virus(REV)
• Deltaretrovirus: enzootic bovine leukosis virus
• Epsilonretrovirus: fish tumor viruses
• Lentivirus: maedi-visna virus, caprine arthritis-encephalitis virus, equine infectious anemia virus,
• feline immune deficiency virus (FIV), bovine immune deficiency virus (BIV), human immune
• deficiency virus (HIV 1, 2)
• Spumaretrovirinae: Spumavirus