RETROVIRUSES

1. General Types of Pathology (birds, mice, sheep, cats, mondeys, goats, horses, humans)
   1. Oncoviruses - sarcomas and leukemias in wide assortment of animals
   2. Spumaviruses - cytophatic, "foamy" inclusions, but not associated with any known disease.
   3. Lentiviruses - chronic encephalopathies, pneumonias, arthritis, immune deficiencies and equine hemolytic anemia.

2. Gross Anatomy
   1. Simialar to most enveloped RNA viruses
      1. Internal nucleocore of proteins and RNA
      2. Cortex is icosahedral
      3. External envelope with some spikes. Envelope is like host cell glycocalyx (cf. bacterial "LPS").
         1. Type specific factors
         2. Group specfiic factors
   2. Dissimilar to other RNA viruses - diploid

      

      where:

      R₅ and R₃ are long terminal repeats,
      gag = internal proteins
      pol = gp-pol = reverse transcriptase
      env = envelope
      src/onc = optional sarcogene/oncogene

   3. Chromosome can integrate into the host chromosome.

3. Chromosome (C), Reverse Transcriptase (RT), and Translation
   1. Chromosome
      1. Two identical ssRNA's but linked near 5'ends
      2. In virions, ssRNA's are tightly linked to needed enzymes co-packaged inside
      3. Replication of the chromosome
         1. A specific tRNA attaches as a primer at P₁

            

         2. Synthesis of strong stop (-)DNA: Reverse transcription by "polymerase" from P₁ to R₅
         3. The two ends of the RNA come close together, and the first jump by "polymerase" is made over to 3' end

            

         4. Elongation of (-)DNA from 3' end to P₁

            

         5. RNase H nicks viral RNA twice yielding P₂ primer.
         6. P₂ primer primes strong stop (+)DNA
         7. RNase H cuts off tRNA
         8. Second jump to P₁ on same or other strand.

            

         9. RNase H removes RNA primer and (-)DNA finishes replication

            

         10. (+)DNA completes replication
         11. Forms rolling circle.
      4. Reverse Transcriptase ("polymerase") has Mg++ and/or Mn++ as cofactor.

         -- (host)--U₃RU₅---gag---pol---env---(src/onc)---U₃RU₅--(host)--

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