Describe the genome of retroviruses
- 2 copies of + sense single stranded RNA
Are retroviruses enveloped?
- yes
How are retroviruses replicated
Intravirion transcriptase = reverse transcriptase
What is the target of retroviruses?
Lymphocytes, monocytes, mesenchymal and epithelial cells
What is the difference between a retrovirus and a lentivirus?
Lentiviruses all contain additional accessory genes
How does the retrovirus hiding strategy differ in nature from a herpes virus?
The retrovirus hides by embedding itself into the host cells genome. The herpes virus does not do this but still finds a way to hide.
Describe the early and late phases of the retroviruses lifecycle:
Early Phase:
- Attachement
- Penetration
- Intravirion reverse transcriptase coverts ss RNA to ss DNA then to ds DNA provirus
- Provirus then embeds itself into the host cells genome
Late Phase:
- Host cell transcriptase transcribes mRNA for protein synthesis and viral RNA for packaging
- Assembly and budding
- Maturation of virion
What shape are retroviruses typically?
Normally an Icosahedral shape
What is the difference between an endogenous and an exogenous retrovirus and what are some of the benefits that are typically offered by endogenous retroviruses?
DNA of all investigated species has endogenous retroviruses within them these often contain many similarities to known exogenous retroviruses
What viruses are typically associated with cancer?
Oncogenic retroviruses- cancer is typically associated with the over-expression of cellular oncogenes. The retrovirus will typically insert itself upstream, typically affecting the normal control of the transcription of the gene
What is the main difference between cis and trans acting retroviruses?
Cis elements act on the same chromosome as the gene that they infect, however trans elements typically act at entirely different sites or different chromosomes
What is a common feature of lentiviruses that differentiates them from other retroviruses?
many more genes have been integrated into their genome
Explain how the testing method for FIV differs from FeLV:
FIV-tests for the antibody
FeLV- tests for the antigen
Why can’t Feline Sarcoma virus replicate on its own?
Feline sarcoma virus is directly oncogenic because it comes from a FeLV that has adopted a c-onc from the host cell that directly makes it into a v-onc. However, the majority of these don’t manage to go through the process without ruining their own genomes and hence it needs a wild FeLV to be able to replicate.
What species does the genus alpharetrovirus normally occur in and what is the most common neoplasm that is observed from it?
- occurs in most chicken flocks
- Most common neoplasm = lymphoid leukosis
What are the main symptoms that are observed in the condition maedi visna?
Maedi- progressive weight loss
Visna- weakness in the limbs that progresses to ataxia
