Virology 24 Retroviruses*
Terms
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- The RNA genome of Retroviruses is converted to a linear DNA molecule via
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Reverse transcription.
Viral DNA integrates into host chromosomes.
Proviral DNA directs the synthesis of viral mRNAs and proteins.
Viral particles bud off cell membrane. - What are three genes associated with simple retroviruses?
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Antigen (gag)
polymerase (pol)
envelope (env) - What relevant additional genes do complex retroviruses have?
- Additional regulatory genes which control viral gene expression
- What are some additional regulatory genes in HTLV-1 and HIV
-
HTLV-1 tax, rex
HIV tat, rev, nef, vpr, vpu, vif - The process by which retroviral insertion occurs randomly in the host chromosome and disrupts host genes is known as:
- Insertional mutagenesis
- Naturally occurring cancer viruses are known as
- Non-acute Oncogenic Retroviruses
- When viral long terminal repeats (LTR) are integrated near or within the host proto-oncogene locus thereby augmenting its transcription, it is known as:
- Cis-activation
- What are endogenous retroviruses?
- Retroviral proviruses or proviral remnants that are incorporated into germ line cells and transmitted vertically, comprising 1-5% of the mammalian cell genome
- Why is HIV being explored as a vector (lentivirus vector) for gene transfer into cells such as neurons
- It is uniquely capable of infecting non-dividing cells
- What are three diseases cause by HTLV-I?
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1. Adult T-cell leukemia/lymphoma
2. A neurodegenerative disease called tropical spastic paraparesis or HTLV-associated myelopathy (TSP/HAM)
3. Other inflammatory diseases such as infective dermatitis, uveitis - Describe Adult T-cell Leukemia
- A rare malignancy of CD4+ T-cells, long clinical latency, invariably fatal.
- Describe Tropical Spastic Parapesis/HTLV-1 Associated Myelopathy
- Activation of CD4+ T-cell, inflammation of the spinal cord, paralysis of the lower extremities
- How is HTLV-I transmitted?
- Via breast milk, by sexual intercourse (rare), and by transfusion of cell-containing blood components
- What are the clinical characteristics of TSP/HAM?
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TSP/HAM is characterized by uncoordinated motor control, and the pyrimidal tracts of the spinal cord which carry motor neurons show degenerative demyelination
Caused by HTLV-1 - What are the three types of retroviruses
-
Oncoviruses
Lentiviruses
Spumaviruses - What is the structure of Retroviruses
- Medium sized, enveloped viruses
- Gag proteins are involved in what
- Retrovirus assembly and packaging of the RNA genome
- What do the env gene products do
- They mediate the attachment of retrovirus to the cell receptor and fusion of the viral envelope with the host cell membrane
- Why can the immune system never eliminate Retroviruses
- Permanent integration into host DNA
- What are retroviral LTRs
- Long terminal repeats, identical regions on each end of the proviral DNA. Retroviral LTRs are among the most potent promoters for gene expression in mammalian cells
- What genes does HTLV-1 tax gene activate
- Many cellular genes, including cytokine genes
- What disease is HTLV-II associated with
- T-cell hairy cell leukemia