Retrovirus Flashcards
What are the types of RNA viruses and give examples
- Double stranded positive sense RNA viruses- rotavirus
- Single stranded positive sense RNA viruses – polio
- Single stranded negative sense RNA viruses – influenza, rabies
name an example of double stranded positive sense RNA viruses
Rotavirus
Name an example of single stranded positive sense RNA viruses
polio
Name an example of single stranded negative sense RNA viruses
influenza
rabies
what are retroviruses
- Enzymes that distinguish them called reverse transcriptase
- Examples include chicken leukaemia virus and rous sarcoma virus (tumour virus)
what are the main components of retroviruses
- Diploid positive sense RNA
- Unique enzyme. – reverse transcriptase – this generates a DNA intermediate which is then integrate into the host genome (called provirus)
- New viral genomes produced by cellular transcriptional machinery such as HIV
describe the structure of a retrovirus
- surface envelope glycoprotein – binds to the cell surface of the target cells and induces its fusion into the cell
- then have a matrix that holds the viral shape – inside the matrix there is a capsid – contains the RNA
- also has an lipid envelope
- protease is present in HIV
- reverse transcriptase enzyme
What are the three sets of genes in retroviruses
Gag
Pol
Env
what do the three sets of genes in retroviruses code fro
- Gag – cods for proteins which make up matrix, capsid and nucleoprotein structures
- Pol – codes for reverse transcriptase and integrase and protease enzymes
- Env – codes for the surface and transmembrane components of the viral envelope protein
What are the two genomes in retroviruses
- HIV01 and HIV02 genomes
What are the enzymes in retroviruses
- Reverse transcriptase – transcription of viral genome RNA to DNA
- Integrase – integration of the ds DNA into the host genome to form the provirus
- Protease – following the release of new virion cleavage of certain proteins is required for viral maturation and infectivity
What are the two types of retroviruses
- Oncovirinae and lentivirinae
What are the conditions that make up oncovirinae
- RSV, HTLV-1, HTLV -2
What does oncovirinae retroviruses do
- Induce oncogenesis and cause tumours
Name some oncogenic viruses
- EBV
- HPV
- Hepatitis B
- Hepatitis C
- Merkel cell polyomavirus
- HTLV-1
What does HTLV-1 cause
- Causes adult T cell leukaemia
- HTLV1 – associated myelopathy (HAM) and tropical spastic paraparesis (TSP)
- Long latency periods of 20-30 years
What does HTLV-2 cause
- Linked with sporadic cases of myelopathy resembling HAM/TSP
- Hairy cell leukaemia
what is adult T cell leukaemia
- A clonal aggressive malignancy of CD4+ T lymphocyte
- Skin involvement is common and occurs in two thirds of cases
What is the treatment of adult cell leukaemia
- Conventional chemotherapy used for lymphoid malignancies often ineffective
- Several ongiogn clinical trails – oral AZT and IFN alpha, arsenic trioxide and IFN alpha
what is HTLV and tropical spastic paraparesis
- Chronic and progressive disease of the nervous system that causes progressive weaknesses tiff muscles, muscle spasms, sensory disturbance and sphincter dysfunction
- Affects adults living in equatorial areas of the world
What is the treatment of HTLV and tropical spastic paraparesis
- IV methylprednisolone
- Daily prednisolone
What is HTLV-2 linked with
- Linked with sporadic cases of myelopathy resembling HAM/TSP as well as hairy cell leukaemia
- Long latency peroids of 20-30 years
What is hairy cell leukaemia
- Leukaemia cells collect in the spleen and the spleen swells
- There also may be too few normal white blood cells in the blood because the leukaemia cells invade the bone marrow
- The marrow cannot produce enough normal white blood cells this can result in a decreased resistance to infections
What is the route of transmission of HTLV
- Mother to child: 15-20% of breast fed children of HTLV-1 seropositive mothers get infected, unprotected sex, contaminatied blood produces
what are the two types of lentivirinae retroviruses
- HIV 1
- HIV 2
How is HIV transmitted
- Transmitted by unprotected sexual intercourse, drug use, vertical transmission
- Infection requires both CD4 and a chemokine receptor (CXCR4/CCR5)
what is the treatment and prevention of HIV
- HAART – highly active antiretroviral therapy – reduces the viral load increases CD4+ count – includes protease inhibitors, intergrase inhibitors, reverse transcriptase inhibitors, fusion inhibitors
- Bone marrow transplant – cure
- Prep – prophylaxis – reduces the risk of HIV infection in people who are at high risk by more than 90%
What are the opportunistic infections for HIV
- EBV
- Oral candidiasis
- Interstitial pneumonia
- CMV – retinitis
What is a tax gene
Tax is produced by members of the retroviral family primate T-lymphotropic virus, which are classified as Deltaretroviruses.
The tax protein produced from HTLV-1 and HTLV-2 have been most extensively studied
Tax acts as a transactivator, causing the transcription (production of mRNA from genetic code) of viral proteins in the long terminal repeat that are essential for replication
What is a clade in terms of HIV
the different subtypes of HIV
What are human endogenous retroviruses
Human endogenous retroviruses (HERVs) are a family of viruses within our genome with similarities to present day exogenous retroviruses.
