Retrovirus

Question 1

What are the types of RNA viruses and give examples

Answer 1

• Double stranded positive sense RNA viruses- rotavirus
• Single stranded positive sense RNA viruses – polio
• Single stranded negative sense RNA viruses – influenza, rabies

Question 2

name an example of double stranded positive sense RNA viruses

Answer 2

Rotavirus

Question 3

Name an example of single stranded positive sense RNA viruses

Answer 3

polio

Question 4

Name an example of single stranded negative sense RNA viruses

Answer 4

influenza

rabies

Question 5

what are retroviruses

Answer 5

• Enzymes that distinguish them called reverse transcriptase
• Examples include chicken leukaemia virus and rous sarcoma virus (tumour virus)

Question 6

what are the main components of retroviruses

Answer 6

• 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

Question 7

describe the structure of a retrovirus

Answer 7

• 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

Question 8

What are the three sets of genes in retroviruses

Answer 8

Gag
Pol
Env

Question 9

what do the three sets of genes in retroviruses code fro

Answer 9

• 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

Question 10

What are the two genomes in retroviruses

Answer 10

• HIV01 and HIV02 genomes

Question 11

What are the enzymes in retroviruses

Answer 11

• 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

Question 12

What are the two types of retroviruses

Answer 12

• Oncovirinae and lentivirinae

Question 13

What are the conditions that make up oncovirinae

Answer 13

• RSV, HTLV-1, HTLV -2

Question 14

What does oncovirinae retroviruses do

Answer 14

• Induce oncogenesis and cause tumours

Question 15

Name some oncogenic viruses

Answer 15

• EBV
• HPV
• Hepatitis B
• Hepatitis C
• Merkel cell polyomavirus
• HTLV-1

Question 16

What does HTLV-1 cause

Answer 16

• Causes adult T cell leukaemia
• • HTLV1 – associated myelopathy (HAM) and tropical spastic paraparesis (TSP)
• Long latency periods of 20-30 years

Question 17

What does HTLV-2 cause

Answer 17

• Linked with sporadic cases of myelopathy resembling HAM/TSP
• Hairy cell leukaemia

Question 18

what is adult T cell leukaemia

Answer 18

• A clonal aggressive malignancy of CD4+ T lymphocyte

- Skin involvement is common and occurs in two thirds of cases

Question 19

What is the treatment of adult cell leukaemia

Answer 19

• Conventional chemotherapy used for lymphoid malignancies often ineffective
• Several ongiogn clinical trails – oral AZT and IFN alpha, arsenic trioxide and IFN alpha

Question 20

what is HTLV and tropical spastic paraparesis

Answer 20

• 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

Question 21

What is the treatment of HTLV and tropical spastic paraparesis

Answer 21

• IV methylprednisolone

- Daily prednisolone

Question 22

What is HTLV-2 linked with

Answer 22

• Linked with sporadic cases of myelopathy resembling HAM/TSP as well as hairy cell leukaemia
• Long latency peroids of 20-30 years

Question 23

What is hairy cell leukaemia

Answer 23

• 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

Question 24

What is the route of transmission of HTLV

Answer 24

• Mother to child: 15-20% of breast fed children of HTLV-1 seropositive mothers get infected, unprotected sex, contaminatied blood produces

Question 25

what are the two types of lentivirinae retroviruses

Answer 25

• HIV 1

- HIV 2

Question 26

How is HIV transmitted

Answer 26

• Transmitted by unprotected sexual intercourse, drug use, vertical transmission
• Infection requires both CD4 and a chemokine receptor (CXCR4/CCR5)

Question 27

what is the treatment and prevention of HIV

Answer 27

• 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%

Question 28

What are the opportunistic infections for HIV

Answer 28

• EBV
• Oral candidiasis
• Interstitial pneumonia
• CMV – retinitis

Question 29

What is a tax gene

Answer 29

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

Question 30

What is a clade in terms of HIV

Answer 30

the different subtypes of HIV

Question 31

What are human endogenous retroviruses

Answer 31

Human endogenous retroviruses (HERVs) are a family of viruses within our genome with similarities to present day exogenous retroviruses.