Session 6 - Blood borne Viruses

Question 1

How does a non-enveloped RNA virus replicate in comparison to an enveloped DNA virus?

Answer 1

non-enveloped lyses the cell membrane and is released.

Enveloped buds through host membrane

Question 2

What are teh characteristics of the HIV?

Answer 2

• HIV is a retrovirus (has a life cycle that involves integrating its genome into human DNA, done randomly)
• Ss+ RNA, linear.
• Spherical virus

Question 3

What are the patient risk factors for HIV?

Answer 3

• Unprotected vaginal, anal or oral sex with an infected person
• IV drug user using infected needles
• Tattooing with infected needle
• Vertically transmitted from mother to child

Question 4

What are the symptoms of a HIV infection?

Answer 4

• Flu like symptoms with possible rash on chest. Occurs 2-6 weeks after acquisition of HIV. Acute symptoms usually resolve within 2-3 weeks
• Symptoms disappear and HIV continues to spread and damage immune system for roughly 10 years.
• Becomes AIDS – Much greater risk of life threatening illnesses and some cancers, e.g. TB and pneumonia.
• Small percentage of population carries the Delta 32 mutation are resistant to HIV. Known as long term nonprogressors (LTNPs)

Question 5

What is the mechanism of infection for HIV?

Answer 5

1. Virus enters blood and binds to and fuses with a CD4 molecule on the CCR5 or CXCR4 receptors.
2. Virus penetrates cell and the contents are emptied into the cell
3. Reverse transcriptase converts the ssRNA of the virus into dsDNA
4. The viral DNA is combined with the cell’s own DNA by the integrase enzyme
5. When infected cell divides, the viral DNA is read and viral proteins are made
6. Sets of viral protein chains come together to form the virus
7. Virus buds out of cell and takes cell membrane with it.

Question 6

How is HIV investigated?

Answer 6

ELISA and confirmed with western blotting

Question 7

How is HIV treated?

Answer 7

HAART - combo of antivirals including an entry inhibitor, 2 nucleoside reverse transcriptase inhibitors and an integrase inhibitor

Question 8

How is HIV prevented?

Answer 8

Don’t share needles,

wear a condom,

lubrication can prevent vaginal and anal tears,

Post exposure prophylaxis (PEP) to be administered within 72 hours of exposure (usually HAART treatment given)

Question 9

What are the characteristics of the Hep B virus?

Answer 9

Circular, ds DNA

Question 10

What are the risk factors associated with Hep B?

Answer 10

• Unprotected sex and sharing needles
• Unsterilized dental surgery
• Common in middle east
• People with kidney disease
• Diabetics over the age of 60
• Vertical transmission, mother to child

Question 11

What are the symptoms of Hep B infection?

Answer 11

• Loss of appetite, nausea, vomiting,
• Mild fever, dark urine
• May progresses to jaundice
• Symptoms occur 40-160 days post exposure.
• If infection lasts longer than 6 months, chronic hep B develops. Leads to liver disease and cirrhosis if not treated.

Question 12

What is the mechanism of infection by Hep B?

Answer 12

1. Enters hepatocytes via NTCP receptor. Internalised by endocytosis
2. Core particle enters the nucleus and is converted into cccDNA
3. cccDNA is converted by host to viral mRNA which then forms viral proteins
4. Viral proteins assemble in cytoplasm and are taken to the ER where surface proteins are attached
5. Virus leaves cell Damage to hepatocytes occurs due to host immune response which attempt to clear the virus and kill hepatocytes by doing so. Cytotoxic T lymphocytes do this.

Question 13

How is Hep B investigated?

Answer 13

Enzyme assays to detect antibodies in the blood PCR to detect HBV DNA

Question 14

How is hep B treated?

Answer 14

Antivirals e.g. hepsera

Question 15

How is Hep B prevented?

Answer 15

Vaccination

Post exposure prophylaxis

Proper sexual protection