Virus

Question 1

What the features of a virus (normally 20-300nm)?

Answer 1

1. RNA or DNA in Viral genome
2. Capsid - A protein coat around genome and core proteins
3. Envelope - Lipid bilayer around capsid of some viruses
4. Spike glycoproteins

Question 2

What are Hep A and Hep E viruses transmitted? (1)

Answer 2

Fecal-orally

Question 3

What are the different ways Vertical transmission can occur? (3)

Answer 3

1. In utero (during pregnancy)
2. Intra Partum (at childbirth)
3. Through Breast Feeding

Question 4

How does a Virus Replicate? (6)

Answer 4

1. Attaches to target cell and uses glycoproteins to interact with cell receptor.
2. Penetrates the cell (often by receptor-mediated endocytosis)
3. Uncoating - removes protein coat and sends viral nucleic acid and core proteins into cytoplasm of cell
4. Cell uses ribosomes to produce viral mRNA and produce viral protein
5. Maturation and morphogenesis of new viruses.
6. Release by burst of infected cell or budding through plasma membrane

Question 5

What are the effects of a virus on a host cell? (3)

Answer 5

1. Inhibits/alters various normal cell functions such as cell transcription/translation, membrane permeability, molecule pathways etc
2. Indirect immune-mediated cell death
   3.

Question 6

What is Tropism? What are the factors that affect tropsim (3)

Answer 6

1. Ability of different viruses to affect different cell types.
2. This is based on receptors on various cells, enzymes in cell for viral maturation, temp and pH.

Question 7

What are the 4 Viral Disease mechanisms and some examples of associated diseases? (4)

Answer 7

1. Direct Cytopathic Effect - West Nile Virus, Ebola Virus
2. Antibody-mediated Immunity - Dengue Fever
3. Virus-initiated Autoimmunity - Guillain-Barre Syndrome
4. Virus-Induced Tumorigenesis - HPV (cervical Cancer), HBV, HCV (Hepatocellular carcinoma).

Question 8

How can viral Infections be diagnosed? (2)

Answer 8

1. Direct Detection using microscopy/PCR or RT-PCR/serology/culture etc
2. Indirect detection (detecting human antibodies against virus). e.g Hemagglutination Inhibtion test, Complement fixation test, Enzyme linked immunosorbent assay

Question 9

What is Serology? (1)

Answer 9

Examination of blood serum for different antibodies or other markers.

Question 10

What are the types of chronic viral infection?

Answer 10

1. Continuous viral replication e.g HBV, HIV
2. Latency and reactivation e.g Shingles after Chicken pox
3. Invasion of genome from vertical transmission

Question 11

How are Viruses treated? Give an example (2)

Answer 11

1. Use of Antivirals. Such as Remdesivir in inhibition of RNA-dependent RNA polymerase for Sars Cov2.
2. Antiretrovirals. e.g in HIV, Inhibiting any component of the components of pathways of the virus replication.

Question 12

How can HIV be prevented through medication? (3)

Answer 12

1. Treatment as Prevention (TasP)
2. PreP
3. PEP after sexual exposure