Intro to Virology

Question 1

Virus lifecycle

Answer 1

Step 1. Adherence
Non-specific, chance encounters

Step 2. Binding
Attach to ‘specific’ cell surface receptors

Step 3. Fusion and entry
Entry into cells and release of viral genome into the cytoplasm
Cell entry types-
Macropinocytosis
Clathrin-dependent endocytosis
Plasma membrane fusion
Clathrin-independent endocytosis

Question 2

Simple, naked virus entry

Answer 2

Poliovirus VP1 binds to CD155.
Conformational change VP1extruded and insert into plasma membrane.
A pore is formed in the membrane by VP1.
RNA is released into cytoplasm.

Question 3

Enveloped virus entry

Answer 3

Glycoprotein used for virus entry

Question 4

Classification of viruses

Answer 4

ssDNA viruses-DNA dependent DNA polymerase
dsDNA viruses-DNA dependent RNA polymerase

Cells cannot copy a negative strand RNA virus (-ssRNA) genome
RNA-dependent RNA polymerase (RdRp) is required to copy –ssRNA genome
Nearly every –ssRNA virus brings with it (and encodes) an RdRp
RdRp is used to make mRNA (+ssRNA) from –ssRNA to make protein
+ssRNA viruses RNA dependent RNA polymerase
Don’t need to bring in their own RdRp
encode their RdRp and make it in the cell.
dsRNA viruses
Also need RdRp

RT virus
+ssRNA/ dsDNA
Reverse transcriptase

Question 5

Implications for Vaccines

Answer 5

Neutralizing Antibodies: Vaccines often aim to induce antibodies that block the virus from binding to its receptor or fusing with the host membrane.

Receptor Blocking: Designing vaccines that mimic viral binding sites can prevent the virus from attaching to host cells.