Basic Virology

Question 1

What are viruses made of?

Answer 1

1. Basic life form
   Protein coat (capsid) that surrounds genetic material. No organelles or ribosomes. May be further enclosed by external lipid bilayer membrane
   which contains glycoproteins (carbohydrate groups attached to
   polypeptide chain
2. Genetic material either DNA or RNA
   * Contains all the genetic information, but not the enzymes needed to build millions of replicas of the original virus
3. Energy less entities
4. Replication of the genetic material occurs when the virus takes
   control of the host cell’s synthetic machinery

Question 2

What are the different types of viruses?

Answer 2

Helical Capsid

Icosahedral Capsid

Spherical Capsid

Prolate (Tail-Head) Capsid

Question 3

What is the Helical Capsid virus made of?

Answer 3

Helical Capsid
* Protein capsomers are bound to RNA and coiled into a helical nucleoprotein capsid.
* Rhabdoviridae (Rabies virus) / Filoviridae (Ebola virus, Marburg virus)

Question 4

What is the Icosahedral Capsid made of?

Answer 4

Icosahedral Capsid
* Chains of protein folded in globular subunits
* Arranged into an equilateral triangle
* Triangle bind together to form an icosahedron
capsid-DNA or RNA packaged inside

Question 5

What is the Spherical Capsid virus made of?

Answer 5

Spherical Capsid
* Consist of an outer envelope made of lipids and glycoproteins. Glycoproteins are essential for viruses to infect cells while lipids are derived from the host and used for avoiding the host’s immune system.

Question 6

What is the Prolate (Tail-Head) Capsid made of?

Answer 6

Prolate (Tail-Head) Capsid
* An elongated icosahedron is a common shape for the heads of bacteriophages. Such a structure is composed of a cylinder with a cap at either end. The cylinder is composed of 10 elongated triangular faces.

Question 7

What is the viral replication lifecycle?

Answer 7

1. Adsorption and penetration
2. Uncoating of the virus
3. Synthesis and assembly of viral
   products
   * Inhibition of host cells own DNA, RNA,
   protein synthesis
4. Release of virions from the host
   cells
   * Lysis of cell or budding

Question 8

What is the different host cell outcomes?

Answer 8

Cell Death
* Apoptosis or necrosis
* Viral infection shuts down host cells homeostatic functions
* Cell lysis
* Immune destruction of host cell

Cell Transformation
* Host cells have altered function
* Infection can activate or introduce
oncogenes
* Uncontrolled and uninhibited cell
growth

Latent infection
* Virus viable in host cell but in non-active state
* Not producing clinically overt infection
* Can re-activate and replicate in future

Chronic slow infection
* Cause disease only after many years/decades of indolent (little or no pain) infection