Introduction to viruses

Question 1

Describe basic features of viruses

Answer 1

Cannot replicate on its own (requires host cell)
Have protein coat called capsid which encloses genetic material
Smaller than bacteria
Some have outer envelope made of lipids which helps them infect host cells
Use protein coat/envelope to attach to host cells & inject genetic material

Question 2

Describe basic features of prions

Answer 2

Composed of protein & lack genetic material
Infect host cells by changing shape of normal cellular proteins into abnormal prion proteins
Damage brain & nervous system
Cant be destroyed by sterilisation

Question 3

Describe Baltimore classification of viruses

Answer 3

Based on virus genome:

DNA or RNA
Single or double stranded
Negative or positive sense

Question 4

How do viruses cause disease

Answer 4

1. Entry into host
2. Attachment & penetration of host cells
3. Releasing genetic material in cell
4. Replication

Question 5

Describe host cell immune response to viral infection

Answer 5

Innate immune response
Macrophages, NK & dendritic cells detect viral PAMPs using PRRs
Produce cytokines

Interferon response
Proteins produced by host cells in response to viral infections
Inhibit viral replication in infected cells
Induce antiviral state in neighbouring cells (making them resistant)

Adaptive immune response
T & B cell receptors produce antibodies that neutralise virus

Inflammation
Contains spread of virus

Apoptosis
Infected cells undergo apoptosis

Question 6

How can viruses be identified

Answer 6

Direct detection of viral particles

Viral culture

Nucleic acid detection

Serology

Question 7

Methods of controlling & treating viral infections

Answer 7

Antiviral medication
Vaccinations
Symptomatic treatment
Quarantine & isolation