Infection and vaccines

Question 1

Pathogenicity and virulence

Answer 1

Pathogenicity is ability to cause disease in the host (qualitative)

Virulence is the effect of the pathogen on the host (quantitative)

Question 2

Immune response to viruses

Answer 2

obligate intracellular pathogens
DNA/RNA detected as PAMPs
Type I interferons (IFN-alpha and beta) are produced by the infected cell or by APCs
Interferons signal to establish an anti-viral state in the infected cell and neighbours

Question 3

Interferon response

Answer 3

Induce resistance to viral replication in all cells (Mx proteins, adenosine oligomers)
Increase MHCI expression and antigen presentation in all cells
Activate DCs and macrophages
Activate NK cells to kill infected cells
Induce chemokines to recruit lymphocytes

Question 4

Immune response to intracellular bacteria

Answer 4

Killing of infected cells by NK cells and cytotoxic T cells

Question 5

Immune response to extracellular bacteria

Answer 5

Antibody neutralisation of toxins
Complement activation and lysis
Opsonisation
C3a/5a anaphylatoxins stimulate mast cell degranulation
Attraction of neutrophils and macrophages

Question 6

Immune response to parasites

Answer 6

Th2 response

IgE antibodies and activation of granulocytes (mast cells and eosinophils)

Question 7

Immune response to fungal infections

Answer 7

Innate mechanisms often sufficient
Macrophages detect cell wall components with Toll-like receptors and Dectin-1 receptor
Antibodies and complement enhance phagocytosis

Question 8

Evasion of adaptive immunity

Answer 8

Point mutations due to error-prone polymerase yield a non-recognisable protein (Antigenic drift)

Co-infection with different strains in an animal host creates a new virus with different surface proteins (Antigenic shift)

Question 9

Immunisation and vaccination

Answer 9

Immunisation is the generation of long-lived immune protection against a pathogen

Vaccination is the intentional exposure to components of pathogens that do not cause disease

Question 10

Vaccine components

Answer 10

Antigens that can be recognised by T/B cells and antibodies

Adjuvants that help activate the innate immune system (pathogen components, synthetic formulations)

Question 11

mRNA vaccines

Answer 11

mRNA synthesised with cap analogue and modified bases (pseudouridine prevents recognition by RIG-I)
Sequence optimised to maximise expression
Encodes antigen on receptor binding domain of the spike protein
mRNA encapsulated in a lipid nanoparticle for uptake