Immuno Lec 5: Vaccinations

Define Active Immunisation

• Stimulates the body’s own immune system

• Activates innate and adaptive immune system

Define Passive Immunisation

• Provides immunity by transfer of antibodies

• Temporary protection

Active vs Passive Immunisation

	Passive	Active
Source	Other human/animal	Own body
Effectiveness	Low to Moderate	High
Protection Duration	Days/Weeks	Years
Development time	Immediate	Days/Weeks
Use	Prevention/Treatment	Prevention/Treatment

Purpose of Vaccination

Prophylatic/Preventative

Herd Immunity

Therapeutic

Eradicative

Describe the mechanism of a Live attenuated vaccine

• Pathogen is weakened → can still replicate, cant cause diseases

• Mild symptoms, occur after 7-21 days incubation period

• Immune response similar to natural infection

Creating live-attenuated vaccines by culturing in non-human cells

1) Pathogenic virus is isolated and grown in human cultured cell

2) Cultured virus infects monkey cells

3) Cultured virus mutates, allowig it to grow well in monkey cells

4) Virus no longer grows well in human cells after mutations (attenuated)

Using recombinant DNA tecnhiques in creating live-attenuated cells

1) Isolate pathogenic virus

2) Isolate virulence gene

3) Delete/mutate virulence gene

Describe the mechanism of an inactivated vaccine

• Microbes killed by radiation/heat/chemicals

• 3D conformation of most epitopes preserved

Live-attenuated vs Inactivated

	Attenuated	Inactivated
Effectiveness	Very effective Mimics realinfection Requires only single injection	Less effective Usually requires booster shots
Induced immunity	Cell-mediated Humoral	Humoral
Side effects	May cause unexpected side effects in immunocompromised patients	Lower chance of causing side effects in all target patient groups
Virulence	Possible to regain virulence due to mutations	No danger of regaining virulence

Subunit vaccines

• Components of pathogen that do not replicate

• For highly immunogenic antigens

• Require the use of adjuvants

Advantages of Subunit vaccines

• Simpler production and QC

• No worries of under-activation/reversion

Disadvantages of Subunit vaccines

• Difficult and time consuming to identify good antigens

• Less immunogenic

• Requires boosters/adjuvants

• May fail to stimulate cell-mediated immunity

Toxoid vaccines

• Toxins from toxin-secreting pathogens are deactivated/treated with Formalin

• Inactivated toxins (Toxoids) introduced to the body to stimulate immune response

Recombinant subunit vaccine

• Gene encoding for immunogenic proteins are cloned and expressed in a host cell

• Immunogenic peptides are synthesised by the cells

• Immunogenic are used as antigens for vaccines and are processed by MHC-II Pathway

Adjuvants

Substances which are administered together with vaccine to enhance the immune response towards the vaccine

• Induce inflammation

• Accelerate antigen presentation

mRNA vaccines

• mRNA sequence enclosed by lipid nanoparticle

• enters humans cells via cell membrane

• proteins are syntehsised by transcription/translation, and are broken down by proteasome/secreted out of the cell to be engulfed by antigen-presenting cell