Principles of Immunisation Flashcards
What are the two main types of immunity?
adaptive - responsible for memory and specificity
innate- protective barriers which don’t change for e.g. mucosal layers that prevent infection
What are the typical cells of adaptive immune system?
lymphocytes and the two important lymphocytes being t cells (drive antibody immune responses) and b cells (antibody producing cells)
What are the two states of the adaptive immune system?
Active (natural and artificial forms of immunity) and passive (natural and artificial forms of immunity) (receive immunity but your immune system hasn’t had to do any work)
What are the methods of passive immunity? (adaptive)
(Natural)
placental transfer of IgG
colostral transfer of IgA
(Artificial)
Immunoglobulin
therapy or
Immune cells
What are the methods of active immunity? (adaptive)
(Natural)
infection or exposure
(artificial)
immunisation vaccines
Differences between active and passive immunity?
ACTIVE
-you’re either infected or vaccinated
-develop antibody and t cell responses that will respond to every challenge with infection
-immune system specific for pathogen and drives memory immune response
PASSIVE
-test tube full of antibodies against a particular pathogen and administer to uninfected individual.
-Will help to prevention of disease
-immune system specific for pathogen
-no memory of infection from immune system
-doesn’t drive memory immune response
Advantages and disadvantages of passive immunity?
Advantages:
Gives immediate protection
A quick fix
Disadvantages:
Short term effect – no immunological memory
Serum sickness – incoming antibody is recognised as a foreign antigen by the recipient and results in anaphylaxis
Graft versus host disease (cell grafts only) – incoming immune cells reject the recipient
Why are maternal immunoglobulins transferred to the foetus or neonate naturally using a specialised mechanism involving the neonatal Fc receptor?
The neonatal Fc receptor transfers the antibody through cells and into the neonates bloodstream. This provides a certain amount of immunity to the baby for any recent pathogens.
Give examples of passive immunity?
Snake or spider bites, scorpion or fish stings
- passive infusion of antibody specific for the toxin
Hypogammaglobulinaemia – primary or secondary
Infusion of g-globulins to reduce infection
Rabies Immunoglobulin -“Post-exposure prophylaxis”
together with vaccination
Which are immunoglobulins for post exposure prophylaxis?
Human Normal Immunoglobulin (HNIG)
Hepatitis A
Measles
Polio
Rubella
Specific Immunoglobulins
Hepatitis B
Rabies
Tetanus
Varicella-Zoster Virus
What is vaccination?
administration of antigenic material (a vaccine) to stimulate an individual’s immune system to develop adaptive immunity to a pathogen
Describe killed whole organism vaccine?
Target organism, e.g., polio virus is killed
Effective and relatively easy to manufacture
Booster shots likely required
Virus must be heat killed effectively – any live virus can result in vaccine-related disease
Describe attenuated whole organism?
An avirulent strain of target organism is isolated
Can be very powerful and better than killed
Simulate natural infection
Reversion back to virulent form
Refrigeration required
Describe how you get a weaker form of the virus?
pathogenic virus is isolated from a patient and grown in human cultured cells
the cultured virus is used to infect monkey cells
the virus acquires many mutations that allow it to grow well in monkey cells
the virus no longer grows well in human cells (it is attenuated) and can be used as a vaccine
Describe recombinant proteins as vaccines?
Generally, very safe
Easy to standardise
Not very immunogenic without an effective adjuvant
Need to understand how to generate immunity
Examples
Hepatitis B surface antigen (HBsAg)
Human papilloma virus (HPV) proteins
Describe toxoid (modified toxin) vaccine?
Toxin is treated with formalin
Toxoid retains antigenicity but has no toxic activity
Only induces immunity against the toxin, not the organism that produces it
e.g. tetanus, diphtheria
What are the contraindications of vaccination?
febrile illness- cannot be immunocompromised as immune system has to do a lot of the work
pregnancy- slightly immunocompromised
allergy- immunocompromised
Immunocompromised – cannot be given live attenuated vaccines as individuals may develop disease from the vaccine strain
What is herd immunity’s purpose?
vaccine coverage of 90-95%
Vaccinated individuals are less likely to be a source of infection to others
Reduces the risk of unvaccinated individuals being exposed to infection
Individuals who cannot be vaccinated will still benefit from routine vaccination programmes
What makes a good vaccine?
Potent antibody response – high antibody titers
Potent CD8+ cytotoxic T cell response
CD4+ T helper response
Memory
Do we need t cell responses for vaccines?
If want vaccine to generate potent IgG response you need a T cell response as T cells act to optimise antibody production.
Drive b cells to make more effective antibody responses against pathogens.
What are the challenges facing vaccines?
Conventional vaccines cannot elicit immunity against all infectious disease
Persistence – ideally vaccines should give life-long protection
Generation of memory cells
Protection of vulnerable groups
The very young, the elderly and immunocompromised individuals
Antigenic shift and drift, and strain diversity in general
Bird and swine influenza pandemics
The cold chain network
Role of protein receptors, Hemagglutinin and neuramidase?
Genes encode two really important protein receptors hemagglutinin H and other neuramidase N (H1 and N1).
Hemagglutinin all about virus entering host cell and infecting cell and neuramidase all about exiting cell .
Describe antigenic shift?
Influenza virus has eight separate RNA strands
Co-infection of a host with the virus allows genetic reassortments that give rise to novel antigenically distinct virus particles
Immune evasion and step increase in virulence
(body not able to deal effectively with flu strains)
e.g., the H1N1 influenza virus in 2009
What is antigenic drift?
slight mutations in the human genome which give rise to slight differences in the receptors
Describe the vulnerability of neonates?
not very good at mounting immune responses against particular types of pathogen, particularly polysaccharide coated pathogens.
Vulnerability <18–24 months to encapsulated bacteria such as pneumococcus, Hib and meningococcus
Fewer FDC, and B cells do not express costimulatory molecules
Short term antibody production
Describe vulnerability of the elderly?
Reduced efficacy or responsiveness to vaccination
Oligoclonal responses lacking specificity
Reduced plasma cell survival niches (in bone)
What is a B cell?
Something that is stimulated by a viral pathogen.
Will the undergo development such that it changes aspects of its cell phenotype and basically becomes an antibody producing factor.
Have b cell receptors on cell surface but change to becoming an antibody producing factory type cell - plasma cell. No longer has B cell receptor on surface but it secretes lots of antibody into the bloodstream.
Describe the conjugate vaccine?
The antigen is the carbohydrate capsule (polysaccharide antigens)
Carbohydrates are poor antigens (do not stimulate the immune system as broadly as protein antigens), especially in babies
Conjugation of the carbohydrate to a protein carrier makes them more effective
Describe checkpoint inhibitors?
New type of antibody immunotherapy used to treat a number of different cancers and they’re very powerful. Boost immune response against the cancer cells.
And can have vaccine effect - stop cancer relapsing.
Describe personalised vaccines?
first test the individuals immunity against broad range of potential vaccines
take blood sample and incubate with panel
look to see which is generating certain amount of immunity
