Lecture 32 - Vaccination II Flashcards
Compare **empirical **and rational approaches to vaccine development
List vaccines that have been developed in these ways
Empirical
- “Trial & error” methodologies
- Based on knowledged gained by direct observation of an experiment
- Many traditional vaccines
Rational
- Based on logic and deduction
- Using data from experiements to guide and inform
- HPV (Gardasil; VLP), HBsAg subunit vaccine
What is the imporance of Dendritic cells in vaccine design?
A good vaccine strategy needs to license / activate DCs
- DCs play a crucial role in shaping the immune response
- Become activated by sensing ‘Danger’
- Intracellular transduction pathway
- Transcription of genes
- Activation of DCs
- Recognise PAMPs / DAMPs through PRRs
- TLRs
- C-type lectin receptors
- RLRs
- NLRs
- Recognise PAMPs / DAMPs through PRRs
- Release of pro-inflammatory cytokines that regulate:
- Adaptive immune response generation
- Proliferation
- Inflammation
- Apoptosis
- Immune regulation
What is therapeutic vaccination?
Vaccination after establishment of infection / disease
eg. Improvement of T cell immunity to tumours
How has basic research in the field of immunology impacted modern therapeutics?
- Understanding mechanisms of immune induction
- Role of innate immunity
- Requirements of lymphocyte activation
- Induction of immune memory
- Understanding cell mediated immunity
- Clearance of intracellular infection
- Recognition of tumour Ags by CD8 T cells
- Therapeutic vaccination
- eg in tumour immunotherapy
What can techniques such as ELISA & MHC-peptide tetramer staining tell us?
- Can tell us about the responses elicited by vaccines
- Whether or not the vaccine is effective
How can vaccine efficacy be measured?
- Ab responses
- ELISA
- Titre (magnitude of response)
- Isotype
- IgG: memory formation
- IgA: mucosal immunity
- Surface plasmon resonance technology
- Binding affinity
- ELISA
- Cell mediated responses
- Intracellular cytokine staining assays
- pMHC tetramers
- Detection of specific T cells (ie specific for vaccine Ag)
- Look at the proliferation of these specific T cells
- Dye-base in vivo and in vitro killing assays
- Ability of T cells to kill infected cells
- Bead arrays & ELISA
- Overall cytokine levels in blood & tissue
What do molecular biology techniques allow in vaccine development?
- DNA sequencing
- Sequence pathogen genomes
- Identify important genes for virulence
- Determine antigenic determinants of pathogens
- Mutation of pathogen
- Rational attenuation for production of vaccine strains
Which things must be considered for rational design of a vaccine?
- Type of vaccine
- Attenuated, inactivated, subunit, DNA?
- eg might need to use subunit vaccine, as the pathogen cannot be attenuated
- Type of response required
- Cell mediated or humoral?
- Based on the type of infection caused by the pathogen (intra- or extracellular)
- Target
- The pathogen itself?
- Product? (toxin, secretory factor)
- Safety profile & risk
- Toxicity, AEs, tolerance
How were pathogens attenuated in the past?
- Passage of the pathogen through cells or other organisms
- The pathogen must adapt to this new environment:
- Different selective pressures
- Mutation of the pathogen
- In so doing, the pathogen loses its ability to infect humans
- Disadvantages:
- Do not know which mutations have occurred
- If there aren’t enough mutations, pathogen can revert to virulence
Describe the process of rational attenuation of pathogens
Example approach by reverse genetics:
- Clone genome of pathogen
- Identify genes:
- Virulence
- Replication
- Antigenic proteins
- Mutate or delete virulence gene, whilst leaving others in tact
- Mutate by selective mutagenesis
- Deletion is safer: can’t revert to virulence
- But can the virus still replicate?
- Pathogen can no longer cause harm, but can infect and induce an immune response
Describe vector vaccines
Which vectors are used?
What are the advantages and disadvantages of this method?
Bacteria or viruses
- Approach
- Attenuated pathogen
- Engineered to express Ags from another organism
- Example vehicles:
- Adenoviruses
- Attenuated Salmonella
- Poxviruses
- Vaccinia
- Canarypox
- Genomes are quite large, and thus can accommodate additional genes without compromise
- Advantages:
- Mimics natural infection
- High levels of expressed Ag
- Mucosal administration
- Elicits both T & B cell responses
- Antigens are properly folded
- Important for conformational Ags
- Maintain proper 2° and 3° structure
- Disadvantages
- Can be dangerous in the immunocompromised
- The vector can be the target of an immune response with repeated use
List the various types of subunit vaccines
- Recombinant proteins
- Peptide vaccines
- VLPs: virus-like particles
How are recombinant proteins made?
What are the disadvantages of these vaccines?
- Generation:
- Using recombinant DNA technology
- Plasmid encoding the Ag is introduced into an organism
- Yeast
- Bacteria
- Insect cells
- Organism produces the Ag
- Using recombinant DNA technology
- Disadvantages
- Low immunogenicity
- Requires adjuvants
- Need to identify the protective Ag
- Can be difficult to manufacture (purification of recomb. proteins)
Describe the features of peptide vaccines
How are they manufactured?
What are the advantages and disadvantages?
- Composition:
- Peptide represents epitope of:
- B cell
- CD8 T cell
- CD4 T cell
- Adjuvant
- TLR agonists
- ISCOMs
- Peptide represents epitope of:
- Manufacture
- Synthetically generated
- Advantages
- Very safe
- Very defined composition
- No risk of reversion
- Disadvantages
- Not very immunogenic
- B cell determinants are often not native-like
- Often linear sequences: thus limited to immune responses against non-conformational antigens
- T cell determinants are MHC restricted
- eg only HLA-A2
- The vaccine would thus only work in individuals with this haplotype
What are ISCOMs?
Immune Stimulating COMplexes
- Used in peptide vaccines
- Like an adjuvant
- Helps the take up of the peptides by DCs
