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Summary Drug Delivery
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Summary of the BPS Lecture Series Drug Delivery: Vaccine Development including notes.
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Drug Delivery: Vaccine DevelopmentVaccine immunology
Innate vs Adaptive immune system
Antigens are processed by APC’s and presented to T-cells
Intact Antigens are recognized by B-cells – produce antibodies
Innate responses
• Some immune responses
• are not pathogen specific
• do not induce memory (disappear when the pathogen is gone)
• These are innate responses (i.e. not acquired)
• Therefore not considered relevant for vaccine development
• Neglected until it became clear
• without innate responses vaccines do not work
• classical vaccines contain innate
stimuli Dc and macrophages are important,
NK cells and T
Parts of innate response
The complement system
Innate response: PAMP recognition
Pathogen Associated Molecular Patterns
- Are evolutionary conserved molecular
structures
- Interact with sensors and receptors of
cells dedicated to danger sensing
- Receptor interaction results in pro inflammatory cytokines
,The DAMS can also be recognized → Damage associated Molecular Patterns
Toll Like Receptors are the best known PAMP receptors
TLR activation supports the induction of adaptive immune response
- Signalling pathways proceed via NF-kb and IRF3/7
- Supports the up-regulation of co-stimulatory molecules MHC class II CD80/CD68
- Triggers the production of pro-inflammatory cytokines and chemokines
TLRs recognize common microbial components, such as lipopolysaccharide. (LPS)
Many vaccines contain intrinsic activators of innate immunity → adjuvants
- Outer membrane Vesicles (OMV) = strong adjuvant, exist in gram negative bacteria. Express
pathogen-associated molecular patters that can be recognized by the innate and acquired
immune system
Acquired responses:
- Antibodies, cytotoxic T-cell and memory B and Tcells take time to develop
- A naive person needs usually several weeks and repeated or prolonged antigen exposure to
develop immunity.
- Upon (re)infection the person is protected by
• circulating antibodies and CTLs or
• memory B or T cells that respond within a week by differentiation into antibody producing
plasma cells or CTLs.
,Antibodies
- Antibodies bind to intact antigens
- Interaction is between paratope (antibody) and epitope (antigen)
- Neutralisation of pathogen by
➔ Aggregation of antigen
➔ Steric hindrance preventing receptor binding
➔ Looking conformation preventing induced fir treceptor binding or uncoating
➔ Destabilisation of antigen
➔ Opsonisation/Fc mediated phagocytosis/antibody-dependent cytotoxicity
➔ Complement activation
6 complementarity determining regions (CDR) bind
antigens
- 3 loops on heavy chain
- 3 loops on light chain
Heavy chains determines antibody class
Light chain → lambda or kappa antibody
IgG most prevalent, complement activation, good
opsonin
IgM pentamer, produced, excellent complement
fixation
IgA secreted to mucosal surfaces, no complement
fixation
IgD antigen receptor on B-cells
IgE Strong binder of Fc receptors on basophils and mast cells, involved in allergy and some parasitic
diseases, no complement activation
Antibodies bind to epitopes on antigens
- 15-22 amino acids
- 5-6 amino acids contribute most to binding energy
- 75-120 hydrogen bridges
- Other electrostatic interactions as well as hydrophobic interactions
- Conformation is often crucial
- B-cell epitopes are surface exposed
Antigen-Antibody interactions
- Electrostatic interactions
- Hydrogen bonds
- Van der Waals forces
, - Hydrophobic forces
Interaction is based on complementarity with regard to charge and conformation and similarity with
regard to hydrophobicity. Water molecules (light blue) contribute significantly to the interaction by
providing additional hydrogen bonds.
Ab effectivity determined by
- Binding kinetics: how FAST is the binding?
- Two rate constants:
- Ka or kon, rate of complex formation (recognition)
- Kd or Koff
Affinity via Fab: how STRONG is the binding? equilibrium
constant K
Affinity and binding kinetics are related
Affinity ranges
Ag-Ab: 10-5–10-12 M
Ag peptide-TCR: 10-4–10-5 M
Streptavidin-Biotin: 10-14 M
Induced fit: epitope and paratope can change conformation to induce the fit of binding
Antibodies are produced by plasma cells
Plasma cells are activated B-cells
B-cells become plasma cells in the presence of antigen and signals of Thelper cells
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