Immunotherapy Flashcards
What are 2 broad forms of immunotherapy?
1) Antibody immunotherapy
2) Adaptive (cellular) immunotherapy
What are the differences between polyclonal and monoclonal Abs?
Polyclonal Abs are a mixture of Abs that target multiple epitopes on the same Ag
Monoclonal Abs are copies of 1 Ab that target the same epitope on Ag
What are some clinical uses of pAbs?
1) Hep B Igs for eg. Post-liver transplant, newborns to HBV+ mothers, Passive immunisation to infected
2) IV Ig for Kawasaki disease (auto-Ab mediated cytopenia)
Describe the process of mAbs synthesis.
1) Mouse are immunised with the Ag
2) Spleen cells are removed and fused with immortalised myeloma cells to form hybridomas (in vitro)
3) Culture in HAT medium and select for positive cells
4) Harvest mAb
Why did subsequent uses of CAMPATH (anti-Human CD-25) fail in clinical trials?
It is a mouse mAb, so px developed a immune response to the murine Ab upon secondary innoculation
Why do mouse Abs rarely work in humans/What is the HAMA effect?
Human Anti-Mouse Abs (HAMA) are present in >10% of px plasma
- bind to Ig of other species (heterophilic)
- most target Fc portion of non-endogenous Ab
Describe the process of chimerisation of murine antibodies into chimerised human-mouse variants.
Fab genes from mouse hybridoma are pasted onto a human Ab Fc scaffold in a recombinant plasmid, resulting in 2/3 human Ab with a mouse Fab
What are some clinical applications of chimeric antibodies?
1) anti-CD20 in Non-Hodgkin’s Lymphoma
- depletes CD20+ cells
2) anti-TNFα in RA
- Rheumatoid Arthritis primarily fuelled by pro-inflammatory TNFα
How are Humanised antibodies different from Chimeric antibodies?
Only the complementarity-determining region (CDR) genes within the murine Fab are pasted onto human Ab gene scaffold, resulting in a 90-95% human Ab rather than a 2/3 human Ab in chimeric antibodies
How are fully human antibodies produced in mAb therapy?
1) Take blood sample from px with promising Ab response to target antigen
2) CD20+ selection → isolate B cells
3) Automated display, screening and cloning (computational modelling, machine-learning bioinformatics, single cell PCR, etc.)
4) Recombinant exp. and functional testing → human mAbs
What are the advantages and disadvantages of human mAbs?
Advantages:
- ↑ binding specificity
- ↓ immunogenicity/toxicity
- can be tailored via Fc domain modification
Disadvantages:
- Cost and manufacturing complexity
- low tissue perfusion (size often >150kDa)
What are some side effects of antibody immunotherapy?
1) Hypersensitivity-like reaction (eg. fever, malaise, diarrhoea, hypotension, rashes, etc.)\
2) Specific side effects of function (eg. Bevacizumab → anti-angiogenesis → HBP, bleeding, blood clots, poor wound healing, etc.)
What are 2 mechanisms by which antibodies are used in immunotherapy?
1) Neutralisation of inflammatory cytokines (eg. Infliximab → anti-TNFα chimeric Ab in RA)
2) Direct and indirect tumour targeting
- Direct: eg. Rituximab → anti-CD20 in Non-Hodgkin’s Lymphoma
- Indirect eg. Daclizumab → anti-PD-L1 checkpoint inhibitor
What are some future directions in antibody immunotherapy?
1) Bi-specific Abs
2) Ab conjugates (eg. immunotoxins, ADEPT: Ab-directed enzyme pro-drug therapy, chemo/radiolabelled Abs)
What is adoptive/cellular immunotherapy?
Immune cells collected from px → cultured in lab
→ (i) ex-vivo T cell subset or (ii) tumour Ag DC loading
→ returned to px
