Lecture 18 - Car T Cell Therapy Flashcards
What is the importance of T cell signalling
-regulate t cell effector function, memory, cell proliferation and differentiation
- 2 concurrent signals needed for full activation
1. antigen presentation and recognition by TCR
2. costimulatory signal
What strategies do tumor cells have to evade immune system surveillance and elimination
- decreased expression of immunologic markers
- MHC gene mutations
- expression of negative costimulatory molecules
- creating immunosuppresive microenvironments
What does CAR allow us to do
reprogram Th cells into Thunter cells that target specific tumor antigens
What is the CD3Z signaling domain
- the intracellular domain
- initiates phosphorylation signalling for Tcell activation
What is the costimulatory signaling domain
- transmembrane
- anchors CAR to the membrane
- essential for signal transduction that sustains Tcell activation
- mediates cytokine release
What is the antigen-binding domain
- extracellular target binding domain
- derived from both light and heavy chain portions of a single variable fragment from the antigen binding site of a monoclonal antibodu
- affords tumor specificity –> T cells recognize any cell surface molecule to which an antibody can be made
What are the advantages of an antigen-binding domain
- protein, glycoprotein and glycolipids can all serve as potential targets
- recognition is not MHC restricted ( no requirement for antigen processing/presentation)
What is the hinge region
- flexible peptide linker binds transmembrane domain to extracellular target binding domain
What are first generation CARs
- TCR complex and antigen recognition domain
- showed low efficacy (insufficient t-cell persistence)
- could not prime resting t cells or direct lasting t cell responses
- no sustained cytokines
What are second generation CARs
- added costimulatory domain
- incorporate 2nd signal leading to improved actication, enhanced survival and effective expansion of modified t cells
- increased anti-tumor activity
- basis of all currently approved clinical CAR T cellular therapies
What are third generation CARs
- combines signaling potential of atleast 2 costimulatory domains
- showed improvement in some cancer treatment but not all
What are fourth generation CARs (TRUCKs)
- further modified CARs receptor
- includes transgene receptor domains to regulate cytokine release
- in multiple clinical trials
- can link multiple CAR receptors together and link CARs with TRUCKs
Car-T cell Manufacturing
- CAR DNA is built into carrier vector
- the vector is inserted into a virus-producer cell which can infect a t-cell but not replicate itself
- produces replicated deficient virus with the CAR DNA
- CAR DNA is built into the genome
- CAR DNA is translated into CAR protein
What are the steps of CAR T cell therapy
- remove blood from patient to get T cells
- make CAR T cells in the lab
- grow millions of CAR T cells
- infuse CAR T cells into patient
What is t-cell activation in CAR-T cell therapy
antibody coated beads act as dendritic cells and activate tcells
What is transduction in CAR T cell therapy
activated t cells are genetically reprogrammed ex vivo using lentiviral mediated transduction to construct encoding of car receptor on T cell
What is expansion in CAR-T cell therapy
- stimulate t cells with or wihtout additional costimulatory antibodies
- significant increase in number until sufficient dose
What is the mechanism of action of CAR Tcells
- selectively kill tumor cells
- proliferate
- migrate in/out of lymph nodes
- regulated identically to normal t cells
- persist for multiple years
- long term cancer remission
What is the ideal CAR T target receptor
- tumor specific
- universally expressed on tumor cells
- not expressed on self cells
- cell surface molecule
-CD19 is most frequent target
What are the signs of CAR T toxicity
- insertional oncogenesis
- cytokine release syndrome
- neurological toxicity
- on target off tumor toxicity
- anaphylaxis/allergy
What is cytokine release syndrome
- systemic inflamatory response
- increased inflammatory cytokines, interferon gamma, IL10, IL6
- causes fever, fatigue, nausea, tachycardia, hypotension
- expansion and progressive immune activation of transfered CAR T cells
therapy ro mitigate
What are the pros and cons of CAR-T cells and T cells
pro: non-HLA restricted, targetting non-peptide antigens, better targetting, avoid tumor escape, increased in vivo persisitance
con: cannot target intracellular pathogens, doesnt deal well with escape mechanisms
What are the pros and cons of CAR-T cells and IVIg
pro: more potent due to t cell cytotoxic activity and killing mechanism, long term effect due to memory, currative
con: t cell infusion toxicity, significant cost
What are additional challenges of CAR T immune therapy
- high price
- feasibility
- patients must be well enough to withstand therapy
- controversies about carrier, effectiveness of costimulatory
- keeping up with clinical trials
- manufacturing failures
- disease may progress before cells ready
What is allogenic CAR T
- donor T cells are pooled and utilized off the shelf similar to IVIg
