DC based immunology Flashcards
Why are DCs so important?
They are the link between the innate and the adaptive immune system. The DC determines whether there is going to be an immune response or a tolerogenic response.
When was the first DC-based immunotherapeutic treatment approved?
Steinman first described DCs in 1973. 1996 first DC-based immunotherapies were in clinical trial. 2010 first regulatory approval of the DC-based immunotherapeutic siguleucel-T.
How does DC based immunotherapy work?
- Leukapheresis
- Monocyte or CD34+ precursor isolation
- Stimulation with growth factors to make immature DCs
(Alternatively, do direct isolation of immature DCs) - Add peptide/protein, do transfection, add tumour lysate
- Do DC-tumour cell fusion
- Inject the mature DCs back into the patient, where they can now induce a CTL response against the tumour
What are the best antigens for DC-based cellular vaccines?
It is difficult to compare which antigen is the best, this may differ from tumour to tumour and from patient to patient.
Choice depends on availability and what you know might work for this tumour. E.g. if the tumour antigens are known.
What is Sipuleucel-T (provance)?
One registered DC-based immunotherapy: Sipuleucel-T (product name: provance). It is registered for prostate cancer. GM-CSF with a prostetic acid posphotate fusion protein is used for stimulation of monocytes into DCs. So, during stimulation, they already put in the antigen.
It is effective: in certain patients they live 20 months longer, so the effect is not that much. Side effects are not really severe –> not life threatening=the main pro of DC-based immunotherapy.
How could you improve Sipuleucel-T (provance)?
Maybe by adding an adjuvant
•You need to enhance strength and duration of antigen-specific immune response
•Educate DCs to overcome problems of e.g. suppressive tme
•You want to compensate for a high need of antigen dose. A high dose of antigen in your DC may be expensive or effect the DC.
•You want a stable vaccine. You want something you can store for a while
•You want to broaden your immune response: the response not to one antigen, but multiple. Also cross-presentation once the immune response is started, to let your DCs pick up other tumour antigens.
What is the optimal DC phenotype for cancer immunotherapy?
Optimal DC phenotype for cancer immunotherapy:
•High CCR7: allow migration do draining lymph node where they can antigen present to the T-cells
•High CD80/CD86: signal 2. Needed for proper activation of T-cell response
•High IL-12/IL-27: signal 3 for Th1-cells and CTLs
•High lifespan
•GM-CSF!
•TNF-alfa!: makes a DC more mature, upregulates costimulatory molecules and therefore will induce a stronger T-cell response.
•PGE2!: enhances maturation and upregulates CCR7 on DCs. Needed for migration
•TLR-L (R848, pl:C)!: specifically ones that CD8+ T-cells like the ones (mentioned). They target the endosomal TLRs and mimic a virus response to induce a proper CD8+ T-cell response.
•Research: signal 1-4 for DC-T-cell interaction (think, costimulatory molecules)
1. Antigen presentation
2. Costimulation signal
3. Polarizing signal (e.g. IL12, IL27)
4. Homing signal: attract T-cells to site of the tumour (or infection)
Where do you inject the DCs?
Difficult to research.
•Intraveniously is not used, because it drains to the spleen and you lose your DCs
•Subcutaniously, intradermally or intranodally are being researched. Not much difference between these. When you inject intradermally, you find the DCs at other sites than the injection site, while if you inject intranodally, you only find the DCs at the site of injection.
o However still not that much difference in number of targeted lymph nodes and redistribution of cells between different injection sites
Why are DC-based immunotherapies less effective?
Because the tumour cells sometimes express a lot of these negative regulating factors that instruct the immune response to be tolerogenic. Check-point inhibitors combined with the DC-based immunotherapies seem far more promising. These trials are mainly still ongoing.
Which DC subset has been implicated to be important in the induction of a CTL response?
CD141+ DCs have been implicated to be important in the induction of the cytotoxic T-cell response. This is the response you want. They are the equivalent of CD8-alfa+ DCs in the mouse. Very little amounts are present in human peripheral blood. This makes leukophoresis even more important, because only 0.05% of your mononeuclear cells are the cells you want. They express TLR1, TLR3, TLR6, TLR7 and TLR8. TLR1 & TLR6 pair up with TLR2 and on their own they are useless. The co-expression with TLR6-8 already implies that they are important in antiviral CD8+ responses and therefore very usefull for anti-cancer immunotherapy.
How are/were more subsets of DCs discovered?
In 2017 even more subsets were discovered using single-cell RNA-seq. The function of all these subsets is still unknown.
Are primary myeloid DCs good to use in cancer therapy and are they better than using monocyte-derived DCs?
Primary myeloid DCs are safe and give a good immune response in metastatic myeloma patients.
Comperisons to monocyte-derived DCs are difficult. Trials to compare them are ethically difficult because of this.
Can DC-based immunotherapy be used for auto-immunity and allergy?
Research has been started for this. Immune suppressive response with Tregs is needed. Antigen is different and far less well studied. Even more important here is that you instruct the DCs to induce the tolerogenic responses. This has been tried with several adjuvants: NFkappaB inhibitors, vitamin D3, RA (retenoic acid).
You want to treat the patient at the earliest symptomatic stage to stop them from progressing to worse disease.
What are disadvantages of DC-based immunotherapy?
Disadvantages of DC-based immunotherapy:
•Isolation has to be in a clean room
•Really really really expensive
•Limited amount of cells
•It has to be made specifically for the patient
•The culturing of the cells can induce a change in functionality of these cells
•Monocytic derived DCs that now are used are not the natural type of DC
What is an alternative to using DCs?
Make liposomes that you can induce in vivo. You can put in and attach all kind of stuff to these little lipid balls. E.g. : allergen in and adjuvant like vitamin D and attach targeting molecule to make sure the lipid binds to the right DC subset.
