Bone Marrow Transplantation Flashcards
What is the marker of maximum tolerated dose?
Bone Marrow
What is the most resistant to radiation?
CNS
What is the least resistant to radiation?
Bone Marrow
What is the risk of dying from a bone marrow transplant?
>50%
What is an Autologous transplant?
o GCSF given and obtain a CD34+ population of cells from the bone marrow (the stem cells)
o These are preserved in the freezer
o A high dose of chemotherapy is given to eradicate the bone marrow -> reinfuse the stem cells
What is an autologous SCT suitable for?
Acute leukaemia, myeloma, lymphoma, CLL
Solid tumours
Autoimmune disease
What is an allogenic SCT?
o Used when patient’s disease is unlikely to be eradicated from the bone marrow by standard chemotherapy
o Give them high dose chemoradiotherapy to ablate the bone marrow (malignant and normal cells)
o Then give them some bone marrow from a healthy donor
o Issue with BM transplantation is that donor immune cells recognise patient as foreign
What is an allogenic SCT used for?
Acute leukaemia, Chronic leukaemia, Myeloma, Lymphoma
Thalassaemia, SCD
Bone marrow failure
Congenital immune deficiencies
What are the principles of transplantation?
o Identify disease unlikely to respond to standard treatment
o Treat patient to remission
o Identify donor -> collect stem cells
o Give patient myeloablative therapy
o Infuse stem cells
o Continue immunosuppression and support patient through period of cytopaenia
What are the standard parameters of outcome?
Overall survival (OS)
Disease-free survival (DFS) – better than OS
Transplant-related mortality (TRM)
Relapse incidence (RI)
How do you select a donor?
HLA matching
Serological vs DNA matching
Ideally a sibling (one in four chance of matching with each sib)
If not, a volunteer unrelated donor or minimally mismatched family member
More recently, increased use of haploidentical family member – almost every patient has a donor
How do HLA types contribute to donor selection?
• Donors are selected based upon -> well matched for tissue type (HLA type):
o Ideally a sibling (1 in 4 chance with each sibling)
Probability of having a match with a sibling is = 1-(3/4) number of siblings
o If not, a volunteer unrelated donor or minimally mismatched family member
Why is serological vs DNA matching important?
o Low-resolution / SEROLOGICAL -> A*02
o High-resolution / DNA -> A*0201, A*0202, A*0203, …, A*0260
More likely to match at high resolution in a sibling match
Allele frequencies vary depending upon the ethnicity of the patient (for each allele – i.e. A*0202)
What is required for harvesting?
Procedure and Harvesting – required 2 x 10^6 CD34+ cells/harvest
What is bone marrow sampling?
• Bone marrow sampling (1.5L, 1% CD34+ -> 15mL CD34)
o Difficult -> involves anaesthetising the patient and sampling some bone marrow from their pelvis
o Puncturing the bone and getting into the medulla damages it, meaning that the first few millilitres that you collect will contain stem cells, however, the rest of it will be blood flooding into the damages site
o So, you keep re-puncturing the bone, collecting a small amount at a time until you have a good harvest
What is peripheral blood sampling?
(10L, 1% CD34+ 100mL CD34)
o Hormones (e.g. G-CSF) can be used to stimulate granulocyte production (given 5 days before)
o This leads to the bone marrow releasing some white cells as well as some stem cells
o The donor is connected to a centrifuge device which spins the blood, removes the white cell component, reassembles the red cells and plasma and reinfuses it into the patient
What is umbilical cord stem cells?
(0.1L, 1% CD34+ -> 1mL CD34) -> stem cells can be harvested at the time of delivery
Which method of harvesting is best?
out of all the methods of harvesting, CD34+ stem cells will only make up about 1% of the sample
o Important because success of transplant depends on the number of CD34 cells per kg of weight of the recipient
o Therefore, in cord blood (only harvest 0.1L), there is fewer CD34 cells and so can only really be used for babies
What are the complications of SCT?
o Graft failure
o Infections
o Graft-versus-host disease (GVHD): allografting only
o Relapse
What is the EBMT risk score?
o Age <20=0,20-40=1,>40=2
o Disease phase Early=0, int=1, late=2
o Gender of R/D Female into male = 1 Donor
o Time to BMT <1 yr = 0, >1 yr = 1
o Donor Sib = 0, VUD = 1
Higher score = less chance of successful outcome
VUD = Volunteer Unrelated
How does the EBMT score predict survival?
Overall 80% survival in 0-1 score
70% survival in 2 score
50% survival in 3 score
30% survival in 4 score
15% survival in 5-7 score
What are the RFs for infection?
Neutropenia
Breakdown of protective barriers
Decreased antibody levels
Depressed T cell immune responses
What’s the problem with immunodeficiency in allogenic BM transplants?
o Different infections at different times
o Immune defect is frequently of long duration
o Risk of infection is mostly disease-independent
What is aspergillosis?
- This is ubiquitous (i.e. is found everywhere)
- Invasive aspergillosis = high mortality (10-15% deaths due to aspergillosis -> 92% mortality)
What is CMV?
- Remains latent because T cells are able to keep it under control
- CMV pneumonia is a large cause of deaths in HSCT
What are RFs for CMV?
Patient’s serological status
Donor’s serological status
Type of stem cells donor (monocytes)
Type of transplant
CMV viral load
What is GvHD?
• An immune response when the donor cells recognise the patient as foreign
What is Acute GvHD?
<100 days
Skin: rash, itchy, red
GI tract : diarrhoea
Liver :hepatitis, jaundice
What is chronic GvHD?
(>100 days) effects – similar to Sjögren’s; ranked by severity (04):
o Skin rash
o Liver hepatitis, jaundice
o Mucosal membranes dry, mouth ulcers
o Lungs SoB
o Eyes dry
o Joints arthritis
How does chemo interact with SCT?
- Damaging the skin, GI tract and various other tissues by giving chemotherapy will cause the release of cytokines which activates APCs, which then present the antigens to the donor lymphocytes -> immune reaction against the host tissue
- You could wait for longer after the chemoradiotherapy for the effects to die down before giving the stem cell transplant, however, this increases the time during which they are susceptible to infection
What are the RFs for GvHD?
N.B. twins have no risk of GvHD…
o Degree of HLA disparity
Recipient age
o Conditioning regimen
R/D gender combination (D: M -> R: F get worse GvHD)
o Stem cell source
Disease phase
o Viral infections
What is the treatment of GvHD?
o Corticosteroids
o Cyclosporin A
o FK506
o Mycophenolate mofetil
o Monoclonal antibodies
o Photopheresis
Total lymphoid irradiation
How do you prevent GvHD?
Corticosteroids
Ciclosporin A + methotrexate
FK506
T-cell depletion
Post-transplant cyclophosphamide
What is the goal of autologous GvHD?
Autologous HSCT -> goal to kill all leukaemia with radio/chemo
What is the goal of allogenic GvHD?
• Allogenic HSCT -> accepted you cannot kill leukaemia from radio/chemo -> rely on BM from donor
• Infusion of more donor lymphocytes can restore remission in one where a leukaemia begins to reappear
• Infusion of more donor lymphocytes can restore remission in one where a leukaemia begins to reappear
Where do the lymphocytes come from in GvHD?
because GvHD happens soon after the transplant, it is likely that the reaction is happening because of the mature lymphocytes in the donated sample rather than because of the lymphocytes that are produced from the stem cells
Is it possible to identify and select out the specific T cells?
it is impossible to identify and select out the specific T cells, you just insert a population of cells that contains stem cells (some of the other cells will be mature lymphocytes)
o However, you also do NOT want to isolate the stem cells and give them alone because it increases the risk of relapse (i.e. the donor lymphocytes are important in the prevention of relapse)
What future therapies may exist?
CAR-T cells
Chimeric antigen receptor
What is CAR-T?
(1) Leukapheresis (T-cells are collected)
(2) T-cell activation (engineered chimeric-TCR put into a virus which infects the collected T-cells)
(3) Modified T-cell expansion (new T cells are expanded)
(4) Quality and release testing: potency checks and infection checks
(5) Chemotherapy
(6) Modified T-cell infusion
What is chimeric antigen receptor?
o Retains the more effective intracellular components of the TCR (CD28 and CD3 intracellular components)
o Extracellular portions (non-TCR) are engineered in
o These extracellular portions recognise CD19
What can CAR-T do?
- ALL relapsed in adults has a very poor outcome
- CAR T can achieve remission in children and adults in relapsed ALL
What are the side effects of CAR-T?
o Tumour lysis syndrome (rarely occurs)
o Cytokine release syndrome (potentially fatal – chimeric T-cells can release massive amounts of cytokines)
o Neurologic toxicity, cytopaenia (macrophage activation syndrome), B-cell aplasia (hypogammaglobulinaemia)
What are the principles of cyclical chemotherapy?
Normal body cells should mostly be ok eventually
Cancer cells should die due to their rapid division
HOWEVER, you can’t keep doing chemo because it will affect haemopoeisis (if AML therapy)
How are genes important in AML?
There are a lot of implicated genes
What is the survival post transplant in the 3 risk categories?
Early - about 60% in 5yrs
Intermediate - a little less than early
Advanced - closer to 20% in 5 yrs
What did we find out about radiation during the cold war?
Identifying something in the spleen and bone marrow that protected against irradiation and restored blood counts
The concept of the blood (haemopoietic) stem cell
What did Medawar, Billingham and Brent find?
Autologous skin grafts survive, grafts from donors do not
Early in life, develop ability to distinguish self and non-self (Frank Burnet)
Injected cells from murine embryos across strains and demonstrated subsequent survival of skin grafts between adults of different strains.
Introduce concept of acquired tolerance
What did Vinca and George Mathe do?
Accidental exposure of 6 workers at a nuclear powerplant in Vinca in 1958
5 treated in Paris with infusion of bone marrow by George Mathe, all survived
Why did they initially stop BMT?
GvHD- diffuse maculopapular rash
What did Loutit and Barnes do?
The transplanted graft must contain immunologically competent cells
The recipient must be incapable of rejecting or eliminating transplanted cells
The recipient must express tissue antigens that are not present in the transplant donor, thus the recipient antigens are recognized as foreign by donor cells
What is the HLA system?
A person’s tissue type comprises a set of distinct proteins called Human Leukocyte Antigens (HLA), found on the surface of most nucleated cells.
HLA molecules, or proteins, relevant in transplantation – HLA-A, -B, -C, (class I), present peptide to CD8+ (cytotoxic T-cells) HLA-DP,-DQ and -DR (class II), present peptide to CD4+ (helper T-cells)
HLA encoded by the Major Histocompatibility Complex, MHC, on chromosome 6.
Function – present foreign peptides to T cells
Routinely, HLA-A, -B and DR are typed for compatibility purposes.
How good are siblings as matches?
Each sibling has a 35% chance of being HLA-identical with the patient. Given n siblings the probability that at least one with be HLA0identical is given by the formula 1 – 3n/4n
What is the difference between low resolution and high resolution?
Serology gives low resolution (e.g. allele)
DNA gives high resolution (e.g. mutations within HLA type)
What are the principles of transplantation?
Identify disease unlikely to respond to standard treatment
Treat patient to remission
Identify a donor and collect stem cells
Give patient myeloablative therapy
Infuse stem cells
Continue immunosuppression & support patient through period of cytopenia
How do point mutations cause problems?
Within a HLA, there may be point mutations which switch things within HLA genes (e.g. within HLA-A2 gene, there may be multiple point mutations on loci which may cause a reaction)
What is the timeline of WBC in the first transplants?
(first transplants lecture)
Restricted interaction
Positive pressure ventilation
Where do HSC come from?
Bone marrow
- Aphoresis (and G-CSF) for 5 days (more than 5 days the cells go back into the bones and it doesn’t work)
- Surgery (old)
Umbilical cord/ placenta
- Foetal
Then centrifugation:
- red cells sent back
- white cells harvested
Need 2 million (CD34+) stem cells per kg of recipient weight
What are the complications of SCT?
Graft failure
Infections
Graft-versus-host disease (GVHD): allografting only
Relapse
What is GvHD?
An immune response when donor cells recognise the patient as ‘foreign’
Acute GvHD affects skin, gastrointestinal tract and liver
Chronic GvHD affects skin, mucosal membranes, lungs, liver, eyes, joints
What is this?
GvHD of the skin
Why do we get GvHD?
Alloimmune response:
Acute: cytokine storm, dead cells in radiation release loads of cytokines which causes massive inflammation
How do you stage and grade GvHD?
(picture)
What are the RFs for acute GvHD?
Degree of HLA disparity
Recipient age
Conditioning regimen
R/D gender combination
Stem cell source
Disease phase
Viral infections
What is the treatment of acute GvHD?
Corticosteroids
Calcineurin inhibitors: cyclosporin A, tacrolimus, sirolimus
Mycophenylate mofetil
Monoclonal antibodies
Photopheresis
Total lymphoid irradiation
Mesenchymal stromal cells
What is the prevention of acute GvHD?
Methotrexate
Corticosteroids
Calcineurin inhibitors: cyclosporin A, tacrolimus, sirolimus
CsA plus MTX
T-cell depletion
Post-transplant cyclophosphamide
What is Chronic GvHD?
Diagnosis within 6 months of transplant, lasts 2-5 years
85% of survivors can discontinue treatment at that time
5-year survival is 70–80%, in persons with low risk cGVHD and those responding to corticosteroids.
Five-year survival is 30–40% for those with high-risk disease +/- failure of steroids
(Immune dysregulation
Immune deficiency,
Impaired end-organ function
Decreased survival.)
What does Chronic GvHD look like?
Autoantibodies
M-skeletal
Infections
Endocrine
Metabolism
Nutrition
Pain
Quality of life
Disability
What are the RFs for chronic GvHD?
Prior acute GvHD
Increased degree of HLA disparity
Male recipient: female donor
Stem cell source (PB>BM>UCB)
T-cell replete
Older donor age
Use of DLI
Affects 50% of patients who survive >1 year from transplant
What are the main sources of neutropenic sepsis?
Vascular access (G+ve) GI tract (Gram -ve)
How do bacteria cause problems in transplant?
In neutropenic patients, the causative organism is identified in approximately one third of patients
The most frequently isolated organisms are gram positive eg, staph epidermidis
Most deaths from sepsis are due to gram negative organisms eg e.coli, pseudomonas aeruginosa
Reduced incidence of infection using isolation measures and broad spectrum oral antibiotics
How do you manage neutropenic sepsis?
Emergency situation
Defined as temperature >38 sustained for one hour, or single fever >39, in a patient with neutrophils <1.0 x 109/L
Assess patient: temperature, pulse, oxygen saturation and blood pressure. History and examination for evidence of source
Blood cultures, MSU, CXR
Initiate empirical broad spectrum antibiotics and supportive care
Where do fungi come from?
Yeasts from translocation from the intestinal mucosa, or indwelling catheters
Moulds: inhalation, chronic sinusitis, skin, mucosa
What is CMV?
Member of herpes virus family: primary infection usually as a child, remains latent
Can be reactivated if immunosuppressed
Reactivation does not always result in infection
How does CMV manifest?
Pneumonitis
Retinitis
Gastritis – colitis
Encephalitis
How do we prevent CMV?
Twice weekly quantitative monitoring of peripheral blood viraemia to day 100
Thresholds for treatment together with evidence of increasing viral load
Ganciclovir/valganciclovir: oral and IV preparations.
Minimum of 2/52 treatment with clear evidence of reduction in viral load
What are the other viral complications of SCT?
EBV: acute infection, PTLD
Respiratory viruses: influenza, parainfluenza, respiratory syncytial virus, rhino, metapneumovirus, COVID-19
PAPOVA viruses: BK and haemorrhagic cystitis
Adenovirus
What affects the outcome of transplant?
Age (20+ = 1, 40+ = 2) Disease phase (Intermediate = 1, late = 2) Gender of R/D (F to M = 1) Time to BMT (\>1yr = 1) Donor (sibling = 0, VUD = 1)
What are the pros and cons of lymphocytes in BMT?
Control infection, no leukaemia transplant BUT GvHD
How does survival change with EBMT score in allo-BMT pts in CML?
Higher score (higher mismatches) = lower survival
When patients re-transfuse with donor cells in relapse what happens?
They go back into remission
Autografting, rather than allografting, is the preferred option for treating myeloma because…
Transplant related mortality after allografting is unacceptably high in most patients with myeloma
What is the strongest prognostic factor for cGvHD?
Prior acute GvHD
When is Cytomegalovirus reactivation more common?
is more common in CMV seropositive compared to seronegative
