Strategies to help highly sensitised patients get a

transplant

Derek O’Neill

National Histocompatibility & Immunogenetics Service for Solid Organ Transplantation, Beaumont Hospital, Dublin

Overview

• HLA antibodies - what are they and where do they come from?

• Different patterns of antibody formation• Why are HLA antibodies important?• Can we get rid of HLA antibodies?• Does this work?• Strategies to get Highly Sensitised

Patients transplanted!

Strategies

• Acceptable Mismatch Programme• Living Donors• Desensitisation• Risk Assessments of individual patients and a

transplant planMost recent approach:• For 100% PGen Patients – a different risk

assessment to identify potential donors with a higher rejection risk than an antibody compatible donor but still feasible to do

How Big is the Problem?

Currently we have 540 patients on the renal waiting list

112 patients have a PGen of 100%50 patients have PGens between 95 – 99%

30% of our patient population is by our definition Highly Sensitised

What do the terms mean?

• PRA - Panel Reactive Antibodies or it can be referred to as Percentage Reactive Antibodies.

• PGen - as you will find it on our tranpoollistings is the equivalent of PRA over the patient’s lifetime.

• PGen – is calculated by comparing the HLA antibodies that a patient has and seeing how many of 1,000 Irish donors would have been unsuitable for that patient.

• It is the best measure of how difficult it will be to find an antibody compatible donor for them.

With100 donors

PGen = 0% all 100 donors would be HLA compatible

PGen = 99% only 1 donor statistically in the 100 donors would be HLA compatible

• PGen = 100%

• Actually this does not mean that NOdonors would be suitable despite what I have been saying - what it actually means is that less than 1% of donors will be suitable - hence the patients wait a long time.

How do we detect antibodies?

• We use Luminex technology to detect HLA antibodies

• Like all assays it isn’t perfect but currently it is the best there is.

• Lets review what you find on patients cells

No assay is perfect!Crossmatch

Thousands of Different cell surface proteins Positive result if antibodies to any of themOnly relevant if anti-HLA

Luminex Beads

Covered with HLA moleculesSome native, some denaturedAmount of HLA varies between beads & batchesOnly relevant if to native HLA

• Since we know that no assay is perfect we use them in combination to assess the risk.

• >30% of all transplants done here are through positive crossmatches as long as the antibody assays show no DSA. Standard Risk and unique to this centre.

What causes HLA antibodies?

They are formed due to• Pregnancy• Transfusion including platelets• Previous allograft• Previous heart valve graft/ bone graft• Infection

Antibody production - boosting

A1 B44 Dr5 A2 B8 Dr5

A1 B44 Dr5 + A2 B8 Dr5

Tf Tf

100 %Patient 1

Patient 2

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• If an antibody has ‘gone away’ is it still important and why?

• YES because of Immunological Memory and Amnestic responses

• B memory lymphocytes are thought to live up to 40+ years

Different Antibody Patterns

• Different patients as you have seen show different patterns of antibody production.

• Constant production• Sporadic production• A mix of both

Definitions

• What is a highly sensitised patient?

• Traditionally it was regarded as anyone with a PRA >80% or 85%

• However as I am about to show you -audits of the transplants here in Beaumont tell us differently for our population.

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Transplants 2005 to April 2009

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So that resulted in defining 4 different categories of patient in our service.

1 – PGen = 0% Negative 2 – Pgen 1 – 49% Low or Moderate

Sensitisation3 – PGen 50 – 94% Significantly Sensitised4 – PGen 95 – 100% Highly Sensitised

Strategy 1 to transplant them

• The next thing we did was to adjust the computer algorithms in our matching program as follows:

For any given donor the computer searches for Significantly Sensitised Patients who are suitable and lists them separately

Strategy 1

It then searches the active list of patients for those Highly Sensitised Patients who are compatible regardless of HLA match and lists them in the Acceptable Mismatched Category.

Strategy 1

• The ranking order of patients on the Donor Offer lists were readjusted in priority and now is:

• ABO/SPK Patients• Paediatric Patients• Acceptable Mismatched Patients • Significantly Sensitised Patients• ETC

Strategy 2 - Living Donors

• For a highly sensitised patient especially a patient with 100% PGen the best option is a fully matched HLA identical sibling. No risk of rejection due to HLA.

• For 100% PGen patients we will even consider the option of an ABO incompatible transplant

Strategy 3 - Desensitisation

• About 8 years back over a three year period we did a trial on desensitisation.

• Rx: Rituxumab, Plasma Exchange x 5 six weeks later. High dose IvIg monthly and full high level HLA antibody monitoring monthly

Desensitisation

• 15 patients in total were enrolled 3 – 4 at any given time. Crossmatched against every ABO compatible donor.

• Tough on the patients – one patient went through the process twice and ended up in ICU with sepsis

• 2 severe haemorrhages at time of transplant

• High expected level of AMR with rescue treatment

Desensitisation

• 14 of the 15 patients were eventually transplanted.

• All except the last patient functioned almost immediately, so for the first three years we had 100% 1 year graft survival.

• However, when we looked at the 5 year graft survival a different picture emerged.

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Desensitisation

• Really it wasn’t a good strategy

• Class II antibodies proved extremely difficult to remove

• All patients had recurrence of the antibodies removed before the transplant

• All patients developed symptoms of accelerated chronic rejection rapidly

Strategy 3

In rare cases we have removed a very low level antibody prior to a living donor transplant when it was Class I.

Where to now?

• So we needed to develop another approach to transplanting this cohort of patients.

• We were aware that not all antibodies detected were clinically significant so we set up a study to determine what antibodies were important.

Patients

• 204 Patients transplanted between 1998 and 2007– 30 blood transfusions only– 56 pregnancy +/- transplant. – 103 previous transplant(s).

• 15 patients biopsy-proven antibody mediated rejection.

We tested the patients using two different kits on the premise that if both kits detected the antibody then it was probably real and significant.

We subsequently tested the patients with the C1q kit to determine complement fixing ability of the antibodies.

Results

• 59 DSA - both One Lambda and Genprobe SAB.

• 34 DSA - One Lambda only (Single Technique Antibody)

• 19 DSA - Genprobe only (STA)• 92 negative by both SAB assays

Renal Allograft Survival

Negative both assays

Graft Survival

Graft Survival

p

P = 0.027

Graft Survival

3 months 1 year 3years 5years 10 years

DSA+C1q+

n=13

78 71 64 64 55

DSA+C1q-

n=46

91 85 82 76 67

No sig.

Abs.

n=145

98 97 94 86 80

% median graft survival

AMR

• 3 negative for DSA• 12 positive for DSA

– 3 C1q positive (all failed within 4 months)– 9 C1q negative ( 4 failed within 6 months;

5 long term survivors)

Strategy 4

• Category of patients who get this High Level Screening and monitoring:

• ABO Patients• Paediatrics• In the Living Donor assessments • 100% ‘Adopted’ Patients

Results for Patients

• 2010 we transplanted 8 patients from Living Donors and 2 more with deceased donors with STAs.

• 2011 – 7 Living Donor transplants and 3 from deceased donors with STAs

• 2012 – 4 Living Donor transplants and 2 from deceased donors with STAs so far.

Strategy 5

The ‘ADOPT A 100% Percenter’

campaign!

• Criteria:

• PGen = 100%

• Self Modulating patients – i.e. not all antibodies still circulating currently

• Adopted by length of time on the pool

What do we do?

• The chosen patients are assessed by all of our antibody screening techniques i.e. Luminex Single Antigen screening by both Kits.

• C1q screening by Luminex if appropriate• CDC screening if appropriate

• Review of every antibody they have listed as unacceptable

• How strong is it ?• Is it confirmed or an STA• Is it still circulating?• When was it last seen?• What caused the sensitisation i.e. previous

transplant, transfusion, pregnancy?

• Transplantation is possible though historic antibodies, however, it does come with a higher rejection risk than an antibody compatible transplant.

• The immunosuppression needs to be increased.

But it could well be a 100% PGen person’s only chance

Increased Risk TransplantsConfirmed DSA

• 2009 – 2 patients transplanted with DSA (One desensitised)

• 2010 – 6 patients transplanted with DSA• 2011 – 1 patient transplanted with DSA• 2012 – 2 patients transplanted with DSA

Except in 1 case all DSA was negative for over 12 months

• Round 1 of the ‘Adoptions’ saw 17 patients assigned to the experienced scientists in the department.

• When the review is finished – it then goes to myself and our immunologists for final decisions – more testing may be requested.

• The process is expensive and time consuming -our estimate is approx. 8 days per patient

• To date 14 of the reviews are complete

Round 1 – the changes made

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Round 2

• The round 2 patients have been adopted and their reviews start in January.

• We hope to get a minimum of 25 done during the year.

So are we having any success with the different

strategies?

It is succeeding!

• 100% patients– 2 (1 from the ‘Adopted’ Review and 1

routinely)– 3 from living donors.

• Acceptable Mismatch Programme 95-99%– 5 from deceased donors

– 1 from a living donor.

We are really pleased!

• Significantly Sensitised Programme >50%– 43 from deceased donors

– 9 from living donors

Total of 149 transplants year to date

Total highly or significantly sensitised patients transplanted = 63 (42% of Txs)

Targeting these Difficult Patients

Our strategies:• Ranking system in the matching

programme• Risk assessments for STAs• Desensitisation• Increased risk protocol and cross historic

DSA for selected patients• Living Donor programme

Thank You

These strategies result from collaboration of all the multi-

disciplinary team and are definitely showing benefit

for the patients!