predicting the immunogenicity of structural hla class i epitopes reyna goodman n.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
Predicting the immunogenicity of structural HLA class I epitopes Reyna Goodman PowerPoint Presentation
Download Presentation
Predicting the immunogenicity of structural HLA class I epitopes Reyna Goodman

Loading in 2 Seconds...

play fullscreen
1 / 20

Predicting the immunogenicity of structural HLA class I epitopes Reyna Goodman - PowerPoint PPT Presentation


  • 337 Views
  • Uploaded on

Predicting the immunogenicity of structural HLA class I epitopes Reyna Goodman. Introduction. Between 5-10% of patients waiting for a renal transplant are classified as highly sensitised (Panel Reactive Activity ≥85% IgG)

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Predicting the immunogenicity of structural HLA class I epitopes Reyna Goodman' - Jimmy


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
introduction
Introduction
  • Between 5-10% of patients waiting for a renal transplant are classified as highly sensitised (Panel Reactive Activity ≥85% IgG)
  • Highly sensitised renal dialysis patients wait longer for a suitable crossmatch negative donor compared to non-sensitised patients
  • Identification of acceptable HLA mismatches increases the likelihood of transplantation
hla specific antibody screening using single antigen beads
HLA specific antibody screening using single antigen beads
  • Beads are coated with single HLA specificities
  • Each bead population has a different ratio of two dyes which allows identification of up to 100 individual HLA specificities
  • Analysed using a Luminex platform
hlamatchmaker
HLAMatchmaker
  • A computer algorithm that determines HLA compatibility at a structural level by comparing differences between polymorphic amino acid triplets in the antibody accessible region of the HLA molecule
  • HLAMatchmaker performs inter-locus and intra-locus comparisons between the patient’s HLA type and each mismatched HLA specificity and calculates the number of amino acid triplet mismatches
slide5
Aim
  • To determine whether HLAMatchmaker could be used to predict the immunogenicity of structural epitopes
    • comparing acceptable HLA mismatches identified using single antigen HLA specific antibody detection beads with those predicted using the HLAMatchmaker computer algorithm
  • To identify acceptable HLA mismatches for highly sensitised patients
patient cohort
Patient cohort

Of 406 patients on the Addenbrooke’s Hospital renal transplant waiting list, 24 were identified as highly sensitised and selected for study

data analysis
Data analysis
  • Single antigen beads detect antibody to 65 individual HLA-A and -B specificities of which 64 are represented in the HLAMatchmaker algorithm
  • Patient HLA class I types and each mismatched HLA specificity represented on the single antigen beads were entered into the HLAMatchmaker program to determine the number of triplet mismatches
  • Logistic regression analysis was used to determine the relationship between the detection of antibody using single antigen beads and the number of amino acid triplet mismatches for each HLA specificity determined by HLAMatchmaker
hla specific antibody screening using single antigen beads1
HLA specific antibody screening using single antigen beads
  • The serum sample with the highest PRA was selected for study
  • Of 1,451 mismatched HLA specificities, 972 (67%) were antibody positive
  • A mean of 19 (range 1 - 41) acceptable mismatches were identified for each patient
  • For 19 patients there were 10 or more acceptable mismatches identified including some common antigens
slide10
Logistic regression analysis of antibody binding to single HLA specificities stratified by number of triplet mismatches

% antibody positive

40

20

0

P<0.001

Number of amino acid triplet mismatches

slide11

Patient 1

Patient 2

Patient 3

Patient 4

Patient 5

Patient 6

Patient 12

Patient 7

Patient 8

Patient 9

Patient 10

Patient 11

Patient 13

Patient 14

Patient 15

Patient 16

Patient 17

Patient 18

Patient 23

Patient 24

Patient 20

Patient 21

Patient 22

Patient 19

Individual logistic regression analyses of antibody binding to single HLA specificities stratified by number of triplet mismatches

Proportion antibody positive

Number of triplet mismatches

conclusions
Conclusions
  • HLAMatchmaker is an effective tool for predicting the immunogenicity of a particular HLA mismatch
  • The number and nature of triplet mismatches for a given HLA type correlates with the risk of humoral sensitisation
  • The presence of a single triplet amino acid mismatch is often sufficient to invoke a strong antibody response
  • In combination with single antigen beads, acceptable mismatches were identified for highly sensitised patients, increasing access to the donor pool
          • Goodman et al Transplantation 2006;81:1331-1336
triplets versus eplets
Triplets versus eplets
  • Examine the extent to which the structural information provided by triplet and eplet epitope analysis of HLA compatibility enables the prediction of:
    • Acceptable mismatches
    • Magnitude of the antibody response
data analysis1
Data analysis
  • Sera obtained from 34 highly sensitised patients were screened using single antigen beads, to determine the presence and magnitude of HLA alloantibody
  • Patient HLA class I types and each mismatched HLA specificity represented on the single antigen beads were entered into the HLAMatchmaker program to determine the number of triplet and eplet mismatches
  • A total of 85 sera were screened (median 2 sera per patient, range 1 to 6) and 2,088 mismatched combinations examined
  • The qualitative and quantitative relationship between alloantibody levels to each HLA specificity and the number of triplet and eplet mismatches was determined
slide15

Frequency

Frequency

0 50 100 150 200 250 300

0 50 100 150 200 250 300

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

0 1 2 3 4 5 6 7 8 9 10 11 12 13

Triplets

Eplets

Number of triplet & eplet mismatches present within mismatched HLA specificities

P<0.001

slide16

Proportion Antibody

Positive

Proportion Antibody

Positive

P<0.001

P<0.001

P<0.001

P<0.001

Triplets

Eplets

Relationship between triplet & eplet mismatches and alloantibody production

slide17

Median Fluorescence

Intensity

Median Fluorescence

Intensity

Triplets

Eplets

Relationship between triplet & eplet mismatches and alloantibody levels

P>0.001

P>0.001

conclusions1
Conclusions
  • The number of triplet and eplet mismatches between an alloantigen and the recipient HLA type correlates closely with both the development and strength of an alloantibody response
  • Eplets offer additional epitope discrimination but do not improve HLA immunogenicity prediction
  • Self triplets and eplets may form immunogenic epitopes when expressed in a different conformation on mismatched HLA alloantigens
slide19

Acknowledgements

H&I department

Cambridge University Hospitals NHS Foundation Trust, Addenbrooke’s Hospital

Dr Craig Taylor

Miss Cheryl O’Rourke

Mr Tim Key

Department of Surgery,

University of Cambridge, Addenbrooke’s Hospital

Prof J Andrew Bradley

Mr Vasilis Kosmoliaptsis

Centre for Applied medical statistics, University of Cambridge

Mr Andrew Lynch

Dr Linda Sharples

patient follow up
Patient follow-up
  • 5/24 patients transplanted