Optimal RBC products for RBC exchange for patients with sickle cell disease

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1 Optimal RBC products for RBC exchange for patients with sickle cell disease Stella T. Chou, MD ASFA Annual Meeting Fort Lauderdale, FL May 6, 2016

2 I have no conflicts of interest to disclose

3 Outline Apheresis program for patients with SCD requiring chronic transfusion Minority donor program for patients with SCD Rates of alloimmunization Role of RH genetic variation Delayed transfusion reactions Serologic vs DNA-based approach for blood group antigen typing of patients and donors Discuss challenges to identifying best approach for transfusion for patients with SCD

4 Erythrocytapheresis for patients with SCD at CHOP 78 active patients in 2015/ % for a neurologic indication Median age: 22 yrs, Range: 6-46 yrs Median units: 575 units, Range: units Total units: 52,253 units

5 Erythrocytapheresis for patients with SCD RBC unit selection ABO/D, prophylactic C, E, K matched RBCs Minority donor units (if possible) Hgb S negative, < 21 days old Leukoreduced, Irradiated (institutional) Alloimmunization 122 alloantibodies identified in these 78 patients Prevalence = 68% Rate = 0.23/100 units

6 Alloimmunization: current challenges Remains problematic despite phenotype matching strategies Shortens RBC survival Delayed hemolytic transfusion reactions (DTHRs) can be life-threatening Complicates crossmatching difficulty finding blood, delays transfusion labor and costs Many patients with multiple antibodies Therapy becomes impossible for some

7 Effectiveness of antigen matching Alloimmunization prevalence Rate (alloantibodies per 100 units) ABO, D 27-75% C, E, K 5-27% Jk a /Jk b, Fy a /Fy b 7% 0.1, S * Some programs only provide prophylactic antigen matching after patient forms first alloantibody Ambruso, Transfusion 1987; Rosse, Blood 1997; Vichinsky, NEJM 1990; Sakhalkar, Ann N Y Acad Sci 2005; Vinchinsky NEJM 2001; O Suoji, PBC 2013; Debaun, NEJM 2014; Chou, Blood 2013; Lasalle-Williams,Transfusion 2011; Tahhan, Transfusion 1994.

8 Alternative strategy: transfusion from minority donors Goal of many blood centers in US to increase African-American donors 26% AAs C-, E-, K-, Fya-, Jkb-, vs 2% Causcasians Blue Tie Tag Program (1995) SCD Association of America American Red Cross Children s Hospital of Philadelphia Directs blood from African-American donors to children with SCD Donors self-identify ethnicity donations/month

9 Rh antibodies most common despite Rh-matched RBCs from minority donors 182 patients, 44,482 total exposures over 15 year period Two-thirds of antibodies directed No against anti-k Rh Antibodies to antigens more common in AAs Few cases of anti-jk, -Fy Chou and Westhoff, Blood 2013

10 Alloimmunization in chronically transfused patients receiving C, E, K matched RBCs Study STOP trial Vichinsky, Transfusion 2001 (14% alloimmunized) SIT trial Debaun, NEJM 2014 (6% alloimmunized) Philadelphia single center Chou, Blood 2013 (58% alloimmunized) Alloimmunization events/100 units transfused 0.49/100 units 0.21/100 units = anti-rh 0.28/100 units 0.16/100 units = anti-rh 0.30/100 units 0.21/100 units = anti-rh # Patients # RBC units 63 patients 1830 RBC units 99 patients 3235 RBC units 123 patients RBC units Majority of antibodies made are directed against the Rh system

11 Rh blood group system Five principal Rh antigens: D, C, c, E, e Most immunogenic following ABO system RhD RhCE C/c Ser103Pro E/e Pro226Ala ce ce Ce CE C or c and E or e antigens on one protein ~60 Rh antigens defined serologically Most are specific to particular ethnic group Serologic Rh typing detects the five principal antigens

12 RHD and RHCE are inherited as haplotype Chr 1 RHD RHCE 5 SMP1 5 >500 different alleles >150 different alleles Gene Conversion RHD RHCE Generates hybrid alleles and proteins Part of RHD into RHCE, or Part of RHCE into RHD Results in partial Rh antigens with loss of Rh epitopes and/or generates new antigens 5 5 RH variants occur in ~1% Europeans Much more frequent in Africans

13 Common RH haplotype in African Blacks RHD Hybrid DIII-CE(4-7)-D RHCE ce S W16C L245V G336C D- C+ (partial) c+ (partial) e+ (partial) 20-30% of African-Americans who type C+ Problem: red cells type as C+, but >30% make anti-c when exposed to conventional C+ donor red cells Better served with prophylactic C- donor units Tournamille, Transfusion 2010

14 One-third of RHD alleles are altered in patients with SCD Deleted D RHDψ DIIIa-CE(4-7)-D RHD conventional DAU0 DAU3 DAU4 DAU5 DIIIa DIVa DIVa-3 Weak partial D 4.0 DFR DAR D(48C) Frequency DOL DWN D(835A) D(667G,800T) Partial C Type C+ At risk for anti-c Partial D Type D+ At risk for anti-d 988 patients

15 Three-fourths of RHCE*ce alleles in patients with SCD are altered ce conventional ce(48c) ce(733g) ce(48c,733g) ce(254g) ces ceti cemo cecf cehar cejal cear ceek ceti type 2 Frequency cebl ce-d(9-10) ce(733g,1006t) ce(254g,733g) ce(48c,254g,733g) Altered/partial ce antigen Type as c+ and e+ At risk for anti-e or -c At risk for anti-hr S or -hr B 988 patients

16 Altered RH is a frequent risk factor RH diversity in patients contributes to high rate of Rh alloimmunization despite Rh matched RBCs Despite Rh matching, anti-rh antibodies are most common Standard RBC antigen typing does not distinguish Rh variants Cost-effective DNA-based methods needed to improve RBC matching n=988 patients

17 % Hemoglobin S Hemoglobin (gm/dl) Delayed transfusion reactions can be clinically subtle ID 65 Anti-e Anti-e Z = Z = week intervals 3 week intervals Clinically significant DTR = a difference in % hemoglobin S or hemoglobin levels > 2 x SD of their individual mean Baseline % hemoglobin S and hemoglobin = mean pre-transfusion levels in the 6-12 months preceding the antibody detection

18 One-third of antibodies are associated with a delayed transfusion reaction 33% of antibodies were associated with laboratory evidence of DTR 171 antibodies total Specificity

19 RBC exposures at initial antibody detection 221 antibodies Median unit exposure = 91 *anti-c 1359 exposures, *anti-jsa 1299 exposures

20 Can molecular tools help optimize RBC product selection and improve transfusion outcomes?

21 Human Erythrocyte Antigen (HEA) DNA array 8 different samples miniature beads on a silicone chip First FDA-approved as test of record Used for patients and donors Detects 24 RBC SNPs associated with 38 antigens Excludes ABO and RhD # of mutations that result in Group O or RhD (-) phenotypes exceeds # of markers possible to interrogate on an array All mutations responsible for group O or RhD (-) are not known RHD arrays targeting more common RHD variants are available (RHCE as well)

22 DNA-based antigen prediction is highly reliable Compared genotype prediction with historical serological phenotype in 494 patients with SCD (13 antigens) Among 6360 antigen comparisons, 66 discrepancies (1.1%) Repeat serologic typings agreed with genotype in 64/66 cases Genotype is highly reliable primary test at our institution Casas Transfusion 2015

23 RBC genotyping refines antibody identification Antigen Positive Negative hr B U Jo a Hy Do b V VS Js a patients with SCD High prevalence antigens - Abs can appear like a warm autoantibody - Anti-hr B often has an anti-e pattern - Abs against these antigens are difficult to detect since antigen(-) RBCs rare Low prevalence in general population (<1%) % of patients with SCD antigen (+) - Similar frequency in African-American donors - Abs against these antigens may be missed since screening cells usually (-) - Serologic crossmatch incompatibility with negative antibody screen Can subsequently inform RBC unit selection Casas Transfusion 2015

24 What are next steps to improve RBC matching for patients with SCD?

25 AA donors are necessary to support transfusion therapy for SCD Would RH genotype matched RBCs be feasible?

26 African-American donors have similar RH diversity RHD frequency RHCE frequency Gene Patients AA Donors P value Gene Patients AA Donors P value Deleted D ce conventional RHDψ ce(48c) DIIIa-CE(4-7)-D ce(733g) RHD conventional ce(48c,733g) < DAU ce(254g) Weak partial D ces DIVa ceti DAU cemo DAU cecf DIIIa cear DAR ceek DOL ceti type DAU cejal DIVa ce(733g,1006t) DFR cebl D(48C) cehar RHDψ-like Ce conventional DAU CeRN D-CE(3-7)-D Ce(733G) Weak D type CeCW Weak D type ce conventional D(667G,800T) ce(48c) RHD and 22 RHCE alleles among 594 AA donors, 621 patients

27 %Patient demand met The Future: RH genotype matched RBCs is feasible D- units only for D- patients Current serologic matching RHD RHCE genetic matching Units screened per day African American donors Caucasian donors Perry Evans

28 Summary: optimal RBCs for SCD ABO/D, CEK prophylactic matched RBCs at a minimum Investigate unexpected antibodies or incompatible crossmatches to inform RBC selection RBC genotype for chronically transfused RHD, RHCE and extended blood group antigen profile Provide prophylactic C- RBCs to individuals with hybrid gene encoding partial C antigen Consider prophylactic D- RBCs for individuals with partial D expression only Raised awareness for antibodies against high or low prevalence antigens Improved NGS technology may cost and accessibility May facilitate extended matched or RH genotype matched transfusions

29 Acknowledgements CHOP David Friedman Tannoa Jackson Sarita Coleman Perry Evans Kim Smith Whitley Janet Kwiatkowski K Ohene-Fremprong Patients and families Blood bank staff NY Blood Center Connie Westhoff Sunitha Vege Penn-Jersey ARC Margaret Keller Sandra Nance Baylor College of Medicine Jonathan Flanagan Cincinnati Children s Russell Ware St. Jude Children s Jane Hankins Mitch Weiss

30 Thank you!