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A-Antigen Specific Tolerance in a Novel Transgenic Mouse Model of ABO-Incompatible Heart Transplantation (ABOi HTx)
S176
The Journal of Heart and Lung Transplantation, Vol 34, No 4S, April 2015
4( 64) A-Antigen Specific Tolerance in a Novel Transgenic Mouse Model of ABO-Incompatible Heart Transplantation (ABOi HTx) B. Motyka,1 K. Labonte,1 F.H. Rahman,1 J. Pearcey,1 K. Tao,1 M. Mengel,2 B. Sis,3 P.J. Cowan,4 L.J. West .5 1Pediatrics, Alberta Transplant Institute, University of Alberta, Edmonton, AB, Canada; 2Laboratory Medicine & Pathology, Alberta Transplant Institute, University of Alberta, Edmonton, AB, Canada; 3Laboratory Medicine & Pathology, University of Alberta, Edmonton, AB, Canada; 4St Vincent’s Hospital, Melbourne, Australia; 5Pediatrics, Surgery and Medical Microbiology & Immunology, Alberta Transplant Institute, University of Alberta, Edmonton, AB, Canada. Purpose: ABOi HTx can be performed safely in infants when ABO antibody (Ab) levels are low or absent. Following ABOi HTx, immune tolerance develops to the donor A/B antigen(s) by mechanisms not well understood. For further study of ABO-related immunobiology in the transplant setting, we generated transgenic mice (A-Tg, C57BL/6 [B6] background) expressing blood group A-antigen on vascular endothelium, and modeled ‘A into O’ ABOi HTx using A-Tg mice as donors and B6 wild-type (WT) mice as recipients. We previously showed in adult WT recipients with anti-A Ab that A-Tg heart grafts undergo Ab-mediated rejection (AMR). We hypothesized that, in contrast, exposure of young WT mice without anti-A Ab to A-antigen-expressing grafts will result in tolerance induction. Methods: WT mice were transplanted at 4 wk of age with A-Tg hearts (n= 12); serum anti-A Ab were measured every 2 wk by agglutination assay. Transplanted mice and non-transplanted littermates (n= 1 2) were injected with human A-erythrocytes (A-RBC) at either 11 or 17 wk of age to ‘break’ tolerance. Graft survival was evaluated by palpation and by histology for morphological and immunophenotypical features of AMR. Results: Serum anti-A Ab were detected in only 2/12 transplanted mice at very low titre (1:4), whereas 7/12 non-transplanted littermates produced anti-A Ab (median titre 1:8). Following A-RBC injection, anti-A Ab were detected in 6/12 transplanted mice, however titres remained low (median titre 1:4). All grafts survived with a maximal palpation score. No grafts showed morphological features of AMR, however three grafts showed focal C4d deposition. In contrast, in non-transplanted littermates injection of A-RBC resulted in sensitization, inducing production of high titre anti-A Ab in all mice (median titre 1:512). Conclusion: Lack of anti-A Ab production in most transplant recipients compared to non-transplanted littermates, together with failure of A-RBC injection to sensitize transplanted mice substantially, suggests that exposure of juvenile mice to graft A-antigens resulted in A-antigen specific tolerance induction. The absence of graft damage in recipients that produced detectable but low titre anti-A Ab suggests combined partial tolerance and graft accommodation. This mouse model will prove useful for addressing cellular mechanisms of tolerance/accommodation in ABOi HTx. 4( 65) BAG3 Variant Is Associated With Ventricular Remodeling But Not Clinical Outcomes in Chronic Heart Failure E. Vorovich ,1 B. French,1 R. Hu,1 M. Morley,1 J. Brandimarto,1 S.E. Kimmel,2 T.P. Cappola.1 1Penn Cardiovascular Institute, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA; 2Department of Biostatistics and Epidemiology, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA. Purpose: Common genetic variants at 1p36 (rs1739843), 6p21 (rs9262636) and 10q26 (rs2234962) show replicated associations with heart failure (HF) risk. We hypothesized that these variants would associate with HF severity and clinical outcomes in chronic HF. Methods: We performed genome-wide genotyping in a subcohort of 1334 genetically-inferred Caucasians of a multi-center cohort of chronic HF outpatients. We used multivariable regression models to test the association between risk alleles at rs1739843, rs9262636, and rs2234962 and measures of cardiac remodeling (ejection fraction, EF; left ventricular end-diastolic dimension index, LVEDDI), NYHA class, and markers of HF severity (systolic blood pressure; serum sodium, SNa; brain natriuretic peptide; soluble toll-like receptor 2). Associations between variants and the composite
endpoint of time to heart transplantation, ventricular assist device implantation, or all-cause death were assessed using Cox regression models. Subgroup analyses were performed stratified by HF etiology. Results: The rs1739843 variant, which is in linkage disequilibrium with a common variant in the CLCNKA renal chloride channel, associated with SNa [+0.34 mEq/L, 95% CI: (0.07 to 0.60), p= 0.014], but not with other cross-sectional measures or outcomes. The rs9262636 variant, which lies within the major histocompatibility complex region, showed no statistically significant associations in cross-sectional or outcome analyses. The rs2234962 variant, a non-synonymous variant in the cytoprotective protein BAG3, associated with EF [-3.2%, 95% CI (-1.6 to - 4.5), p< 0.001] and LVEDDI [+0.9 mm/m2, 95% CI (0.2 to 1.6), p= 0.012]. A priori stratified analyses by HF etiology revealed associations among the non-ischemic subgroup only [EF -4.9%, 95% CI: (-2.7 to -7.2), p< 0.001; LVEDDI 1.4 mm/m2, 95% CI: (0.2 to 2.1), p= 0.016]. The rs2234962 variant was not associated with clinical outcomes. Conclusion: The rs2234962 variant in BAG3, a cytoprotective co-chaperone involved in myocyte integrity, shows significant associations with indexes of ventricular remodeling, particularly in non-ischemic HF. Although variants at all 3 loci are associated with HF risk, they do not have meaningful effects on clinical outcomes. 4( 66) Withdrawn 4( 67) Clinical Outcomes in Patients Receiving Simultaneous Heart and Abdominal Organ Transplantation S. Fedson ,1 C. Murks,1 L. Potter,2 s. Qamar,1 T. Riley,1 G. Kim,1 G. Sayer,1 N. Uriel,1 T. Ota,3 V. Jeevanandam.3 1Medicine, University of Chicago, Chicago, IL; 2Pharmacy, University of Chicago, Chicago, IL; 3Surgery, University of Chicago, Chicago, IL. Purpose: Simultaneous organ transplant accounts for a small fraction of transplants, and is controversial about the fairness of organ allocation, and patient and graft survival. The purpose of this study was to look at the clinical outcome of patients receiving a simultaneous multi organ transplant (sMOT) at the time of heart transplant, and the effect of the recipient age. Methods: 59 patients with at least one year of follow up who underwent sMOT at a single center were included in this retrospective study in accordance with the local IRB. Demographic information, and transplant data, such as panel reactive antibody (PRA), EMB results, and patient survival were collected from the medical records. Patients were grouped into age tertiles for analysis. Results: Of the 59 patients, there were 41 heart kidney (HK), 9 heart liver (HL), 4 heart liver kidney, 4 heart kidney pancreas and one heart pancreas. Patient survival is shown below. There was no difference in survival by donor age, CIT or PRA. 3 HK developed ESRD. There was one acute liver rejection in an HL without cardiac rejection. There was no cardiac rejection greater than a 1B in all patients, and no humoral rejection. For the triple sMOT, mean survival was 7.5yrs in 4/8 pts. Conclusion: sMOT is reasonable to consider with acceptable survival in patients younger than 60. This finding warrants more analysis and may affect patient selection criteria for patients with multi-organ disease.
Survival by Organs and Age Tertiles
Number Age Sex (M/F) Survival All ages 19-49 (n= 21 50-60 (n= 21) 61-67 (n= 17)
All
HK
HL
59 52.9 ± 11.6 47/12
41 54.5 ±12.3 31/10
9 47.7 ± 8.5 8/1
6.03 ± 4.46 8.42 ± 4.56 5.34 ± 3.91 3.92 ± 3.79
5.41 ± 4.2 6.91 ± 4.55 (n= 11) 5.45 ± 4.22 (n= 16) 4.18 ± 3.80 (n= 14)
6.57± 2.99 7.91± 2.07 (n= 6) 5.52± 0.94 (n= 2) 0.57 (n= 1)
The Journal of Heart and Lung Transplantation, Vol 34, No 4S, April 2015
4( 64) A-Antigen Specific Tolerance in a Novel Transgenic Mouse Model of ABO-Incompatible Heart Transplantation (ABOi HTx) B. Motyka,1 K. Labonte,1 F.H. Rahman,1 J. Pearcey,1 K. Tao,1 M. Mengel,2 B. Sis,3 P.J. Cowan,4 L.J. West .5 1Pediatrics, Alberta Transplant Institute, University of Alberta, Edmonton, AB, Canada; 2Laboratory Medicine & Pathology, Alberta Transplant Institute, University of Alberta, Edmonton, AB, Canada; 3Laboratory Medicine & Pathology, University of Alberta, Edmonton, AB, Canada; 4St Vincent’s Hospital, Melbourne, Australia; 5Pediatrics, Surgery and Medical Microbiology & Immunology, Alberta Transplant Institute, University of Alberta, Edmonton, AB, Canada. Purpose: ABOi HTx can be performed safely in infants when ABO antibody (Ab) levels are low or absent. Following ABOi HTx, immune tolerance develops to the donor A/B antigen(s) by mechanisms not well understood. For further study of ABO-related immunobiology in the transplant setting, we generated transgenic mice (A-Tg, C57BL/6 [B6] background) expressing blood group A-antigen on vascular endothelium, and modeled ‘A into O’ ABOi HTx using A-Tg mice as donors and B6 wild-type (WT) mice as recipients. We previously showed in adult WT recipients with anti-A Ab that A-Tg heart grafts undergo Ab-mediated rejection (AMR). We hypothesized that, in contrast, exposure of young WT mice without anti-A Ab to A-antigen-expressing grafts will result in tolerance induction. Methods: WT mice were transplanted at 4 wk of age with A-Tg hearts (n= 12); serum anti-A Ab were measured every 2 wk by agglutination assay. Transplanted mice and non-transplanted littermates (n= 1 2) were injected with human A-erythrocytes (A-RBC) at either 11 or 17 wk of age to ‘break’ tolerance. Graft survival was evaluated by palpation and by histology for morphological and immunophenotypical features of AMR. Results: Serum anti-A Ab were detected in only 2/12 transplanted mice at very low titre (1:4), whereas 7/12 non-transplanted littermates produced anti-A Ab (median titre 1:8). Following A-RBC injection, anti-A Ab were detected in 6/12 transplanted mice, however titres remained low (median titre 1:4). All grafts survived with a maximal palpation score. No grafts showed morphological features of AMR, however three grafts showed focal C4d deposition. In contrast, in non-transplanted littermates injection of A-RBC resulted in sensitization, inducing production of high titre anti-A Ab in all mice (median titre 1:512). Conclusion: Lack of anti-A Ab production in most transplant recipients compared to non-transplanted littermates, together with failure of A-RBC injection to sensitize transplanted mice substantially, suggests that exposure of juvenile mice to graft A-antigens resulted in A-antigen specific tolerance induction. The absence of graft damage in recipients that produced detectable but low titre anti-A Ab suggests combined partial tolerance and graft accommodation. This mouse model will prove useful for addressing cellular mechanisms of tolerance/accommodation in ABOi HTx. 4( 65) BAG3 Variant Is Associated With Ventricular Remodeling But Not Clinical Outcomes in Chronic Heart Failure E. Vorovich ,1 B. French,1 R. Hu,1 M. Morley,1 J. Brandimarto,1 S.E. Kimmel,2 T.P. Cappola.1 1Penn Cardiovascular Institute, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA; 2Department of Biostatistics and Epidemiology, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA. Purpose: Common genetic variants at 1p36 (rs1739843), 6p21 (rs9262636) and 10q26 (rs2234962) show replicated associations with heart failure (HF) risk. We hypothesized that these variants would associate with HF severity and clinical outcomes in chronic HF. Methods: We performed genome-wide genotyping in a subcohort of 1334 genetically-inferred Caucasians of a multi-center cohort of chronic HF outpatients. We used multivariable regression models to test the association between risk alleles at rs1739843, rs9262636, and rs2234962 and measures of cardiac remodeling (ejection fraction, EF; left ventricular end-diastolic dimension index, LVEDDI), NYHA class, and markers of HF severity (systolic blood pressure; serum sodium, SNa; brain natriuretic peptide; soluble toll-like receptor 2). Associations between variants and the composite
endpoint of time to heart transplantation, ventricular assist device implantation, or all-cause death were assessed using Cox regression models. Subgroup analyses were performed stratified by HF etiology. Results: The rs1739843 variant, which is in linkage disequilibrium with a common variant in the CLCNKA renal chloride channel, associated with SNa [+0.34 mEq/L, 95% CI: (0.07 to 0.60), p= 0.014], but not with other cross-sectional measures or outcomes. The rs9262636 variant, which lies within the major histocompatibility complex region, showed no statistically significant associations in cross-sectional or outcome analyses. The rs2234962 variant, a non-synonymous variant in the cytoprotective protein BAG3, associated with EF [-3.2%, 95% CI (-1.6 to - 4.5), p< 0.001] and LVEDDI [+0.9 mm/m2, 95% CI (0.2 to 1.6), p= 0.012]. A priori stratified analyses by HF etiology revealed associations among the non-ischemic subgroup only [EF -4.9%, 95% CI: (-2.7 to -7.2), p< 0.001; LVEDDI 1.4 mm/m2, 95% CI: (0.2 to 2.1), p= 0.016]. The rs2234962 variant was not associated with clinical outcomes. Conclusion: The rs2234962 variant in BAG3, a cytoprotective co-chaperone involved in myocyte integrity, shows significant associations with indexes of ventricular remodeling, particularly in non-ischemic HF. Although variants at all 3 loci are associated with HF risk, they do not have meaningful effects on clinical outcomes. 4( 66) Withdrawn 4( 67) Clinical Outcomes in Patients Receiving Simultaneous Heart and Abdominal Organ Transplantation S. Fedson ,1 C. Murks,1 L. Potter,2 s. Qamar,1 T. Riley,1 G. Kim,1 G. Sayer,1 N. Uriel,1 T. Ota,3 V. Jeevanandam.3 1Medicine, University of Chicago, Chicago, IL; 2Pharmacy, University of Chicago, Chicago, IL; 3Surgery, University of Chicago, Chicago, IL. Purpose: Simultaneous organ transplant accounts for a small fraction of transplants, and is controversial about the fairness of organ allocation, and patient and graft survival. The purpose of this study was to look at the clinical outcome of patients receiving a simultaneous multi organ transplant (sMOT) at the time of heart transplant, and the effect of the recipient age. Methods: 59 patients with at least one year of follow up who underwent sMOT at a single center were included in this retrospective study in accordance with the local IRB. Demographic information, and transplant data, such as panel reactive antibody (PRA), EMB results, and patient survival were collected from the medical records. Patients were grouped into age tertiles for analysis. Results: Of the 59 patients, there were 41 heart kidney (HK), 9 heart liver (HL), 4 heart liver kidney, 4 heart kidney pancreas and one heart pancreas. Patient survival is shown below. There was no difference in survival by donor age, CIT or PRA. 3 HK developed ESRD. There was one acute liver rejection in an HL without cardiac rejection. There was no cardiac rejection greater than a 1B in all patients, and no humoral rejection. For the triple sMOT, mean survival was 7.5yrs in 4/8 pts. Conclusion: sMOT is reasonable to consider with acceptable survival in patients younger than 60. This finding warrants more analysis and may affect patient selection criteria for patients with multi-organ disease.
Survival by Organs and Age Tertiles
Number Age Sex (M/F) Survival All ages 19-49 (n= 21 50-60 (n= 21) 61-67 (n= 17)
All
HK
HL
59 52.9 ± 11.6 47/12
41 54.5 ±12.3 31/10
9 47.7 ± 8.5 8/1
6.03 ± 4.46 8.42 ± 4.56 5.34 ± 3.91 3.92 ± 3.79
5.41 ± 4.2 6.91 ± 4.55 (n= 11) 5.45 ± 4.22 (n= 16) 4.18 ± 3.80 (n= 14)
6.57± 2.99 7.91± 2.07 (n= 6) 5.52± 0.94 (n= 2) 0.57 (n= 1)