The influence of histocompatibility on graft rejection and graft survival within a single center population of heart transplant recipients

Significance of HLA-matching and anti-HLA antibodies in heart transplant patients receiving induction therapy?

OBJECTIVES

Though Human Leukocyte Antigen (HLA) matching benefits are demonstrated in renal transplantation, evidence in heart transplantation is lacking, and its clinical feasibility is uncertain. Post-transplantation anti-HLA antibodies are being increasingly studied in organ transplantation, with diverging conclusions between transplantated organs.

METHODS

We analyzed retrospectively the influence of HLA matching and anti-HLA antibodies on overall survival, acute rejection and chronic allograft vasculopathy in 309 patients receiving induction therapy and triple-drug immunosuppression.

RESULTS

The average number of HLA-A/B/DR mismatches between donor and recipient was 4.9 ± 1. The majority of mismatches was for Class I HLA-A/B with an average of 3.3, then for Class I HLA-DR with an average of 1.6. Overall, the HLA-A/-B/-DR mismatches had no influence on the cardiac allograft survival (p = 0.28). However, HLA-DR mismatches were negatively correlated to severe cellular and/or humoral allograft rejection (p = 0.04). Our analysis found anti-HLA antibodies in 27% of recipients, de novo anti-HLA antibodies in 16% of recipients, and donor-specific anti-HLA (DSA) antibodies in 8% of recipients. Furthermore, de novo DSA had no influence on the 5-year survival (78% with DSA vs. 92% without DSA; p = 0.49), which may be masked by the limited number of recipients in analysis By univariable analysis, anti-HLA antibodies (preexisting or de novo) unrelated or related to the donor had no influence on severe cellular and/or humoral rejection or on chronic allograft vasculopathy.

CONCLUSIONS

HLA-DR mismatch was negatively correlated to severe cellular and/or humoral allograft rejection but had no influence on cardiac allograft survival. In this study, anti-HLA antibodies (preexisting or de novo) unrelated or related to the donor had no influence on cellular and/or humoral rejection or on chronic allograft vasculopathy. The results of this study add to the controversy on the impact of allo-antibodies in heart transplant recipients receiving induction therapy and contemporary immunosuppression.

Association of HLA Antigen Mismatch With Risk of Developing Skin Cancer After Solid-Organ Transplant

Importance

Risk factors for the development of skin cancer after solid-organ transplant can inform clinical care, but data on these risk factors are limited.

Objective

To study the association between HLA antigen mismatch and skin cancer incidence after solid-organ transplant.

Design, Setting, and Participants

This retrospective cohort study is a secondary analysis of the multicenter Transplant Skin Cancer Network study of 10 649 adults who underwent a primary solid-organ transplant between January 1, 2003, and December 31, 2003, or between January 1, 2008, and December 31, 2008. These participants were identified through the Scientific Registry of Transplant Recipients standard analysis files, which contain data collected mostly by the Organ Procurement and Transplantation Network. Participants were matched to skin cancer outcomes by medical record review. This study was conducted from August 1, 2016, to July 31, 2017.

Main Outcomes and Measures

The primary outcome was time to diagnosis of posttransplant skin cancer, including squamous cell carcinoma, melanoma, and Merkel cell carcinoma. The HLA antigen mismatch was calculated based on the 2016 Organ Procurement and Transplantation Network guidelines. Risk of skin cancer was analyzed using a multivariate Cox proportional hazards regression model.

Results

In total, 10 649 organ transplant recipients (6776 men [63.6%], with a mean [SD] age of 51 [12] years) contributed 59 923 years of follow-up. For each additional mismatched allele, a 7% to 8% reduction in skin cancer risk was found (adjusted hazard ratio [HR], 0.93; 95% CI, 0.87-0.99; P = .01). Subgroup analysis found the protective effect of HLA antigen mismatch to be statistically significant in lung (adjusted HR, 0.70; 95% CI, 0.56-0.87; P = .001) and heart (adjusted HR, 0.75; 95% CI, 0.60-0.93; P = .008) transplant recipients but not for recipients of liver, kidney, or pancreas. The degree of HLA-DR mismatch, but not HLA-A or HLA-B mismatch, was the most statistically significant for skin cancer risk (adjusted HR, 0.85; 95% CI, 0.74-0.97; P = .01).

Conclusions and Relevance

The HLA antigen mismatch appears to be associated with reductions in the risk of skin cancer after solid-organ transplant among heart and lung transplant recipients; this finding suggests that HLA antigen mismatch activates the tumor surveillance mechanisms that protect against skin cancer in transplant recipients and that skin cancer risk may be higher in patients who received a well-matched organ.

The Man with 2 Hearts: 25 Years from Heterotopic to Orthotopic Heart Transplantation

Substantial technological advances in mechanical circulatory support have caused a shift in the management of end-stage heart failure. From the 1970s through the 1990s, heterotopic heart transplantation was routinely performed in patients in whom orthotopic transplantation was likely to fail. Heterotopic heart transplantation is now performed less often because modern mechanical circulatory assist devices are routinely used as bridges to orthotopic transplantation; regardless, the operation has helped numerous patients who would not otherwise have received adequate allografts. We describe the case of a man with idiopathic nonischemic cardiomyopathy who, at age 17, was given an ABO- and size-matched heterotopic allograft that was a complete human leukocyte antigen mismatch. The graft functioned normally for 20 years until the patient had a myocardial infarction that necessitated placement of a coronary artery stent. Subsequent treatments involved many interventions, including insertion of an intra-aortic balloon pump, medical therapy for heart failure, implantation of a total artificial heart, and, ultimately, orthotopic transplantation. To our knowledge, our patient is the longest surviving recipient of a heterotopic heart transplant, with a remarkable 25-year graft survival despite poor histocompatibility and an almost complete lack of native heart function. The strategies used for his treatment make him a living case study that can add valuable information to the history of cardiac support.

The influence of human leukocyte antigen matching on outcomes in pediatric heart transplantation

Previous adult heart transplantation studies have demonstrated that donor-recipient human leukocyte antigen (HLA) matching results in reduced graft failure and improved patient survival. No study has examined these effects in children. This study investigated the effect of HLA matching on outcomes in pediatric heart transplantation. All pediatric heart transplantation data for patients 0-18 years of age available from the United Network for Organ Sharing Transplant Registry from 1987 to 2009 were analyzed retrospectively. Donor-recipient HLA matching at loci A, B, and DR (0-6) was compared with graft survival and recipient survival. For this study, 3,751 pediatric cardiac transplantation events with complete HLA matching data were identified and grouped as having 0 to 2 matches (3,416 events) or 3 to 6 matches (335 events). The 3- to 6-match group had less graft failure than the 0- to 2-match group (28.7% vs 34.4%; p = 0.035) and greater patient survival by 5 years (81% vs 72%; p = 0.045) and 10 years (66% vs 55%; p = 0.005) after transplantation. The HLA-DR matching alone resulted in less graft failure (p = 0.038) and improved patient survival (p = 0.017). A higher degree of HLA matching in pediatric heart transplantation is associated with decreased graft failure and improved patient survival. In this study, decreased graft failure rates and superior survival also were seen with DR matching alone.

Human leukocyte antigen matching in heart transplantation: systematic review and meta-analysis

Allocation of donors with regard to human leukocyte antigen (HLA) is controversial in heart transplantation. This paper is a systematic review and meta-analysis of the available evidence. PubMed, Embase, and the Cochrane Library were searched systematically for studies that addressed the effects of HLA matching on outcome after heart transplantation. Fifty-seven studies met the eligibility criteria. 34 studies had graft rejection as outcome, with 26 of the studies reporting a significant reduction in graft rejection with increasing degree of HLA matching. Thirteen of 18 articles that reported on graft failure found that it decreased significantly with increasing HLA match. Two multicenter studies and nine single-center studies provided sufficient data to provide summary estimates at 12 months. Pooled comparisons showed that graft survival increased with fewer HLA-DR mismatches [0-1 vs. 2 mismatches: risk ratio (RR) = 1.09 (95% confidence interval (CI): 1.01-1.19; P = 0.04)]. Having fewer HLA-DR mismatches (0-1 vs. 2) reduced the incidence of acute rejection [(RR = 0.81 (0.66-0.99; P = 0.04)]. Despite the considerable heterogeneity between studies, the short observation time, and older data, HLA matching improves graft survival in heart transplantation. Prospective HLA-DR matching is clinically feasible and should be considered as a major selection criterion.

Human leukocyte antigen-DR matching improved skin graft survival from transgenic pigs to accommodate SCID mice reconstituted with human peripheral blood mononuclear cells

The shortage of human organs has encouraged scientists to develop genetically modified pigs for xenotransplantation, such as CD55 or CD46, and CD59 transgenesis as well as alpha-galactosyl transferase gene knockouts. In allotransplantation, the match of human leukocyte antigen class II (HLA-II) may improve graft survival although the role of HLA-II in xenotransplantation is unknown. HLA-II transgenic pigs, including DP, DQ, and DR, have been successfully generated and HLA-DR15+ transgenic pig skin pieces grafted onto severe congenital immunodeficiency (SCID) mice reconstituted intraperitoneally with HLA-DR15+ or HLA-DR15(-) human peripheral blood mononuclear cells (hPBMCs). This study sought to develop an animal model to evaluate the effects of HLA-DR matching on xenograft survival. Human CD4+ and CD8+ were detected from days 7 to 29 after hPBMC reconstitution in SCID mice. Both CD4+ and CD8+ cells of HLA-DR15(-) reconstituted SCID mice were significantly higher at day 29 postgrafting compared with HLA-DR15+ reconstituted SCID mice. An HLA-DR15+ transgenic pig dermal graft survived and integrated into SCID mice reconstituted with hPBMCs/HLA-DR15+ as proven by the histopathological finding that the collagen layer remained intact with little lymphocytic response. In contrast, the transgenic pig dermal graft showed more collagen disruption as well as mild to moderate lymphocytic infiltration when reconstituted in an hPBMC/HLA-DR15(-) SCID mouse. The results suggested that HLA-DR matching eased xenograft rejection; however, it was not yet clear that the response was mediated by T cells.

Long-term survival of HLA-DR15+ pig skin in SCID mice after reconstitution with human peripheral blood mononuclear cells and under short-term immunosuppression

In allotransplantation, donor-recipient human leukocyte antigen (HLA) matches improve graft survival. For studies of the role of donor-recipient HLA II matching on xenotransplantation, we successfully generated HLA-DR15+ transgenic pigs the the skins of which were transplanted to SCID mice, which were thereafter reconstituted with HLA-DR15+ or -DR15(-) hPBMC. Cyclosporine was given intraperitoneally to SCID mice for 12 days. Human T cells were observed in SCID mice after reconstitution. Mixed lymphocytes responses showed greater responses by HLA-DR15(-) human peripheral blood mononuclear cells (hPBMC) against HLA-DR15+ porcine PBMC. HLA-DR15+ porcine skins survived more than 100 days in all SCID mice. HLA-DR15+ porcine skins were rejected in all non-SCID (Balb/c) mice. The histologic pictures of transplanted HLA-DR15+ porcine skins showed surviving porcine epithelium in remodeling murine dermis and little lymphocyte infiltration into the murine dermis. The long-term survival of HLA-DR15+ pig skin in all hPBMC-SCID mice might be due to poor engraftment or function of reconstituted T cells. Further studies are needed to clarify the role of donor-recipient matching of HLA-DR15.

The MDR1/ABCB1 Gene, a High-Impact Risk Factor for Cardiac Transplant Rejection

BACKGROUND

Variations in the expression and activity levels of the multidrug-resistance MDR1/ABCB1 encoded P- glycoprotein (P-gp) have an impact on the therapeutic efficacy of many drugs. C3435T and G2677 polymorphisms of the MDR1/ABCB1 gene correlate with cellular expression levels of P-gp, a membrane-bound efflux pump which removes a multitude of drugs, including chemotherapy drugs and immunosuppressants, from cells. We aimed to investigate whether the phenomenon of drug resistance, mediated by the MDR1/ABCB1 gene and seen in tumor cells to chemotherapeutic agents, is important in the field of transplantation, predisposing some patients to resistance to immunosuppressants.

METHODS

G2677 and C3435T polymorphisms of the ABCB1 gene were determined by PCR in 170 heart transplant recipients. We examined the relationship between MDR1/ABCB1 polymorphisms and endomyocardial biopsy-proven rejection (EBPR) determined by biopsy performed at set intervals according to a standard protocol.

RESULTS

A significant relationship was found between a patient's C3435T genotype and freedom from first grade > or =3A rejection episode. 3435-CC recipients were 1.8 times (1.05-3.09; P = 0.03) more likely to undergo a > or =3A rejection episode in the first 12 months. Haplotypes derived from the G2677 and C3435T polymorphisms (GG/CC, GT/CT and TT/TT) amplified this phenomenon further (log rank, P = 0.03; HR 2.18; 1.21-4.26; P = 0.02).

CONCLUSIONS

ABCB1 polymorphisms correlate with freedom from grade > or =3A EBPR and we believe that this may be attributed to MDR1/ABCB1 encoded P-gp mediating the efflux of immunosuppressants out of leukocytes, with depleted immunosuppressant levels in leukocytes manifesting as increased cellular rejection.

Protein expression of lymphocytes in HLA-DR transgenic pigs by a proteomic approach

Matching donor and recipient human leucocyte antigen (HLA-II) could conquer cell-mediated rejection following transplantation. Transgenic pigs carrying HLA genes that "humanize" porcine organs, tissues, and cells were successfully generated. This study further clarifies the effect of HLA-DR transgenes on lymphocyte protein expression, via a proteomic approach. Lymphocytes were isolated from two HLA-DR transgenic pigs and three nontransgenic littermates on 157 d after birth. Soluble protein of 1x10(7) cells was separated using 2-DE. In total, 301 colloidal CBB-stained protein spots detected on all five 2-D gels were quantified. Thirty-three proteins were differentially expressed by a factor of 1.5. These proteins were subsequently identified by MALDI-TOF MS and MALDI-TOF/TOF MS/MS. These proteins were sorted into the following categories: chaperones, T-lymphocyte function, DNA/RNA processing, cytoskeleton-associated proteins, signal transduction, enzymes, and unknown. Previous studies have suggested that some of the identified proteins are associated with lymphocyte activation/proliferation. The identities of the unidentified spots and the systematic effect of these up- and down-regulated proteins on T-cell function in HLA-DR transgenic pigs require further exploration.

Clinical determinants of ventricular sympathetic reinnervation after orthotopic heart transplantation

BACKGROUND

It has been demonstrated that ventricular sympathetic reinnervation after cardiac transplantation improves exercise performance. The extent of reinnervation increases with time but is variable. Little is known about other influencing factors.

METHODS AND RESULTS

Seventy-seven nonrejecting transplant recipients were cross-sectionally studied by PET with the catecholamine analogue C-11 hydroxyephedrine at 4.8+/-3.5 years after transplantation. Results were compared with history-derived parameters related to recipient's clinical course before, during, and after surgery; donor characteristics; and immunogenetics. Partial reinnervation was observed in 52 patients (extent, 21+/-16% of left ventricle). Complete denervation was found in 25 patients at various times after transplantation. Reinnervation extent correlated with time after surgery (r=0.387; P<0.001) but also inversely with donor age (r=-0.309, P=0.006) and recipient age (r=-0.243, P=0.032). Maximal hydroxyephedrine retention correlated inversely with frequency of rejection episodes (r=-0.267, P=0.019), was reduced when aortic complications occurred perioperatively (9 patients), and correlated inversely with aortic cross-clamp time (r=-0.331, P=0.006). Other parameters were not associated with reinnervation. Patients were surveyed for clinical complications over >12 months after PET (until 7.3+/-4.2 years after transplantation), but significant effects of reinnervation on outcome were not observed.

CONCLUSIONS

The present data suggest that sympathetic reinnervation after cardiac transplantation is not simply a function of time. Reinnervation is more likely with young age, fast and uncomplicated surgery, and low rejection frequency. Despite few effects on prognosis in otherwise healthy recipients, improved understanding of clinical determinants may contribute to enhance allograft reinnervation and thereby augment exercise capacity in the future.

Reduction of human-to-pig cellular response by alteration of porcine MHC with human HLA DPW0401 exogenes

BACKGROUND

In pig-to-human discordant xenotransplantation, the xenograft can be rejected by a formidable human xenogenic T-cell response, even if the graft has gone through hyperacute rejection or delayed xenograft rejection (acute vascular rejection). We therefore examined, in this study, whether the human-to-pig cellular response could be attenuated through the generation of a transgenic pig for human HLA II.

METHODS

With the technique of microinjection, we produced the HLA DPw0401 transgenic pig. The expression of the HLA DPw0401 gene on peripheral blood mononuclear cells (PBMCs) of the transgenic pig was examined by reverse transcriptase-polymerase chain reaction and flow cytometry. The antigenicity of the transgenic HLA DPw0401 molecule was tested by the HLA DPw0401-primed lymphocyte test reagent. The cellular response was analyzed by xenogenic mixed lymphocyte culture.

RESULTS

The mRNA and protein of HLA DPw0401 were expressed in the PBMCs of the transgenic pig. The PBMCs of the HLA transgenic pig induced a stronger cellular reaction to HLA DPw0401-primed lymphocyte test reagents than the nontransgenic littermate pig (n=7, P<0.01). In direct xenogenic mixed lymphocyte culture with responders from HLA DPw0401(+) humans, the PBMCs from the HLA DPw0401 transgenic pig, as compared with those from the normal pig, induced a lower degree of xenogenic cellular response to human PBMCs (n=4, P=0.08).

CONCLUSIONS

Our preliminary data demonstrated the possibility that the human HLA DPw0401 phenotype can be transferred onto porcine cells through the generation of HLA transgenic pigs and make the PBMCs of humans more tolerant to porcine cells.