Reduction of cellular rejection and increase in longer-term survival after heart transplantation after HLA-DR matching

Exploring personalized treatment for cardiac graft rejection based on a four-archetype analysis model and bioinformatics analysis

Heart transplantation is the gold standard for treating patients with advanced heart failure. Although improvements in immunosuppressive therapies have significantly reduced the frequency of cardiac graft rejection, the incidences of T cell-mediated rejection (TCMR) and antibody-mediated rejection remain almost unchanged. A four-archetype analysis (4AA) model, developed by Philip F. Halloran, illustrated this problem well. It provided a new dimension to improve the accuracy of diagnoses and an independent system for recalibrating the histology guidelines. However, this model was based on the invasive method of endocardial biopsy, which undoubtedly increased the postoperative risk of heart transplant patients. Currently, little is known regarding the associated genes and specific functions of the different phenotypes. We performed bioinformatics analysis (using machine-learning methods and the WGCNA algorithm) to screen for hub-specific genes related to different phenotypes, based Gene Expression Omnibus accession number GSE124897. More immune cell infiltration was observed with the ABMR, TCMR, and injury phenotypes than with the stable phenotype. Hub-specific genes for each of the four archetypes were verified successfully using an external test set (accession number GSE2596). Logistic-regression models based on TCMR-specific hub genes and common hub genes were constructed with accurate diagnostic utility (area under the curve > 0.95). RELA, NFKB1, and SOX14 were identified as transcription factors important for TCMR/injury phenotypes and common genes, respectively. Additionally, 11 Food and Drug Administration-approved drugs were chosen from the DrugBank Database for each four-archetype model. Tyrosine kinase inhibitors may be a promising new option for transplant rejection treatment. KRAS signaling in cardiac transplant rejection is worth further investigation. Our results showed that heart transplant rejection subtypes can be accurately diagnosed by detecting expression of the corresponding specific genes, thereby enabling precise treatment or medication.

The impact of human leukocyte antigen mismatch on recipient outcomes in living-donor liver transplantation

Donor-recipient human leukocyte antigen (HLA) compatibility has not been considered to significantly affect liver transplantation (LT) outcomes; however, its significance in living-donor LT (LDLT), which is mostly performed between blood relatives, remains unclear. This retrospective cohort study included 1954 LDLTs at our institution (1990-2020). The primary and secondary endpoints were recipient survival and the incidence of T cell-mediated rejection (TCMR) after LDLT, respectively, according to the number of HLA mismatches at all five loci: HLA-A, HLA-B, HLA-C, HLA-DR, and HLA-DQ. Subgroup analyses were also performed in between-siblings that characteristically have widely distributed 0-10 HLA mismatches. A total of 1304 cases of primary LDLTs were finally enrolled, including 631 adults (recipient age at LT ≥18 years) and 673 children (<18 years). In adult-to-adult LDLT, the more HLA mismatches at each locus, the significantly worse the recipient survival was (p = 0.03, 0.01, 0.03, 0.001, and <0.001 for HLA-A, HLA-B, HLA-C, HLA-DR, and HLA-DQ, respectively). This trend was more pronounced when multiple loci were combined (all p < 0.001 for A + B + DR, A + B + C, DR + DQ, and A + B + C + DR + DQ). Notably, a total of three or more HLA-B + DR mismatches was an independent risk factor for both TCMR (hazard ratio [HR] 2.66, 95% confidence interval [CI] 1.21-5.87; p = 0.02) and recipient survival (HR 2.44, 95% CI 1.11-5.35; p = 0.03) in between-siblings. By contrast, HLA mismatch did not affect pediatric LDLT outcomes at any locus or in any combinations; however, it should be noted that all donor-recipient relationships are parent-to-child that characteristically possesses one or less HLA mismatch at each locus and maximally five or less mismatches in total. In conclusion, HLA mismatch significantly affects not only TCMR development but also recipient survival in adult LDLT, but not in children.

HLA DR Genome Editing with TALENs in Human iPSCs Produced Immune-Tolerant Dendritic Cells

Although human induced pluripotent stem cells (iPSCs) can serve as a universal cell source for regenerative medicine, the use of iPSCs in clinical applications is limited by prohibitive costs and prolonged generation time. Moreover, allogeneic iPSC transplantation requires preclusion of mismatches between the donor and recipient human leukocyte antigen (HLA). We, therefore, generated universally compatible immune nonresponsive human iPSCs by gene editing. Transcription activator-like effector nucleases (TALENs) were designed for selective elimination of HLA DR expression. The engineered nucleases completely disrupted the expression of HLA DR on human dermal fibroblast cells (HDF) that did not express HLA DR even after stimulation with IFN-γ. Teratomas formed by HLA DR knockout iPSCs did not express HLA DR, and dendritic cells differentiated from HLA DR knockout iPSCs reduced CD4⁺ T cell activation. These engineered iPSCs might provide a novel translational approach to treat multiple recipients from a limited number of cell donors.

Acute cellular rejection and HLA mismatch in heart transplantation: insights from a developing country

The notable evolution of heart transplant (HTX) has paralleled the capacity of diagnosing rejection and, consequently, initiating timely treatment. Acute cellular rejection, diagnosed by endomyocardial biopsy, is the most frequent in the first 6 months after HTX. HLA matching is not routinely performed in HTX due to the absence of consensus regarding its usefulness. However, the use of HLA typing might be underscored if it could predict an increased risk of rejection. Therefore, the aim of this study was to evaluate, at a public cardiology center in Brazil, the association between HLA mismatches and the incidence of acute cellular rejection in the first 6 months after HTX. Data were obtained from hospital records and from the National Transplant System. Overall, there was no association between the number of HLA mismatches and the frequency of acute cellular rejection, but there was a tendency toward a higher incidence of rejection with HLA-DR incompatibility.

Racial and ethnic disparities in outcomes after heart transplantation: A systematic review of contributing factors and future directions to close the outcomes gap

The demographics of patients undergoing heart transplantation in the United States have shifted over the last 10 years, with an increasing number of racial and ethnic minorities undergoing heart transplant. Multiple studies have shown that survival of African American patients after heart transplantation is lower compared with other ethnic groups. We review the data supporting the presence of this outcome disparity and examine the multiple mechanisms that contribute. With an increasingly diverse population in the United States, knowledge of these disparities, their mechanisms, and ways to improve outcomes is essential.

CODUSA--customize optimal donor using simulated annealing in heart transplantation

In heart transplantation, selection of an optimal recipient-donor match has been constrained by the lack of individualized prediction models. Here we developed a customized donor-matching model (CODUSA) for patients requiring heart transplantations, by combining simulated annealing and artificial neural networks. Using this approach, by analyzing 59,698 adult heart transplant patients, we found that donor age matching was the variable most strongly associated with long-term survival. Female hearts were given to 21% of the women and 0% of the men, and recipients with blood group B received identical matched blood group in only 18% of best-case match compared with 73% for the original match. By optimizing the donor profile, the survival could be improved with 33 months. These findings strongly suggest that the CODUSA model can improve the ability to select optimal match and avoid worst-case match in the clinical setting. This is an important step towards personalized medicine.

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.

HLA compatibility index: does it have a role in patients after heart transplantation?

AIMS

To determine the impact of HLA compatibility measured by the Compatibility Index, on survival, rate of rejections, malignancies and infections in patients after heart transplantation (HTx).

METHODS

We carried out a retrospective analysis of 182 consecutive patients who underwent heart transplantation in our center from January 2001 to April 2010. According to degree of HLA-A, B and DR matching (Compatibility Index, CI) the patients were divided in two groups, Group A (n=83) with an IC 0-17 and group B (n=99) with an IC 18-26. There was no significant difference in demographic parameters between recipients and donors.

RESULTS

We found no difference in rates of rejections or infections between Group A and Group B (AR: 22 (26.5%) vs. 34 (34.3%), P=0.2539; infections: 21 (25.3%) vs. 27 (27%) P=0.7637). The distribution of infections in terms of type (bacterial, viral, fungal, including Aspergillus) was similar in both groups. The incidence of malignant tumours was infrequent (3 (3.6%) vs. 4 (4.0%), P=0.8817). We found trend toward lower level of tacrolimus in Group A. Long term survival was similar in both groups.

CONCLUSIONS

Based on the results of our single-center trial, we found no impact of higher degree of HLA-A,-B, and -DR matching on survival, rejection episodes or infection. Further large studies are necessary to confirm our hypothesis that subjects with better HLA compatibility could require lower dose immunosuppression.

Simple score to assess the risk of rejection after orthotopic heart transplantation

BACKGROUND

The aim of this study was to derive and validate a risk score for rejection after orthotopic heart transplantation.

METHODS AND RESULTS

The United Network for Organ Sharing registry was used to identify patients undergoing orthotopic heart transplantation between 1998 and 2008. A total of 14 265 eligible patients were randomly divided into derivation (80%; n=11 412) and validation (20%; n=2853) cohorts. The primary outcome was drug-treated rejection within 1 year of orthotopic heart transplantation. Covariates found to be associated (exploratory univariate P<0.2) with rejection were entered into a multivariable logistic regression model. Inclusion of each variable in the model was assessed by improvement in the McFadden pseudo-R(2), likelihood ratio test, and c index. A risk score was then generated through the use of relative magnitudes of the odds ratios from the derivation cohort, and its ability to predict rejection was tested independently in the validation cohort. A 13-point risk score incorporating 4 variables (age, race, sex, HLA matching) was created. The mean scores in the derivation and validation cohorts were 8.3±2.2 and 8.4±2.1, respectively. Predicted 1-year rejection rates based on the derivation cohort ranged from 16.2% (score=0) to 50.7% (score=13; P<0.001). In weighted regression analysis, there was a strong correlation between these predicted rates of rejection and actual, observed rejection rates in the validation cohort (r(2)=0.96, P<0.001). Logistic regression analysis also demonstrated a significant association (odds ratio, 1.13; P<0.001). The c index of the composite score was equivalent in both the derivation and validation cohorts (c=0.67).

CONCLUSIONS

This novel 13-point risk score is highly predictive of clinically significant rejection episodes within 1 year of orthotopic heart transplantation. It has potential utility in tailoring immunosuppressive regimens and in research stratification in orthotopic heart transplantation.

A single human leukocyte antigen-antibody test after heart or lung transplantation is predictive of survival

A single posttransplant test for human leukocyte antigen (HLA) antibodies in heart and lung graft patients was examined for its predictive value for graft survival as part of the 13th and 14th international histocompatibility workshops. We included patients with HLA antibodies who were tested 6 or more months after transplantation. They were followed for 3 to 5 years. Kaplan-Meier survival curves were used to analyze the data. Of the 235 heart transplant patients, 24.7% had HLA antibodies, whereas 13.3% of the 150 lung transplant recipients, tested positive for HLA antibodies. Heart transplant patients with antibodies had a 5-year survival of 42% vs. 58% for those without antibodies (P=0.0065). For lung transplant patients, the 5-year graft survival was 27% for those with antibodies vs. 56% for those without (P<0.0001). These results indicate that for heart and lung transplant patients, a single test after transplantation of HLA antibodies is predictive of graft survival.

No Evidence for an Improvement of Long-Term Survival by HLA Matching in Heart Transplant Recipients

It has been assumed that better HLA matching improves midterm survival in cardiac transplantation. However, statistically reliable data on long-term survival according to HLA matching are scanty. We performed a retrospective analysis of all patients who underwent orthotopic heart transplantation at our heart center between 1989 and 2005. HLA typing data (major histocompatability complex [MHC] class I and II) were available in 923 patients and their heart donors. Univariate and multivariate analyses were performed to assess the impact of HLA matching on long-term survival. The average follow-up period was 6.1 +/- 4.3 years (range, 0.0 to 15.0 years). In total, the 923 patients accrued 5625 patient-years of observation. Zero, one, and two mismatches occurred at each locus in between 0.3% (HLA-B) to 6.6% (HLA-C), 16.6% (HLA-B) to 39.4% (HLA-DQ), and 55.4% (HLA-DQ) to 83.3% (HLA-B), respectively. Two hundred eleven patients died during follow-up (22.9%). Survival at 1, 2, 5, and 10 years was 87.7%, 86.2%, 78.4%, and 63.9%, respectively. In the multivariate analysis, age, transplant era, presence of MHC class I and II antibodies, and high urgency status but not HLA mismatches were independent predictors of long-term survival. Moreover, diagnoses other than dilated cardiomyopathy increased long-term mortality risk. In summary, our data demonstrate that HLA matching is not an independent risk factor for longterm survival in heart transplant recipients. However, several pretransplant factors and transplant era were independently associated with mortality risk.

The Cumulative Effect of Acute Rejection on Development of Cardiac Allograft Vasculopathy

BACKGROUND

Acute rejection increases the inflammatory burden of the transplanted organ and predisposes to cardiac allograft vasculopathy (CAV). In this study we aim to determine the magnitude of the association, and to differentiate between the effects of mild vs severe rejection episodes.

METHODS

Between 1988 and 2003, 489 1-year survivors of heart transplantation underwent 1,435 angiograms. These patients were classified as having no CAV (0% stenosis), mild/moderate CAV (<70%) or severe CAV (>70%). Acute rejection was considered either mild (Grades 1A, 1B and 2 untreated) or moderate/severe (Grade 2 treated on a clinical basis and Grades 3A, 3B and 4). We used multi-state Markov models to examine risk factors for the onset of CAV.

RESULTS

Expressed as relative risk, the onset of CAV was significantly increased by donor age (1.26 per 10 years, 95% confidence interval [CI] 1.12 to 1.42), male recipient (1.72, 95% CI 1.01 to 2.94), pre-transplant recipient ischemic disease (1.53, 95% CI 1.14 to 2.06) and cumulative number of moderate/severe rejections (1.10 per episode, 95% CI 1.03 to 1.18). Human leukocyte antigen (HLA) and cytomegalovirus (CMV) matching, donor gender, recipient age, smoking, cumulative CMV infections and mild rejections were not significant risk factors. Estimated annual onset rate of CAV was 11.3% for patients with no moderate/severe rejection, rising to 13.6% for those with two and 18.0% for those with five such rejections.

CONCLUSIONS

Acute moderate/severe cellular rejection has a cumulative impact on CAV onset, whereas mild, untreated rejection is not associated with CAV.

Influence of HLA Matching on Survival in Heart Transplantation

BACKGROUND

In renal transplantation, the degree of HLA matching has been reported to be negatively correlated with graft loss, with the number of rejections with complications. This association is less clear in heart transplantation, where there are contradictory studies, although most are consistent with those in renal transplantation. The objective of this study was to analyze differences in the probability of survival and the incidence of complications during follow-up according to the degree of HLA-A, -B, and -DR matching.

MATERIALS AND METHODS

Two hundred forty-three consecutive patients transplanted over a 13-year period were analyzed for age, gender, pretransplant factors associated with mortality, number of rejections and infections, incidence of acute graft failure, arterial hypertension, diabetes, and survival time with cause of death with reference to the number of HLA matches (zero to six). Exclusion criteria included retransplants, heart-lung transplants, pediatric transplants, and perioperative mortality. Groups were compared using the chi(2) and ANOVA (Bonferroni posthoc test) tests. Kaplan-Meier survival curves were compared using the log rank test. The significance level was set at P < .05.

RESULTS

The overall probability of survival of our series at 1, 5, and 10 years was 85%, 77%, and 60%, respectively. HLA-A, -B, and -DR compatibility: No significant differences were found when the curves were compared (log-rank: .005). The best survival rates were obtained with lower degrees of matching. No significant differences were found in the number of rejections or infections, although survival rates (P = .007) were higher among those with the lower degrees of matching.

CONCLUSIONS

A higher degree of HLA-A, -B, and -DR matching did not have a positive effect on heart transplant patient survival, rejection episodes or infections.

Immunoglobulin M-to-Immunoglobulin G Anti-Human Leukocyte Antigen Class II Antibody Switching in Cardiac Transplant Recipients Is Associated With an Increased Risk of Cellular Rejection and Coronary Artery Disease

Background— Activation of T cells induces immunoglobulin (Ig)M-to-IgG B-cell isotype switching via costimulatory regulatory pathways. Because rejection of transplanted organs is preceded by alloantigen-dependent T-cell activation, we investigated whether B-cell isotype switching could predict acute cellular rejection and the subsequent development of transplantation-related coronary artery disease (TCAD) in cardiac transplant recipients.

Methods and Results— Among 267 nonsensitized heart transplant recipients, switching from IgM to IgG anti-human leukocyte antigens (HLA) antibodies directed against class II but not against class I antigens was associated with a shorter duration to high-grade rejection, defined as International Society for Heart and Lung Transplantation grade 3A or higher ( P <0.001), a higher cumulative rejection frequency ( P =0.002), accelerated development of TCAD ( P =0.04), and decreased late survival ( P =0.03). Conversely, the persistence of IgM anti-HLA antibodies against class II but not against class I antigens for >30 days and the lack of IgG isotype switching were associated with protection against both acute rejection ( P =0.02) and TCAD ( P =0.05). Alloisotype switching coincided with T-cell activation, as evidenced by increased serum levels of soluble CD40 ligand costimulatory molecules. Finally, a case-control study showed that reduction of cardiac allograft rejection by mycophenolic acid was accompanied by reduced CD40 ligand serum levels and the prevention of IgM-to-IgG anti-HLA class II antibody switching.

Conclusions— T-cell-dependent B-cell isotype switching and the consequent production of IgG anti-HLA class II antibodies are strongly correlated with acute cellular rejection, a high incidence of recurrent rejections, TCAD, and poor long-term survival. Detecting this isotype switch is a clinically useful surrogate marker for in vivo T-cell activation and may provide a noninvasive approach for monitoring the efficacy of T-cell targeted immunosuppressive therapy in heart transplant recipients.

Allograft Aortic Valve Replacement in the Adult: A Review

Aortic valve replacement using an allograft has been used continuously for over 40 years. Its advantages are excellent haemodynamic function, low thrombogenicity, resistance to infection and avoidance of the complications of anticoagulation. The main concern is its long-term durability, with the high hazard phase for failure between 10 and 20 years. We have only recently been able to judge the true long-term behaviour of the contemporary allograft with two recently published series of patients having reached follow-up beyond 20 years in significant numbers. This review of allograft aortic valve replacement in the adult covers the areas of history, benefits, techniques of sterilisation and preservation, operative methods and outcomes.

Risk of lymphoid neoplasia after cardiothoracic transplantation: the influence of underlying disease and human leukocyte antigen type and matching

BACKGROUND

It has been known for more than 20 years that there is an increased risk of lymphoid neoplasia after cardiothoracic transplantation. Recent studies have demonstrated the importance of primary Epstein-Barr virus (EBV) infection and type of immunosuppressive therapy to the cause of these neoplasms, but the contribution of other factors remains equivocal.

METHODS

The authors followed 1,562 patients undergoing cardiothoracic transplantation at Harefield Hospital, United Kingdom, and used standard cohort methods of analysis to examine whether posttransplant lymphoma risk was related to the underlying disease requiring transplantation or the human leukocyte antigen (HLA) type and matching. Lymphomas were categorized into EBV-associated lymphoproliferative disease (LPD) and EBV-negative non-Hodgkin's lymphoma (NHL), and the authors carried out separate analyses of these.

RESULTS

The authors found no significant association between the underlying disease necessitating transplantation and the risk of lymphoid neoplasia. There was also no evidence of a relation of lymphoma risk with the presence or absence of any particular HLA antigen, although significant protective effects of HLA-B14 and -B57 were found when analyses were conducted without adjustment for multiple testing. Risk of LPD was not associated with degree of HLA mismatching, but there was a significant effect of mismatching on risk of EBV-negative tumors.

CONCLUSIONS

The differential effect of HLA mismatching on the risks of LPD and EBV-negative NHL provides further evidence that these two tumors are distinct etiologic entities. The authors' results suggest that the immunologic cause of EBV-negative NHL may be different from that of LPD. Investigation of the relation of risk of EBV-negative NHL to degree of immunosuppression is needed.

Interleukin-2 receptor blockade in cardiac transplantation: influence of HLA-DR locus incompatibility on treatment efficacy

BACKGROUND

Because allograft rejection results from specific T-cell activation by donor human leukocyte antigens (HLA), new immunomodulatory therapies for organ-transplant recipients are used to selectively block T-cell activity without global immunosuppression. We investigated whether blockade of the high-affinity interleukin (IL)-2 receptor effectively prevented T-cell alloreactivity in cardiac transplantation.

METHODS AND RESULTS

A study of a humanized monoclonal antibody against the high-affinity IL-2 receptor (daclizumab) was performed in 70 adult, cardiac-transplant recipients. Patients were stratified based on the degree of donor-recipient HLA-DR matches. Primary and secondary endpoints were incidence and frequency of high-grade allograft rejections, IL-2-dependent, T-cell outgrowth from biopsy sites as measured by lymphocyte growth assay, and production of anti-HLA antibodies. Treatment with daclizumab significantly prevented development of high-grade acute rejection in recipients with at least one donor HLA-DR locus match during the first 3 months posttransplantation; in this group 0 of 13 (0%) treated with daclizumab experienced at least one high-grade rejection versus 3 of 13 (23%) controls (P=0.05). In addition, 1 of 12 (9%) daclizumab-treated patients experienced one or more episodes of IL-2-dependent, T-cell outgrowth versus 5 of 12 (42%) patients in the untreated group (P=0.05). In contrast, daclizumab used at the same dose and schedule was not as effective in fully HLA-DR-mismatched recipients. After cessation of daclizumab, allograft rejection increased to levels seen in controls.

CONCLUSIONS

IL-2-receptor blockade is effective for preventing alloreactivity and high-grade rejection in cardiac transplantation; however, its efficacy seemed to be influenced by the degree of donor-recipient, HLA-DR locus mismatching.

Evaluation of peripheral blood CD4 and CD8 lymphocyte subsets, CD69 expression and histologic rejection grade as diagnostic markers for the presence of cardiac allograft rejection

We investigated the dynamics of the CD4+ and CD8+ lymphocyte subsets, and the expression of activation markers in cardiac transplant recipients. We tested 132 peripheral blood samples from 62 cardiac transplant recipients using fluorescent staining and flow cytometry analysis. The results were correlated with histological rejection grade of concurrently taken biopsies, and 5-year survival of the recipients. A decrease in the total T lymphocyte subset, and in CD4+ lymphocytes was associated with higher rejection grade and lesser survival. An increase (5-11%) of double positive CD4+ CD8+ lymphocytes was observed; these were mostly CD4brightCD8dim. The CD4/CD8 ratio was significantly (P < 0.00) lower in the transplant recipients than in normal individuals. CD69 expression was higher than CD54 and CD154 expression on CD4 and CD8 lymphocytes of cardiac transplant recipients; correlation between these activation markers was excellent (P < 0.001). Fluorescent staining for CD69 was often of low intensity. Multiple regression for % CD8+ CD69+ cells and survival, and for % CD69+ T cells and rejection grade yielded a significant correlation (P < 0.050). Both % CD8+ CD69+ and % CD69+ T cells were significantly higher in samples with severe and moderate rejection grade (grades 3A, 3B and 4) than in samples which showed no, minimal or mild rejection (grades < or = 2); P-values were 0.052 and 0.003, respectively. Preliminary results indicated that false negative results could be contributed to increased immunosuppression. We conclude that CD69 expression on circulating CD4 and CD8 lymphocytes is a useful parameter for the diagnosis of moderate and severe rejection.

Role of HLA compatibility in pediatric living-related liver transplantation

BACKGROUND

Human leukocyte antigen (HLA) matching is, at present, not used for the allocation of cadaveric hepatic allografts because the liver is generally believed to be less susceptible to HLA-mediated rejection. However, the exact role of HLA compatibility in the long-term outcome of liver transplantation is not yet clearly defined. One of the advantages of living-related liver transplantation (LRLT) could be a better histocompatibility between donor and recipient. This study aimed at an assessment of the influence of HLA compatibility in a large series of LRLTs.

METHODS

A total of 321 pediatric patients who underwent ABO-identical or ABO-compatible primary LRLT from the parental donors in the period between June 1990 and August 2000 were involved in the study. Graft survival, rejection episodes, and immunosuppression were evaluated from the viewpoint of HLA compatibility.

RESULTS

The overall 1- and 5-year graft survivals were 85.7% and 84.1%, respectively. The cumulative 5-year graft survivals in HLA 0-, 1-, 2- and 3-mismatch groups (A, B, and DR) were 100% (n=10), 78.9% (n=19), 86.2% (n=87), and 82.9% (n=205), respectively (P=0.525). The overall incidence of rejection during the follow-up period (median 66 months, range 16-139 months) was 46.1%. No significant difference was found in the incidence of rejection and rejection-free survival among the four groups. However, steroid-resistant rejection that necessitated OKT3 treatment (n=6) and chronic rejection (n=2) were recognized only in the 3-mismatch group. The whole-blood trough level of tacrolimus and the duration of steroid administration were not significantly different among the groups. The rate of the patients who succeeded in withdrawal from immunosuppression was also similar among the groups. However, the trough level of tacrolimus needed for maintenance of an acceptable liver function test during the chronic phase tended to be lower in well-matched pairs, and a high percentage of immunosuppressant-free patients were found in the 0-mismatch group. Fatal graft-versus-host disease developed in one patient with a complete one-way HLA-matched transplant.

CONCLUSION

We could not find any supportive evidence of beneficial effects of HLA-matching in pediatric LRLT. The potential benefit of HLA-matching for the reduction protocol for immunosuppressants may play a role in the withdrawal program. It appears unnecessary to pay attention to HLA compatibility in donor selection in LRLT, except for one-way HLA matching, or to adjust immunosuppression according to HLA compatibility.

Effect of HLA-DR matching on acute rejection after clinical heart transplantation might be influenced by an IL-2 gene polymorphism

BACKGROUND

To examine whether genetic factors are involved in the development of acute rejection (AR), we investigated a (CA)m(CT)n repeat in the 3'-flanking region of the interleukin (IL)-2 gene.

METHOD

We genotyped 290 heart transplant recipients with and without AR (International Society for Heart and Lung Transplantation criteria > or =3A) and 101 controls.

RESULTS

The frequency of allele 135 of the repeat and its genotype distribution (carriers/noncarriers) were significantly associated with freedom from AR (P=0.03 and P=0.02, respectively). We also found interaction between allele 135 and HLA-DR matching. More carriers of allele 135 with no or one mismatch remained free from AR compared to patients without the allele (P=0.01). This was not found in the HLA-DR group with two mismatches.

CONCLUSION

HLA-DR matching might only be effective in reducing AR after heart transplantation in recipients who carry allele 135 of the (CA)m(CT)n repeat in the 3'-flanking region of the IL-2 gene.

Screening of a HUVEC cDNA library with transplant-associated coronary artery disease sera identifies RPL7 as a candidate autoantigen associated with this disease

A HUVEC cDNA library was screened with sera from two patients who had developed transplant-associated coronary artery disease (TxCAD) following cardiac transplantation. A total of six positive clones were isolated from a primary screen of 40 000 genes. Subsequent DNA sequence analysis identified these to be lysyl tRNA synthetase, ribosomal protein L7, ribosomal protein L9, beta transducin and TANK. Another gene whose product could not be identified showed homology to a human cDNA clone (DKFZp566M063) derived from fetal kidney. Full-length constructs of selected genes were expressed as his-tag recombinant fusion proteins and used to screen a wider patient base by ELISA to determine prevalence and association with TxCAD. Of these ribosomal protein L7 showed the highest prevalence (55.6%) with TxCAD sera compared to 10% non-CAD.

Valve interstitial cells induce donor-specific T-cell anergy

OBJECTIVES

Valve allografts produce an immune response, which can influence their performance. The exact role of the interaction between recipient T cells and the different cellular components of the donor valve in stimulating an immune response is not known. Therefore the T-cell response to valve endothelial and interstitial cells was investigated in vitro.

METHODS

Valve endothelial and interstitial cells were characterized for cell-surface molecules before and after interferon gamma treatment by means of a panel of specific monoclonal antibodies and flow cytometry. The proliferative response of highly purified T lymphocytes was used to assess the immunogenicity of cultured valve endothelial and interstitial cells. This was further investigated by using a 2-step tolerance-induction protocol.

RESULTS

Valve endothelial and interstitial cells express similar levels of human leukocyte antigens and adhesion and costimulatory molecules, which are either induced or upregulated after interferon gamma treatment. T-cell responses to endothelial cells were detected after interferon gamma treatment, but responses to interferon gamma-treated interstitial cells were not detected. This lack of response resulted in the induction of T-cell anergy, which was reversed by the presence of the costimulatory molecule B7-1.

CONCLUSIONS

Although valve endothelial and interstitial cells express a similar range of cell-surface molecules, it is only the endothelial cells that are immunogenic. In addition, we have shown that these 2 cell types interact in a donor-specific manner to orchestrate the immune response and therefore may have clinical relevance in the allogeneic response of the heart valve recipients.

Anti-HLA class I antibodies and pulmonary homograft function after the Ross procedure

BACKGROUND

The Ross procedure provides excellent long-term results in the majority of patients. However, degeneration of the pulmonary homograft in some patients remains an unresolved problem that may be related to immunologic factors. Therefore, we studied the prevalence of antihuman leukocyte antigen (HLA) class I antibodies and echocardiographic results of homograft function at rest.

METHODS

Forty-seven patients (37 men, 10 women; 47 +/- 15 years) were seen for echocardiography 1.1 to 63.9 months (median, 27 months) postoperatively. The presence of anti-HLA antibodies was tested against a panel of lymphocytes of 50 donors.

RESULTS

Twenty-seven (57%) of the patients produced anti-HLA class I antibodies. No difference in the maximal or mean transhomograft pressure gradient, or in the frequency of homograft regurgitation according to the presence or absence of anti-HLA antibodies was found. However, the right ventricle was slightly but significantly larger in antibody-positive patients (26.3 +/- 4.2 versus 30.7 +/- 3.5 mm; p = 0.001).

CONCLUSIONS

In the first years after the Ross procedure, we could not detect significant evidence of an association between anti-HLA class I antibodies and echocardiographic results of homograft function at rest in adults.

Factors affecting long-term survival (>10 years) after cardiac transplantation in the cyclosporine era

OBJECTIVES

The aim of this study was to determine long-term survival (>10 years) after cardiac transplantation in the cyclosporine era and identify risk factors influencing long-term survival.

BACKGROUND

Despite the availability of newer modalities for heart failure, cardiac transplantation remains the treatment of choice for end-stage heart disease.

METHODS

Between 1983 and 1988, 195 patients underwent heart transplantation at a single center for the treatment of end-stage heart disease. Multivariable logistic regression analysis of pretransplant risk factors affecting long-term survival after cardiac transplantation included various recipient and donor demographic, immunologic and peritransplant variables.

RESULTS

Among the group of 195 cardiac transplant recipients, actuarial survival was 72%, 58% and 39% at 1, 5 and 10 years respectively. In the 65 patients who survived >10 years, mean cardiac index was 2.91/m2 and mean ejection fraction was 58%. Transplant-related coronary artery disease (TRCAD) was detected in only 14 of the 65 patients (22%). By multivariable analysis, the only risk factor found to adversely affect long-term survival was a pretransplant diagnosis of ischemic cardiomyopathy (p = 0.04).

CONCLUSIONS

Long-term survivors maintain normal hemodynamic function of their allografts with a low prevalence of TRCAD. It is possible that similar risk factors that lead to coronary artery disease in native vessels continue to operate in the post-transplant period, thereby contributing to adverse outcomes after cardiac transplantation. Aggressive preventive and therapeutic measures are essential to limit the risk factors for development of coronary atherosclerosis and enable long-term survival after cardiac transplantation.

The influence of conventional and cross-reactive group HLA matching on cardiac transplant outcome: an analysis from the United Network of Organ Sharing Scientific Registry

BACKGROUND

The short tolerable cold ischemia time and the importance of other risk factors have generally superseded the role of HLA matching in the allocation of donor hearts. Recent advances in the accuracy and time required to perform HLA typing and crossmatching, however, have led us to re-examine the United Network of Organ Sharing Transplant Registry for the effects of the HLA incompatibility on outcome in relation to other possible risk factors.

METHODS

These include conventional HLA-A, -B, and cross-reactive group (CREG) mismatching (mm), HLA-DR mm, pretransplantation panel-reactive antibody (PRA), recipient and donor race and donor age, cold ischemia time, and the pretransplantation use of either a left ventricular assist device or an intra-aortic balloon pump.

RESULTS

Three-year survival was clearly inferior in non-white (0.6921) as compared with white (0.7632) recipients, but this difference could not be accounted for by the degree of donor-recipient HLA mm that had occurred by chance. Nevertheless, the degree of mm that did occur seemed to have an impact on survival. The importance of HLA-DR mm was confirmed, and it ranked only behind the use of an assist device and recipient race in the multivariate analysis. HLA-A and B mm exerted an additional effect, but this was only true in white recipients. Of these, HLA-A achieved statistical significance as an independent risk factor. In general, CREG mm was not a significant variable. However, more than twice as many 0-1 or 0-2 CREG, 0 DR mm as compared with 0-1 or 0-2 A,B, 0 DR mm transplants enjoyed approximately equal and very good 1- and 3-year survival. Assuming no change is cold ischemia time, the potential number of 0 CREG, 0 DR mm, ABO-compatible transplants that could be achieved when an Organ Procurement Organization had 50-100 patients on their waiting list was calculated. The surprisingly high frequency of approximately 24-36% suggests that this favorable match could be considered along with other important factors in the local allocation process. When pretransplantation PRA was analyzed as a continuous variable from 0 to 100%, it was a highly significant risk factor, but this effect was more strikingly evident when the PRA was analyzed in 20% increments above zero. Recently, left ventricular assist device usage has become increasingly common, and it has been associated with strikingly increased pretransplantation PRA levels. When they occur together, the data indicates that these patients are at a very high risk for graft failure.

CONCLUSIONS

We believe that newer typing and crossmatching techniques make it possible to add HLA criteria to the allocation protocol of donor cardiac organs and would lead to improved long-term survival.

Targeting of the chemokine receptor CCR1 suppresses development of acute and chronic cardiac allograft rejection

Although mononuclear cell infiltration is a hallmark of cellular rejection of a vascularized allograft, efforts to inhibit rejection by blocking leukocyte-endothelial cell adhesion have proved largely unsuccessful, perhaps in part because of persistent generation of chemokines within rejecting grafts. We now provide, to our knowledge, the first evidence that in vivo blockade of specific chemokine receptors is of therapeutic significance in organ transplantation. Inbred mice with a targeted deletion of the chemokine receptor CCR1 showed significant prolongation of allograft survival in 4 models. First, cardiac allografts across a class II mismatch were rejected by CCR1(+/+) recipients but were accepted permanently by CCR1(-/-) recipients. Second, CCR1(-/-) mice rejected completely class I- and class II-mismatched BALB/c cardiac allografts more slowly than control mice. Third, levels of cyclosporin A that had marginal effects in CCR1(+/+) mice resulted in permanent allograft acceptance in CCR1(-/-) recipients. These latter allografts showed no sign of chronic rejection 50-200 days after transplantation, and transfer of CD4(+) splenic T cells from these mice to naive allograft recipients significantly prolonged allograft survival, whereas cells from CCR1(+/+) mice conferred no such benefit. Finally, both CCR1(+/+) and CCR1(-/-) allograft recipients, when treated with a mAb to CD4, showed permanent engraftment, but these allografts showed florid chronic rejection in the former strain and were normal in CCR1(-/-) mice. We conclude that therapies to block CCR1/ligand interactions may prove useful in preventing acute and chronic rejection clinically.

Ten year survival after heart transplantation: palliative procedure or successful long term treatment?

OBJECTIVE

To investigate the long term outcome and prognostic factors after heart transplantation.

SETTING

University hospital.

SUBJECTS

120 heart transplant patients (98 male, 22 female; underlying disease: dilated cardiomyopathy in 69, coronary artery disease in 42, miscellaneous in nine) who had undergone heart transplantation between October 1984 and October 1987. Immunosuppressive treatment was comparable in all patients and rejection episodes were treated in a uniform manner.

METHODS

Functional status, quality of life, and potential predictors for long term survival were investigated.

RESULTS

Actuarial survival rates were 65% at five years and 48% at 10 years; 58 patients survived > 10 years. The major causes of death were cardiac allograft vasculopathy (39%), acute rejection (18%), infection (11%), and malignancy (11%). Long term survivors had good exercise tolerance assessed by the New York Heart Association classification: 47 (81%) in grade I/II; 11 (19%) in grade III/IV. Echocardiography showed good left ventricular function in 48 patients. On angiography, severe allograft vasculopathy was present in only 16 patients (28%). Renal function was only slightly impaired, with mean (SD) serum creatinine of 148.5 (84.9) micromol/l. Multiple potential predictors of long term survival were analysed but none was found useful.

CONCLUSIONS

Heart transplantation represents a valuable form of treatment. Survival for more than 10 years with a good exercise tolerance and acceptable side effects from immunosuppression can be achieved in about 50% of patients.

The significance of HLA matching in cardiac transplantation

It is argued that HLA matching is not worthwhile in heart transplantation. However, transplanting HLA compatible hearts enhances graft survival and should significantly reduce infection and malignancies related to aggressive immunosuppression. It is our view that the problem is technical and we offer a potential solution.

Heart allograft vascular disease: an obliterative vascular disease in transplanted hearts

More than 30 years have passed since the first human heart transplantation was performed. Since then, short-term survival after heart transplantation has been markedly improved, but this development has not been paralleled with a similar improvement in long-term survival. One of the major reasons for this is the subsequent development of heart allograft vascular disease, an obliterative disease in the coronary arteries of the transplanted heart. The dubious effect of re-vascularization in this disease, the less favorable outcome after repeat heart transplantation, and the low donor supply have called for intensified research for new and efficient prophylactic therapies against heart allograft vascular disease. This research has lead to improved knowledge about diagnosis, etiology, pathogenesis, prophylaxis, and treatment possibilities. The most important among these seem to be: (i) the introduction of intravascular ultrasound for early detection of the disease; (ii) evidence to suggest that hyperlipidemia, insufficient immunosuppressive therapy, human leukocyte antigen (HLA)-mismatch, and infection with cytomegalovirus (CMV) all may promote allografts vascular disease; and (iii) the introduction of at least two promising prophylactic therapies in humans namely 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors and calcium entry blockers, and others potentially promising e.g. angiotensin-converting enzyme-inhibitors, angiopeptin, mycophenolate mofetil and rapamycin. This review summarizes present knowledge on the possibilities of inhibiting or treating heart allograft vascular disease incorporating evidence from both human and experimental studies.

Effect of HLA mismatching and antibody status on "homovital" aortic valve homograft performance

BACKGROUND

Recipients of "homovital" aortic valve homografts are known to produce specific antibodies to human leukocyte antigen (HLA) determinants present on the cellular compartment of the valve tissue; however, the clinical significance of these antibodies is unknown. Data from 182 patients receiving homovital aortic valve homografts has been analyzed to determine the impact of HLA disparity and HLA antibody production on survival and function of the homograft.

METHODS

Human leukocyte antigen mismatch data were available for 127 patients (mean follow-up, 6.02+/-0.26 years). Two patients were considered well matched for HLA A+B antigens (zero or one mismatch) compared with 125 poorly matched (two to four mismatches). Nine patients had a zero HLA-DR mismatch compared with 52 with one mismatch and 59 patients completely mismatched for DR antigens.

RESULTS

There was no significant association between the degree of HLA mismatch for either class I or class II antigens whether the loci were considered alone or in combination (ie, A, B, DR, AB, or ABDR mismatching) with markers of long-term valve function including patient mortality, reoperation, valve degeneration, valve stenosis, presence of regurgitation, and postoperative New York Heart Association class. One hundred thirty-six of 167 (82%) were found to have produced antibodies after operation (mean time after operation, 6.42+/-0.58 years). In 61 cases both antibody specificity and donor HLA typing was available. In 92% of these, the antibodies were of the IgG subclass and were specific for the HLA class I molecules of the donor. The presence of HLA antibodies was associated with an increase in the frequency of mild valve stenosis (not significant) compared with those patients who did not develop HLA antibodies (antibody negative = 9.7%; panel reactive antibodies <50% = 29.1%; and panel reactive antibodies >50% = 22.2%; not significant). There was also an increased prevalence of valve degeneration associated with HLA antibodies. The actuarial freedom from valve degeneration for the 35 HLA antibody-negative patients was 100% at 1, 5, and 10 years compared with 100% at 1 year, 97% at 5 years, and 92% at 10 years for 55 patients with panel reactivity less than 50%, and 98% at 1 year, 94% at 5 years, and 88% at 10 years for the 77 patients who were highly sensitized (not significant). There was no correlation with other markers of long-term valve function.

CONCLUSIONS

The influence of the immune response on valve function requires further studies involving large numbers of patients followed for a longer period of time. We believe prospective matching for HLA antigens is warranted to produce a well-matched cohort of patients for analysis and to reduce antibody sensitization, which would help to clarify this issue.

An immunological algorithm to predict risk of high-grade rejection in cardiac transplant recipients

BACKGROUND

Transplant-related coronary-artery disease (TCAD) develops frequently in cardiac-allograft recipients, and limits long-term survival. We examined the relation between this disorder and cumulative frequency of high-grade rejection, and investigated whether concomitant use of three immunological factors at the time of a low-grade endomyocardial biopsy can predict progression to high-grade rejection.

METHODS

We investigated the relation between the cumulative annual frequency of high-grade rejection and TCAD in 198 recipients of cardiac transplantation between 1992 and 1996 by means of Kaplan-Meier actuarial life-tables. Endomyocardial biopsy, lymphocyte-growth assays, and anti-HLA antibody measurements were compiled over 12 months in 102 patients during their first post-transplant year. We calculated predictive values for high-grade rejection within 90 days by chi2, Kaplan Meier survival curves, and by multivariable logistic regression analyses.

FINDINGS

We found a direct correlation between cumulative annual frequency of rejection and TCAD onset with highest risk in those with more than 0.75 rejections per year (p=0.0002). After a low-grade endomyocardial biopsy (0 or 1A), one or more donor-recipient HLA-DR matches protected against high-grade rejections (p<0.001). Among individuals with one or two DR matches, the negative predictive value for progression from a low-grade biopsy to a high-grade rejection was 87% in the presence of a negative lymphocyte-growth assay. Among individuals with no DR matches, the presence of either a positive lymphocyte-growth assay or IgG anti-major-histocompatibility complex (MHC) class II antibodies was independently associated with high probability of progression to rejection (64% and 66%, respectively, p<0.0005). When both assays were positive, concomitantly with a low-grade endomyocardial biopsy, the positive predictive value for progression to a high-grade rejection was 86% (p<0.0001). For endomyocardial-biopsy grades 1B or 2, a positive lymphocyte-growth assay alone was associated with high-grade rejection in 100% of cases.

INTERPRETATION

Use of an algorithm combining three immunological factors at the time of a low-grade endomyocardial biopsy enables prospective stratification of cardiac transplant recipients into risk categories for progression to high-grade rejection. Low-risk individuals require fewer biopsies, moderate-risk individuals require an ongoing schedule of surveillance biopsies, and high-risk individuals require rational organisation of interventional strategies aimed at preventing rejection. Additional predictive factors are needed to identify moderate-risk individuals who will progress to rejection. Ultimately, successful intervention may have an impact on the subsequent complication of TCAD.

Matching for private or public HLA epitopes reduces acute rejection episodes and improves two-year renal allograft function

BACKGROUND

The current role of HLA matching in renal transplantation is controversial. Public HLA epitope matching has been suggested to be as advantageous as private HLA matching, with the added benefit of increasing recipients' access to well-matched grafts.

METHODS

In this single-center study of 105 renal transplant recipients, we examined the association of HLA matching with early (0-3 months) and late (4-6 months) rejection episodes (RE), as well as renal allograft function up to 2 years after transplant.

RESULTS

Poor HLA-DR, but not HLA-A or -B, matching was associated with early RE (0 DR matches, RE=2.7+/-0.19, 1 DR match, RE=2.37+/-0.18, vs. 2 DR matches, RE=1.5+/-0.38; P < 0.01). In contrast, poor HLA-B, but not HLA-A or -DR, matching was associated with late rejections (0 HLA-B matches, RE=1.1+/-0.51 vs. 1-2 HLA-B matches, RE=0.51+/-0.1; P < 0.004). HLA-B matching was also associated with a significantly lower serum creatinine (SCr) level at 24 months (0 HLA-B matches, SCr=178+/-20 micromol/L vs. SCr=132+/-6 micromol/L for 1-2 HLA-B matches; P < 0.025). Matching for 10 supertypic HLA-A and -B cross-reactive groups was associated with reduced late graft rejection (0-2 residue matches, RE=1.15+/-0.18 vs. RE=0.62+/-0.12 for 3 to 7 residue matches; P < 0.013) as well as a significantly lower SCr level at 24 months (0-2 residue matches, SCr=205+/-29 micromol/L vs SCr=131+/-6 micromol/L for 3 to 7 residue matches; P < 0.001) after transplantation.

CONCLUSIONS

HLA-DR matching was associated with a reduced frequency of early rejection episodes, whereas HLA-B or residue/cross-reactive group matching was associated with a reduced frequency of late rejection episodes and improved graft function at 2 years.

Role of HLA compatibility in pediatric liver transplantation

BACKGROUND

The influence of HLA mismatching in liver transplantation remains controversial. To date, few studies have focused solely on the pediatric population, and none have investigated DR and DQ mismatches using molecular genotyping. We sought to investigate HLA-A, -B, -DR, and -DQ mismatches in a large series of primary pediatric liver transplant recipients. Living-related liver transplants were excluded.

METHODS

A total of 138 consecutive first liver transplants performed between January 1991 and July 1996 were studied. Minimum follow-up was 1 year, and both patient and graft survival rates were assessed. The incidence of the most common complications was analyzed. HLA-A and -B phenotyping was performed by complement-dependent microcytotoxicity or polymerase chain reaction (PCR)-sequence-specific primer protocols in 133 of 138 patients. HLA-DR and -DQ genotyping was performed by standard PCR-sequence-specific oligonucleotide and/or PCR-sequence-specific primer protocols in 135 patients.

RESULTS

Overall, there was no influence of HLA mismatching on either graft or patient survival rates. However, patients with two mismatches at the A locus showed a significantly lower incidence of acute rejection than those with one A mismatch (52% vs. 72%; P < 0.03) and patients with two B locus mismatches had a better graft survival rate at 5 years than those with one mismatch (76% vs. 62%), although this was of only borderline significance (P < 0.09). No differences were found in the severity of the episodes of rejection, incidence of chronic rejection, cytomegalovirus hepatitis, and other causes of graft loss.

CONCLUSION

This study indicates that HLA-A, -B, -DR, and -DQ mismatches are not detrimental in primary pediatric liver transplantation.

Persistent allopeptide reactivity and epitope spreading in chronic rejection of organ allografts

The role of the indirect allorecognition pathway in acute allograft rejection has been documented both in organ recipients and in experimental models. However, it is unknown whether self-restricted recognition of donor alloantigens also contributes to chronic allograft rejection. The aim of this study was to determine the relationship between allopeptide reactivity, epitope spreading, and chronic rejection. Using synthetic peptides corresponding to the hypervariable region of 32 HLA-DR alleles, we have followed the specificity of self-restricted T cell alloresponses to the donor in a population of 34 heart allograft recipients. T cells from sequential samples of blood collected from the patients up to 36 mo after transplantation were studied in limiting dilution analysis for allopeptide reactivity. The incidence of coronary artery vasculopathy (CAV) was significantly higher in patients who displayed persistent alloreactivity late after transplantation than in patients who showed no alloreactivity after the first 6 mo after transplantation. Both intra- and intermolecular spreading of epitopes was observed with an increased frequency in patients developing CAV in less than 2 yr, compared with patients without CAV; this suggests that diversification of the immune response against the graft contributes to chronic rejection. These data provide a strategy for identifying patients at risk of developing CAV and a rationale for therapeutic intervention aimed to prevent the progression of the rejection process.

A prospective study in heart and lung transplant recipients correlating persistent Epstein-Barr virus infection with clinical events

BACKGROUND

A 2-year prospective study was set up with 30 cardiothoracic transplant recipients to study Epstein-Barr virus (EBV) infection and immunity and their correlation with clinical events.

METHODS

Regression assays were used to measure EBV-specific cytotoxic T lymphocyte (CTL) function. Tissue culture, immunoblotting, and polymerase chain reaction were used for EBV detection and isolate variation studies.

RESULTS

CTL activity was significantly lower in pretransplant seropositive patients than in healthy controls (P<0.001). CTL response was undetectable in all patients during the first 6 months after transplantation, but returned at levels significantly lower than pretransplant and control levels during the second posttransplant year (P<0.001). Return of CTL function was directly correlated with time of last treated rejection episode (P<0.003) and duration of high plasma levels of cyclosporine (over 400 ng/ml; P<0.003). Significantly higher levels of EBV were detected in peripheral blood during the first 6 months than in pretransplant or control samples (P<0.05). Excretion of EBV in throat washings was significantly lower during the first 3 months when all patients were receiving acyclovir than in pretransplant and control samples (P=0.02). An increase in virus shedding was noted 3-6 months after transplantation, which was significantly higher than in pretransplant patients and controls (P<0.05). Comparison of recipients' and donors' virus isolates in 11 cases showed that seropositive recipients retained their original EBV isolate and did not acquire the donor virus.

CONCLUSIONS

Immunosuppression decreased EBV-specific host immune function, which in turn favored increased EBV load in peripheral blood and increased excretion in the oropharynx. The transfer of donor virus to the seropositive recipients was not observed.

The immunogenicity of the extracellular matrix in arterial xenografts

BACKGROUND

Determinants of xenograft immunogenicity are poorly characterized. We showed previously that decellularized arterial xenografts (DAXs) dilate, whereas decellularized arterial isografts (DAIs) and allografts do not, suggesting an interspecies, rather than an intraspecies, immunogenicity of the arterial extracellular matrix leading to chronic rejection. Now we have investigated the immunogenicity of the arterial extracellular matrix in xenografts and its impact on chronic injury (elastin lysis) and remodeling (graft dilation).

METHODS

Diameter and elastin content were measured in DAIs and DAXs from hamster to rat (concordant combination) and guinea pig to rat (discordant combinations) at 8 weeks. We also characterized the immune effectors infiltrating DAIs and DAXs by immunohistochemistry after 6 hours to 4 weeks of implantation. Results were compared with nondecellularized isografts and xenografts. Last, the impact of the donor-recipient phylogenetic distance on monocyte-macrophage penetration into the media was assessed in three xenograft combinations.

RESULTS

DAXs from guinea pig, but not from hamster, were aneurysmal at 8 weeks. Elastin lysis paralleled graft dilation. DAXs, but not DAIs, were infiltrated by monocytes, macrophages, T lymphocytes, and immunoglobulins. The donor-recipient combination did not affect the phenotype of the inflammatory infiltrate in DAXs, but it modified the kinetics of monocyte-macrophage penetration into the media. The absence of decellularization changed the inflammatory infiltrate phenotype (absence of macrophages) but had little impact on DAX injury and remodeling.

CONCLUSIONS

DAX immunogenicity accounts for most of chronic arterial xenograft injury, which is modulated by the donor-recipient combination. The immunogenicity of arterial xenografts, unlike allografts, is supported by the extracellular matrix in addition to the cells and could influence the long-term fate of xenografts.

Idiopathic dilated cardiomyopathy: familial prevalence and HLA distribution

OBJECTIVES

To compare HLA distribution in familial and non-familial dilated cardiomyopathy, because a serum marker that could identify families at risk of developing dilated cardiomyopathy should be of use in screening for the disease.

PATIENTS

100 patients with dilated cardiomyopathy.

METHODS

200 first degree relatives from 56 of the proband families were screened for dilated cardiomyopathy by echocardiography. The HLA profile of the patients with dilated cardiomyopathy, as well as of the familial and non-familial subgroups, was compared with that of 9000 normal controls.

RESULTS

The familial prevalence of dilated cardiomyopathy in this patient group was "definite" in 14 of 56 (25%) and "possible" in 25 of 56 (45%). The HLA-DR4 frequency in the 100 patients with dilated cardiomyopathy was similar to that in the 9000 controls (39% v 32%). However, the DR4 subtype was significantly more common in the 25 probands with a familial tendency to dilated cardiomyopathy than in the 31 probands with non-familial dilated cardiomyopathy (68% v 32%; P < 0.05).

CONCLUSIONS

The present finding supports an HLA linked predisposition to familial dilated cardiomyopathy. The HLA type DR4 was significantly more common in familial than in non-familial cases. The DR4 halotype was associated with two thirds of the families at risk for dilated cardiomyopathy.

Human leukocyte antigen compatibility in heart transplantation: evidence for a differential role of HLA matching on short- and medium-term patient survival

BACKGROUND

Studies of the influence of human leukocyte antigen (HLA) matching on cardiac transplant outcome have proved inconclusive, mainly due to the lack of well-matched grafts. However, a growing number of studies report improved clinical course and patient survival in cases with increased HLA compatibility. Opelz et al. believe these benefits justify the introduction of prospective HLA-matching strategies.

METHODS

We performed univariate and multivariate analyses to examine the short- and medium-term influence of HLA matching on 556 consecutive primary heart transplants performed at a single center between 1983 and 1994. Overall graft survival at 1, 3, and 5 years was 80%, 74%, and 67% respectively. Sixteen (2.9%) grafts failed within 5 days and were not considered in the analysis of the HLA matching and graft survival data.

RESULTS

Complete HLA-A, -B, and -DR typing data were available on 477 transplant pairs. The results demonstrate a 12% 1-year survival advantage for 31 patients with zero to two HLA antigen mismatches compared with three to six mismatches. The influence of each individual locus was 6.1%, 8.4%, and 5.4% for zero HLA-A, -B, and -DR mismatches, respectively, compared with two mismatches. However, when outcome from 1 to 5 years was considered, analysis of the role of each locus revealed marked differences. HLAA-matched grafts (n=45) had a 24% lower survival rate compared with two-antigen-mismatched grafts (n=148; 88% [SE 3.1] vs. 64% [SE 8.2], respectively; P=0.009). Furthermore, 34% of HLA-A-matched grafts failed between 1 and 5 years, compared with only 5% of HLA-B-matched grafts (P=0.013).

CONCLUSIONS

These data suggest that although HLA matching is effective at reducing acute graft loss, in the longer term, HLA-A matching may impair survival. HLA-A may serve as a restriction element for indirect presentation of allopeptides or tissue-specific minor histocompatibility antigens, facilitating chronic graft loss. Therefore, we advocate a differential role for HLA matching over two epochs. A blanket approach to prospective matching for heart transplants may be premature for optimal long-term survival.

Immunosuppressive agents in clinical trials in transplantation

Many new agents are in or near clinical trials in organ transplantation. The small molecule antibioticlike drugs are inhibitors of key enzymes in T-cell signal transduction (calcineurin target of rapamycin [TOR], and inosine monophosphate dehydrogenase). Calcineurin inhibitors include cyclosporine microemulsion formulation generic cyclosporine preparations, and tacrolimus. Rapamycin (also known as sirolimus) acts on target of rapamycin to abrogate signals necessary for clonal expansion and is now in phase III. Recent trials of mycophenolate mofetil, an inhibitor of inosine monophosphate dehydrogenase, have shown that it reduces acute renal graft rejection when used with steroids and cyclosporine. New protein reagents in trials include polyclonal antilymphocyte antibodies, mouse monoclonal antibodies, "humanized" mouse monoclonals, and engineered proteins based on naturally occurring signalling molecules. Humanized antibodies against the interleukin-2 receptor are promising because humanized antibodies should combine low toxicity with the potential for long-term use. Engineered human proteins designed to block costimulatory molecules on antigen-presenting cells could have similar potential for low toxicity and extended use. These agents are designed to reduce acute rejection and the toxicity of the existing drugs and eventually improve long-term patient and graft survival. Organ transplant practice will probably change considerably as these agents become available.