Long-term follow-up of donor chimerism and tolerance after human liver transplantation

Delayed Donor Bone Marrow Infusion Induces Liver Transplant Tolerance

BACKGROUND

Nonmyeloablative conditioning followed by donor bone marrow infusion (BMI) to induce tolerance has not been robustly tested in liver transplantation (LT) and may be unsafe at the time of LT. We hypothesized T cell-depleted BMI is effective in inducing tolerance when delayed after LT, resulting in potentially safer future clinical applications.

METHODS

Nonimmunosuppressed syngeneic (Lewis to Lewis) and allogeneic (ACI to Lewis) rat LT transplants were initially performed as controls. Three experimental allogeneic LT groups were treated with tacrolimus (TAC) for 3 to 4 weeks and then underwent: (1) TAC withdrawal alone; (2) nonmyeloablative conditioning (anti-αβTCR mAb + total body irradiation [300 cGy]) followed by TAC withdrawal; (3) Nonmyeloablative conditioning + donor BMI (100 × 10 T cell-depleted bone marrow cells) followed by TAC withdrawal.

RESULTS

All group 1 recipients developed chronic rejection. Group 2 had long-term survival but impaired liver function and high donor-specific antibody (DSA) levels. In contrast, group 3 (conditioning + BMI) had long-term TAC-free survival with preserved liver function and histology, high mixed chimerism and blood/liver/spleen CD4 + CD25 + Foxp3+ regulatory T cells, and low DSA titers, similar to syngeneic grafts. While donor-specific tolerance was observed post-BMI, graft-versus-host disease was not.

CONCLUSIONS

These results support that donor-specific tolerance can be achieved with BMI even when delayed after LT and this tolerance correlates with increased mixed chimerism, regulatory T cell generation, and diminished DSA.

Immunosuppression in pediatric liver transplant recipients: Unique aspects

Pediatric liver transplantation has experienced improved outcomes over the last 50 years. This can be attributed in part to establishing optimal use of immunosuppressive agents to achieve a balance between minimizing the risks of allograft rejection and infection. The management of immunosuppression in children is generally more complex and can be challenging when compared with the use of these agents in adult liver transplant patients. Physiologic differences in children alter the pharmacokinetics of immunosuppressive agents, which affects absorption, distribution, metabolism, and drug excretion. Children also have a longer expected period of exposure to immunosuppression, which can impact growth, risk of infection (bacterial, viral, and fungal), carcinogenesis, and likelihood of nonadherence. This review discusses immunosuppressive options for pediatric liver transplant recipients and the unique issues that must be addressed when managing this population. Further advances in the field of tolerance and accommodation are needed to relieve the acute and cumulative burden of chronic immunosuppression in children. Liver Transplantation 23 244-256 2017 AASLD.

A fast and simple method for detecting and quantifying donor-derived cell-free DNA in sera of solid organ transplant recipients as a biomarker for graft function

Timely detection of graft rejection is an important issue in the follow-up care after solid organ transplantation. Until now, biopsy has been considered the “gold standard” in the diagnosis of graft rejection. However, non-invasive tests such as monitoring the levels of cell-free DNA (cfDNA) as a sensitive biomarker for graft integrity have attracted increasing interest. The rationale of this approach is that a rejected organ will lead to a significant release of donor-derived cfDNA, which can be detected in the serum of the transplant recipient.

We have developed a novel quantitative real-time PCR (qPCR) approach for detecting an increase of donor-derived cfDNA in the recipient’s serum. Common insertion/deletion (InDel) genetic polymorphisms, which differ between donor and recipient, are targeted in our qPCR assay. In contrast to some other strategies, no specific donor/recipient constellations such as certain gender combinations or human leukocyte antigen (HLA) discrepancies are required for the application of our test.

The method was first validated with serial dilutions of serum mixtures obtained from healthy blood donors and then used to determine donor-derived cfDNA levels in patients’ sera within the first 3 days after their kidney transplantation had been performed.

Our method represents a universally applicable, simple and cost-effective tool which can potentially be used to detect graft dysfunction in transplant recipients.

Immunological considerations in in utero hematopoetic stem cell transplantation (IUHCT)

In utero hematopoietic stem cell transplantation (IUHCT) is an attractive approach and a potentially curative surgery for several congenital hematopoietic diseases. In practice, this application has succeeded only in the context of Severe Combined Immunodeficiency Disorders. Here, we review potential immunological hurdles for the long-term establishment of chimerism and discuss relevant models and findings from both postnatal hematopoietic stem cell transplantation and IUHCT.

A systematic review and meta-analysis on the prevalence of Dupuytren disease in the general population of Western countries

BACKGROUND

Dupuytren disease is a fibroproliferative disease of palmar fascia of the hand. Its prevalence has been the subject of several reviews; however, an accurate description of the prevalence range in the general population--and of the relation between age and disease--is lacking.

METHODS

Embase and PubMed were searched using database-specific Medical Subject Headings; titles and abstracts were searched for the words "Dupuytren," "incidence," and "prevalence." Two reviewers independently assessed the articles using inclusion and exclusion criteria, and rated the included studies with a quality assessment instrument. In a meta-analysis, the median prevalence, as a function of age by sex, was estimated, accompanied by 95 percent prediction intervals. The observed heterogeneity in prevalence was investigated with respect to study quality and geographic location.

RESULTS

Twenty-three of 199 unique identified articles were included. The number of participants ranged from 37 to 97,537, and age ranged from 18 to 100 years. Prevalence varied from 0.6 to 31.6 percent. The quality of studies differed but could not explain the heterogeneity among studies. Mean prevalence was estimated as 12, 21, and 29 percent at ages 55, 65, and 75 years, respectively, based on the relation between age and prevalence determined from 10 studies.

CONCLUSIONS

The authors describe a prevalence range of Dupuytren disease in the general population of Western countries. The relation between age and prevalence of Dupuytren disease is given according to sex, including 95 percent prediction intervals. It is possible to determine disease prevalence at a certain age for the total population, and for men and women separately.

Immunosuppression: trends and tolerance?

Advances in pharmacologic immunosuppression are responsible for the excellent outcomes experienced by recipients of liver transplants. However, long-term follow-up of these patients reveals an increasing burden of morbidity and mortality that is attributable to these drugs. The authors summarize the agents used in contemporary liver transplantation immunosuppression protocols and discuss the emerging trend within the community to minimize or eliminate these agents from use. The authors present recently published data that may provide the foundation for immunosuppression minimization or tolerance induction in the future and review studies that have focused on the utility of biomarkers in guiding immunosuppression management.

A systematic review and meta-analysis on the prevalence of Dupuytren disease in the general population of Western countries

BACKGROUND

Dupuytren disease is a fibroproliferative disease of palmar fascia of the hand. Its prevalence has been the subject of several reviews; however, an accurate description of the prevalence range in the general population--and of the relation between age and disease--is lacking.

METHODS

Embase and PubMed were searched using database-specific Medical Subject Headings; titles and abstracts were searched for the words "Dupuytren," "incidence," and "prevalence." Two reviewers independently assessed the articles using inclusion and exclusion criteria, and rated the included studies with a quality assessment instrument. In a meta-analysis, the median prevalence, as a function of age by sex, was estimated, accompanied by 95 percent prediction intervals. The observed heterogeneity in prevalence was investigated with respect to study quality and geographic location.

RESULTS

Twenty-three of 199 unique identified articles were included. The number of participants ranged from 37 to 97,537, and age ranged from 18 to 100 years. Prevalence varied from 0.6 to 31.6 percent. The quality of studies differed but could not explain the heterogeneity among studies. Mean prevalence was estimated as 12, 21, and 29 percent at ages 55, 65, and 75 years, respectively, based on the relation between age and prevalence determined from 10 studies.

CONCLUSIONS

The authors describe a prevalence range of Dupuytren disease in the general population of Western countries. The relation between age and prevalence of Dupuytren disease is given according to sex, including 95 percent prediction intervals. It is possible to determine disease prevalence at a certain age for the total population, and for men and women separately.

Tolerance and chimerism and allogeneic bone marrow/stem cell transplantation in liver transplantation

The liver has particular tolerogenic properties that allow its spontaneous acceptance in some animal species. Liver structure is considered to favor a tolerogenic environment. The peripheral tolerance mechanisms also play a role in spontaneous tolerance to liver graft. In a clinical setting, the main challenge nowadays facing liver transplantation is minimization of immunosuppression with the goal of donor-specific tolerance. Mechanisms involved in tolerance to transplanted organs are complex and partly unknown. A significant mechanism in tolerance induction is chimerism. Chimerism can be induced through transplantation of allogeneic donor bone marrow/stem cells under appropriate host conditioning. This review focuses on the tolerance mechanisms in liver transplantation and highlights the role of chimerism and allogeneic bone marrow/stem cell transplantation in tolerance development.

KIR gene mismatching and KIR/C ligands in liver transplantation: consequences for short-term liver allograft injury

BACKGROUND

Killer immunoglobulin-like receptors (KIRs) bind human leukocyte antigen (HLA) class-I (HLA-I) ligands and regulate functions of natural killer cells and subsets of T cells. KIR/HLA-I interactions allow predicting natural killer cell alloreactivity in hematopoietic stem cell transplantation and in HLA-compatible kidney transplants, but its meaning in liver transplantation remains controversial.

METHODS

KIR and HLA genotypes were studied in 402 liver transplants, using sequence-specific oligonucleotides and primer methods. Recipients and donor KIRs, HLA-C genotypes, KIR gene mismatches (MMs) between recipient-donor pairs, and KIR/HLA-ligand combinations were analyzed in overall transplantations, in the acute rejection (AR; n=110) and non-AR (n=292) groups.

RESULTS

KIR gene MMs between recipients and donors, mainly in activating KIRs, and KIR2DL3 and KIR2DS1 of recipients in the presence of donor C2 ligands, significantly enhanced early AR rate (P<0.05), with KIR2DL3 and KIR2DS1 exhibiting a synergic effect in dependence of the donor C2 ligand number (χ2=7.662, P=0.022). KIR2DL3, KIR2DS1, and also KIR2DS4 significantly influenced short-term graft survival, with a benefit for transplantations combining KIR2DL3 recipients and donors having C1 ligands (log rank, P<0.019 at 1 year; hazards ratio [HR], 0.321; 95% confidence interval [CI], 0.107-0.962; P=0.042), whereas KIR2DS1 and KIR2DS4 recipients combined with donors lacking C1 ligands (C2/C2) exhibited a worse graft survival (log rank, P=0.035 at 6 months; HR, 7.713; 95% CI, 2.156-27.369; P=0.002 for KIR2DS1; and log rank, P=0.006 at 1 year; HR, 3.794; 95% CI, 1.267-11.365; P=0.017 for KIR2DS4).

CONCLUSIONS

This study shows that KIR gene-gene MMs increase AR and that KIRs/C ligands associated to AR and KIR2DS4/C ligands also influence short-term graft survival.

Acute graft versus host disease after orthotopic liver transplantation

Graft versus host disease (GVHD) is an uncommon complication after orthotopic liver transplantation (OLT) with an incidence of 0.1–2%, but an 80–100% mortality rate. Patients can present with skin rashes, diarrhea, and bone marrow aplasia between two to eight weeks after OLT. Diagnosis of GVHD is made based on clinical and histologic evidence, supported by chimerism studies showing donor HLA alleles in the recipient bone marrow or blood. Several therapeutic approaches have been used for the management of GVHD after OLT including increased immunosuppression, decreased immunosuppression, and cellular therapies. However, success rates have been low, and new approaches are needed.

Microchimerism in promoting graft acceptance in clinical transplantation

PURPOSE OF REVIEW

Infusions of bone marrow-derived cells together with 'space making' continue to be tested in clinical organ transplant tolerance protocols. These trials are based on the hypothesis that this might produce initial multilineage chimerism. There is some evidence that this in turn induces regulatory cells that control alloimmunity. Although a wealth of knowledge is available from animal models, this review deals with what we know or can speculate about donor bone marrow cells and chimerism in human organ transplantation.

RECENT FINDINGS

Calcineurin inhibitors are employed in most of these protocols to blunt the initial immune response. One protocol also has a stepwise regulatory cell generating treatment with sirolimus before total withdrawal. A number of donor chimeric lineages including stem cells, dendritic cells, myeloid precursors, and various lymphoid subpopulations have been described. Currently, it is recognized that the nature of cells that make up the chimerism could influence graft rejection versus acceptance. Tolerogenic donor chimeric cells may also generate regulatory subsets, thus controlling alloimmunity on two fronts.

SUMMARY

It might be speculated that prolonged and sustained regulation or possible anergy induced by chimerism may eventually lead to clonal deletion, thereby bringing about classical immunologic tolerance.

Microchimerism in salivary glands after blood- and marrow-derived stem cell transplantation

Blood- and marrow-derived stem cells (BMDSCs) provide disease-ameliorating effects for cardiovascular and autoimmune diseases. Microchimerism from donor BMDSCs has been reported in several recipient tissues. We hypothesized that this finding suggests a potential use of BMDSCs in the treatment of salivary dysfunctions. We investigated the presence of Y chromosome-positive cells in salivary gland biopsies of 5 females who had received a marrow or blood stem cell transplant from male donors. One to 16 years after transplantation, all recipients exhibited scattered Y chromosome-positive cells in the acini, ducts, and stroma of their salivary glands (mean of 1.01%). Potentially, these cells can be markers of transplantation tolerance, contribute to neoplastic epithelial tissues, or engraft at sites of injury. In addition, transplantation of BMDSCs could be used for treatment of Sjögren's syndrome and salivary glands damaged by therapeutic irradiation for cancers of the head and neck.

Operational tolerance: past lessons and future prospects

Every liver transplant (LT) center has had patients who either self-discontinue immunosuppressive (IS) therapy or are deliberately withdrawn due to a research protocol or clinical concern (ie, lymphoproliferative disorder [LPD], overwhelming infection). This is understandable because maintenance IS therapy, particularly calcineurin inhibitors (CNI), is associated with significant cost, side effects, and considerable long-term morbidity and mortality. Detrimental effects of IS therapy include increased risk of cardiovascular disease, metabolic syndrome, bone loss, opportunistic and community-acquired infections, and malignancy. In fact, LT recipients have among the highest rates of chronic kidney disease and associated mortality among all nonkidney solid organ recipients. This mortality is only ameliorated by undergoing a curative kidney transplant, usurping costs and valuable organ resources. The search for improved treatment algorithms includes trial and error CNI dose minimization, the use of alternative IS agents (antimetabolites, mammalian target of rapamycin [mTOR] inhibitors), or even complete CNI withdrawal. Yet those who are successful in achieving such operational tolerance (no immunosuppression and normal allograft function) are considered lucky. The vast majority of recipients will fail this approach, develop acute rejection or immune-mediated hepatitis, and require resumption of IS therapy. As such, withdrawal of IS following LT is not standard-of-care, leaving clinicians to currently maintain transplant patients on IS therapy for life. Nonetheless, the long-term complications of all IS therapies highlight the need for strategies to promote immunologic or operational tolerance. Clinically applicable biomarker assays signifying the potential for tolerance as well as tolerogenic IS conditioning are invariably needed if systematic, controlled rather than "hit or miss" approaches to withdrawal are considered. This review will provide an overview of the basic mechanisms of tolerance, particularly in relation to LT, data from previous IS withdrawal protocols and biomarker studies in tolerant recipients, and a discussion on the prospect of increasing the clinical feasibility and success of withdrawal.

Gender-specific differences associated with living donor liver transplantation: a review study

Living donor liver transplantation (LDLT) has developed into an important therapeutic option for liver diseases. For living donor kidney transplantation (LDKT), gender-specific differences have been observed among both donors (two-thirds being women and one-third being men) and recipients (two-thirds being men and one-third being women). The aim of this study was to determine whether there is a gender disparity for LDLT. We contacted 89 national and international transplantation registries, single transplant centers, and coordinators. In addition, a sample of 274 articles dealing with LDLT and its outcomes was reviewed and compared with the registry data. The data included the gender of the donors and recipients, the country of transplantation, and the donor-recipient relationship. The investigation showed that overall there were slightly more men among the donors (53% male and 47% female). As for the recipients, 59% of the organs were distributed to males, and 41% were distributed to females. Differences in the gender distribution were observed with respect to individual countries. Worldwide, 80% of the donors were blood-related, 11% were not blood-related, and 9% were spouses. The data acquired from the publications were similar to the registry data. Our research has shown that there are hardly any registry data published, a lot of countries do not have national registries, or the access to these data is difficult. Even widely ranging published studies often do not give information on the gender distribution or the donor-recipient relationship. Further investigations are needed to understand the possible medical, psychosocial, or cultural reasons for gender distribution in LDLT and the differences in comparison with LDKT.

Induction of tolerance in renal transplantation using splenic transplantation: experimental study in a canine model

OBJECTIVE

To evaluate in a canine model the induction of tolerance to renal transplantation after splenectomy and splenosis.

MATERIALS AND METHODS

This prospective, experimental, comparative, longitudinal study included 4 experimental groups, each comprising 4 dogs. Group 1 (control group) underwent renal transplantation only; group 2 underwent renal transplantation and splenectomy; group 3 underwent renal transplantation and splenosis; and group 4 underwent renal transplantation, splenectomy, and splenosis. Survival and degree of rejection were compared between the 4 groups.

RESULTS

Splenosis improved renal function after transplantation, as indicated by increased serum creatinine concentration (group 3, 6.2 mg/dL vs group 1, 12.9 mg/dL). Comparison of weighted survival curves (corrected for degree of rejection) demonstrated a significant difference between group 2 (66.0 days) and group 4 (66.2 days) vs group 1 (52.7 days) and group 3 (41.2 days) (P = .05, Wilcoxon rank sum test).

CONCLUSION

These results suggest that in this experimental model of renal transplantation, splenosis and splenectomy induce clinical tolerance, as indicated by improved renal function and prolonged recipient survival.

Biomarkers to discern transplantation tolerance after allogeneic hematopoietic cell transplantation

Although it is commonly accepted that allogeneic hematopoietic cell transplant (HCT) recipients develop transplantation tolerance and can quickly discontinue all immunosuppressive drugs, existing data does not support this concept. Most patients will require a prolonged duration of immunosuppression, lasting commonly several years. This has even greater importance, as the majority of transplants are now performed utilizing peripheral blood mobilized stem cells, which are associated with an increased risk of chronic graft-versus-host disease (cGVHD) and prolonged duration of immunosuppression. Despite these challenges, the approach to liberation from immunosuppression after HCT is empiric, and biomarkers of operational tolerance after HCT are lacking. Conversely, investigators in solid organ allografting have begun to examine tolerance associated gene expression in renal and hepatic allograft recipients. Significant challenges in the design and interpretation of these studies potentially limit comparisons. However, a relatively unified model is beginning to emerge, which largely recapitulates previously established mechanisms of immune tolerance. This evidence supports a state of immune quiescence with reduced expression of costimulation and immune response genes, and upregulation of cell cycle control genes. Data indirectly supports the importance of tumor growth factor (TGF)-beta, supports the role of CD4(+)CD25(+) regulatory T cells, and offers new insights into the role of natural killer (NK) cells. Distinct in hepatic allograft tolerance, emerging evidence highlights the importance of gammadeltaT cells, and selection of the Vgammadelta1+ subtype among the gammadeltaT cell population. The deficiencies in the current understanding of transplantation tolerance after HCT, as well as the inadequacies evident in the current empiric approach to immunosuppressive medication (IS) management after HCT make clear the rationale for investigation aimed at elucidating tolerance associated biomarkers after HCT.