Risk factors for mixed chimerism in children with hemophagocytic lymphohistiocytosis after reduced toxicity conditioning.

BACKGROUND: Reduced toxicity conditioning for hematopoietic stem cell transplantation of patients with hemophagocyticlymphohistiocytosis (HLH) results in favorable survival, however at the expense of relevant rates of mixed chimerism. Factors predisposing to mixed chimerism remain to be determined. PROCEDURE: Patients with primary HLH transplanted 2009-2016 after treosulfan- or melphalan-based conditioning regimens were analyzed in a retrospective multicenter study for survival, engraftment, chimerism, and adverse events. Mixed chimerism was considered substantial if < 25% donor chimerism occurred and/or if secondary cell therapy was administered. Donor type, graft source, type of alkylating agent, type of serotherapy, and remission status were analyzed as potential risk factors in a multivariable logistic regression model. RESULTS: Among 60 patients, engraftment was achieved in 95%, and the five-year estimated overall survival rate was 75%. Prevalence of any recipient chimerism was 48%. Substantial recipient chimerism was recorded in 32% of patients. Secondary post-HSCT cell therapy was administered in 30% of patients. A human leukocyte antigen (HLA)-mismatched donor (< 10/10) was the only significant risk factor for the occurrence of substantial recipient chimerism (P = 0.01; odds ratio, 5.8; CI 95%, 1.5-26.3). CONCLUSION: The use of an HLA-matched donor is the most important factor to avoid substantial recipient chimerism following treosulfan -or melphalan-based conditioning in primary HLH.

Post-Transplant CD34+ Selected Stem Cell "Boost" for Mixed Chimerism after Reduced-Intensity Conditioning Hematopoietic Stem Cell Transplantation in Children and Young Adults with Primary Immune Deficiencies.

Mixed chimerism and eventual graft loss occurs in a proportion of children with primary immune deficiencies receiving alemtuzumab, fludarabine, and melphalan reduced-intensity conditioning (RIC) regimens before allogeneic hematopoietic stem cell transplantation (HSCT). We investigated the usefulness of a CD34+ selected stem cell "boost" without conditioning to treat mixed chimerism in children and young adults who received predominantly an alemtuzumab, fludarabine, and melphalan RIC regimen for primary immune deficiencies and reported the outcomes. Patients with a primary immune deficiency disorder who were either enrolled on a prospective CD34+ boost study for treatment of mixed chimerism from 2011 to 2014 (n = 9) or treated with a CD34+ boost on a clinical basis from 2014 to 2016 (n = 3) were included in this analysis. Response to a CD34+ boost was defined as a rise in donor chimerism by ≥15% with donor chimerism of at least 20%, stabilization was defined as a rise in chimerism by <15% with donor chimerism ≥ 20%, and no response was defined as any decline in donor chimerism or need for a second HSCT after a CD34+ boost. Twelve patients received alemtuzumab, fludarabine, and melphalan. Median age was 4.5 years (range, .9 to 20.6), and median whole blood donor chimerism before the boost was 25% (range, 3% to 61%). Three patients (25%) met criteria for response, 1 patient (8%) was considered to have stabilization, and 8 patients (67%) had no response 12 months after the boost. None of the patients developed any complications from a CD34+ boost, including no acute graft-versus-host disease (GVHD). All patients are alive with a median follow-up of 32 months (range, 8 to 79). We conclude that a CD34+ selected stem cell boost can be considered for treatment of mixed chimerism after alemtuzumab, fludarabine, and melphalan RIC HSCT in children and young adults with primary immune deficiencies. Approximately one-third of patients can be expected to benefit from a CD34+ selected stem cell boost and may avoid the need for a second HSCT. Lack of any GVHD or toxicity makes a stem cell boost an attractive option compared with donor lymphocyte infusions for treatment of mixed chimerism.

Preclinical and clinical studies for transplant tolerance via the mixed chimerism approach.

Based upon observations in murine models, we have developed protocols to induce renal allograft tolerance by combined kidney and bone marrow transplantation (CKBMT) in non-human primates (NHP) and in humans. Induction of persistent mixed chimerism has proved to be extremely difficult in major histocompatibility complex (MHC)-mismatched primates, with detectable chimerism typically disappearing within 30-60 days. Nevertheless, in MHC mismatched NHP, long-term immunosuppression-free renal allograft survival has been achieved reproducibly, using a non-myeloablative conditioning approach that has also been successfully extended to human kidney transplant recipients. CKBMT has also been applied to the patients with end stage renal disease with hematologic malignancies. Renal allograft tolerance and long-term remission of myeloma have been achieved by transient mixed or persistent full chimerism. This review summarizes the current status of preclinical and clinical studies for renal and non-renal allograft tolerance induction by CKBMT. Improving the consistency of tolerance induction with less morbidity, extending this approach to deceased donor transplantation and inducing tolerance of non-renal transplants, are critical next steps for bringing this strategy to a wider range of clinical applications.

A 15-year-old boy with severe combined immunodeficiency, fungal infection, and weight gain.

Hematopoietic stem cell transplantation (HSCT) outcomes in X-linked severe combined immune deficiency are most effective when performed with patients <3 months of age and without coexisting morbidity, and with donor cells from a matched sibling. Even under such favorable circumstances, outcomes can be suboptimal, and full cellular engraftment may not be complete, which results in poor B or natural killer cell function. Protein losing enteropathies can accompany persistent immune deficiency disorders with resultant low serum globulins (immunoglobulin A [IgA], IgG, IgM) and lymphopenia. Patients with immune disorders acquire infections that can be predicted by their immune dysfunction. Fungal infections are typically noted in neutropenic (congenital or acquired) and T-cell deficient individuals. Coexisting fungal infections are rare, even in hosts who are immunocompromised, and they require careful evaluation. Antifungal treatment may result in drug-drug interactions with significant complications.

Chimerism status after unrelated donor bone marrow transplantation with fludarabine-melphalan conditioning is affected by the melphalan dose and is predictive of relapse.

Little is known regarding the chimerism status after reduced-intensity conditioning transplantation when bone marrow is used as a stem cell source. We prospectively analyzed lineage-specific chimerism and retrospectively evaluated clinical outcomes in 80 adult patients who underwent unrelated donor bone marrow transplantation (URBMT) with fludarabine plus melphalan (FM) as the conditioning regimen. Mixed donor chimerism (MDC) was seen in 43 and 10 % of patients at days 14 and 28, respectively. Melphalan at ≤130 mg/m(2) was associated with an increased incidence of MDC at day 28 (P = 0.03). Patients with MDC at day 14 showed a marginally increased risk of primary graft failure and a marginally decreased risk of graft-versus-host disease. In multivariate analysis, MDC at day 14 was associated with higher overall mortality (hazard ratio (HR) = 2.1; 95 % confidence interval (CI), 1.1-4.2; P = 0.04) and relapse rate (HR = 3.0; 95 % CI, 1.2-7.5; P = 0.02), but not with non-relapse mortality (HR = 1.8; 95 % CI, 0.70-4.6; P = 0.23). Thus, the FM regimen yields prompt complete donor chimerism after URBMT, but the melphalan dose significantly impacts the kinetics of chimerism. Chimerism status evaluation at day 14 may be instrumental in predicting relapse after URBMT with the FM regimen.

Reduced-intensity conditioning for allogeneic stem cell transplant in primary immune deficiencies.

Conventional myeloablative conditioning regimens prior to hematopoietic cell transplantation (HCT) are associated with significant transplant-related morbidity and mortality in children affected by primary immunodeficiency disorders. Reduced-intensity conditioning regimens have been extensively used without severe acute toxicity in patients with pre-HCT comorbidities, with the additional advantage of reducing or avoiding long-term sequelae such as infertility and growth retardation. Compared with myeloablative HCT, reduced-intensity conditioning regimens are associated with an increased incidence of mixed donor chimerism and graft rejection. While mixed donor engraftment is likely to correct the phenotypic expression of most children with primary immunodeficiency disorders, the use of donor lymphocyte infusion to increase donor chimerism or second HCT procedures may be required in some cases. Here we discuss the most recent data on the use of different reduced-intensity conditioning protocols in children with primary immunodeficiency disorders, highlighting significant clinical lessons and areas that need additional study.

Fetal cell microchimerism develops through the migration of fetus-derived cells to the maternal organs early after implantation.

Fetus-derived cells are present in the blood and tissues of the maternal body over a long period of time, even after delivery, resulting in fetal cell microchimerism. The exact process by which fetal cells cross the placental barrier to enter the maternal circulation is unclear. The objective of this paper was to determine the time during pregnancy that fetal cells with multilineage potential migrate to the maternal organs. Wild type female mice were crossbred with male transgenic mice, expressing enhanced green fluorescent protein (EGFP). Total hysterectomies were performed at different time points of pregnancy. On day 60 after surgery, mice were injected with either streptozotocin (STZ) to induce insulin-dependent diabetes mellitus, or vehicle. Detection and quantification of fetal cells were then undertaken in a variety of maternal organs via fluorescent microscopy and quantitative PCR amplification of the gfp transgene. In vehicle control mice, fetal cells were detected only in the maternal bone marrow. However on day 30 after STZ injection, fetal cells were detected not only in bone marrow but also in the maternal pancreas, liver and kidney. Histological analysis showed differentiated fetal cells within the pancreatic acinar cells, hepatocytes and tubular epithelial cells. Their morphological appearance was indistinguishable from their maternal counterparts, and their frequency in these organs was constant, regardless of the timing of hysterectomy. These results indicate that most fetal cells with multilineage potential in maternal tissues migrate to the maternal body early after implantation, and thereafter sustain their population over the long term after delivery.

HDAC inhibitor reduces cytokine storm and facilitates induction of chimerism that reverses lupus in anti-CD3 conditioning regimen.

In allogeneic hematopoietic cell transplantation (HCT), donor T cell-mediated graft versus host leukemia (GVL) and graft versus autoimmune (GVA) activity play critical roles in treatment of hematological malignancies and refractory autoimmune diseases. However, graft versus host disease (GVHD), which sometimes can be fatal, remains a major obstacle in classical HCT, where recipients are conditioned with total body irradiation or high-dose chemotherapy. We previously reported that anti-CD3 conditioning allows donor CD8(+) T cells to facilitate engraftment and mediate GVL without causing GVHD. However, the clinical application of this radiation-free and GVHD preventative conditioning regimen is hindered by the cytokine storm syndrome triggered by anti-CD3 and the high-dose donor bone marrow (BM) cells required for induction of chimerism. Histone deacetylase (HDAC) inhibitors such as suberoylanilide hydroxamic acid (SAHA) are known to induce apoptosis of cancer cells and reduce production of proinflammatory cytokines by nonmalignant cells. Here, we report that SAHA inhibits the proliferative and cytotoxic activity of anti-CD3-activated T cells. Administration of low-dose SAHA reduces cytokine production and ameliorates the cytokine storm syndrome triggered by anti-CD3. Conditioning with anti-CD3 and SAHA allows induction of chimerism with lower doses of donor BM cells in old nonautoimmune and autoimmune lupus mice. In addition, conditioning with anti-CD3 and SAHA allows donor CD8(+) T cell-mediated GVA activity to reverse lupus glomerulonephritis without causing GVHD. These results indicate that conditioning with anti-CD3 and HDAC inhibitors represent a radiation-free and GVHD-preventative regimen with clinical application potential.