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Leishmaniasis is considered a neglected tropical disease that is commonly found in Asia, Africa, South America, and Mediterranean countries. Visceral leishmaniasis (VL) is the most severe form of the disease and is almost universally fatal if left untreated. The symptoms of VL overlap with many infectious diseases, malignancies, and other blood disorders. The most common findings include fever, cytopenias, and splenomegaly. Given the nonspecific symptoms, the diagnosis requires detailed laboratory investigations, including bone marrow examination, that can be challenging in low- and middle-income countries. Diagnostic limitations likely lead to the underdiagnosis or delay in diagnosis of VL. We describe, to our knowledge, the first case report of VL in Cambodia in a child presenting with fever, anemia, and thrombocytopenia. The diagnosis required a liver biopsy and multiple bone marrow biopsies to visualize intracellular Leishmania spp. Our case illustrates the diagnostic challenges and the importance of timely diagnosis. This case also highlights the need for heightened awareness of the diagnostic findings of VL and improved reporting of tropical diseases.

Diffuse alveolar hemorrhage (DAH) is a life-threatening complication of hematopoietic cellular therapy (HCT). This study aimed to evaluate the effect of DAH treatments on outcomes using data from consecutive HCT patients clinically diagnosed with DAH from 3 institutions between January 2018-August 2022. Endpoints included sustained complete response (sCR) defined as bleeding cessation without recurrent bleeding, and non-relapse mortality (NRM). Forty children developed DAH at a median of 56.5 days post-HCT (range 1-760). Thirty-five (88%) had at least one concurrent endothelial disorder, including transplant-associated thrombotic microangiopathy (n=30), sinusoidal obstructive syndrome (n=19), or acute graft versus host disease (n=10). Fifty percent had a concurrent pulmonary infection at the time of DAH. Common treatments included steroids (n=17, 25% sCR), inhaled tranexamic acid (INH TXA,n=26, 48% sCR), and inhaled recombinant activated factor VII (INH fVIIa, n=10, 73% sCR). NRM was 56% 100 days after first pulmonary bleed and 70% at 1 year. Steroid treatment was associated with increased risk of NRM (HR 2.25 95% CI 1.07-4.71, p=0.03), while treatment with INH TXA (HR 0.43, 95% CI 0.19- 0.96, p=0.04) and INH fVIIa (HR 0.22, 95% CI 0.07-0.62, p=0.005) were associated with decreased risk of NRM. Prospective studies are warranted to validate these findings.

Organ infiltration by donor T cells is critical to the development of acute graft-versus-host disease (aGVHD) in recipients after allogeneic hematopoietic stem cell transplant (allo-HCT). However, deconvoluting the transcriptional programs of newly recruited donor T cells from those of tissue-resident T cells in aGVHD target organs remains a challenge. Here, we combined the serial intravascular staining technique with single-cell RNA sequencing to dissect the tightly connected processes by which donor T cells initially infiltrate tissues and then establish a pathogenic tissue residency program in a rhesus macaque allo-HCT model that develops aGVHD. Our results enabled creation of a spatiotemporal map of the transcriptional programs controlling donor CD8+ T cell infiltration into the primary aGVHD target organ, the gastrointestinal (GI) tract. We identified the large and small intestines as the only two sites demonstrating allo-specific, rather than lymphodepletion-driven, T cell infiltration. GI-infiltrating donor CD8+ T cells demonstrated a highly activated, cytotoxic phenotype while simultaneously developing a canonical tissue-resident memory T cell (TRM) transcriptional signature driven by interleukin-15 (IL-15)/IL-21 signaling. We found expression of a cluster of genes directly associated with tissue invasiveness, including those encoding adhesion molecules (ITGB2), specific chemokines (CCL3 and CCL4L1) and chemokine receptors (CD74), as well as multiple cytoskeletal proteins. This tissue invasion transcriptional signature was validated by its ability to discriminate the CD8+ T cell transcriptome of patients with GI aGVHD from those of GVHD-free patients. These results provide insights into the mechanisms controlling tissue occupancy of target organs by pathogenic donor CD8+ TRM cells during aGVHD in primate transplant recipients.

Hematopoietic cell transplantation (HCT) is the only readily available cure for many life-threatening pediatric nonmalignant diseases (NMD), but most patients lack a matched related donor and are at higher risk for graft-versus-host disease (GVHD). Use of abatacept (Aba) to target donor T-cell activation has been safe and effective in preventing GVHD after unrelated donor (URD) HCT for malignant diseases (Aba2 trial). Our primary objective was to evaluate the tolerability of Aba added to standard GVHD prophylaxis (cyclosporine and mycophenolate mofetil) in pediatric patients with NMD undergoing URD HCT. In this single-arm, single-center phase 1 trial, 10 patients receiving reduced intensity or nonmyeloablative conditioning underwent URD HCT. Immune reconstitution was assessed longitudinally via flow cytometry and compared to pediatric patients on Aba2. Nine patients successfully engrafted, with 1 primary graft rejection in the setting of inadequate cell dose; secondary graft rejection occurred in 1 patient with concurrent cytomegalovirus viremia. Two deaths occurred, both unrelated to Aba. One patient developed probable posttransplant lymphoproliferative disease, responsive to rituximab and immune suppression withdrawal. No patients developed severe acute or chronic GVHD, and 8 patients were off systemic immunosuppression at 1 year. Immune reconstitution did not appear to be impacted by Aba, and preservation of naïve relative to effector memory CD4+ T cells was seen akin to Aba2. Thus, 4 doses of Aba were deemed tolerable in pediatric patients with NMD following URD HCT, with encouraging preliminary efficacy and supportive immune correlatives in this NMD cohort.

Transplant-associated thrombotic microangiopathy (TA-TMA) and sickle cell disease (SCD) share features of endothelial and complement activation. Thus, we hypothesized that SCD is a risk factor for TA-TMA and that prehematopoietic cellular transplantation (HCT) markers of endothelial dysfunction and complement activation would be higher in patients with SCD. Children who underwent initial haploidentical or matched sibling donor HCT between January 2015 and June 2020 were included in this institutional review board–approved, single institution, retrospective study. Of the 115 children, 52 had SCD, and 63 underwent HCT for non-SCD indications. There was no significant difference in severe grade 3 to 4 acute graft-versus-host disease (GVHD) between recipients of HCT with or without SCD. The non-SCD cohort had significantly more cytomegalovirus-positive recipients, radiation-containing preparative regimens, and peripheral blood stem cell graft sources (P ≤ .05), all described risk factors for developing TA-TMA. Despite this, 7 of 52 patients (13%) with SCD developed TA-TMA compared with 1 of 63 patients (2%) without SCD (P = .015). Risk was highest in those who underwent haploidentical HCT (odds ratio [OR], 33; 95% confidence interval [CI], 1.4-793.2). Adjusting for HLA match, GVHD, post-HCT viral infection, stem cell source, and myeloablation, SCD remained a risk for developing TA-TMA (OR, 12.22; 95% CI, 1.15-129.6). In available pre-HCT samples, there was no difference in complement biomarkers between those with SCD and those without, though patients with SCD did have significantly higher levels of markers of endothelial activation, soluble vascular cell adhesion molecule 1, and P-selectin. In conclusion, children with SCD merit careful screening for TA-TMA after HCT, particularly those receiving a haploidentical HCT.

In the United States, Blacks and Hispanics are less likely than Whites to survive acute leukemias and other serious hematologic malignancies.1-3 Allogeneic hematopoietic cell transplantation (HCT) plays an important role in the treatment of high-risk hematologic malignancies, and 1 factor likely contributing to this disparity is the limited availability of 8/8 HLA-matched unrelated donors for persons of color (POC).4 Although most POC have access to 7/8 matched unrelated donors, mismatching is associated with increased risk for acute graft-versus-host disease (aGVHD), transplant-related mortality (TRM), and diminished overall survival (OS).

Fanconi anemia (FA) is the most common inherited bone marrow failure syndrome and is related to defects in DNA repair pathways that predispose affected individuals to malignancies.1 Monomorphic posttransplant lymphoproliferative disorder (PTLD) is a rare complication of hematopoietic cell transplantation (HCT) and behaves like an aggressive malignancy, often treated with alkylator-based chemotherapy. The underlying DNA repair defect in FA increases susceptibility to significant HCT treatment-related morbidity and mortality and makes standard monomorphic PTLD therapy challenging. We hypothesized that the novel approach of blinatumomab immunotherapy would have efficacy against PTLD that expresses CD19, with minimal toxicity. A 6-year-old male with FA, FANCA subtype, received an HLA-C 1-allele mismatched unrelated donor bone marrow HCT for progressive pancytopenia without evidence of myelodysplasia that was unresponsive to androgen therapy. On pretransplant evaluation, he was immunoglobulin G (IgG)–negative for Epstein-Barr virus (EBV). The donor’s EBV serologic status was unknown. He was enrolled in a phase 2 clinical trial (registered on ClinicalTrials.gov as #NCT03924401) and, per protocol, received a preparative regimen of thymoglobulin (12 mg/kg), fludarabine (150 mg/m2), and cyclophosphamide (30 mg/kg). Graft-versus-host disease (GVHD) prophylaxis included tacrolimus (serum target level, 8-12 ng/dL), mycophenolate mofetil through day 30, and the study drug abatacept on days −1, +5, +14, +28, +56, +87, +112, and +150. The patient had an uneventful early transplant course, with neutrophil engraftment on day +18. He was discharged on day +30 without evidence of GVHD and was on our institutional standard infectious prophylactic agents: acyclovir, Bactrim, and voriconazole at discharge.

Although stable mixed-hematopoietic chimerism induces robust immune tolerance to solid organ allografts in mice, the translation of this strategy to large animal models and to patients has been challenging. We have previously shown that in MHC-matched nonhuman primates (NHPs), a busulfan plus combined belatacept and anti-CD154-based regimen could induce long-lived myeloid chimerism, but without T cell chimerism. In that setting, donor chimerism was eventually rejected, and tolerance to skin allografts was not achieved. Here, we describe an adaptation of this strategy, with the addition of low-dose total body irradiation to our conditioning regimen. This strategy has successfully induced multilineage hematopoietic chimerism in MHC-matched transplants that was stable for as long as 24 months posttransplant, the entire length of analysis. High-level T cell chimerism was achieved and associated with significant donor-specific prolongation of skin graft acceptance. However, we also observed significant infectious toxicities, prominently including cytomegalovirus (CMV) reactivation and end-organ disease in the setting of functional defects in anti-CMV T cell immunity. These results underscore the significant benefits that multilineage chimerism-induction approaches may represent to transplant patients as well as the inherent risks, and they emphasize the precision with which a clinically successful regimen will need to be formulated and then validated in NHP models.

Graft-versus-host disease (GVHD) is the most common complication of hematopoietic stem cell transplant (HCT). However, our understanding of the molecular pathways that cause this disease remains incomplete, leading to inadequate treatment strategies. To address this, we measured the gene expression profile of nonhuman primate (NHP) T cells during acute GVHD. Utilizing microarray technology, we measured the expression profiles of CD3+ T cells from five cohorts: allogeneic transplant recipients receiving (i) no immunoprophylaxis (No Rx), (ii) sirolimus monotherapy (Siro), (iii) tacrolimus-methotrexate (Tac-Mtx), as well as (iv) autologous transplant recipients (Auto) and (v) healthy controls (HC). This comparison allowed us to identify transcriptomic signatures specific for alloreactive T cells and determine the impact of both mTOR (mechanistic target of rapamycin) and calcineurin inhibition on GVHD. We found that the transcriptional profile of unprophylaxed GVHD was characterized by significant perturbation of pathways regulating T cell proliferation, effector function, and cytokine synthesis. Within these pathways, we discovered potentially druggable targets not previously implicated in GVHD, prominently including aurora kinase A (AURKA). Utilizing a murine GVHD model, we demonstrated that pharmacologic inhibition of AURKA could improve survival. Moreover, we found enrichment of AURKA transcripts both in allo-proliferating T cells and in sorted T cells from patients with clinical GVHD. These data provide a comprehensive elucidation of the T cell transcriptome in primate acute GVHD and suggest that AURKA should be considered a target for preventing GVHD, which, given the many available AURKA inhibitors in clinical development, could be quickly deployed for the prevention of GVHD.