Hematopoietic Cellular Transplantation Research Articles

Transplant Eligible and Ineligible Elderly Patients with AML-A Genomic Approach and Next Generation Questions.

The management of elderly patients diagnosed with acute myelogenous leukemia (AML) is complicated by high relapse risk and comorbidities that often preclude access to allogeneic hematopoietic cellular transplantation (allo-HCT). In recent years, fast-paced FDA drug approval has reshaped the therapeutic landscape, with modest, albeit promising improvement in survival. Still, AML outcomes in elderly patients remain unacceptably unfavorable highlighting the need for better understanding of disease biology and tailored strategies. In this review, we discuss recent modifications suggested by European Leukemia Network 2022 (ELN-2022) risk stratification and review recent aging cell biology advances with the discussion of four AML cases. While an older age, >60 years, does not constitute an absolute contraindication for allo-HCT, the careful patient selection based on a detailed and multidisciplinary risk stratification cannot be overemphasized.

#46 A Multicenter Study Exploring the Epidemiology and Outcomes of COVID-19 Among Pediatric Hematopoietic Cell Transplant, Cellular Therapy and Solid Organ Transplant Recipients: Preliminary Results from the Pediatric COVID-19 U.S. Registry.

BackgroundWhile most pediatric patients with COVID-19 experience mild disease, children with a history of hematopoietic cell transplant or cellular therapy (HCT/CT) or solid organ transplant (SOT) may be at increased risk for severe disease. Despite this, there is a dearth of data from multicenter studies examining COVID-19 outcomes among pediatric HCT/CT and SOT recipients. We present descriptive results from the Pediatric COVID-19 U.S. registry to characterize COVID-19 illness among pediatric HCT/CT and SOT recipients across the United States.MethodDemographic, medical history, and COVID-19 related data were extracted from HCT/CT and SOT recipient medical records and submitted to the Pediatric COVID-19 U.S. Registry, a passive surveillance registry of pediatric patients less than 21 years old diagnosed with COVID-19 between March 2020 and April 2021. Participating US centers (n=170) submitted de-identified information for inpatients and outpatients at 7- and 28-days post COVID-19 diagnosis via a publicly available REDCap electronic survey. Data were summarized descriptively to characterize COVID-19 hospitalizations among HCT/CT and SOT recipients.ResultsOf the 13,140 registry COVID-19 cases, a total of 202 (1.5%) were patients with history of HCT/CT (n=58) or SOT (n=144). Median age at COVID-19 diagnosis among HCT/CT was 9.5 years (range 0.66 to 18) and SOT was 13.5 years (range 1 to 20). Over half of HCT (64%) and SOT (53.8%) patients were White/Caucasian and 26% of HCT and 39% of SOT here Hispanic/Latino. Hospitalizations among HCT/CT and SOT accounted for approximately 12% of all hospitalizations reported to the registry (n = 1683). Almost half of the reported HCT/CT (48%) and SOT (44%) cases were hospitalized. In those hospitalized, 11 (19%) HCT and 18 (12.5%) SOT cases required ICU admission. Half (50%) of HCT hospitalized cases received oxygen support and 3 (11%) required mechanical ventilation while only 2 (0.6%) SOT cases received oxygen support, and none required mechanical ventilation. The majority of HCT/CT cases (64%) were hospitalized between Days 100 and 365 post-transplant. Approximately half (48%) of the HCT cases had received an allogenic HCT. Myeloablative conditioning was the most common regimen reported (48%) among hospitalized HCT cases. Approximately half of SOT hospitalized cases had received a kidney transplant (48%) followed by liver (30%) and heart (19%). Of the 63 hospitalized SOT cases, the majority (87%) were receiving tacrolimus at COVID-19 diagnosis. One SOT death related to COVID-19 was reported, while no related deaths were reported in the HCT/CT group.ConclusionAlthough HCT/CT and SOT cases were low in comparison to all cases submitted to the registry, almost half of these cases required hospitalization. Only one COVID-19 related death was reported (SOT group); however, up to 20% of cases received ICU care. This data may aid clinicians developing future prospective studies examining COVID-19 risk mitigation and effective treatment strategies among this increased-risk population.

Prenatal Rejecter NK Cells Enhance Allo-specific Th17/Tc17 Cell Responses via TGF-beta1, IL-6 and GM-CSF.

Abstract In utero hematopoietic cellular transplantation (IUHCT) has the potential to treat congenital benign cellular disease without chemotherapy or radiation. Prenatal tolerance is essential in this regard. Previous studies involving prenatally created chimeras have shown that immunologically tolerant NK cells (friendly, fNK) from engrafter mice suppress allo Tc1 responses, while intolerant NK cells (hostile, hNK) from rejecter mice enhance allo Tc1 responses. Given that Th17 cells are also involved in allograft rejection, we sought to determine if rejecter hNK cells induce/expand allo-specific Th17/Tc17 cells. We examined the helper potential of prenatally educated hNK cells in non-tolerant prenatal Balb/c --- > B6.Thy1.2 rejecter chimeras. Naïve Thy1.1+ responder T cells and allogenic target cells were adoptively transferred into rejecter or naïve hosts that had been depleted of endogenous T cells and fNK cells. We found increased Th17/Tc17 alloimmunity in the responder Thy1.1+T cell population in rejecters when compared to naïve hosts. Additionally, through ELISPOT, we confirmed increased IL-17A production by responder T cells when co-cultured with allo-specific hNK cells from rejecter mice. Hostile NK cells from rejecter mice produce higher levels of Th17 driving cytokines, TGF-beta 1, IL-6 and GM-CSF when compared to naïve hNK. From these results, we conclude that prenatal rejecter hNK cells have an enhanced helper effect on Th17/Tc17 alloimmunity in vivo and in vitro. These findings support an evolving paradigm that prenatally educated NK cell can regulate the balance between Th1/Th17 and Treg functions. Supported by NIH R01HL103745 Lurie Children’s Hospital Research Foundation (to A.F.S.)

194. Combinatorial Polyfunctionality Analysis of Antigen-specific T-cell Subsets (COMPASS) as a Predictor for Clinically Significant CMV Infection in the Letermovir Era

BackgroundIncreased CMV reactivation is observed following discontinuation of letermovir prophylaxis after hematopoietic cellular transplantation (HCT) and decreased CMV-specific polyfunctional T-cell immunity has been proposed as a possible mechanism (BBMT 2020;26:S68). COMPASS is a novel analytical tool that integrates polyfunctional T-cell cytokine responses into a single score value (Nat Biotechnol 2015;33:610). We employed COMPASS for the first time in the HCT setting to determine if CMV-specific immunodeficiency is associated with late CMV events in a prospective cohort of allogeneic HCT recipients receiving either letermovir or preemptive therapy.MethodsPeripheral blood mononuclear cells were collected 3 months post-HCT and assessed with a 13-color intracellular cytokine staining (ICS) assay that includes 5 functional markers. Intermediate early-1 (IE-1) antigen and phosphoprotein 65 (pp65) were used to stimulate polyfunctional T-cell responses that were defined using COMPASS generated polyfunctionality scores (PFS). CMV DNAemia was monitored by weekly plasma PCR and patients who reactivated were treated with preemptive therapy per institutional standards. Cumulative incidence of clinically significant CMV infection (cs-CMV; ≥500 IU/mL or CMV disease) by day 270 was assessed. Univariable and multivariable Cox regression were used to estimate the association of polyfunctional T-cell responses (upper quartile versus lower 3 quartiles) with cs-CMV infection by day 270 post-HCT.Results56 letermovir recipients and 93 preemptive controls were evaluated. Time to first clinically significant CMV (cs-CMV) infection after HCT and among day 100 survivors in both groups is shown in Figure 1. COMPASS PFS at 3 months were significantly lower in letermovir recipients (Figure 2). After adjusting for CMV infection before day 100, CD4 and CD8 PFS to IE-1 and pp65 below the upper quartile were associated with higher risk of late cs-CMV infection, with IE-1 CD8 PFS reaching statistical significance (Figure 3). ConclusionOur findings demonstrate that COMPASS is a valuable tool to evaluate multiple, T-cell cytokine responses to CMV in HCT recipients. COMPASS appears to be useful to identify patients at risk for late cs-CMV infection.Disclosures Elizabeth Duke, MD, Merck (Grant/Research Support) Michael Boeckh, MD PhD, AlloVir (Consultant)EvrysBio (Advisor or Review Panel member, Other Financial or Material Support, share options)Gilead (Consultant, Grant/Research Support)GSK (Consultant)Helocyte (Advisor or Review Panel member, Shareholder)Lophius (Grant/Research Support)Merck (Consultant, Grant/Research Support)SymBio (Consultant)VirBio (Consultant, Grant/Research Support)

Hematopoietic Stem Cell Transplantation, Where Have We Come and Where Do We Go.

Hematopoietic cellular transplantation (HCT) has impacted medicine beyond simply treating certain diseases. Allogeneic HCT was the first documented successful immunological cellular therapy. Its usage continues to increase. The immunological disparity between donor and recipient has been associated with better antitumor efficacy as well as immunological toxicities. Through active clinical trials and research, considerable improvements in HCT therapy have been made over the past 50 years. The HCT international outcomes registry has considerably contributed to these improvements by identifying factors that could never be studied by a single center. With the use of unrelated donors, international collaboration increased as donor cell access through registries was not inhibited by international boundaries. HCT as a field pioneered the development of organizations for self-regulation that were assessing the entire program as an integrated whole rather than simply assessing facilities and providers separately.

Allo-specific NK cells differentially regulate T cell allo-immunity depending on prenatal education

Abstract Allospecific NK cell hyporesponsiveness develops after in utero hematopoietic cellular transplantation (IUHCT) in mice who exhibit stable long-term engraftment. Conversely, allospecific NK cell responses are normal in mice that reject their graft. We hypothesized that these alternate NK cell responses also differentially influence T cell responses after IUHCT. To challenge this hypothesis, we compared the helper or suppression potential of prenatally educated NK cells between prenatal recipients with stable engraftment (engrafter mice) and littermates that rejected their graft (rejecter mice) in a Balb/c --- > a B6 model of IUHCT. Allospecific NK cells from engrafter, rejecter, or naïve mice were co-cultured with naïve responder T cells (B6) and irradiated allogeneic target cells (Balb/c) in an in vitro IFN-g assay. Intracellular production of IFN-g was measured by flow cytometry of the naïve responder T cells after 66 hrs of co-culture. We found that responder T cells displayed increased IFN-gamma production when co-cultured with allospecific NK cells from rejecter mice compared to co-culture with allospecific NK cells from naive control mice. Conversely responder T cells displayed decreased IFN-g production when co-cultured with allospecific NK cells from engrafter mice compared to co-culture with NK cells from naïve control mice. From these results, we conclude that allospecific NK cells can influence the allospecific response of T cells in vitro depending on the context of their prenatal education. Further studies are needed to determine if similar mechanisms support engraftment or rejection in vivo.

The Patient Perspective: Exploring the Meaning of Bedside Handoff on an Inpatient Hematopoietic Cellular Transplant Unit

Topic Significance & Study Purpose/Background/Rationale Delivery of patient-centered care in the hematopoietic cellular transplant (HCT) setting is grounded in communication between patients, caregivers and clinicians. Bedside shift handoff (BSH) provides a consistent forum for this communication and is designed to improve the patient care experience. Surrogate indicators of the patient's perception of care quality at our institution are reflected in the Hospital Consumer Assessment of Healthcare Providers and Systems (HCAHPS) scores and leadership rounding. Neither source reflects indicators chosen by the patient, but instead by the institution and governing organizations. In 2016, BSH was implemented as an institution-wide initiative; however, HCT nursing staff continue to resist this change. Reasons cited by staff include the unit's consistently high HCAHPS scores and lack of a tailored BSH format for HCT recipients who often have prolonged inpatient stays and consistent nursing care. Nurses report that the current BSH can be “awkward”, “repetitive”, and “disruptive”. In practice, there is a recognized gap between nurses' commitment to meeting both the HCT patient's needs and alignment with the current BSH format. The purpose of this quality improvement initiative is to first understand the value of the current BSH format for patients admitted to the inpatient HCT unit. By collecting this data, we aim to increase staff compliance with and tailor BSH by infusing patient's perception of meaning and preferences. Methods, Intervention, & Analysis Following a review of the literature, two tools were developed. The first is an 11-item structured patient interview adopted from Wakefield, et al. (2012). This tool was designed to evaluate the patient/caregiver's perception of how well key elements of the current BSH were explained. The second tool is a 5-item survey designed to explore the value of key elements of BSH from the patient's perspective. Following review from our Institutional Review Board, these two tools will be offered one time during each admission to all patients admitted to the HCT unit for a period of three consecutive months. Aggregate data will be reviewed to inform development of a revised BSH tool, if indicated, for the HCT unit. Findings & Interpretation Summative data and the revised BSH format will be presented. Discussion & Implications In her theory of Bureaucratic Caring, Ray (1989) outlines unique dominant caring behaviors across clinical care settings. All are elements of the caring dimension, but adapted to the different needs of the patient population. For medical surgical units, the two dominant behaviors are “team” and “involvement”. Though both are clearly supported during BSH, we believe that the “one size fits all” standardized approach may not be optimal. We are looking to our patients with the hope of assigning increased meaning of BSH for both nurses, and most importantly, patients and their caregivers.

Acute Graft-Versus-Host Disease (aGVHD, Non-Relapse Mortality) Risk Prediction Assay: Validation and Initial Reference Lab Experience

Introduction aGVHD affects 40% to 60% of hematopoietic cellular transplant (HCT) patients, targeting the skin, liver, and gastrointestinal tract with a median onset approximately 1 month after transplant. In 2017, an interpretive algorithm based on serum ST2 and REG3α levels was clinically validated (JCI Insight 2017;2(3):e89798). Objectives This report details validation, inter-lab correlation and initial results from clinical analysis. Methods ST2 and REG3α levels were analyzed in serum using enzyme immunoassays. ST2 and REG3α values are analyzed through an equation to provide an index value that can be used for predicting non-relapse mortality and aGVHD risk for pre-symptomatic (low/high risk), symptomatic onset (low/medium/high risk) and post treatment (low/high risk) HCT patients. Results were compared with the research lab where the equation was established (Mount Sinai Medical Center, MSMC). Results The inter-assay precision ranged from 12 to 26 %CV for ST2 and REG3a, while those for the calculated indices ranged from 17 to 18%. Accuracy was compared against biomarker values and indices reported by MSMC for 106 serum samples. Among samples with biomarker concentrations within the assays' measuring range, the relative error was Conclusions The aGVHD index and its component input assays, ST2 and REG3a, were validated for clinical use. Notably, excellent concordance was observed on a large sample set (106 sera) with MSMC. In addition, initial results indicate that the aGVHD index may prove useful for risk-stratifying HCT patients.

An early-biomarker algorithm predicts lethal graft-versus-host disease and survival.

BACKGROUND. No laboratory test can predict the risk of nonrelapse mortality (NRM) or severe graft-versus-host disease (GVHD) after hematopoietic cellular transplantation (HCT) prior to the onset of GVHD symptoms. METHODS. Patient blood samples on day 7 after HCT were obtained from a multicenter set of 1,287 patients, and 620 samples were assigned to a training set. We measured the concentrations of 4 GVHD biomarkers (ST2, REG3α, TNFR1, and IL-2Rα) and used them to model 6-month NRM using rigorous cross-validation strategies to identify the best algorithm that defined 2 distinct risk groups. We then applied the final algorithm in an independent test set (n = 309) and validation set (n = 358). RESULTS. A 2-biomarker model using ST2 and REG3α concentrations identified patients with a cumulative incidence of 6-month NRM of 28% in the high-risk group and 7% in the low-risk group (P < 0.001). The algorithm performed equally well in the test set (33% vs. 7%, P < 0.001) and the multicenter validation set (26% vs. 10%, P < 0.001). Sixteen percent, 17%, and 20% of patients were at high risk in the training, test, and validation sets, respectively. GVHD-related mortality was greater in high-risk patients (18% vs. 4%, P < 0.001), as was severe gastrointestinal GVHD (17% vs. 8%, P < 0.001). The same algorithm can be successfully adapted to define 3 distinct risk groups at GVHD onset. CONCLUSION. A biomarker algorithm based on a blood sample taken 7 days after HCT can consistently identify a group of patients at high risk for lethal GVHD and NRM. FUNDING. The National Cancer Institute, American Cancer Society, and the Doris Duke Charitable Foundation.

Maternal and Fetal Immune Response to In Utero Stem Cell Transplantation

In Utero Hematopoietic Cellular Transplantation (IUHCT) is a promising intervention for the non-toxic treatment of congenital disease that hinges on the assumption of fetal immunologic immaturity and an inability to reject a hematopoietic allograft. However, clinical IUCHT has failed except in cases where the fetus is severely immunocompromised. The current review examines recent studies of engraftment barriers stemming from either the fetal or maternal immune system. New reports have illuminated roles for maternal humoral and cellular immunity and fetal innate cellular immunity in the resistance to allogeneic IUHCT. These experimental findings have inspired new approaches to overcome these barriers. Despite these advances, postulates regarding a maternal immune barrier to IUHCT provide an inadequate explanation for the well-documented clinical success only in the treatment of fetal immunodeficiency with normal maternal immunity. Characterization of the maternal and fetal immune response to allogeneic IUHCT provides new insight into the complexity of prenatal tolerance. Future work in this area should aim to provide a unifying explanation for the observed patterns of success and failure with clinical IUHCT.

483 - Improving Survival Outcomes for Hematopoietic Cellular Transplant (HCT) Recipients

483 - Improving Survival Outcomes for Hematopoietic Cellular Transplant (HCT) Recipients

492 - Proactive Quality Manager Replacement and Succession Planning is Vital to Seamless Viability of Hematopoietic Cellular Transplantation (HCT) Program Quality Management

492 - Proactive Quality Manager Replacement and Succession Planning is Vital to Seamless Viability of Hematopoietic Cellular Transplantation (HCT) Program Quality Management

490 - Seventy Nine Miles, Two Sites and One Fact Accreditation: Integrating Effective Quality Management Between Two Affiliated but Physically Remote Hematopoietic Cellular Transplantation (HCT) Facilities

490 - Seventy Nine Miles, Two Sites and One Fact Accreditation: Integrating Effective Quality Management Between Two Affiliated but Physically Remote Hematopoietic Cellular Transplantation (HCT) Facilities

An early-biomarker algorithm predicts lethal graft-versus-host disease and survival

BACKGROUND. No laboratory test can predict the risk of nonrelapse mortality (NRM) or severe graft-versus-host disease (GVHD) after hematopoietic cellular transplantation (HCT) prior to the onset of GVHD symptoms. METHODS. Patient blood samples on day 7 after HCT were obtained from a multicenter set of 1,287 patients, and 620 samples were assigned to a training set. We measured the concentrations of 4 GVHD biomarkers (ST2, REG3α, TNFR1, and IL-2Rα) and used them to model 6-month NRM using rigorous cross-validation strategies to identify the best algorithm that defined 2 distinct risk groups. We then applied the final algorithm in an independent test set (n = 309) and validation set (n = 358). RESULTS. A 2-biomarker model using ST2 and REG3α concentrations identified patients with a cumulative incidence of 6-month NRM of 28% in the high-risk group and 7% in the low-risk group (P < 0.001). The algorithm performed equally well in the test set (33% vs. 7%, P < 0.001) and the multicenter validation set (26% vs. 10%, P < 0.001). Sixteen percent, 17%, and 20% of patients were at high risk in the training, test, and validation sets, respectively. GVHD-related mortality was greater in high-risk patients (18% vs. 4%, P < 0.001), as was severe gastrointestinal GVHD (17% vs. 8%, P < 0.001). The same algorithm can be successfully adapted to define 3 distinct risk groups at GVHD onset. CONCLUSION. A biomarker algorithm based on a blood sample taken 7 days after HCT can consistently identify a group of patients at high risk for lethal GVHD and NRM. FUNDING. The National Cancer Institute, American Cancer Society, and the Doris Duke Charitable Foundation.

An Early Biomarker Algorithm Predicts Lethal Graft-Versus-Host Disease and Survival after Allogeneic Hematopoietic Cell Transplantation

No laboratory test can predict non-relapse mortality (NRM) after hematopoietic cellular transplantation (HCT) prior to the onset graft-versus-host disease (GVHD). Recently, we have shown that a signature of three GVHD plasma biomarkers (TNFR1, ST2, and REG3α) can predict response to GVHD therapy and NRM at the onset of clinical GVHD (Levine, Lancet Haem, 2015). Our goal in the current study was to identify a blood biomarker signature that could predict lethal GVHD and six-month NRM well in advance of the onset of GVHD symptoms. Patient samples on day +7 after HCT were obtained from 1,287 patients from 11 HCT centers in the Mount Sinai Acute GVHD International Consortium (MAGIC). Samples from two large centers (n = 929) were combined and randomly assigned to a training set (n = 620) and test set (n = 309). 358 patients from nine others centers constituted an independent validation set. The overall cumulative incidences of 6-month NRM were 11%, 12%, and 13% for the training, test, and validation sets respectively. The incidence of lethal GVHD, defined as death without preceding relapse while under steroid treatment for acute GVHD, were 18%, 24%, and 14% in the same groups, respectively. The median day of GVHD onset was 28 days in the training set and 29 days in the test and validation sets. We measured four GVHD related biomarkers [ST2, REG3α, TNFR1, and IL2Rα] in all samples and used the training set alone to develop competing risks regression models that used all 13 possible combinations of one to four biomarkers to predict 6-month NRM. The best algorithm, which we rigorously confirmed through Monte Carlo cross-validation of 75 different combinations of training sets, included ST2 and REG3α. No combination of one, three, or four biomarkers was superior to the combination of these two biomarkers. The day 7 algorithm identified high risk (HR) and low risk (LR) groups with 6-month NRMs of 28% and 7%, respectively (p<0.001) (Fig 1A). The relapse rates did not differ between risk groups so that overall survival (OS) was 60% for HR and 84% for LR (p<0.001) (Fig 1B). When applied to the test set (Fig 1C/D), the algorithm identified 54/309 (17%) of the patients as HR with an NRM of 33% vs 7% for LR patients (p<0.001) and 6-month OS of 57% and 81% for HR and LR patients, respectively (p<0.001). In the independent validation set (Fig 1 E/F), the algorithm identified 72/358 (20%) of the patients as HR with an NRM of 26% vs 10% for LR patients (p<0.001) and OS of 68% and 85% for HR and LR patients, respectively (p<0.001). High risk patients were three times more likely to die from GVHD than LR patients in each cohort (p<0.001) (Fig 2). The GI tract is the GVHD target organ that is most resistant to treatment and represents a major cause of NRM, and we observed twice as much severe GI GVHD (stage 3 or 4) in HR patients as in LR patients (p<0.001, data not shown). The algorithm successfully separated HR and LR strata for 6 month NRM in several groups with differing risks for GVHD and NRM, including donor type, degree. of HLA-match, age group, and conditioning regimen intensity (Fig 3).In conclusion, we have developed a blood biomarker algorithm that predicts the development of lethal GVHD seven days after HCT, which performed successfully in large multicenter validation sets. The GVH reaction is already in progress by day +7, even though clinical symptoms may not occur until days or weeks later. We speculate that the blood biomarker concentrations at this early time point reflect subclinical GI pathology, a notion that is reinforced by the fact that ST2 and REG3α, the two biomarkers in the algorithm, are closely associated with GI GVHD. The algorithm identified HR and LR strata in several patient groups with different overall risk for lethal GVHD (donor, HLA match, conditioning regimen intensity, age). This day +7 algorithm should prove useful in clinical BMT research by identifying patients at high risk for lethal GVHD who might benefit from aggressive preemptive treatment strategies. [Display omitted] [Display omitted] [Display omitted] DisclosuresChen:Novartis: Research Funding; Incyte Corporation: Consultancy, Membership on an entity’s Board of Directors or advisory committees, Research Funding. Jagasia:Therakos: Consultancy. Kitko:Therakos: Honoraria, Speakers Bureau. Kroeger:Novartis: Honoraria, Research Funding. Levine:Viracor: Patents & Royalties: GVHD biomarkers patent. Ferrara:Viracor: Patents & Royalties: GVHD biomarkers patent.

Plasma angiopoietin-2 outperforms other markers of endothelial injury in prognosticating pediatric ARDS mortality.

Angiopoietin-2 (Ang-2) is a key mediator of pulmonary vascular permeability. This study tested the association between plasma Ang-2 and mortality in pediatric acute respiratory distress syndrome (ARDS), with stratification for prior hematopoietic cellular transplantation (HCT), given the severe, yet poorly understood, ARDS phenotype of this subgroup. We enrolled 259 children <18 years of age with ARDS; 25 had prior HCT. Plasma Ang-2, von Willebrand Factor antigen (vWF), and vascular endothelial growth factor (VEGF) were measured on ARDS days 1 and 3 and correlated with patient outcomes. Day 1 and day 3 Ang-2 levels were associated with mortality independent of age, sex, race, and P/F ratio [odds ratio (OR) 3.7, 95% CI 1.1-11.5, P = 0.027; and OR 10.2, 95% confidence interval (CI) 2.2-46.5, P = 0.003, for each log10 increase in Ang-2]. vWF was associated with mortality (P = 0.027), but VEGF was not. The association between day 1 Ang-2 and mortality was independent of levels of both vWF and VEGF (OR 3.6, 95% CI 1.1-12.1, P = 0.039, for each log10 increase in Ang-2). 45% of the cohort had a rising Ang-2 between ARDS day 1 and 3 (adjusted mortality OR 3.3, 95% CI 1.2-9.2, P = 0.026). HCT patients with a rising Ang-2 had 70% mortality compared with 13% mortality for those without (OR 16.3, 95% CI 1.3-197.8, P = 0.028). Elevated plasma levels of Ang-2 were associated with mortality independent of vWF and VEGF. A rising Ang-2 between days 1 and 3 was strongly associated with mortality, particularly in pediatric HCT patients, suggesting vulnerability to ongoing endothelial damage.

Prenatal Allogeneic Tolerance in Mice Remains Stable Despite Potent Viral Immune Activation.

Transplanting stem cells before birth offers an unparalleled opportunity to initiate corrective treatment for numerous childhood diseases with minimal or no host conditioning. Although long-term engraftment has been demonstrated following in utero hematopoietic cellular transplantation during immune quiescence, it is unclear if prenatal tolerance becomes unstable with immune activation such as during a viral syndrome. Using a murine model of in utero hematopoietic cellular transplantation, the impact of an infection with lymphocytic choriomeningitis virus on prenatal allospecific tolerance was examined. The findings in this report illustrate that established mechanisms of donor-specific tolerance are strained during potent immune activation. Specifically, a transient reversal in the anergy of alloreactive lymphocytes is seen in parallel with the global immune response toward the virus. However, these changes return to baseline following resolution of the infection. Importantly, prenatal engraftment remains stable during and after immune activation. Collectively, these findings illustrate the robust nature of allospecific tolerance in prenatal mixed chimerism compared with models of postnatal chimerism and provides additional support for the prenatal approach to the treatment of congenital benign cellular disease.

NK cell tolerance as the final endorsement of prenatal tolerance after in utero hematopoietic cellular transplantation.

The primary benefits of in utero hematopoietic cellular transplantation (IUHCT) arise from transplanting curative cells prior to the immunologic maturation of the fetus. However, this approach has been routinely successful only in the treatment of congenital immunodeficiency diseases that include an inherent NK cell deficiency despite the existence of normal maternal immunity in either setting. These observations raise the possibility that fetal NK cells function as an early barrier to allogeneic IUHCT. Herein, we summarize the findings of previous studies of prenatal NK cell allospecific tolerance in mice and in humans. Cumulatively, this new information reveals the complexity of the fetal immune response in the setting of rejection or tolerance and illustrates the role for fetal NK cells in the final endorsement of allospecific prenatal tolerance.

Self-education via Ly49 receptor engagement of donor and host iNKT cells following in utero hematopoietic cellular transplantation (TRAN1P.874)

Abstract Invariant NKT (iNKT) cells recognize glycolipid-CD1d complexes via their TCR but also express inhibitory Ly49 receptors (iLy49s) specific for MHC I ligands. However, little is known regarding the importance of iLy49s in the self-recognition of MHC I by iNKT cells during development. We hypothesized that self-engagement of iLy49s during development alters the phenotype and function of self-responsive iNKT cells. We examined this hypothesis in prenatal Balb/c to B6 and B6 to Balb/c allogeneic chimeras that were established by in utero hematopoietic cellular transplantation (IUHCT) of E14 fetal liver light density cells into age-matched fetal recipients. After birth, we compared iLy49 expression and the functional response of iNKT cells in the allogeneic chimeras to age-matched controls. The levels of allospecific iLy49s on host iNKT and donor iNKT were significantly reduced in all organs tested suggesting developmental recognition of both donor and host MHC class I had occurred. In contrast, the expression of irrelevant receptors was not altered. Lastly, iNKT cells from chimeric mice that expressed allospecific iLy49s exhibited significantly increased production of IL-4 in response to TCR stimulation suggesting that a shift toward a regulatory phenotype had occurred. Future studies will directly evaluate the impact of self-recognition by iNKT cells in the developmental pathogenesis of autoimmunity, allergy and allospecific tolerance.

Self-Engagement Of An NKT Cell Inhibitory Receptor During Development Alters Receptor Expression and Cellular Function

Invariant NKT (iNKT) cells have been shown to be pro-inflammatory or anti-inflammatory in many pathologic conditions including infections, cancer, autoimmune diseases and allergy. Additionally, early expansion of iNKT cells correlates with successful engraftment and low incidence of graft-versus host disease suggesting a role for iNKT cells in tolerance to allogeneic transplantation. iNKT cells recognize glycolipids bound to CD1d via their T cell receptor (TCR), but also express the inhibitory receptors for MHC class I ligands (MHC I.) Little is known regarding the importance of iNKT cell self-recognition of MHC I during development and the occurrence of autoimmunity, allergy or tolerance to in utero hematopoietic cellular transplantation (IUHCT). Given the importance of NK cell self-recognition during development, we hypothesized that, like NK cells, self-engagement of MHC I inhibitory receptors during development alters the phenotype and function of self-responsive iNKT cells. Prenatal allogeneic chimeras were established by in utero transplantation of Balb/c fetal liver light density cells at E14 into age-matched C57BL/6 fetal recipients. A kinetic evaluation of iNKT cell receptor expression and function was performed after birth. iNKT cells were evaluated for expression of activating (Ly49D) and inhibitory (Ly49A, F, G) receptors specific for the donor MHC I (H-2d.) The functional response of iNKT cell subsets was measured following in vivo activation with KRN7000, the ligand for iNKT cells. Intracellular cytokine production (IFN-gamma and IL-4) production was assessed in the alloresponsive Ly49A+ iNKT cell subset and compared to naïve controls and B10.D2 (H2d) mice. We found that a negligible fraction of iNKT cells expressed the activating Ly49D receptor in either chimera or controls (&lt;1%.) In chimeric mice, the frequency of iNKT cells expressing Ly49A, F, or G did not change significantly. However, the levels of Ly49A expression were significantly reduced on iNKT cells from all organs tested suggesting developmental recognition of donor class I ligands had occurred. These reduced receptor levels did not appear to be due to sequestration as acid stripping did not alter the phenotype. Lastly, Ly49A+ but not Ly49A- iNKT cells in chimeric mice exhibited significantly increased production of IL-4 in response to TCR stimulation suggesting a shift toward a regulatory phenotype. Consistent with this finding, IFN-gamma levels in chimeras were minimally changed compared to controls. These findings indicate that inhibitory receptor self-engagement during development leads to: 1) alterations in receptor expression; 2) shift toward a tolerogenic phenotype in self-responsive iNKT cell phenotypes; and 3) no change in the receptor expression or function of non-responsive iNKT cell phenotypes. Further studies will directly evaluate the impact of self-recognition of iNKT cells in the pathogenesis of autoimmunity and allergy or tolerance following IUHCT. Disclosures: No relevant conflicts of interest to declare.