A common allele of HLA is associated with asymptomatic SARS-CoV-2 infection.

Studies have demonstrated that at least 20% of individuals infected with SARS-CoV-2 remain asymptomatic1-4. Although most global efforts have focused on severe illness in COVID-19, examining asymptomatic infection provides a unique opportunity to consider early immunological features that promote rapid viral clearance. Here, postulating that variation in the human leukocyte antigen (HLA) loci may underly processes mediating asymptomatic infection, we enrolled 29,947 individuals, for whom high-resolution HLA genotyping data were available, in a smartphone-based study designed to track COVID-19 symptoms and outcomes. Our discovery cohort (n = 1,428) comprised unvaccinated individuals who reported a positive test result for SARS-CoV-2. We tested for association of five HLA loci with disease course and identified a strong association between HLA-B*15:01 and asymptomatic infection, observed in two independent cohorts. Suggesting that this genetic association is due to pre-existing T cell immunity, we show that T cells from pre-pandemic samples from individuals carrying HLA-B*15:01 were reactive to the immunodominant SARS-CoV-2 S-derived peptide NQKLIANQF. The majority of the reactive T cells displayed a memory phenotype, were highly polyfunctional and were cross-reactive to a peptide derived from seasonal coronaviruses. The crystal structure of HLA-B*15:01-peptide complexes demonstrates that the peptides NQKLIANQF and NQKLIANAF (from OC43-CoV and HKU1-CoV) share a similar ability to be stabilized and presented by HLA-B*15:01. Finally, we show that the structural similarity of the peptides underpins T cell cross-reactivity of high-affinity public T cell receptors, providing the molecular basis for HLA-B*15:01-mediated pre-existing immunity.

The health risk of social disadvantage is transplantable into a new host.

Low socioeconomic status (SES) is a risk factor for mortality and immune dysfunction across a wide range of diseases, including cancer. However, cancer is distinct in the use of allogeneic hematopoietic cell transplantation (HCT) as a treatment for hematologic malignancies to transfer healthy hematopoietic cells from one person to another. This raises the question of whether social disadvantage of an HCT cell donor, as assessed by low SES, might impact the subsequent health outcomes of the HCT recipient. To evaluate the cellular transplantability of SES-associated health risk, we analyzed the health outcomes of 2,005 HCT recipients who were transplanted for hematologic malignancy at 125 United States transplant centers and tested whether their outcomes differed as a function of their cell donor's SES (controlling for other known HCT-related risk factors). Recipients transplanted with cells from donors in the lowest quartile of SES experienced a 9.7% reduction in overall survival (P = 0.001) and 6.6% increase in treatment-related mortality within 3 y (P = 0.008) compared to those transplanted from donors in the highest SES quartile. These results are consistent with previous research linking socioeconomic disadvantage to altered immune cell function and hematopoiesis, and they reveal an unanticipated persistence of those effects after cells are transferred into a new host environment. These SES-related disparities in health outcomes underscore the need to map the biological mechanisms involved in the social determinants of health and develop interventions to block those effects and enhance the health of both HCT donors and recipients.

Telomere length and clonal chromosomal alterations in peripheral blood of patients with severe aplastic anaemia.

Severe aplastic anaemia (SAA) is a rare and life-threatening bone marrow failure disorder. We used data from the transplant outcomes in aplastic anaemia study to characterize mosaic chromosomal alterations (mCAs) in the peripheral blood of 738 patients with acquired SAA and evaluate their associations with telomere length (TL) and survival post-haematopoietic cell transplant (HCT). The median age at HCT was 20.4 years (range = 0.2-77.4). Patients with SAA had shorter TL than expected for their age (median TL percentile for age: 35.7th; range <1-99.99). mCAs were detected in 211 patients (28.6%), with chr6p copy-neutral loss of heterozygosity (6p-CNLOH) in 15.9% and chr7 loss in 3.0% of the patients; chrX loss was detected in 4.1% of female patients. Negative correlations between mCA cell fraction and measured TL (r = -0.14, p = 0.0002), and possibly genetically predicted TL (r = -0.07, p = 0.06) were noted. The post-HCT 3-year survival probability was low in patients with chr7 loss (39% vs. 72% in patients with chr6-CNLOH, 60% in patients with other mCAs and 70% in patients with no mCAs; p-log rank = 0.001). In multivariable analysis, short TL (p = 0.01), but not chr7 loss (p = 0.29), was associated with worse post-HCT survival. TL may guide clinical decisions in patients with SAA.

HLA-DQ heterodimers in hematopoietic cell transplantation.

HLA-DQ heterodimers increase the susceptibility to autoimmune diseases, but their role in hematopoietic cell transplantation is unknown. We tested the hypothesis that outcome after HLA-matched and HLA-DQ-mismatched hematopoietic cell transplantation is influenced by HLA-DQ heterodimers. Heterodimers were defined in 5164 HLA-matched and 520 HLA-DQ-mismatched patients and their transplant donors according to well-established crystallographic criteria. Group 1 (G1) heterodimers are any DQA1*02/03/04/05/06α paired with any DQB1*02/03/04ß. Group 2 (G2) heterodimers are DQA1*01α paired with any DQB1*05/06ß. Multivariable models identified significantly higher relapse risk in G1G2 and G2G2 compared with G1G1 HLA-matched patients with malignant disease; risk increased with an increasing number of G2 molecules. In HLA-DQ-mismatched transplantation for malignant diseases, matching or mismatching for G2 increased relapse risk. G2 lowered disease-free survival after both HLA-matched and HLA-DQ-mismatched transplantation. A paradigm based on HLA-DQ heterodimers provides a functional definition of the hematopoietic cell transplantation barrier and a means to lower risks for future patients.

Genetic testing in severe aplastic anemia is required for optimal hematopoietic cell transplant outcomes.

Patients with severe aplastic anemia (SAA) can have an unrecognized inherited bone marrow failure syndrome (IBMFS) because of phenotypic heterogeneity. We curated germline genetic variants in 104 IBMFS-associated genes from exome sequencing performed on 732 patients who underwent hematopoietic cell transplant (HCT) between 1989 and 2015 for acquired SAA. Patients with pathogenic or likely pathogenic (P/LP) variants fitting known disease zygosity patterns were deemed unrecognized IBMFS. Carriers were defined as patients with a single P/LP variant in an autosomal recessive gene or females with an X-linked recessive P/LP variant. Cox proportional hazard models were used for survival analysis with follow-up until 2017. We identified 113 P/LP single-nucleotide variants or small insertions/deletions and 10 copy number variants across 42 genes in 121 patients. Ninety-one patients had 105 in silico predicted deleterious variants of uncertain significance (dVUS). Forty-eight patients (6.6%) had an unrecognized IBMFS (33% adults), and 73 (10%) were carriers. No survival difference between dVUS and acquired SAA was noted. Compared with acquired SAA (no P/LP variants), patients with unrecognized IBMFS, but not carriers, had worse survival after HCT (IBMFS hazard ratio [HR], 2.13; 95% confidence interval[CI], 1.40-3.24; P = .0004; carriers HR, 0.96; 95% CI, 0.62-1.50; P = .86). Results were similar in analyses restricted to patients receiving reduced-intensity conditioning (n = 448; HR IBMFS = 2.39; P = .01). The excess mortality risk in unrecognized IBMFS attributed to death from organ failure (HR = 4.88; P < .0001). Genetic testing should be part of the diagnostic evaluation for all patients with SAA to tailor therapeutic regimens. Carriers of a pathogenic variant in an IBMFS gene can follow HCT regimens for acquired SAA.

HLA informs risk predictions after haploidentical stem cell transplantation with posttransplantation cyclophosphamide.

Hematopoietic cell transplantation from HLA-haploidentical related donors is increasingly used to treat hematologic cancers; however, characteristics of the optimal haploidentical donor have not been established. We studied the role of donor HLA mismatching in graft-versus-host disease (GVHD), disease recurrence, and survival after haploidentical donor transplantation with posttransplantation cyclophosphamide (PTCy) for 1434 acute leukemia or myelodysplastic syndrome patients reported to the Center for International Blood and Marrow Transplant Research. The impact of mismatching in the graft-versus-host vector for HLA-A, -B, -C, -DRB1, and -DQB1 alleles, the HLA-B leader, and HLA-DPB1 T-cell epitope (TCE) were studied using multivariable regression methods. Outcome was associated with HLA (mis)matches at individual loci rather than the total number of HLA mismatches. HLA-DRB1 mismatches were associated with lower risk of disease recurrence. HLA-DRB1 mismatching with HLA-DQB1 matching correlated with improved disease-free survival. HLA-B leader matching and HLA-DPB1 TCE-nonpermissive mismatching were each associated with improved overall survival. HLA-C matching lowered chronic GVHD risk, and the level of HLA-C expression correlated with transplant-related mortality. Matching status at the HLA-B leader and HLA-DRB1, -DQB1, and -DPB1 predicted disease-free survival, as did patient and donor cytomegalovirus serostatus, patient age, and comorbidity index. A web-based tool was developed to facilitate selection of the best haploidentical-related donor by calculating disease-free survival based on these characteristics. In conclusion, HLA factors influence the success of haploidentical transplantation with PTCy. HLA-DRB1 and -DPB1 mismatching and HLA-C, -B leader, and -DQB1 matching are favorable. Consideration of HLA factors may help to optimize the selection of haploidentical related donors.

Donor germ-line variants associate with outcomes of allogeneic hematopoietic stem cell transplantation in patients with myelodysplastic syndromes.

Overall survival probability for MDS patients who underwent allo-HCT and were matched to donors that are wild-type (red) and heterozygous (blue) for the rs111224634 SNP.

Genome-wide Association Study Identifies HLA-DPB1 as a Significant Risk Factor for Severe Aplastic Anemia.

Severe aplastic anemia (SAA) is a rare disorder characterized by hypoplastic bone marrow and progressive pancytopenia. The etiology of acquired SAA is not understood but is likely related to abnormal immune responses and environmental exposures. We conducted a genome-wide association study of individuals with SAA genetically matched to healthy controls in discovery (359 cases, 1,396 controls) and validation sets (175 cases, 1,059 controls). Combined analyses identified linked SNPs in distinct blocks within the major histocompatibility complex on 6p21. The top SNP encodes p.Met76Val in the P4 binding pocket of the HLA class II gene HLA-DPB1 (rs1042151A>G, odds ratio [OR] 1.75, 95% confidence interval [CI] 1.50-2.03, p = 1.94 × 10-13) and was associated with HLA-DP cell surface expression in healthy individuals (p = 2.04 × 10-6). Phylogenetic analyses indicate that Val76 is not monophyletic and likely occurs in conjunction with different HLA-DP binding groove conformations. Imputation of HLA-DPB1 alleles revealed increased risk of SAA associated with Val76-encoding alleles DPB1∗03:01, (OR 1.66, p = 1.52 × 10-7), DPB1∗10:01 (OR 2.12, p = 0.0003), and DPB1∗01:01 (OR 1.60, p = 0.0008). A second SNP near HLA-B, rs28367832G>A, reached genome-wide significance (OR 1.49, 95% CI 1.22-1.78, p = 7.27 × 10-9) in combined analyses; the association remained significant after excluding cases with clonal copy-neutral loss-of-heterozygosity affecting class I HLA genes (8.6% of cases and 0% of controls). SNPs in the HLA class II gene HLA-DPB1 and possibly class I (HLA-B) are associated with SAA. The replacement of Met76 to Val76 in certain HLA-DPB1 alleles might influence risk of SAA through mechanisms involving DP peptide binding specificity, expression, and/or other factors affecting DP function.

The distribution and accumulation of the shortest telomeres in telomere biology disorders.

Individuals with telomere biology disorders (TBDs) have very short telomeres, high risk of bone marrow failure (BMF), and reduced survival. Using data from TBD patients, a mean leukocyte Southern blot telomere length (TL) of 5 kilobases (kb) was estimated as the 'telomere brink' at which human survival is markedly reduced. However, the shortest telomere, not the mean TL, signals replicative senescence. We used the Telomere Shortest Length Assay (TeSLA) to tally TL of all 46 chromosomes in blood-derived DNA and examined its relationship with TBDs. Patients (n = 18) had much shorter mean TL (TeSmTL) (2.54 ± 0.41 kb vs. 4.48 ± 0.52 kb, p < 0.0001) and more telomeres <3 kb than controls (n = 22) (70.43 ± 8.76% vs. 33.05 ± 6.93%, p < 0.0001). The proportion of ultrashort telomeres (<1.6 kb) was also higher in patients than controls (39.29 ± 10.69% vs. 10.40 ± 4.09%, p < 0.0001). TeS <1.6 kb was associated with severe (n = 11) compared with non-severe (n = 7) BMF (p = 0.027). Patients with multi-organ manifestations (n = 10) had more telomeres <1.6 kb than those with one affected organ system (n = 8) (p = 0.029). Findings suggest that TBD clinical manifestations are associated with a disproportionately higher number of haematopoietic cell telomeres reaching a telomere brink, whose length at the single telomere level is yet to be determined.

The clinical and functional effects of TERT variants in myelodysplastic syndrome.

Germline pathogenic TERT variants are associated with short telomeres and an increased risk of developing myelodysplastic syndrome (MDS) among patients with a telomere biology disorder. We identified TERT rare variants in 41 of 1514 MDS patients (2.7%) without a clinical diagnosis of a telomere biology disorder who underwent allogeneic transplantation. Patients with a TERT rare variant had shorter telomere length (P < .001) and younger age at MDS diagnosis (52 vs 59 years, P = .03) than patients without a TERT rare variant. In multivariable models, TERT rare variants were associated with inferior overall survival (P = .034) driven by an increased incidence of nonrelapse mortality (NRM; P = .015). Death from a noninfectious pulmonary cause was more frequent among patients with a TERT rare variant. Most variants were missense substitutions and classified as variants of unknown significance. Therefore, we cloned all rare missense variants and quantified their impact on telomere elongation in a cell-based assay. We found that 90% of TERT rare variants had severe or intermediate impairment in their capacity to elongate telomeres. Using a homology model of human TERT bound to the shelterin protein TPP1, we inferred that TERT rare variants disrupt domain-specific functions, including catalysis, protein-RNA interactions, and recruitment to telomeres. Our results indicate that the contribution of TERT rare variants to MDS pathogenesis and NRM risk is underrecognized. Routine screening for TERT rare variants in MDS patients regardless of age or clinical suspicion may identify clinically inapparent telomere biology disorders and improve transplant outcomes through risk-adapted approaches.

Associations of minor histocompatibility antigens with outcomes following allogeneic hematopoietic cell transplantation.

The role of minor histocompatibility antigens (mHAs) in mediating graft versus leukemia and graft versus host disease (GvHD) following allogeneic hematopoietic cell transplantation (alloHCT) is recognized but not well-characterized. By implementing improved methods for mHA prediction in two large patient cohorts, this study aimed to comprehensively explore the role of mHAs in alloHCT by analyzing whether (1) the number of predicted mHAs, or (2) individual mHAs are associated with clinical outcomes. The study population consisted of 2249 donor-recipient pairs treated for acute myeloid leukemia and myelodysplastic syndrome with alloHCT. A Cox proportional hazard model showed that patients with a class I mHA count greater than the population median had an increased hazard of GvHD mortality (hazard ratio [HR] = 1.39, 95% confidence interval [CI] = 1.01, 1.77, p = .046). Competing risk analyses identified the class I mHAs DLRCKYISL (GSTP), WEHGPTSLL (CRISPLD2), and STSPTTNVL (SERPINF2) were associated with increased GVHD mortality (HR = 2.84, 95% CI = 1.52, 5.31, p = .01), decreased leukemia-free survival (LFS) (HR = 1.94, 95% CI = 1.27, 2.95, p = .044), and increased disease-related mortality (DRM) (HR = 2.32, 95% CI = 1.5, 3.6, p = .008), respectively. One class II mHA YQEIAAIPSAGRERQ (TACC2) was associated with increased risk of treatment-related mortality (TRM) (HR = 3.05, 95% CI = 1.75, 5.31, p = .02). WEHGPTSLL and STSPTTNVL were both present within HLA haplotype B*40:01-C*03:04 and showed a positive dose-response relationship with increased all-cause mortality and DRM and decreased LFS, indicating these two mHAs contribute to the risk of mortality in an additive manner. Our study reports the first large-scale investigation of the associations of predicted mHA peptides with clinical outcomes following alloHCT.

Following Transplantation for Acute Myelogenous Leukemia, Donor KIR Cen B02 Better Protects against Relapse than KIR Cen B01.

In the treatment of acute myelogenous leukemia with allogeneic hematopoietic cell transplantation, we previously demonstrated that there is a greater protection from relapse of leukemia when the hematopoietic cell transplantation donor has either the Cen B/B KIR genotype or a genotype having two or more KIR B gene segments. In those earlier analyses, KIR genotyping could only be assessed at the low resolution of gene presence or absence. To give the analysis greater depth, we developed high-resolution KIR sequence-based typing that defines all the KIR alleles and distinguishes the expressed alleles from those that are not expressed. We now describe and analyze high-resolution KIR genotypes for 890 donors of this human transplant cohort. Cen B01 and Cen B02 are the common CenB haplotypes, with Cen B02 having evolved from Cen B01 by deletion of the KIR2DL5, 2DS3/5, 2DP1, and 2DL1 genes. We observed a consistent trend for Cen B02 to provide stronger protection against relapse than Cen B01 This correlation indicates that protection depends on the donor having inhibitory KIR2DL2 and/or activating KIR2DS2, and is enhanced by the donor lacking inhibitory KIR2DL1, 2DL3, and 3DL1. High-resolution KIR typing has allowed us to compare the strength of the interactions between the recipient's HLA class I and the KIR expressed by the donor-derived NK cells and T cells, but no clinically significant interactions were observed. The trend observed between donor Cen B02 and reduced relapse of leukemia points to the value of studying ever larger transplant cohorts.

Short telomere length predicts nonrelapse mortality after stem cell transplantation for myelodysplastic syndrome.

Allogeneic hematopoietic stem cell transplantation is the only potentially curative treatment for patients with myelodysplastic syndrome (MDS), but long-term survival is limited by the risk of transplant-related complications. Short telomere length, mediated by inherited or acquired factors, impairs cellular response to genotoxic and replicative stress and could identify patients at higher risk for toxicity after transplantation. We measured relative telomere length in pretransplant recipient blood samples in 1514 MDS patients and evaluated the association of telomere length with MDS disease characteristics and transplantation outcomes. Shorter telomere length was significantly associated with older age, male sex, somatic mutations that impair the DNA damage response, and more severe pretransplant cytopenias, but not with bone marrow blast count, MDS treatment history, or history of prior cancer therapy. Among 1267 patients ≥40 years old, telomere length in the shortest quartile was associated with inferior survival (P < .001) because of a high risk of nonrelapse mortality (NRM; P = .001) after adjusting for significant clinical and genetic variables. The adverse impact of shorter telomeres on NRM was independent of recipient comorbidities and was observed selectively among patients receiving more intensive conditioning, including myeloablative regimens and higher dose melphalan-based reduced-intensity regimens. The effect of shorter telomeres on NRM was prominent among patients who developed severe acute graft-versus-host disease, suggesting that short telomere length may limit regenerative potential of mucosal tissues after acute injury. MDS patients with shorter telomere length, who have inferior survival driven by excess toxicity, could be considered for strategies focused on minimizing toxic effects of transplantation.

HLA-B leader and survivorship after HLA-mismatched unrelated donor transplantation.

Hematopoietic cell transplantation (HCT) from HLA-mismatched unrelated donors can cure life-threatening blood disorders, but its success is limited by graft-versus-host disease (GVHD). HLA-B leaders encode methionine (M) or threonine (T) at position 2 and give rise to TT, MT, or MM genotypes. The dimorphic HLA-B leader informs GVHD risk in HLA-B-mismatched HCT. If the leader influences outcome in other HLA-mismatched transplant settings, the success of HCT could be improved for future patients. We determined leader genotypes for 10 415 patients receiving a transplant between 1988 and 2016 from unrelated donors with one HLA-A, HLA-B, HLA-C, HLA-DRB1, or HLA-DQB1 mismatch. Multivariate regression methods were used to evaluate risks associated with patient leader genotype according to the mismatched HLA locus and with HLA-A, HLA-B, HLA-C, HLA-DRB1, or HLA-DQB1 mismatching according to patient leader genotype. The impact of the patient leader genotype on acute GVHD and mortality varied across different mismatched HLA loci. Nonrelapse mortality was higher among HLA-DQB1-mismatched MM patients compared with HLA-DQB1-mismatched TT patients (hazard ratio, 1.35; P = .01). Grades III to IV GVHD risk was higher among HLA-DRB1-mismatched MM or MT patients compared with HLA-DRB1-mismatched TT patients (odds ratio, 2.52 and 1.51, respectively). Patients tolerated a single HLA-DQB1 mismatch better than mismatches at other loci. Outcome after HLA-mismatched transplantation depends on the HLA-B leader dimorphism and the mismatched HLA locus. The patient's leader variant provides new information on the limits of HLA mismatching. The success of HLA-mismatched unrelated transplantation might be enhanced through the judicious selection of mismatched donors for a patient's leader genotype.

Unlicensed Umbilical Cord Blood Units Provide a Safe and Effective Graft Source for a Diverse Population: A Study of 2456 Umbilical Cord Blood Recipients.

Umbilical cord blood (UCB) transplantation (UCBT) is a curative procedure for patients with hematologic malignancies and genetic disorders and expands access to transplantation for non-Caucasian patients unable to find a fully matched unrelated donor. In 2011, the US Food and Drug Administration required that unrelated UCBT be performed using either licensed UCB or unlicensed UCB under the Investigational New Drug (IND) program. The National Marrow Donor Program manages an IND under which 2456 patients (1499 adults and 957 children, 564 with malignant diseases and 393 with nonmalignant diseases) underwent single or double UCBT between October 2011 and December 2016. The median patient age was 31 years (range, <1 to 81 years), and 50% of children and 36% of adults were non-Caucasian. The median time to neutrophil engraftment (ie, absolute neutrophil count ≥500/mm3) was 22 days for adults, 20 days for pediatric patients with malignant diseases, and 19 days for pediatric patients with nonmalignant diseases, with corresponding rates of engraftment at 42 days of 89%, 88%, and 90%. In these 3 groups of patients, the incidence of acute graft-versus-host disease (GVHD) grade II-IV was 35%, 32%, and 24%; the incidence of chronic GVHD was 24%, 26%, and 24%; and 1-year overall survival (OS) was 57%, 71%, and 79%, respectively. In multivariate analysis, younger age, lower Hematopoietic Cell Transplantation-Specific Comorbidity Index, early-stage chemotherapy-sensitive disease, and higher performance score were predictive of improved OS for adults. In a subset analysis of children with malignancies undergoing single UCBT, the use of either licensed UCB (n = 48) or unlicensed UCB (n = 382) was associated with similar engraftment and survival. The use of unlicensed UCB units is safe and effective and provides an important graft source for a diverse population.

Population Frequency of Fanconi Pathway Gene Variants and Their Association with Survival After Hematopoietic Cell Transplantation for Severe Aplastic Anemia.

Severe aplastic anemia (SAA) is most frequently immune-mediated; however, rare inherited bone marrow failure syndromes, such as Fanconi anemia (FA), may be causal and can present as aplastic anemia (AA). FA is primarily an autosomal recessive disorder caused by the presence of 2 pathogenic variants in a single FA/BRCA DNA repair pathway gene. Patients with SAA often undergo genetic testing during clinical evaluation that may identify single deleterious alleles in FA pathway genes. We quantified the rate of germline single deleterious alleles in 22 FA genes using both a general population database (3234 variants, 125,748 exomes) and in a cohort of patients with SAA undergoing hematopoietic cell transplantation (HCT) (21 variants in 730 patients). The variants were classified as deleterious using in silico tools (REVEL, MetaSVM, VEP) and database resources (ClinVar, LOVD-FA). We found similar rates of single deleterious alleles in FA genes in both groups (2.6% and 2.9%). The presence of a single deleterious variant in a gene for FA in SAA HCT recipients did not affect the overall survival after HCT (hazard ratio, 0.85; 95% CI, 0.37 to 1.95; P  = 0.71), or post-HCT cancer risk (P = 0.52). Our results demonstrate that the identification of a germline monoallelic deleterious variant in an FA gene in patients with idiopathic SAA does not influence the outcome of HCT. Our findings suggest that there is no need for special treatment considerations for patients with SAA and a single deleterious FA allele identified on genetic testing.

Current Use of and Trends in Hematopoietic Cell Transplantation in the United States.

Hematopoietic cell transplantation (HCT) is a well-established treatment to control and/or cure many malignant and nonmalignant diseases involving the hematopoietic system and some solid tumors. We report information about HCT procedures performed in the United States in 2018 and analyze trends and outcomes of HCT as reported to the Center for International Blood and Marrow Transplant Research (CIBMTR). Overall, compared with 2017, the number of allogeneic HCTs performed in the United States increased by 1%, and the number of autologous HCTs decreased by 5%. Key findings are fewer autologous HCTs performed for non-Hodgkin lymphoma and increasing numbers of haploidentical HCTs, nearly all of which use post-transplantation cyclophosphamide for graft-versus-host disease prophylaxis. There is a continuing increase in HCT in adults age >70 years, particularly for acute myelogenous leukemia and myelodysplastic syndromes. Survival rates by disease, disease stage, donor type, and age are presented. This report, prepared annually by the CIBMTR, provides a snapshot of current transplant activity in the United States.

Pre-transplant short telomeres are associated with high mortality risk after unrelated donor haematopoietic cell transplant for severe aplastic anaemia.

Telomeres are essential for chromosomal stability and markers of biological age. We evaluated the effect of pre-transplant short (<10th percentile-for-age) or very short (<5th or <1st percentile-for-age) leucocyte telomere length on survival after unrelated donor haematopoietic cell transplantation (HCT) for acquired severe aplastic anaemia (SAA). Patient pre-transplant blood samples and clinical data were available at the Center for International Blood and Marrow Transplant Research. We used quantitative real time polymerase chain reaction to measure relative telomere length (RTL) in 490 SAA patients who received HCT between 1990 and 2013 (median age = 20 years). One hundred and twelve patients (22·86%) had pre-HCT RTL <10th percentile-for-age, with the majority below the 5th percentile (N = 80, 71·43%). RTL <10th percentile-for-age was associated with a higher risk of post-HCT mortality (hazard ratio [HR] = 1·78, 95% confidence interval [CI]=1·18-2·69, P = 0·006) compared with RTL ≥50th percentile; no survival differences were noted in longer RTL categories (P > 0·10). Time-dependent effects for post-HCT mortality were only observed in relation to very short RTL; HR comparing RTL <5th versus ≥5th percentile = 1·38, P = 0·15 for the first 12 months after HCT, and HR = 3·91, P < 0·0001, thereafter, P-heterogeneity = 0·008; the corresponding HRs for RTL <1st versus ≥1st percentile = 1·29, P = 0·41, and HR = 5·18, P < 0·0001, P-heterogeneity = 0·005. The study suggests a potential role for telomere length in risk stratification of SAA patients in regard to their HCT survival.

Prognostic Mutations in Myelodysplastic Syndrome after Stem-Cell Transplantation.

BACKGROUND: Genetic mutations drive the pathogenesis of the myelodysplastic syndrome (MDS) and are closely associated with clinical phenotype. Therefore, genetic mutations may predict clinical outcomes after allogeneic hematopoietic stem-cell transplantation. METHODS: We performed targeted mutational analysis on samples obtained before transplantation from 1514 patients with MDS who were enrolled in the Center for International Blood and Marrow Transplant Research Repository between 2005 and 2014. We evaluated the association of mutations with transplantation outcomes, including overall survival, relapse, and death without relapse. RESULTS: TP53 mutations were present in 19% of the patients and were associated with shorter survival and a shorter time to relapse than was the absence of TP53 mutations, after adjustment for significant clinical variables (P<0.001 for both comparisons). Among patients 40 years of age or older who did not have TP53 mutations, the presence of RAS pathway mutations was associated with shorter survival than was the absence of RAS pathway mutations (P=0.004), owing to a high risk of relapse, and the presence of JAK2 mutations was associated with shorter survival than was the absence of JAK2 mutations (P=0.001), owing to a high risk of death without relapse. The adverse prognostic effect of TP53 mutations was similar in patients who received reduced-intensity conditioning regimens and those who received myeloablative conditioning regimens. By contrast, the adverse effect of RAS pathway mutations on the risk of relapse, as compared with the absence of RAS pathway mutations, was evident only with reduced-intensity conditioning (P<0.001). In young adults, 4% of the patients had compound heterozygous mutations in the Shwachman-Diamond syndrome-associated SBDS gene with concurrent TP53 mutations and a poor prognosis. Mutations in the p53 regulator PPM1D were more common among patients with therapy-related MDS than those with primary MDS (15% vs. 3%, P<0.001). CONCLUSIONS: Genetic profiling revealed that molecular subgroups of patients undergoing allogeneic hematopoietic stem-cell transplantation for MDS may inform prognostic stratification and the selection of conditioning regimen. (Funded by the Edward P. Evans Foundation and others.).

Donor telomere length and causes of death after unrelated hematopoietic cell transplantation in patients with marrow failure.

Previous studies have suggested that longer donor leukocyte telomere length (TL) is associated with improved survival after hematopoietic cell transplantation (HCT) in severe aplastic anemia (SAA). This study aimed to determine whether cell-specific lymphocyte TL is associated with certain post-HCT causes of death. We used flow cytometry and fluorescence in situ hybridization to measure TL in donor total lymphocytes and subsets: naïve enriched T cells (CD45RA+CD20-), memory enriched T cells (CD45RA-CD20-), natural killer (NK) fully differentiated T cells (CD45RA+CD57+), and B cells (CD45RA+CD20+). Competing risk survival regression was used for cause-specific death analyses. Clinical data and biospecimens were available from the Center for International Blood and Marrow Transplant Research database and biorepository. The study included 197 patients who underwent unrelated-donor HCT for SAA between 1988 and 2004. The median age at HCT was 15 years (range, 0.5-40 years), and the median follow-up was 5 years (range, <1 month to 20.7 years). Longer donor TL in all cell subsets was associated with lower risk of all-cause mortality (P < .01). In cause-specific mortality analyses, longer TL in B cells (hazard ratio [HR], 0.63; 95% confidence interval [CI], 0.46-0.87; P = .006) and possibly NK fully differentiated T cells (HR, 0.7; 95% CI, 0.51 to 0.97; P = .03) was associated with lower risk of infection-related death. Donor TL in other tested lymphocyte subsets was not statistically significantly associated with death resulting from graft-versus-host disease or graft failure (P > .05). However, a trend toward excess risk of graft-versus-host mortality was noted (HR for total lymphocyte TL, 1.26; P = .15). In conclusion, longer donor TL was associated with reduced rate of infection-related deaths after HCT for SAA.