How Ancestry Influences the Chances of Finding Unrelated Donors: An Investigation in Admixed Brazilians

Hematopoietic stem cell transplantation in inborn errors of metabolism-a retrospective analysis on behalf of the pediatric disease working party from the Brazilian Society of Bone Marrow Transplantation and Cellular Therapy

Hematopoietic stem cell transplantation (HSCT) is an established treatment for selected patients with inborn errors of metabolism. In this first report from the PDWP-SBTMO, we included 105 patients transplanted between 1988 and 2021 across six Brazilian HSCT centers. The most prevalent diseases were X-linked adrenoleukodystrophy (n = 61) and mucopolysaccharidosis (type I n = 20; type II n = 10), with a median age at HSCT of 8.7 years and 2.1 years, respectively. Most conditioning regimens were myeloablative and busulfan-based. With a median follow-up of 6.7 years, the 5-years overall survival (OS) was 75% (95% CI, 0.65-0.82) with a superior 5-years OS for those transplanted after 2010 (87% vs. 63%, p = 0.01). Higher risk of death was associated with the use of haploidentical donor (HR8.86, p 0.021), unrelated cord blood (HR 8.76, p 0.005), unrelated donor (HR 5.91, p 0.02), and for HSCT performed before 2010 (HR 4.16, p = 0.0015). The CI of acute GVHD was 24.8%, while chronic GVHD was 9.5%. Major causes of death were infections (n = 8), GVHD (n = 6), and neurologic progression (n = 3). Despite improvements in transplant outcomes since 2011, challenges persist, emphasizing the need for early diagnosis, timely transplantation and expanding HSCT centers with expertise in the field.

Common, Intermediate and Well-Documented HLA Alleles in the Brazilian Population: An Analysis of the Brazilian Bone Marrow Donor Registry (REDOME)

This study investigates the HLA allele diversity in Brazil, a reflection of the country's unique history of population admixture. The international comparison of findings emphasises the importance of incorporating underrepresented populations into global HLA databases. We present a comprehensive analysis of HLA alleles within the Brazilian population, utilising high-resolution sequencing data from 298,000 unrelated haematopoietic stem cell volunteer donors registered with the Brazilian Bone Marrow Donor Registry (REDOME). Our research encompasses donors from all regions of Brazil, identifying HLA alleles that are catalogued as common, intermediate or well-documented (CIWD Version 3.0). We evaluated the alleles of HLA-A, HLA-B, HLA-C, HLA-DRB1, HLA-DQA1, HLA-DQB1, HLA-DPA1 and HLA-DPB1. At a two-field resolution, we identified 1969 alleles: 418 were classified as common, 358 as intermediate and 1193 as non-CIWD in Brazil. Notably, we report HLA alleles that, while not classified as common or intermediate in the CIWD 3.0 catalogue, are prevalent within the Brazilian population. A detailed list of alleles from the registry, presented at a two-field resolution and supplemented with grouped ARD levels, including three- or four-field resolution when available, serves as an essential reference for HLA typing frequencies specific to the Brazilian population.

Genetic ancestry and the colonial legacies of race in genomics: a cross-disciplinary dialogue

As genomics initiatives have spread around the world-often in the name of genetic diversity and inclusion-they have not only invoked promises of a medical revolution, but also revived categories of human difference that resemble erstwhile racial classifications. This is despite the fact that geneticists broadly dismissed racial categories as obsolete and unfounded after the Human Genome Project was completed in 2003. In fact, contemporary genomics initiatives have often ended up reinforcing ethnocentric and nativist conceptions of difference, drawing intense criticism from activists and critical social scientists. This roundtable brings leading population geneticists grappling with the question of genetic identity and ancestry, especially in the global South, together with some of the most prominent scholars of race in genomics. The result is an engaging and insightful dialogue on questions that have vexed the field for decades. How do we-indeed "can" we reconcile the boundaries of biological and social difference? How do notions of "genetic ancestry" and "biogeographical ancestry differ from erstwhile racial and ethnic categories? Can racial categories ever be shorn of their colonial and oppressive legacies? Here we scrutinise the methodological and epistemological frameworks in contemporary genomics that work to define populations and shape our understanding of biology, society, health, and disease. We seek to clarify perspectives across the disciplinary divide, and to advance constructive and grounded critiques that contend with the question of justice in genomics.

Steroid-Resistant Nephrotic Syndrome Is Associated With a Unique Genetic Profile in a Highly Admixed Pediatric Population

Introduction

The profile of genetic and nongenetic factors associated with progression to kidney failure (KF) in steroid-resistant nephrotic syndrome (SRNS) is largely unknown in admixed populations.

Methods

A total of 101 pediatric patients with primary SRNS were genetically assessed targeting Mendelian causes and APOL1 status with a 62-NS-gene panel or whole exome sequencing, as well as genetic ancestry. Variant pathogenicity was evaluated using the American College Medical of Genetics and Genomics (ACMG) criteria.

Results

Focal segmental glomerulosclerosis (FSGS) was diagnosed in 54% of patients whereas familial disease was reported by 13%. The global genetic ancestry was 65% European, 22% African, 10.5% Native American, and 2% East-Asian, while 96% of cases presented with the first 3 components. APOL1 high-risk genotypes were identified in 8% of families and causative Mendelian variants in 12%: NPHS1 = 3, NPHS2 = 3, PLCE1 = 2, WT1 = 2, COQ2 = 1, and CUBN = 1. Two novel causative variants arose in the Native American background. The percentage of African genetic ancestry did not associate with the number of APOL1 risk alleles. Forty-four percent of all patients progressed to KF. Mendelian forms and APOL1 high-risk genotypes were associated with faster progression to KF. Cox regression analyses revealed that higher non-European genetic ancestry, self-declared non-White ethnicity, age of onset <1 year or ≥9 years, and non-minimal change disease (MCD) histology associated with higher risk of KF, independently of genetic findings.

Conclusion

Mendelian variants and APOL1 high-risk genotype compose a unique causative genetic profile associated with pediatric SRNS in this highly admixed population, accounting for approximately 20% of families. This ancestry pattern is consistent with the identification of APOL1 high-risk genotypes in children with low proportion of African genetic ancestry. Self-declared ethnicity, age of manifestation and histology were independently associated with the risk of KF.

Optimisation of global stem cell donor recruitment based on analysis of unsuccessful donor searches

Despite over 41 million registered potential volunteer stem cell donors worldwide, many patients in need of a transplant do not find an HLA-matched unrelated donor or cord blood units, with the respective odds differing significantly between various populations. In this study, we analysed data of 2205 unsuccessful real-life donor searches sent to the DKMS Registry to identify populations in which further donor recruitment would be associated with particularly large patient benefits. For that purpose, we estimated haplotype frequencies of 67 donor populations at various sample sizes and entered them into two different mathematical models. These models assessed patient benefits from population-specific donor recruitment, operationalised by the number of originally unsuccessful searches that may become successful due to new donors. Consistently, across the different mathematical models and sample sizes, we obtained several countries from East and Southeast Asia (Thailand, Vietnam, China, and the Philippines) and the population of Asians in the USA as countries/populations where donor recruitment activities would be particularly beneficial for patients. We also identified various countries in Southeast and Central Europe as possible target regions for donor recruitment with above-average patient benefits. The results presented are registry-specific in the sense that they were obtained by optimising unsuccessful searches that had been sent to the DKMS Registry. Therefore, it would be desirable to apply the presented methods to a global data set that includes all unsuccessful stem cell donor searches worldwide and uses population-specific haplotype frequencies based on all donors available in the WMDA Search & Match Service.

HLA alleles and antiseizure medication-induced cutaneous reactions in Brazil: A case-control study

In this observational case-control study, 107 cutaneous adverse reaction (CAR) cases (CAR+) manifesting up to 12 weeks after the start of treatment with antiseizure medication (ASM) were identified. Control groups consisted of 98 epilepsy patients without a history of CAR (CAR-) and 3965 healthy individuals in the Brazilian National Registry of Bone Marrow Donors. All participants were HLA typed by high-resolution Next Generation Sequencing for HLA-A, B, C, DQB1 and DRB1; HLA-DPA1, DPB1, DQA1, DRB3, DRB4 and DRB5 were also sequenced in samples from CAR+ and CAR- individuals. The relationship between the carrier frequency of each allele, CAR type and ASM for all participants was investigated. The ASMs most frequently associated with CAR were carbamazepine (48% of CAR+ subjects), lamotrigine (23%), phenytoin (18%), phenobarbital (13%) and oxcarbazepine (5%). The main alleles associated with a risk of CAR were HLA-A*02:05 (OR = 6.28; p = 0.019, carbamazepine or oxcarbazepine); HLA-DPA1*02:02 (OR = 4.16, p = 0.003, carbamazepine); HLA-B*53:01 (OR = 47.9, p = 0.014, oxcarbazepine), HLA-DPA1*03:01/DPB1*105:01 (OR = 25.7, p = 0.005, phenobarbital); HLA-C*02:10 (OR = 25.7, p = 0.005, phenobarbital) and HLA-DRB1*04:02 (OR = 17.22, p = 0.007, phenytoin). HLA-A*03:01 increased the risk for phenytoin-induced maculopapular exanthema 4.71-fold (p = 0.009), and HLA-B*35:02 was associated with a 25.6-fold increase in the risk of carbamazepine-induced Stevens-Johnson syndrome (p = 0.005). None of the 4170 subjects carried the HLA-B*15:02 allele, and HLA-A*31:01 was not associated with CAR. Hence, HLA-A*31:01 and HLA-B*15:02 were not associated with CAR in this population. Although other HLA class I and II alleles tested were associated with a risk of CAR, none of these associations were strong enough to warrant HLA testing before prescribing ASM.

Prospective donors' perspectives on hematopoietic cell donation for cell and gene therapy research and development

Aim: To explore prospective donors' attitudes and perceptions toward donating hematopoietic stem cells (HSCs) for novel treatments research and development (R&D). Methods: A survey was launched by Anthony Nolan (AN) to assess prospective donors' willingness to donate HSCs for novel therapies R&D, and their degree of comfort with the AN collaborating with and receiving payment from external organizations. Results: Most participants (87%) were willing to donate for novel treatment R&D and were comfortable with AN collaborating with external organizations and receiving payment (91% and 80%, respectively). Conclusion: Results reveal an overall positive response toward donating HSCs for R&D. These findings can support stakeholders and policymakers in outlining donation practices that uphold donors' safety and welfare.

Transplant for non-malignant disorders: an International Society for Cell & Gene Therapy Stem Cell Engineering Committee report on the role of alternative donors, stem cell sources and graft engineering

Hematopoietic stem cell transplantation (HSCT) is curative for many non-malignant disorders. As HSCT and supportive care technologies improve, this life-saving treatment may be offered to more and more patients. With the development of new preparative regimens, expanded alternative donor availability, and graft manipulation techniques, there are many options when choosing the best regimen for patients. Herein the authors review transplant considerations, transplant goals, conditioning regimens, donor choice, and graft manipulation strategies for patients with non-malignant disorders undergoing HSCT.

Population designations in biomedical research: Limitations and perspectives

In biomedical research, population differences are of central interest. Variations in the frequency and severity of diseases and in treatment effects among human subpopulation groups are common in many medical conditions. Unfortunately, the practices in terms of subpopulation labeling do not exhibit the level of rigor one would expect in biomedical research, especially when studying multifactorial diseases such as cancer or atherosclerosis. The reporting of population differences in clinical research is characterized by large disparities in practices, and fraught with methodological issues and inconsistencies. The actual designations such as "Black" or "Asian" refer to broad and heterogeneous groups, with a great discrepancy among countries. Moreover, the use of obsolete concepts such as "Caucasian" is unfortunate and imprecise. The use of adequate labeling to reflect the scientific hypothesis needs to be promoted. Furthermore, the use of "race/ethnicity" as a unique cause of human heterogeneity may distract from investigating other factors related to a medical condition, particularly if this label is employed as a proxy for cultural habits, diet, or environmental exposure. In addition, the wide range of opinions among researchers does not facilitate the attempts made for resolving this heterogeneity in labeling. "Race," "ethnicity," "ancestry," "geographical origin," and other similar concepts are saturated with meanings. Even if the feasibility of a global consensus on labeling seems difficult, geneticists, sociologists, anthropologists, and ethicists should help develop policies and practices for the biomedical field.

Is Severity Score Associated With Indication for Hematopoietic Stem Cell Transplantation in Individuals With Sickle Cell Anemia?

Manifestations of sickle cell disease (SCD) begin early in childhood and cause morbidity and decreased life expectancy. Hematopoietic stem cell transplantation (HSCT) is curative but associated with risk of mortality attributable to the transplant. This risk should be counterbalanced with SCD morbidity and mortality. A severity score using a Bayesian network model was previously validated to predict the risk of death in adult individuals with SCD. The objective of this study is to calculate the severity scores of participants in a multicenter cohort of Brazilians with SCD, using a previously published Bayesian network-derived score, associated with risk of death and then compare the severity scores between participants with and without an indication for HSCT as defined by the Brazilian Ministry of Health (MoH) criteria. This is an observational, retrospective study. We analyzed 2063 individuals with sickle cell anemia from the Recipient Epidemiology and Donor Evaluation Study-III Brazil SCD cohort and applied a Bayesian network-derived score to compare candidates and non-candidates for HSCT according to the Brazilian MoH transplant criteria. Classical statistical methods were used to analyze data and make comparisons. We compared severity scores between cohort members with (n = 431) and without (n = 1632) HSCT indications according to Brazilian MoH. Scores were not different in adult participants with ≥1 HSCT indication when compared to those with no indication (mean 0.342 versus 0.292; median 0.194 versus 0.183, P = .354) and receiver operating characteristic curves did not demonstrate an obvious threshold to differentiate participants with or without HSCT indications. Severity score may predict risk of death but does not differentiate HSCT candidates. Current indications should be evaluated to ensure that patients with more severe disease who might benefit from HSCT are appropriately identified.

The Recipient Epidemiology and Donor Evaluation Study-IV-Pediatric (REDS-IV-P): A research program striving to improve blood donor safety and optimize transfusion outcomes across the lifespan

BACKGROUND

The Recipient Epidemiology and Donor Evaluation Study-IV-Pediatric (REDS-IV-P) is a new iteration of prior National Heart, Lung, and Blood Institute (NHLBI) REDS programs that focus on improving transfusion recipient outcomes across the lifespan as well as the safety and availability of the blood supply.

STUDY DESIGN AND METHODS

The US program includes blood centers and hospitals (22 including 6 free-standing Children's hospitals) in four geographic regions. The Brazilian program has 5 participating hemocenters. A Center for Transfusion Laboratory Studies (CTLS) and a Data Coordinating Center (DCC) support synergistic studies and activities over the 7-year REDS-IV-P program.

RESULTS

The US is building a centralized, vein-to-vein (V2V) database, linking information collected from blood donors, their donations, the resulting manufactured components, and data extracts from hospital electronic medical records of transfused and non-transfused patients. Simultaneously, the Brazilian program is building a donor, donation, and component database. The databases will serve as the backbone for retrospective and prospective observational studies in transfusion epidemiology, transfusion recipient outcomes, blood component quality, and emerging blood safety issues. Special focus will be on preterm infants, patients with sickle cell disease, thalassemia or cancer, and the effect of donor biologic variability and component manufacturing on recipient outcomes. A rapid response capability to emerging safety threats has resulted in timely studies related to Severe Acute Respiratory Syndrome Corona Virus-2 (SARS-CoV-2).

CONCLUSIONS

The REDS-IV-P program endeavors to improve donor-recipient-linked research with a focus on children and special populations while also maintaining the flexibility to address emerging blood safety issues.

How HLA diversity is apportioned: influence of selection and relevance to transplantation

In his 1972 paper ‘The apportionment of human diversity’, Lewontin showed that, when averaged over loci, genetic diversity is predominantly attributable to differences among individuals within populations. However, selection can alter the apportionment of diversity of specific genes or genomic regions. We examine genetic diversity at the human leucocyte antigen (HLA) loci, located within the major histocompatibility complex (MHC) region. HLA genes code for proteins that are critical to adaptive immunity and are well-documented targets of balancing selection. The single-nucleotide polymorphisms (SNPs) within HLA genes show strong signatures of balancing selection on large timescales and are broadly shared among populations, displaying low F_ST values. However, when we analyse haplotypes defined by these SNPs (which define ‘HLA alleles’), we find marked differences in frequencies between geographic regions. These differences are not reflected in the F_ST values because of the extreme polymorphism at HLA loci, illustrating challenges in interpreting F_ST. Differences in the frequency of HLA alleles among geographic regions are relevant to bone-marrow transplantation, which requires genetic identity at HLA loci between patient and donor. We discuss the case of Brazil's bone marrow registry, where a deficit of enrolled volunteers with African ancestry reduces the chance of finding donors for individuals with an MHC region of African ancestry.

This article is part of the theme issue ‘Celebrating 50 years since Lewontin's apportionment of human diversity’.

Increasing access to allogeneic hematopoietic cell transplant: an international perspective

Allogeneic hematopoietic cell transplantation (allo-HCT) is a highly complex, costly procedure for patients with oncologic, hematologic, genetic, and immunologic diseases. Demographics and socioeconomic status as well as donor availability and type of health care system are important factors that influence access to and outcomes following allo-HCT. The last decade has seen an increase in the numbers of allo-HCTs and teams all over the world, with no signs of saturation. More than 80 000 procedures are being performed annually, with 1 million allo-HCTs estimated to take place by the end of 2024. Many factors have contributed to this, including increased numbers of eligible patients (older adults with or without comorbidities) and available donors (unrelated and haploidentical), improved supportive care, and decreased early and late post-HCT mortalities. This increase is also directly linked to macro- and microeconomic indicators that affect health care both regionally and globally. Despite this global increase in the number of allo-HCTs and transplant centers, there is an enormous need for increased access to and improved outcomes following allo-HCT in resource-constrained countries. The reduction of poverty, global economic changes, greater access to information, exchange of technologies, and use of artificial intelligence, mobile health, and telehealth are certainly creating unprecedented opportunities to establish collaborations and share experiences and thus increase patient access to allo-HCT. A specific research agenda to address issues of allo-HCT in resource-constrained settings is urgently warranted.

Population genetic considerations for using biobanks as international resources in the pandemic era and beyond

The past years have seen the rise of genomic biobanks and mega-scale meta-analysis of genomic data, which promises to reveal the genetic underpinnings of health and disease. However, the over-representation of Europeans in genomic studies not only limits the global understanding of disease risk but also inhibits viable research into the genomic differences between carriers and patients. Whilst the community has agreed that more diverse samples are required, it is not enough to blindly increase diversity; the diversity must be quantified, compared and annotated to lead to insight. Genetic annotations from separate biobanks need to be comparable and computable and to operate without access to raw data due to privacy concerns. Comparability is key both for regular research and to allow international comparison in response to pandemics. Here, we evaluate the appropriateness of the most common genomic tools used to depict population structure in a standardized and comparable manner. The end goal is to reduce the effects of confounding and learn from genuine variation in genetic effects on phenotypes across populations, which will improve the value of biobanks (locally and internationally), increase the accuracy of association analyses and inform developmental efforts.