The Duffy-null genotype and risk of infection

Understanding clozapine-related blood dyscrasias. Developments, genetics, ethnicity and disparity: it's a CIN

Clozapine remains the gold standard intervention for treatment-resistant schizophrenia; however, it remains underused, especially for some minority groups. A significant impediment is concern about propensity to neutropenia. The aim of this article is to provide an update on current knowledge relating to: the pattern and incidence of severe blood dyscrasias; the effectiveness of current monitoring regimes in reducing harm; the mechanisms of and the distinctions between clozapine-induced neutropenia and agranulocytosis; benign ethnic neutropenia; and changes to the monitoring thresholds in the USA and other international variations. These all have implications for the practical use of clozapine; specifically, how barriers to initiating, maintaining and restarting clozapine can be understood and in many cases overcome, especially for patients from minority groups, potentially with simpler approaches than the use of lithium or G-CSF.

Absolute neutrophil count clinical trial eligibility criteria for pediatric oncology phase I and phase I/II trials by sponsorship

Normal absolute neutrophil count (ANC) variations, as seen with Duffy-null associated neutrophil count (DANC), are not accounted for in trial eligibility, which may contribute to racial enrollment disparities. We describe ANC eligibility for pediatric oncology phase I/II clinical trials according to primary sponsorship from 2010 to 2023 using ClinicalTrials.gov. Out of 438 trials, 20% were industry-sponsored. Total 17% of trials required ANC ≥1500 cells/μL for enrollment; however, industry-sponsored trials were significantly more likely to require ANC ≥1500 cells/μL than non-industry-sponsored trials (odds ratio 2.53, 95% confidence interval: 1.39-4.62; p < .001). These data suggest laboratory exclusion criteria are one possible mechanism for pediatric clinical trial enrollment disparities.

Clinical and immunological features in ACKR1/DARC-associated neutropenia

ABSTRACT

ACKR1/DARC-associated neutropenia (NP; ADAN; Online Mendelian Inheritance in Man 611862), caused by a variation in the ACKR1/DARC gene (rs2814778), is common in persons of African or Middle Eastern descent. In a cohort of 66 genetically confirmed subjects with ADAN, we show that absolute neutrophil counts (ANCs) may occasionally be lower than previously recognized (0.1 × 109-0.49 × 109/L for 9% of the subjects), which is similar to ANCs in severe congenital NP (SCNP). ANCs often normalized during inflammation, even mild. Individuals with ADAN (of 327 observed person-years) showed no cases of myelodysplastic syndrome (MDS), which is frequently encountered in SCNP. Unexpectedly, 22% presented with autoantibodies to neutrophils, compared with <1% in controls. Compared with healthy donors, subjects with ADAN demonstrated significantly lower human cationic antimicrobial protein-18/pro-leucin leucin-37 plasma levels; higher levels of nonclassical, proinflammatory, 6-sulfo LacNac-expressing monocytes; and differentially expressed plasma levels of 28 of the 239 analyzed cytokines related to immunity/inflammation, cell signaling, neutrophil activation, and angiogenesis. Collectively, more severe neutropenia in ADAN than previously assumed may complicate differential diagnoses compared with other SCNPs, and various (auto)immune/inflammatory reactions with a distinct profile may be a cause or consequence of this hereditary neutropenia.

Ancestry, ACKR1 and leucopenia in patients with systemic lupus erythematosus

OBJECTIVE

SLE is more prevalent in populations of African (AA) than European ancestry (EA) and leucopenia is common. A homozygous variant in ACKR1 (rs2814778-CC) is associated with lower white cell counts; the variant is common in AA but not EA populations. We hypothesised that in SLE: (1) leucopenia is more frequent in patients of AA than EA, and (2) the ACKR1-CC genotype accounts for the higher frequency of leucopenia in AA patients.

METHODS

We performed a retrospective cohort study in patients with SLE at a tertiary care system. Ancestry was defined by genetic principal components. We compared the rate of leucopenia, thrombocytopenia and anaemia between (a) EA and AA patients, and (b) ACKR1-CT/TT and CC genotype in AA patients.

RESULTS

The cohort included 574 patients of EA and 190 of AA; ACKR1-CC genotype was common in AA (70%) but not EA (0%) patients. Rates of leucopenia for ancestry and genotype were AA 60.0% vs EA 36.8 % (p=1.9E-08); CC 67.7% vs CT/TT 42.1% (p=9.8E-04). The rate of leucopenia did not differ by ancestry comparing EA patients versus AA with CT/TT genotype (p=0.59). Thrombocytopenia (22.2% vs 13.2%, p=0.004) and anaemia (88.4% vs 66.2%, p=3.7E-09) were more frequent in AA patients but were not associated with ACKR1 genotype (p=0.82 and p=0.84, respectively).

CONCLUSIONS

SLE of AA had higher rates of anaemia, leucopenia, and thrombocytopenia than those of EA; only the difference in leucopenia was explained by ACKR1-CC genotype. This genotype could affect clinical practice.

Absolute neutrophil count by Duffy status among healthy Black and African American adults

Many people of African ancestry have lower absolute neutrophil counts (ANCs) without increased risk for infection. This is associated with the Duffy-null phenotype (nonexpression of the Duffy antigen on red blood cells), which is commonly found in those of African descent. Currently, there are no studies that compare the ANC of individuals with Duffy-null phenotype to those with Duffy non-null phenotypes within a self-identified Black population. The aim of this study was to assess the impact of Duffy status on ANCs based on complete blood counts with differential and Duffy testing in a healthy population of self-identified Black individuals at a single primary care center. This study found that 66.7% (80 of 120) of Black individuals have the Duffy-null phenotype and that there is a significant difference in ANCs between Duffy-null and Duffy non-null individuals (median, 2820 cells per μL vs 5005 cells per μL; P < .001). Additionally, 19 of 80 (23.8%) Duffy-null individuals had an ANC of <2000 cells per μL compared with no (0) Duffy non-null individuals. The Duffy-null phenotype is clinically insignificant; however, inappropriate reference ranges can propagate systemic racism. Therefore, we advocate for the development of Duffy-null-specific ANC reference ranges as well as replacing the term benign ethnic neutropenia with Duffy-nullassociated neutrophil count.

Race, Genotype, and Azathioprine Discontinuation : A Cohort Study

BACKGROUND

Thiopurines are an important class of immunosuppressants despite their risk for hematopoietic toxicity and narrow therapeutic indices. Benign neutropenia related to an ACKR1 variant (rs2814778-CC) is common among persons of African ancestries.

OBJECTIVE

To test whether rs2814778-CC was associated with azathioprine discontinuation attributed to hematopoietic toxicity and lower thiopurine dosing.

DESIGN

Retrospective cohort study.

SETTING

Two tertiary care centers.

PATIENTS

Thiopurine users with White or Black race.

MEASUREMENTS

Azathioprine discontinuation attributed to hematopoietic toxicity. Secondary outcomes included weight-adjusted final dose, leukocyte count, and change in leukocyte count.

RESULTS

The rate of azathioprine discontinuation attributed to hematopoietic toxicity was 3.92 per 100 person-years among patients with the CC genotype (n = 101) and 1.34 per 100 person-years among those with the TT or TC genotype (n = 1365) (hazard ratio [HR] from competing-risk model, 2.92 [95% CI, 1.57 to 5.41]). The risk remained significant after adjustment for race (HR, 2.61 [CI, 1.01 to 6.71]). The risk associated with race alone (HR, 2.13 [CI, 1.21 to 3.75]) was abrogated by adjustment for genotype (HR, 1.13 [CI, 0.48 to 2.69]). Lower last leukocyte count and lower dosing were significant among patients with the CC genotype. Lower dosing was validated in an external cohort of 94 children of African ancestries prescribed the thiopurine 6-mercaptopurine (6-MP) for acute lymphoblastic leukemia. The CC genotype was independently associated with lower 6-MP dose intensity relative to the target daily dose of 75 mg/m2 (median, 0.83 [IQR, 0.70 to 0.94] for the CC genotype vs. 0.94 [IQR, 0.72 to 1.13] for the TT or TC genotype; P = 0.013).

LIMITATIONS

Unmeasured confounding; data limited to tertiary centers.

CONCLUSION

Patients with the CC genotype had higher risk for azathioprine discontinuation attributed to hematopoietic toxicity and lower thiopurine doses. Genotype was associated with those risks, even after adjustment for race.

PRIMARY FUNDING SOURCE

National Institutes of Health.

Frequency of benign neutropenia among Black versus White individuals undergoing a bone marrow assessment

Healthy individuals in the United States identified as having Black race have lower neutrophil counts, on average, than individuals identified as having White race, which could result in more negative diagnostic evaluations for neutropenia. To test this hypothesis, the proportion of evaluations where the final diagnosis was clinically insignificant neutropenia for Black and White individuals who underwent an evaluation by a haematologist that included a bone marrow (BM) biopsy to investigate neutropenia was assessed. 172 individuals without prior haematological diagnoses who underwent a haematological evaluation to investigate neutropenia. Individuals diagnosed with clinically insignificant neutropenia between Black and White individuals were compared using a propensity-score-adjusted logistic regression. Of 172 individuals, 42 (24%) were classified as Black race, 86 (50%) were males, and the 79 (46%) were over 18 years old. A BM biopsy did not identify pathology in 95% (40 of 42) of Black individuals and 68% (89 of 130) of White Individuals. Black individuals (25 of 42 [60%]) received a final diagnosis of clinically insignificant neutropenia, compared to White individuals (12 of 130 [9%]) (adjusted odds ratio =7.9, 95% CI: 3.1 - 21.1). We conclude that black individuals were more likely to receive a diagnosis of clinically insignificant neutropenia after haematological assessment.

Whole Genome Sequence Analysis of the Plasma Proteome in Black Adults Provides Novel Insights Into Cardiovascular Disease

BACKGROUND

Plasma proteins are critical mediators of cardiovascular processes and are the targets of many drugs. Previous efforts to characterize the genetic architecture of the plasma proteome have been limited by a focus on individuals of European descent and leveraged genotyping arrays and imputation. Here we describe whole genome sequence analysis of the plasma proteome in individuals with greater African ancestry, increasing our power to identify novel genetic determinants.

METHODS

Proteomic profiling of 1301 proteins was performed in 1852 Black adults from the Jackson Heart Study using aptamer-based proteomics (SomaScan). Whole genome sequencing association analysis was ascertained for all variants with minor allele count ≥5. Results were validated using an alternative, antibody-based, proteomic platform (Olink) as well as replicated in the Multi-Ethnic Study of Atherosclerosis and the HERITAGE Family Study (Health, Risk Factors, Exercise Training and Genetics).

RESULTS

We identify 569 genetic associations between 479 proteins and 438 unique genetic regions at a Bonferroni-adjusted significance level of 3.8×10-11. These associations include 114 novel locus-protein relationships and an additional 217 novel sentinel variant-protein relationships. Novel cardiovascular findings include new protein associations at the APOE gene locus including ZAP70 (sentinel single nucleotide polymorphism [SNP] rs7412-T, β=0.61±0.05, P=3.27×10-30) and MMP-3 (β=-0.60±0.05, P=1.67×10-32), as well as a completely novel pleiotropic locus at the HPX gene, associated with 9 proteins. Further, the associations suggest new mechanisms of genetically mediated cardiovascular disease linked to African ancestry; we identify a novel association between variants linked to APOL1-associated chronic kidney and heart disease and the protein CKAP2 (rs73885319-G, β=0.34±0.04, P=1.34×10-17) as well as an association between ATTR amyloidosis and RBP4 levels in community-dwelling individuals without heart failure.

CONCLUSIONS

Taken together, these results provide evidence for the functional importance of variants in non-European populations, and suggest new biological mechanisms for ancestry-specific determinants of lipids, coagulation, and myocardial function.

BGvar: A comprehensive resource for blood group immunogenetics

BACKGROUND

Blood groups form the basis of effective and safe blood transfusion. There are about 43 well-recognised human blood group systems presently known. Blood groups are molecularly determined by the presence of specific antigens on the red blood cells and are genetically determined and inherited following Mendelian principles. The lack of a comprehensive, relevant, manually compiled and genome-ready dataset of red cell antigens limited the widespread application of genomic technologies to characterise and interpret the blood group complement of an individual from genomic datasets.

MATERIALS AND METHODS

A range of public datasets was used to systematically annotate the variation compendium for its functionality and allele frequencies across global populations. Details on phenotype or relevant clinical importance were collated from reported literature evidence.

RESULTS

We have compiled the Blood Group Associated Genomic Variant Resource (BGvar), a manually curated online resource comprising all known human blood group related allelic variants including a total of 1700 International Society of Blood Transfusion approved alleles and 1706 alleles predicted and curated from literature reports. This repository includes 1682 single nucleotide variations (SNVs), 310 Insertions, Deletions (InDels) and Duplications (Copy Number Variations) and about 1360 combination mutations corresponding to 43 human blood group systems and 2 transcription factors. This compendium also encompasses gene fusion and rearrangement events occurring in human blood group genes.

CONCLUSION

To the best of our knowledge, BGvar is a comprehensive and a user-friendly resource with most relevant collation of blood group alleles in humans. BGvar is accessible online at URL: http://clingen.igib.res.in/bgvar/.