Granulocyte antibodies in male blood donors: can they trigger transfusion-related acute lung injury?

Anti-HNA testing of allo-exposed COVID-19 convalescent plasma donors including genetic human neutrophil antigen screening to prevent anti-HNA antibody-mediated transfusion-related acute lung injury

BACKGROUND

Transfusion-related acute lung injury caused by antibodies against human neutrophil antigens (HNA) is a serious but rare complication associated with blood transfusion. The presence of such antibodies is most probable in donors with a transfusion/pregnancy history. During the COVID-19 pandemic period convalescent plasma (CP) containing neutralizing antibodies against SARS-CoV-2 was widely used for COVID-19 patients as a therapy in the absence of any treatment. The aim of the study was to work out a simple diagnostic algorithm of anti-HNA testing of allo-exposed CP donors including genetic HNA screening.

MATERIALS AND METHODS

A total of 457 anti-HLA-negative allo-exposed CP donors were genotyped for HNA-1a/1b, HNA-3a/3b, and HNA-2, and only donors with homozygous HNA-1a/1a; HNA-3b/3b; or HNA-2null genotypes were tested for anti-HNA antibody using LabScreenMulti (One Lambda) and homozygous HNA-1b/1b using the granulocyte immunofluorescence test (GIFT) but verified using LabScreenMulti.

RESULTS

Testing of 83 homozygous HNA-3b/3b; HNA-2null; or HNA-1a/1a donors revealed anti-HNA-3a antibody in one case. Testing of 181 HNA-1b/1b donors using GIFT gave 10 ambiguous results verified using LabScreenMulti which confirmed anti-HNA-1a antibody in one case. The frequency of FCGR3B*01 and *04 encoding HNA-1a was 0.34; FCGR3B*02, *03, and *05 encoding HNA-1b-0.66; SLC44A2*01 encoding HNA-3a-0.80; and SLC44A2*02 encoding HNA-3b-0.20. In 3.7% cases the HNA-2null genotype was revealed.

DISCUSSION

Due to applying HNA genotyping as a primary test before anti-HNA antibody testing the serological work was limited only to HNA-homozygous donors revealing two anti-HNA immunized donors. The distribution of HNA genotypes in the cohort was similar to other Caucasian populations.

Prevalence of leucocyte antibodies in non-transfused male and female platelet apheresis donors

OBJECTIVES

In our study group of Thai PLT apheresis donors, we assessed the prevalence of anti-leucocyte antibodies.

BACKGROUND

Antibodies against human leucocyte antigens (anti-HLA), neutrophil antigens (anti-HNA), and major histocompatibility complex class I related chain A (anti-MICA) in blood products can lead to transfusion-related acute lung injury (TRALI). To reduce the risk of TRALI, some blood centres are implementing strategies based on screening platelet (PLT) apheresis donors for the presence of anti-leucocyte antibodies.

METHODS/MATERIALS

Blood samples were collected from non-transfused individuals, 340 males and 63 females (50 nulliparous and 13 parous). Anti-HLA class I and II and anti-MICA were analysed using the Luminex assay, and anti-HNA-3 was detected using the granulocyte agglutination test.

RESULTS

Anti-HLA was found in 14 of 403 subjects (3.5%). Ten subjects (2.5%) tested positive for HLA class I, 2 (0.5%) for HLA class II, and 2 (0.5%) for both HLA class I and HLA class II. Anti-HLA class I or II were detected in 2 of 13 (15.4%) parous females and only anti-HLA class I was found in 4 (8.0%) nulliparous females. Six of 327 subjects tested (1.8%), all males, were positive for anti-MICA. Anti-HNA-3 was not found in any of the 403 individuals.

CONCLUSIONS

Screening for anti-HLA class I and II should be implemented for Thai PLT apheresis donors. Although immunisation against HNA and MICA seems to be a rare event in Thais, further work is necessary to decide whether our PLT apheresis donors should be screened for HNA and MICA antibodies.

Multicenter Study on Differential Human Neutrophil Antigen 2 Expression and Underlying Molecular Mechanisms

Background

The human neutrophil antigen 2 (HNA-2), which is expressed on CD177, is undetectable in 3-5% of the normal population. Exposure of these HNA-2_null individuals to HNA-2-positive cells can cause immunization and pro-duction of HNA-2 antibodies, which can induce immune neutropenia and transfusion-related acute lung injury. In HNA-2-positive individuals, neutrophils are divided into a CD177^pos. and a CD177^neg. subpopulation. The molecular background of HNA-2 deficiency and the bimodal expression pattern, however, are not completely decoded.

Study Design

An international collaboration was conducted on the genetic analysis of HNA-2-phenotyped blood samples, including HNA-2-deficient individuals, mothers, and the respective children with neonatal immune neutropenia and regular blood donors.

Results

From a total of 54 HNA-2_null individuals, 43 were homozygous for the CD177 *787A>T substitution. Six carried the CD177 *c.1291G>A single nucleotide polymorphism. All HNA-2-positive samples with >40% CD177^pos. neutrophils carried the *787A wild-type allele, whereas a lower rate of CD177^pos. neutrophils was preferentially associated with *c.787AT heterozygosity. Interestingly, only the *c.787A allele sequence was detected in complementary DNA (cDNA) sequence analysis carried out on all *c.787AT heterozygous individuals. However, cDNA analysis after sorting of CD177^pos. and CD177^neg. neutrophil subsets from HNA-2-positive individuals showed identical sequences, which makes regulatory elements within the promoter unlikely to affect CD177 gene transcription in different CD177 neutrophil subsets.

Conclusion

This comprehensive study clearly demonstrates the impact of single nucleotide polymorphisms on the expression of HNA-2 on the neutrophil surface but challenges the hypothesis of regulatory epigenetic effects being implicated in the bimodal CD177 expression pattern.

Antikörper gegen humane Leukozytenantigene (HLA) bei männlichen Apheresespendern ohne klassische Alloimmunisierung

Im Rahmen von Präventivmaßnahmen zur Vermeidung von TRALI (transfusionsassoziierte akute Lungeninsuffizienz) wurden in einer Studie 15 523 männliche und weibliche Apheresespenderinnen und -spender mit und ohne positiver Immunisierungsanamnese (IA) auf HLA-Klasse-I-, HLA-Klasse-II- und HNA-Antikörper (AK) untersucht. Unsere Ergebnisse zeigten, dass bei 3,85% der männlichen Spender ohne IA HLA-AK und bei 0,10% HNA-AK auftraten. Diese Beobachtung stellt die seit Beginn der HLA-Ära vor 50 Jahren klar bewiesene Aussage infrage, dass HLA-AK nur durch eine Alloimmunisierung infolge von Schwangerschaften, Transfusionen oder Transplantationen entstehen können. Wir diskutieren mehrere mögliche Kausalitäten dieser positiven Reaktionen:

Große Aufmerksamkeit richteten wir auf den Ausschluss möglicher falsch positiver Reaktionen, da der LABScreen Multi als höchst sensitiv eingeschätzt wird. Nach Validierung eines neuen positiven Normalized-Background-Cut-offs (NBG: Normalized Background) und der Nachtestung von Rückstellproben der als positiv getesteten männlichen Spender konnten 50% der HLA-Klasse-I- und 43% der HLA-Klasse-II-AK nicht bestätigt werden. Dennoch blieben 1,5% der getesteten männlichen Spender für HLA-Klasse I und 0,5% für HLA-Klasse II positiv. Handelt es sich hier ausschließlich um HLA-spezifische oder um heterophile AK? Welche klinische Bedeutung haben diese AK bei der Prävalenz von TRALI oder für die Transplantationsimmunologie?

Leukocyte-Reactive Antibodies in Female Blood Donors: The Austrian Experience

Introduction

Antibody-mediated transfusion-related acute lung injury (TRALI) is caused by antibodies against human leukocyte antigens (HLAs) or human neutrophil antigens (HNAs), and is one of the most serious complications associated with transfusion medicine. Prevention strategies like testing allo-exposed female blood donors have not yet been introduced nationwide in Austria. To assess the need and feasibility of routine leukocyte antibody testing, the prevalence of leukocyte-reactive antibodies in an Austrian female donor population was been determined using classical cell-based methods which were compared with a high-throughput bead-based method.

Methods

Sera from 1,022 female blood donors were screened using a granulocyte aggregation test (GAT) and a white blood cell immunofluorescence test (WIFT) after retesting and specification of positive samples by granulocyte immunofluorescence test (GIFT) and monoclonal antibody-specific immobilization of granulocyte antigens (MAIGA). Potential HLA reactivities were confirmed using the microbeads assay LabScreen^TM Mixed. The results in 142 donor sera and 38 well-defined reference sera were investigated by the microbeads assay LabScreen^TM Multi and compared with classical cell-based methods.

Results

Reactivity with either granulocytes and/or lymphocytes was detected in 79 sera (7.7%), with the majority being HLA-specific. Antibodies against HNA were obtained in 7 samples (0.7%). The aggregating potential of the detected antibodies was observed in 9 cases (0.9%). Most of the leukocyte-reactive antibodies occurred at a donor age of between 35 and 59 years (n = 61). LabScreen Multi showed good agreement (κ = 0.767) for HNA antibody detection by cell-based assays, but double/multiple specificities (100% of 7 anti-HNA-1b sera) as well as false-negative results (40% of 15 HNA-3-specific sera) occurred.

Discussion

Leukocyte-reactive antibody screening is advised in Austrian female donors for safe blood transfusion, including single-donor convalescent plasma treatment of COVID-19 that may be implemented soon. For the introduction of LabScreen Multi, the combination with GAT should be considered to ensure correct anti-HNA-3a detection.

Time from venipuncture to cell isolation: Impact on granulocyte-reactive antibody testing

BACKGROUND AND OBJECTIVES

Classical neutrophil-reactive antibody testing depends on the quick isolation of neutrophils from freshly taken whole blood. To allow a better logistic preparation before testing, the influence of time interval between venipuncture and cell isolation has been evaluated in this study.

MATERIALS AND METHODS

Neutrophils and whole leukocytes were isolated from EDTA whole blood immediately (T0) as well as 4, 8 and 24 h after blood donation (T4, T8 and T24). These cells were tested against reference sera containing antibodies against HNA-1b, -2, -3a and HLA class I using granulocyte aggregation test (GAT), microscopic granulocyte immunofluorescence test (GIFT) and flow-cytometric white blood cell immunofluorescence test (Flow-GIFT/WIFT).

RESULTS

GAT was the most error-prone test displaying overall weaker aggregation strengths already at T4 (overall accuracy OA = 0.72, κ = 0.58). GIFT results showed good agreement at T4 (OA = 0.86, κ = 0.79) and remained stable until T8, while test results were slightly impaired at T24 (OA = 0.71, κ = 0.55). Flow-GIFT/WIFT was identified as the most robust screening method, remaining stable even at T24. Calculated ratios (sample/negative control) decreased non-significantly and remained highly above the cut-off in all samples.

CONCLUSION

Acceptable time limits for cell isolation are different for each screening method investigated. For GAT, cell isolation should be performed within 4 h, while GIFT tolerates a neutrophil isolation delay of 8 h. Flow-GIFT/WIFT isolation can be performed even after 24 h without impairment of the results. Using the latter test as a stand-alone pre-screening test, whole blood can be used from donors who are not directly accessible.