Simultaneous occurrence of foetal and neonatal alloimmune thrombocytopenia and neonatal neutropenia due to maternal neutrophilic autoantibodies: a case study and review of the literature

Production of recombinant humanized monoclonal anti-human neutrophil antigen (HNA) antibodies with potential applicability as standard antibodies

BACKGROUND

Antibodies against human neutrophil antigen (HNA) are involved in the pathogenesis of neonatal alloimmune neutropenia, autoimmune neutropenia, and transfusion-related acute lung injury. The present methods for anti-HNA antibody identification strongly depend on the presence of standard antisera with known allo/isospecificities. Here, we aimed to produce recombinant humanized antibodies to HNA from available mouse monoclonal antibodies (MoAbs).

STUDY DESIGN AND METHODS

RNAs were extracted from available hybridoma cells producing mouse anti-HNA antibodies recognizing HNA-1a (TAG-1), -1b (TAG-2), -2 (TAG-4), and FcγRIIIb, and the cDNA was synthesized. Recombinant fragments consisting of the variable regions of the H and L chains of the mouse MoAb ligated to the constant region of human IgG were incorporated into an expression vector and transfected into CHO cells. Antibody specificity of the selected humanized monoclonal antibodies was confirmed, and tested by the participants of the ISBT Granulocyte Immunobiology Working Party (GIWP) workshop 2020.

RESULTS

GIFT results confirmed the specific reactivity of TAGH-1 to -4, except for a cross-reactivity of TAGH-2 with HNA-1a/a neutrophils, only in flow-cytometry. MAIGA results showed clear specificity of all humanized antibodies, but the selection of the appropriate capture monoclonal antibody was essential for the test. The results of the ISBT GIWP showed high concordance among the labs.

CONCLUSIONS

These are the first humanized monoclonal antibodies to HNA-1 and HNA-2 antigens produced and they will be important standard reagents for laboratories testing for neutrophil antibodies. We plan to have these humanized MoAbs available through WHO.

Neonatal Immune Incompatibilities between Newborn and Mother

Background: Incompatibilities between the mother and unborn baby can cause complications that must be identified early to initiate the appropriate treatment. For example, neonatal alloimmune thrombocytopenia (NAIT), neonatal alloimmune neutropenia (NAIN), and morbus hemolyticus neonatorum affect children worldwide. Aim: This literature review aims to depict the similarities and differences between these three disorders from a clinical and mechanistic point of view. Material and Methods: The current literature review entailed conducting a systematic search to locate articles on the three conditions. Different electronic databases, including PsycINFO, PubMed, Web of Science, and CINAHL, were searched using the search terms "neonatal alloimmune thrombocytopenia", "neonatal alloimmune neutropenia", "morbus hemolyticus neonatorum", "NAIT", "FNAIT", "fetal", "NAIN", and "hemolytic disease of the newborn". Results: This review shows that these three diseases are caused by incompatibilities between the maternal and fetal immune systems. Furthermore, these conditions can lead to severe complications that hinder fetal development and cause death if not well managed. Discussion: The current literature review shows that NAIT, NAIN, and morbus hemolyticus neonatorum are rare conditions that occur when the mother produces antibodies against the fetal immune system. Thus, there is a need for the early detection of these conditions to initiate appropriate treatment before the child experiences adverse effects. Conclusion: The development of NAIT, NAIN, and morbus hemolyticus neonatorum is linked to the production of antibodies against the fetal immune system and fetal antigens. Further studies are required to determine potential interventions to reduce the risk of developing these three conditions.

Identification of anti-HPA-1a allo-antibodies using IgG platelet antibody detection and crossmatch system assay with Galileo Echo

Fetal/neonatal allo-immune thrombocytopenia is the most frequent and the most dangerous clinical condition involving anti-human platelet antigens (HPA)-1a allo-antibodies. Anti-HPA-1a allo-immunization requires rapid and accurate diagnosis to determine appropriate treatment. The Capture-P Ready-Screen assay (C-PRS) is a new qualitative immunoassay to detect IgG anti-human leukocyte antigen (HLA) and anti-HPA allo-antibodies. The aim of this study is to assess the identification of anti-HPA-1a allo-antibodies using the C-PRS assay, associated with HLA class I stripping reagents, on the automated benchtop analyzer Galileo Echo. Forty-nine sera were analyzed: without anti-HLA class I or anti-HPA allo-antibodies, with anti-HLA class I allo-antibodies, with anti-HPA-1a allo-antibodies, among which with anti-HLA class I allo-antibodies. None of the samples without allo-antibodies were reactive. Only anti-HLA antibodies, detected by cytotoxicity-dependent complement and not by Luminex, remained positive before and after stripping reagents. Of the 13 samples, anti-HPA-1a allo-antibodies that were correctly identified before and after incubation with HLA assassin reagent were 70% and 85%, respectively. Anti-glycoprotein auto-antibodies and anti-HLA allo-antibodies do not interfere with the detection of anti-HPA-1a antibodies. This preliminary study indicates that further improvement of the test will be helpful in developing a clinically useful assay in the future.

Alloimmune neonatal neutropenia in Croatia during the 1998-2008 period

PROBLEM

The aim of this study was to estimate the incidence of the disease and to analyze laboratory data of 23 newborns undergoing serologic testing for alloimmune neonatal neutropenia (ANN) during the 1998-2008 period in Croatia.

METHOD OF STUDY

Laboratory data on 23 newborns undergoing serologic testing for ANN during the 1998-2008 period and epidemiologic data on the number of live births in Croatia were analyzed. Laboratory testing for ANN included serologic screening of maternal and neonatal sera and granulocytes (neutrophils) by immunofluorescence (IF) method. The monoclonal antibody immobilization of neutrophil antigens (MAINA) was employed to determine anti-HNA antibody specificity.

RESULTS

Anti-HNA antibodies were detected in seven (54%) of 13 cases of serologically positive ANN. Only anti-HLA class I antibodies were demonstrated in four (31%) of 13 cases In the 2007-2008 period of prospective data collection, the number of serologically verified ANN cases was one case per 17,323 live births. Results of the prospective study conducted at Maternity Ward, Department of Gynecology and Obstetrics, Sestre milosrdnice University Hospital Center yielded the ANN incidence of one case per 2843 live births.

CONCLUSION

Monitoring of neutrophil count in neonatal blood and serologic testing for ANN in case of isolated neutropenia in the newborn contributed considerably to timely detection of ANN.

DESCRIPTORS

Neonatal alloimmune neutropenia-incidence, serologic diagnosis, antineutrophil antibodies, anti-HNA, anti-HLA class I, Croatia.