A new efficient tool for non-invasive diagnosis of fetomaternal platelet antigen incompatibility

New Horizons in Fetal and Neonatal Alloimmune Thrombocytopenia

Fetal and neonatal alloimmune thrombocytopenia (FNAIT) is a common cause of severe thrombocytopenia in newborns. Intracranial bleeding may lead to severe neurological sequelae and mortality. Current management of pregnancies at risk is suboptimal. Prenatal FNAIT diagnosis commonly requires invasive procedures and therapy is associated with a high treatment burden. The present review explores advances in the field and their potential contribution to modification of the diagnostic and therapeutic landscape. Topics addressed include the role of noninvasive prenatal testing using fetal cell free DNA, insights into novel and prospective therapeutic options achieved through the development of murine models of FNAIT as well as the forecast for the progress in pregnancy risk stratification through advancement in the investigation of biological characteristics of alloantibodies and their association with the risk of fetal bleeding.

Noninvasive Prenatal Testing in Immunohematology-Clinical, Technical and Ethical Considerations

Hemolytic disease of the fetus and newborn (HDFN), as well as fetal and neonatal alloimmune thrombocytopenia (FNAIT), represent two important disease entities that are caused by maternal IgG antibodies directed against nonmaternally inherited antigens on the fetal blood cells. These antibodies are most frequently directed against the RhD antigen on red blood cells (RBCs) or the human platelet antigen 1a (HPA-1a) on platelets. For optimal management of pregnancies where HDFN or FNAIT is suspected, it is essential to determine the RhD or the HPA-1a type of the fetus. Noninvasive fetal RhD typing is also relevant for identifying which RhD-negative pregnant women should receive antenatal RhD prophylaxis. In this review, we will give an overview of the clinical indications and technical challenges related to the noninvasive analysis of fetal RBCs or platelet types. In addition, we will discuss the ethical implications associated with the routine administration of antenatal RhD to all pregnant RhD-negative women and likewise the ethical challenges related to making clinical decisions concerning the mother that have been based on samples collected from the (presumptive) father, which is a common practice when determining the risk of FNAIT.

Preliminary mechanism in fetal alloimmune thrombocytopenia associated with anti-HPA 15b antibodies

OBJECTIVE

Fetal and neonatal alloimmune thrombocytopenia (FNAIT) is a bleeding disease that can cause fetal hydrops, a rare but life-threatening condition in which abnormal amounts of fluid accumulate in one or two areas of the fetus's body. A case of FNAIT with fetal hydrops caused by anti-HPA-15b antibodies was involved in this study, as we investigated whether or not anti-HPA-15b antibodies can induce endothelial angiogenesis and apoptosis.

METHODS

The monoclonal antibody immobilization of platelet antigens assay (MAIPA) was used to identify anti-HPA-15b antibodies. The three groups in Tube formation and apoptosis assays were the PBS group, the AB serum IgG group, and the anti-HPA-15b serum IgG group, all reacted with HPA-15bb HUVEC.

RESULTS

The presence of anti-HPA-15b antibodies was found in this case by MAIPA assay. The OD values are 0.33 and 0.21, reacted with HPA-15bb and HPA-15ab platelets, respectively (cutoff OD value = 0.2). Quantitative analysis revealed that the length of capillary-like tube induced by anti-HPA-15b antibodies was significantly decreased over that of AB serum IgG (*p = 0.0005), but weaker than when incubated with thrombin (**p = 0.0009). The apoptosis results show a significantly increased number of apoptotic endothelial cells in the anti-HPA-15b antibody IgG group when compared with the PBS and AB serum IgG groups (*p < 0.0001, **p < 0.0001). In addition, there is no statistical difference between the PBS and AB serum groups.

CONCLUSION

Anti-HPA-15b antibodies can inhibit angiogenesis and induce apoptosis. This may associate with hydrops fetalis (HF), or fetal hydrops of FNAIT.

Risk Minimization of Hemolytic Disease of the Fetus and Newborn Using Droplet Digital PCR Method for Accurate Fetal Genotype Assessment of RHD, KEL, and RHCE from Cell-Free Fetal DNA of Maternal Plasma

The molecular pathology of hemolytic disease of the fetus and newborn (HDFN) is determined by different RHD, RHCE, and KEL genotypes and by blood group incompatibility between the mother and fetus that is caused by erythrocyte antigen presence/absence on the cell surface. In the Czech Republic, clinically significant antierythrocyte alloantibodies include anti-D, anti-K, anti C/c, and anti-E. Deletion of the RHD gene and then three single nucleotide polymorphisms in the RHCE and KEL genes (rs676785, rs609320, and rs8176058) are the most common. The aim of this study is to develop effective and precise monitoring of fetal genotypes from maternal plasma of these polymorphisms using droplet digital (dd)PCR. Fifty-three plasma DNA samples (from 10 to 18 weeks of gestation) were analyzed (10 RHD, 33 RHCE, and 10 KEL). The ddPCR methodology was validated on the basis of the already elaborated and established method of minisequencing and real-time PCR and with newborn phenotype confirmation. The results of ddPCR were in 100% agreement with minisequencing and real-time PCR and also with newborn phenotype. ddPCR can fully replace the reliable but more time-consuming method of minisequencing and real-time PCR RHD examination. Accurate and rapid noninvasive fetal genotyping minimizes the possibility of HDFN developing.