Foetal and neonatal alloimmune thrombocytopenia

Extraction of naturally occurring peptides versus the tryptic digestion of proteins from fetal versus adult bovine serum for LC-ESI-MS/MS

The naturally occurring peptides and digested proteins of fetal versus adult bovine serum were compared by LC-ESI-MS/MS after correction against noise from blank injections and random MS/MS spectra as statistical controls. Serum peptides were extracted by differential precipitation with mixtures of acetonitrile and water. Serum proteins were separated by partition chromatography over quaternary amine resin followed by tryptic digestion. The rigorous X!TANDEM goodness of fit algorithm that has a low error rate as demonstrated by low FDR q-values (q ≤ 0.01) showed qualitative and quantitative agreement with the SEQUEST cross correlation algorithm on 12,052 protein gene symbols. Tryptic digestion provided a quantitative identification of the serum proteins where observation frequency reflected known high abundance. In contrast, the naturally occurring peptides reflected the cleavage of common serum proteins such as C4A, C3, FGB, HPX, A2M but also proteins in lower concentration such as F13A1, IK, collagens and protocadherins. Proteins associated with cellular growth and development such as actins (ACT), ribosomal proteins like Ribosomal protein S6 (RPS6), synthetic enzymes and extracellular matrix factors were enriched in fetal calf serum. In contrast to the large literature from cord blood, IgG light chains were absent from fetal serum as observed by LC-ESI-MS/MS and confirmed by ELISA.

Cellular surface plasmon resonance-based detection of anti-HPA-1a antibody glycosylation in fetal and neonatal alloimmune thrombocytopenia

Fetal and neonatal alloimmune thrombocytopenia (FNAIT) can occur due to maternal IgG antibodies targeting platelet antigens, causing life-threatening bleeding in the neonate. However, the disease manifests itself in only a fraction of pregnancies, most commonly with anti-HPA-1a antibodies. We found that in particular, the core fucosylation in the IgG-Fc tail is highly variable in anti-HPA-1a IgG, which strongly influences the binding to leukocyte IgG-Fc receptors IIIa/b (FcγRIIIa/b). Currently, gold-standard IgG-glycoanalytics rely on complicated methods (e.g., mass spectrometry (MS)) that are not suited for diagnostic purposes. Our aim was to provide a simplified method to quantify the biological activity of IgG antibodies targeting cells. We developed a cellular surface plasmon resonance imaging (cSPRi) technique based on FcγRIII-binding to IgG-opsonized cells and compared the results with MS. The strength of platelet binding to FcγR was monitored under flow using both WT FcγRIIIa (sensitive to Fc glycosylation status) and mutant FcγRIIIa-N162A (insensitive to Fc glycosylation status). The quality of the anti-HPA-1a glycosylation was monitored as the ratio of binding signals from the WT versus FcγRIIIa-N162A, using glycoengineered recombinant anti-platelet HPA-1a as a standard. The method was validated with 143 plasma samples with anti-HPA-1a antibodies analyzed by MS with known clinical outcomes and tested for validation of the method. The ratio of patient signal from the WT versus FcγRIIIa-N162A correlated with the fucosylation of the HPA-1a antibodies measured by MS (r=-0.52). Significantly, FNAIT disease severity based on Buchanan bleeding score was similarly discriminated against by MS and cSPRi. In conclusion, the use of IgG receptors, in this case, FcγRIIIa, on SPR chips can yield quantitative and qualitative information on platelet-bound anti-HPA-1a antibodies. Using opsonized cells in this manner circumvents the need for purification of specific antibodies and laborious MS analysis to obtain qualitative antibody traits such as IgG fucosylation, for which no clinical test is currently available.

THP-1 cells transduced with CD16A utilize Fcγ receptor I and III in the phagocytosis of IgG-sensitized human erythrocytes and platelets

Fc gamma receptors (FcγRs) are critical effector receptors for immunoglobulin G (IgG) antibodies. On macrophages, FcγRs mediate multiple effector functions, including phagocytosis, but the individual contribution of specific FcγRs to phagocytosis has not been fully characterized. Primary human macrophage populations, such as splenic macrophages, can express FcγRI, FcγRIIA, and FcγRIIIA. However, there is currently no widely available monocyte or macrophage cell line expressing all these receptors. Common sources of monocytes for differentiation into macrophages, such as human peripheral blood monocytes and the monocytic leukemia cell line THP-1, generally lack the expression of FcγRIIIA (CD16A). Here, we utilized a lentiviral system to generate THP-1 cells stably expressing human FcγRIIIA (CD16F158). THP-1-CD16A cells treated with phorbol 12-myristate 13-acetate for 24 hours phagocytosed anti-D-opsonized human red blood cells primarily utilizing FcγRI with a lesser but significant contribution of IIIA while phagocytosis of antibody-opsonized human platelets equally utilized FcγRI and Fcγ IIIA. Despite the well-known ability of FcγRIIA to bind IgG in cell free systems, this receptor did not appear to be involved in either RBC or platelet phagocytosis. These transgenic cells may constitute a valuable tool for studying macrophage FcγR utilization and function.

Mikroangiopathien in der Schwangerschaft

Das Wissen um die Differentialdiagnose der Mikroangiopathien ist auch für Geburtshelfer:innen wichtig. So ist die Kombination aus einer Thrombopenie und Hämolysezeichen wegweisend in der Erkennung der Erkrankung. Es sollten die Differenzialdiagnosen bekannt sein, da diese zu unterschiedlichen Therapienotwendigkeiten führen und Langzeitschäden, beispielsweise für die Niere, vermieden werden müssen. Die Differenzialdiagnosen der Thrombopenie stellen den Einstieg für die weitere Diagnostik dar. In der Kombination mit Hämolysezeichen und Veränderungen der Erythrozytenmorphologie (Fragmentozyten) liegen unterschiedliche Ursachen für die Mikroangiopathie vor. Eine thrombotisch-thrombozytopenische Purpura (TTP) kann während der gesamten Schwangerschaft, aber insbesondere im letzten Trimenon, die Ursache für solche Veränderungen sein. Bei dieser finden sich häufig gastrointestinale oder auch zusätzliche neurologische Symptome. Die Präeklampsie, insbesondere beim HELLP(„hemolysis, elevated liver enzymes, and a low platelet count“)-Syndrom, kann ebenfalls zu einer Mikroangiopathie führen, dieses i.d.R. mit entsprechender Erhöhung des Blutdrucks und insbesondere mit einer deutlichen Erhöhung der Lebertransaminasen, ebenfalls typischerweise im letzten Trimenon kombiniert. Wenn entsprechende Veränderungen nach der Geburt auftreten und diese neben der Hämolyse mit einem Nierenversagen verbunden sind, kann es sich hierbei um ein atypisches hämolytisch-urämisches Syndrom (aHUS) handeln, das spezifisch durch Antikörper therapiert werden sollte. Neben der typischen Gerinnungsaktivierung im Sinne einer Thrombosierung findet sich bei COVID-19 („corona virus disease“) auch das gesamte Bild einer entsprechenden Mikroangiopathie, zum Teil durch entsprechende Aktivierung des Gerinnungssystem, zum Teil durch eine Verstärkung der anderen Mikroangiopathien. Für alle Bereiche werden die Differenzialdiagnosen und mögliche Therapien skizziert.

Diagnostic Ideas and Management Strategies for Thrombocytopenia of Unknown Causes in Pregnancy

Objective

To summarize the clinical characteristics and treatment options together with the maternal and neonatal prognoses in women with different degrees of thrombocytopenia of unknown causes during pregnancy.

Materials and Methods

One hundred twenty-nine cases meeting the inclusion and exclusion criteria were retrospectively analyzed. Patients were divided into group A (50*10⁹/L) and group B (50*10⁹/L to 100*10⁹/L) according to the lowest level of platelet count during pregnancy. Patients were divided into those found to have thrombocytopenia in the relatively early, middle, and late stages according to the detection period of maternal thrombocytopenia during pregnancy.

Results

There were 72 cases in group A, and 57 cases in group B. There existed statistically significant differences in terms of the proportion of primipara, the proportion with a history of thrombocytopenia, and the median length of pregnancy between the two groups (p < 0.05). The proportion of patients with severe thrombocytopenia as an indication for cesarean delivery was higher in group A than in group B (p < 0.05). More cases were detected at the relatively early stages of pregnancy in group A than in group B (p < 0.05). There was no difference in neonatal hemorrhage and events of thrombocytopenia between the two groups.

Conclusion

Patients with platelet counts below 50*10⁹/L were mostly primipara with a history of thrombocytopenia, most often detected at a relatively early stage of pregnancy, and continued pregnancy might lead to aggravation of the disease. Combination therapy was required for patients with platelet counts below 30*10⁹/L to maintain the platelet counts within a safe range. Cesarean delivery was selected to terminate the pregnancies, and platelet counts should be raised above 50*10⁹/L before surgery. Close monitoring was required for those with platelet counts above 30*10⁹/L. There was no direct correlation between the maternal and neonatal platelet counts.

Subamniotic Hemorrhage, a Possible New Presentation of Fetal and Neonatal Alloimmune Thrombocytopenia

BACKGROUND

Fetal and neonatal alloimmune thrombocytopenia (FNAIT) is a rare fetal disease in which maternal antibodies directed toward fetal human platelet antigens (HPA) are formed during pregnancy and cause fetal thrombocytopenia. The diagnosis FNAIT is suspected when a fetus or neonate presents with signs of bleeding.

CASE

We describe a pregnancy complicated by a placental hematoma in the 20th week of gestation as the first manifestation of FNAIT. Further evaluation showed signs of germinal matrix hemorrhage and HPA-5b allo-antibodies. After the diagnosis, intravenous immunoglobulin was administered weekly and a healthy daughter was born at 37 weeks. Histopathological analysis revealed that the hematoma was caused by a subamniotic hemorrhage of fetal origin.

CONCLUSION

A subamniotic hematoma appears to be the first manifestation of FNAIT.

Pancytopenia in a newborn due to maternal piperacillin and human leukocyte antigen antibodies

BACKGROUND

Piperacillin antibody-induced immune hemolytic anemia is not rare in adults, and there have been reports of anti-HLA antibody-induced newborn platelet transfusion refractoriness. However, there has been no report of piperacillin-accompanied anti-HLA antibody-induced newborn pancytopenia.

CASE REPORT

We herein present the case of a newborn with pancytopenia from a mother who carried anti-HLA-B55, anti-HLA-DR11, and piperacillin antibodies. The newborn HLA genotypes were HLA*B55:02 and HLA*DRB1*11:01. IgG antibodies can be transferred to the newborn via the placenta and induce the destruction of the platelet and white blood cells, which carry the corresponding antigens. Piperacillin antibodies coupling with newborn red blood cells (RBCs) led to the destruction of the RBCs and hemolytic anemia.

RESULTS

The direct anti-globulin test was positive for RBCs in the newborn, and piperacillin antibodies were positive in both the newborn and his mother. Anti-HLA antibodies were positive in the maternal serum, whereas homologous antigens were positive in the newborn. The direct anti-globulin test of platelet was weekly positive in the newborn.

CONCLUSION

Piperacillin and anti-HLA antibodies can pass through the placenta, induce incompatible blood cell destruction, and cause a series of clinical syndromes in newborns.

Successful prenatal therapy for anti-CD36-mediated severe FNAIT by deglycosylated antibodies in a novel murine model

Recent studies have shown that maternal anti-CD36 antibodies represent a frequent cause of fetal/neonatal alloimmune thrombocytopenia (FNAIT) in Asian and African populations. However, little is known about the pathomechanism and antenatal treatment of anti-CD36-mediated FNAIT. Here, we established a novel animal model to examine the clinical features of pups from immunized Cd36-/- female mice after breeding with wild-type male mice. Mild thrombocytopenia was observed, but high pup mortality was also documented (40.26%). Administration of intravenous immunoglobulin (IVIG) (1 g/kg) on days 7, 12, and 17 to immunized Cd36-/- mothers after breeding reduced fetal death (12.70%). However, delaying the IVIG administration series on days 10, 15, and 20 did not reduce fetal death (40.00%). In contrast, injection of deglycosylated anti-CD36 (deg-anti-CD36) polyclonal antibodies (5 mg/kg) on days 10, 15, and 20 significantly reduced fetal death (5.26%). Subsequently, monoclonal antibodies (mAbs) against mouse CD36 were developed, and one clone producing high-affinity anti-CD36 (termed 32-106) effectively inhibited maternal antibody binding and was therefore selected. Using the same approach of deg-anti-CD36, the administration of deg-32-106 significantly reduced fetal death (2.17%). Furthermore, immunized Cd36-/- mothers exhibited placental deficiency. Accordingly, maternal anti-CD36 antibodies inhibited angiogenesis of placenta endothelial cells, which could be restored by deg-32-106. In summary, maternal anti-CD36 antibodies caused a high frequency of fetal death in our animal model, associated with placental dysfunction. This deleterious effect could be diminished by the antenatal administration of IVIG and deg-mAb 32-106. Interestingly, treatment with deg-32-106 seems more beneficial considering the lower dose, later start of treatment, and therapy success.

A meta-analysis of neonatal outcomes in pregnant women with immune thrombocytopenic purpura

AIM

Thrombocytopenia is an autoimmune disorder characterized by reduced platelet counts. Neonatal thrombocytopenia incidence has been linked with immune thrombocytopenic purpura in mothers during pregnancy, possibly because antiplatelet antibodies can cross the placental barrier. To date, no study has attempted to evaluate the actual prevalence of neonatal thrombocytopenia in infants born to mothers with immune thrombocytopenic purpura. In this meta-analysis of the available literature, we attempt to fill this gap. We want to evaluate the overall prevalence of neonatal thrombocytopenia, its severity, and the incidence of hemorrhage in infants with thrombocytopenia born from mothers with immune thrombocytopenic purpura.

METHODS

Adhering to PRISMA guidelines, we systematically scanned four academic databases including EMBASE, CENTRAL, Scopus, and MEDLINE to identify relevant literature. We performed a meta-analysis to summarize thrombocytopenia incidence rate and severity in newborn infants of mothers with immune thrombocytopenic purpura.

RESULTS

We identified 21 eligible studies involving 1951 mothers and 1844 neonates. Meta-analysis showed high prevalence for neonatal thrombocytopenia (24%). Within these, severe cases were the most prevalent (41.2%), followed by moderate (37.7%) and mild (17.6%) cases. Hemorrhage was only reported in 4.1% of the observed neonatal thrombocytopenia cases.

CONCLUSION

This review provides preliminary evidence that neonatal thrombocytopenia incidence is high in infants born to mothers with immune thrombocytopenic purpura. This study further reports that the largest proportion of these cases are severe.

Update on the Use of Intravenous Immunoglobulin in Pregnancy

Intravenous immunoglobulin (IVIG) was first administered to humans in the 1980s. The mechanism of action of IVIG is still a subject of debate but the pharmacokinetics have been well characterized, albeit outside of pregnancy. IVIG has been used in pregnancy to treat several nonobstetrical and obstetrical-related conditions. However, current evidence suggests that IVIG use during pregnancy can be recommended for 1) in utero diagnosis of neonatal alloimmune thrombocytopenia; 2) gestational alloimmune liver disease; 3) hemolytic disease of the fetus and newborn for early-onset severe intrauterine disease; 4) antiphospholipid syndrome (APS) when refractory to or contraindicated to standard treatment, or in catastrophic antiphospholipid syndrome; and 5) immune thrombocytopenia when standard treatment is ineffective or rapid increase of platelet counts is needed. All recommendations are based on case series and cohort studies without randomized trials usually because of the rare prevalence of the conditions, the high incidence of adverse outcomes if left untreated, and ethical concerns. In contrast, IVIG therapy cannot be recommended for recurrent pregnancy loss, and the use of IVIG in subgroups of those with recurrent pregnancy loss requires further investigations. For non-obstetrical-related conditions, we recommend using IVIG as indicated for nonpregnant patients. In conclusion, the use of IVIG during pregnancy is an effective treatment in some obstetrical-related conditions with rare serious maternal side effects. However, the precise mechanisms of action and the long-term immunologic effects on the fetus and neonate are poorly understood and merit further investigations.

[Diagnosis and management of severe neonatal thrombocytopenia due to maternal alloimmunization against fetal platelet antigens: case study and literature review]

Thrombocytopenia is a common hematologic disorder in the neonatal period. It can occur in neonates hospitalized in the Intensive Care Unit and in preterm infants. It is characterized by a platelet count of less than 150.000/mm3. In the context of immune thrombocytopenia, neonatal thrombocytopenia due to maternal alloimmunization (estimated at 1 per 1000 live births) is not a rare event but it is often undiagnosed in minor forms. This is caused by maternal immunization against fetal platelet antigens inherited from the father and lacking in the mother. Maternal IgG alloantibodies cross the placenta causing fetal platelet destruction. In severe thrombocytopenia, consequences can be severe, with intracranial bleeding occurring in 10-30% of patients. Diagnosis is essentially based on clinical examination and must be suspected by pediatricians.

Intravenous Immune Globulin Uses in the Fetus and Neonate: A Review

Intravenous immune globulin (IVIG) is made after processing plasma from healthy donors. It is composed mainly of pooled immunoglobulin and has clinical evidence-based applications in adult and pediatric populations. Recently, several clinical applications have been proposed for managing conditions in the neonatal population, such as hemolytic disease of the newborn, treatment, and prophylaxis for sepsis in high-risk neonates, enterovirus parvovirus and COVID-19 related neonatal infections, fetal and neonatal immune-induced thrombocytopenia, neonatal hemochromatosis, neonatal Kawasaki disease, and some types of immunodeficiency. The dosing, mechanism of action, effectiveness, side effects, and adverse reactions of IVIG have been relatively well studied in adults but are not well described in the neonatal population. This review aims to provide the most recent evidence and consensus guidelines about the use of IVIG in the fetus and neonate.

Platelet transfusion for neonates with thrombocytopaenia: protocol for a systematic review

INTRODUCTION

Thrombocytopaenia is one of the most common haemostatic abnormalities among neonates. It affects approximately one-quarter of neonates admitted into neonatal intensive care units and may lead to a high risk of bleeding and mortality, which are substantial causes for concern by neonatologists. Platelet transfusion (PT) is a specific treatment for thrombocytopaenia. To date, PT thresholds are diverse since the associations between low platelet count and negative outcomes are not clear. We propose this protocol for a systematic review to collect and assess evidence concerning the best PT threshold to reduce mortality, bleeding and major morbidity among neonates with thrombocytopaenia.

METHODS AND ANALYSIS

The systematic review will be performed according to the Cochrane Handbook for Systematic Review of Interventions, the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement, and the Grading of Recommendations Assessment, Development and Evaluation system. Two independent researchers will perform the study selection, data extraction/coding, quality assessment and further analyses of the included studies, with disagreements being resolved by a third researcher. A systematic search of the literature will be conducted in the PubMed, Cochrane Library and Embase databases from database inception through 13 October 2020. All randomised controlled trials, cohort studies and case-control studies will be included without any restrictions regarding publication date or language. The primary outcomes will comprise in-hospital mortality and bleeding episodes. Endnote X9 and Review Manager V.5.3 software will be used to manage the selection process and statistical analysis, respectively. If the included studies are sufficient and homogeneous for any of the outcomes, a quantitative synthesis (meta-analysis) may be performed. Otherwise, we will conduct a narrative systematic review of the results.

ETHICS AND DISSEMINATION

Ethical approval is not required for this study because the data will be obtained from published studies and will not include individual patient data. The results of this study are anticipated to be published in a peer-reviewed journal.

PROSPERO REGISTRATION NUMBER

CRD42020169262.

Potential of Next-Generation Sequencing in Noninvasive Fetal Molecular Blood Group Genotyping

Hemolytic disease of the fetus and newborn and fetal and neonatal alloimmune thrombocytopenia are caused by maternal antibodies against fetal alloantigens on red blood cells or platelets that are inherited from the father. After transplacental transport to the fetal circulation, antibodies of the IgG class may cause severe fetal anemia or bleeding complications. The indication for noninvasive fetal blood group genotyping is given if a clinically relevant antibody is detected in a pregnant woman and if the father is heterozygous (or unknown) for the implicated blood group allele. This mini-review will focus on the advantages and current limitations of next-generation sequencing (NGS) for noninvasive diagnosis of fetal blood groups which is, in contrast to fetal aneuploidy screening, proposed only by some research groups. Targeted massively parallel sequencing of short DNA fragments from maternal cell-free plasma samples enables counting of fetal alleles for many single nucleotide polymorphisms in parallel. This information can be utilized for estimation of the fetal fraction of cell-free DNA (cfDNA) as well as detection of the paternal blood group allele in question. Adherence to a cut-off of ≥4% fetal fraction for reporting conclusive results is recommended to avoid false-negative results due to low fetal fraction. For screening purposes of fetal RHD in RhD-negative pregnant women, real-time PCR methods are very well established. However, for diagnostic purposes, the targeted amplicon-based NGS approach has the inherent capability to estimate the fetal fraction of cfDNA. In the future, improving the accuracy of NGS by consensus sequencing of single cfDNA molecules may enable reliable fetal blood group genotyping already in the first trimester of pregnancy.

The use of IVIg in fetal and neonatal alloimmune thrombocytopenia- Principles and mechanisms

Fetal and neonatal alloimmune thrombocytopenia (FNAIT) is a rare neonatal disorder that is caused by alloimmunization against platelet antigens during pregnancy. Although rare, affecting only 1 in 1000 live births, it can cause intracranial hemorrhage and other bleeding complications that can lead to miscarriage, stillbirth and life-long neurological complications. One of the gold-standard therapies for at risk pregnancies is the administration of IVIg. Although IVIg has been used in a variety of different disorders for over 40 years, its exact mechanism of action is still unknown. In FNAIT, the majority of its therapeutic effect is thought the be mediated through the neonatal Fc receptor, however other mechanisms cannot be excluded. Due to safety, supply and other concerns that are associated with IVIg use, alternative therapies that could replace IVIg are additionally being investigated. This includes the possibility of a prophylaxis regimen for FNAIT, similarly to what has been successfully used in hemolytic disease of the fetus and newborn for over 50 years.