6 research outputs found
Anti-human platelet antigen-1α immunoglobulin G preparation intended to prevent fetal and neonatal alloimmune thrombocytopenia
Copyright: © 2016 Weng et al. This is an open
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DOI: 10.1371/journal.pone.0162973Fetal and neonatal alloimmune thrombocytopenia (FNAIT) is a severe disease that is
caused by maternal alloantibodies generated during pregnancy or at delivery as a result of
incompatibility between maternal and fetal human platelet antigens (HPAs) inherited from
the father. Antibody-mediated immune suppression using anti-HPA-1a immunoglobulins is
thought to be able to prevent FNAIT caused by HPA-1a. A fractionation process to prepare
anti-HPA-1a immunoglobulin (Ig) G (IgG) from human plasma was therefore developed.
Anti-HPA-1a plasma was obtained from volunteer mothers who underwent alloimmunization
against HPA-1a during a previous pregnancy. Plasma was cryoprecipitated and the
supernatant treated with caprylic acid and solvent/detergent (S/D), purified by chromatography,
nanofiltered, concentrated, and sterile-filtered. The anti-HPA-1a immunoglobulin fraction
was characterized for purity and safety. PAK12 and quantitative monoclonal antibody
immobilization of platelet antigen (MAIPA) assays were used to detect anti-HPA-1a IgG.
Hepatitis C virus (HCV) removal during nanofiltration was assessed by spiking experiments,
using cell culture-derived reporter HCV and luciferase analysis. The caprylic acid treatment
precipitated non-Ig proteins yielding a 90% pure Ig supernatant. S-HyperCel chromatography
of the S/D-treated supernatant followed by HyperCel STAR AX provided high IgG
recovery (>80%) and purity (>99.5%), and efficient IgA and IgM removal. Concentrations of
complement factors C3 and C4 were < 0.5 and < 0.4 mg/dL, respectively. The final IgG
could be nanofiltered on Planova 20N under conditions removing more than 3 log HCV
infectivity to baseline mock infection level, and concentrated to ca. 30 g/L. Proteolytic activity
and thrombin generation were low in the final fraction. The Pak12 and MAIPA assays
showed good recovery of anti-HPA-1a throughout the process. Clinical-grade HPA-1a IgG can be prepared using a process compliant with current quality requirements opening perspectives
for the prevention of FNAIT
Old tools revisited give hope - new treatment option for families with a history of severe FNAIT complications.
Accepted manuscript version. Published version at http://doi.org/10.1111/aogs.12842
A prospective study of maternal anti-HPA1a antibody level as a potential predictor for alloimmune thrombocytopenia in the newborn
Current perspectives on fetal and neonatal alloimmune thrombocytopenia - Increasing clinical concerns and new treatment opportunities
Differences in platelet type between the fetus and the mother can lead to maternal
immunization and destruction of the fetal platelets, a condition named fetal and neonatal
alloimmune thrombocytopenia (FNAIT). FNAIT is reported to occur in ~1 per 1,000 live born
neonates. The major risk is intracranial hemorrhage in the fetus or newborn, which is associated
with severe neurological complications or death. Since no countries have yet implemented a
screening program to detect pregnancies at risk, the diagnosis is typically established after the
birth of a child with symptoms. Reports on broader clinical impact have increased clinical concern and awareness. Along with new treatment options for FNAIT, the debate around antenatal
screening to detect pregnancies at risk of FNAIT has been revitalized
Fetal exposure to maternal human platelet antigen-1a does not induce tolerance. An analytical observational study
Fetal and neonatal alloimmune thrombocytopenia (FNAIT) is a disease that may cause severe bleeding complications with risk of perinatal death or lifelong disability. The main cause of FNAIT is maternal antibodies against human platelet antigen (HPA)-1a. Both fetomaternal bleeding and transplacental trafficking of fetal cells during pregnancy could be the cause of alloimmunization. Persistence of fetal cells in the mother (fetal microchimerism) and maternal cells in the child (maternal microchimerism) are well-recognized phenomena. Thus, it could be envisaged that fetal exposure to the HPA-1a antigen could tolerize an HPA-1a negative female fetus and prevent production of anti-HPA-1a antibodies later in life if she becomes pregnant with an HPA-1a positive fetus. The objective of the current study was to assess if the risk of producing anti-HPA-1a antibodies and the severity of neonatal thrombocytopenia in HPA-1a negative women with HPA-1a positive mothers (i.e. the mother is HPA-1a/b), was lower than in HPA-1a negative women with HPA-1a negative mothers. HPA-1a negative women with HPA-1a antibodies, identified from a Norwegian screening study (1996–2004), where HPA-1 genotype of their mothers was available, were included in the study. The frequency of HPA-1a positive mothers to HPA-1a immunized daughters were compared to the calculated frequency in the general population. We did not find any difference in the frequency of HPA-1ab among mothers to daughters with HPA-1a antibodies as compared with the general population. Furthermore, acknowledging sample-size limitations, we neither found an association between the mothers’ HPA type and their daughters’ anti-HPA-1a antibody levels or any difference between the two groups of mothers (HPA-1ab vs HPA-1bb), with respect to frequency of thrombocytopenia in the children of their daughters with HPA-1a antibodies. Hence, there was no indication of tolerance against fetal HPA-1a antigen in HPA-1bb women who had been exposed to HPA-1a antigen during fetal development
Anti-human platelet antigen (HPA)-1a antibodies may affect trophoblast functions crucial for placental development: A laboratory study using an in vitro model
Background:
Fetal and neonatal alloimmune thrombocytopenia (FNAIT) is a bleeding disorder caused by maternal
antibodies against paternal human platelet antigens (HPAs) on fetal platelets. Antibodies against HPA-1a are
accountable for the majority of FNAIT cases. We have previously shown that high levels of maternal anti-HPA-1a
antibodies are associated with clinically significant reduced birth weight in newborn boys. Chronic inflammatory
placental lesions are associated with increased risk of reduced birth weight and have previously been reported in
connection with FNAIT pregnancies. The HPA-1a epitope is located on integrin
β
3 that is associated with integrin
α
IIb (the fibrinogen receptor) on platelets and megakaryocytes. Integrin
β
3 is also associated with integrin
α
V
forming the
α
V
β
3 integrin heterodimer, the vitronectin receptor, which is expressed on various cell types, including
trophoblast cells. It is therefore thinkable that maternal anti-HPA-1a antibodies present during early pregnancy may
affect placenta function through binding to the HPA-1a antigen epitope on invasive throphoblasts. The aim of the
study was to examine whether interaction of a human anti-HPA-1a monoclonal antibody (mAb) with HPA-1a on
trophoblast cells affect adhesion, migration and invasion of extravillous trophoblast cells.
Methods:
An in vitro model with human anti-HPA-1a mAb, clone 26.4, and the first trimester extravillous trophoblast
cell line HTR8/SVneo was employed. The xCELLigence system was utilized to assess the possible effect of anti-HPA-1a
mAb on adhesion and migration of HTR8/SVneo cells. Specially designed chambers precoated with Matrigel were used
to assess the effect on the invasive capacity of cells.
Results:
We found that human anti-HPA-1a mAb 26.4 partia
lly inhibits adhesion and migratory capacity of
HTR8/SVneo cells.
Conclusions:
Our findings suggest that anti-HPA-1a antibodies may affect trophoblast functions crucial for normal placental development. Future studies including
primary throphoblast cells and polyclonal anti-HPA-1a
antibodies are needed to confirm these results