Biology subjects

Gstoettner, C.

Publications and source records attributed to Gstoettner, C..

3 recordsLinked to original sources

bioRxiv2026

Patient-derived monoclonal anti-HPA-1a can induce platelet activation through FcγRIIa

Fetal and neonatal alloimmune thrombocytopenia (FNAIT) is a pregnancy-associated disorder caused by maternal alloantibodies targeting paternally inherited human platelet antigens (HPAs). These antibodies traverse the placenta and bind to fetal platelets, causing thrombocytopenia and potentially severe complications including intracranial hemorrhage (ICH). Beyond platelets, antibodies may also target other fetal cells such as endothelial cells and placental trophoblasts thereby exacerbating disease severity. Anti-HPA-1a antibodies, the primary cause of FNAIT, display functional heterogeneity due to differences in epitope specificity, glycosylation, which complicate disease severity prediction. Here, we report the structural and functional characterization of two novel anti-HPA-1a antibodies, D-204 and M-204, derived from a mother with a severe FNAIT case. In comparison to D-204 and other existing anti-HPA-1a antibodies such as B2G1 and 26.4, M-204 bound IIb{beta}3 with different kinetics, reaching only half-maximal binding, as determined by flow cytometry. Notably, only M-204 induced platelet aggregation. To investigate the underlying mechanism behind this aggregation, various antibody formats were generated (Fab, Fab2, bispecific, and IgG-Fc dead). Aggregation required both Fab-arms to engage HPA-1a and intact binding to Fc{gamma}RIIa. Structural models and crystal structures suggest the dual engagement of both Fab-arms is required for Fc{gamma}RIIA-engagement which is a unique feature of M-204 among known HPA-1 monoclonals. Our findings highlight the functional diversity of anti-HPA-1a antibodies and provide new insights into their pathogenic mechanisms.

immunology↗

bioRxiv2025

Increasing Applicability of Automated mD-LC-MS Peptide Mapping for Biopharmaceuticals via Streamlined In-Solution Digestion

Since the introduction of the first multidimensional liquid chromatography mass spectrometry (mD-LC-MS) approach for antibody peak characterization, multiple developments have been reported including integration of various chromatographic approaches and precise fractionation, providing high quality and reliable peptide data in a drastically decreased total analysis time. Most of these platforms rely on the use of immobilized enzyme reactors (IMERs) for digestion, limiting the applicability to few enzymes such as trypsin. Recently, the introduction of in-solution enzymatic digestion in mD-LC-MS systems has been proposed as an alternative to IMERs. Here, we make use of current innovations in 2D-LC commercial systems such as active solvent modulation valves, which permits direct mixing of the fractionated peaks with the endoprotease and reducing agent in an online manner, to integrate in-solution digestion in a straightforward manner in mD-LC-MS peak characterization platforms. Following antibody digestion, the generated peptides are automatically trapped, separated and detected by mass spectrometry. Efficient reduction and tryptic digestion was obtained using short incubation times (15 min). The approach was further expanded to alternative endoproteases such as chymotrypsin and thermolysine with other digestion specificities and allow an easy exchange between enzymes with similar buffer and digestion conditions. As a proof-of-principle that strategy was applied to achieve peptide maps from ion exchanged separated mAb peaks showing good digestion efficiency and high sequence coverages.

biochemistry↗

bioRxiv2021

Structural and functional characterization of SARS-CoV-2 RBD domains produced in mammalian cells

As the SARS-CoV-2 pandemic is still ongoing and dramatically influences our life, the need for recombinant proteins for diagnostics, vaccine development, and research is very high. The spike (S) protein, and particularly its receptor binding domain (RBD), mediates the interaction with the ACE2 receptor on host cells and may be modulated by its structural features. Therefore, well characterized recombinant RBDs are essential. We have performed an in-depth structural and functional characterization of RBDs expressed in Chinese hamster ovary (CHO) and human embryonic kidney (HEK293) cells. To structurally characterize the native RBDs (comprising N- and O-glycans and additional posttranslational modifications) a multilevel mass spectrometric approach was employed. Released glycan and glycopeptide analysis were integrated with intact mass analysis, glycan-enzymatic dissection and top-down sequencing for comprehensive annotation of RBD proteoforms. The data showed distinct glycosylation for CHO- and HEK293-RBD with the latter exhibiting antenna fucosylation, higher level of sialylation and a combination of core 1 and core 2 type O-glycans. Additionally, from both putative O-glycosylation sites, we could confirm that O-glycosylation was exclusively present at T323, which was previously unknown. For both RBDs, the binding to SARS-CoV-2 antibodies of positive patients and affinity to ACE2 receptor was addressed showing comparable results. This work not only offers insights into RBD structural and functional features but also provides a workflow for characterization of new RBDs and batch-to-batch comparison.

biochemistry↗