Biology subjects

Merkely, B.

Publications and source records attributed to Merkely, B..

6 recordsLinked to original sources

bioRxiv2026

Prevention of mRNA vaccine-induced anaphylaxis by peripheral cyclooxygenase inhibitors in an anti-PEG hyperimmune pig model: clinical relevance for nanomedicine-induced infusion reactions

Anti-polyethylene glycol (PEG) hyperimmune pigs, immunized against PEG, provide a sensitive experimental model for the rare anaphylactic reactions induced by mRNA-PEGylated lipid nanoparticle (LNP)-based COVID-19 vaccines, such as Comirnaty. These pseudo-allergic infusion reactions can usually be prevented or attenuated by multicomponent anti-inflammatory premedication regimens; however, no established protocol exists for mRNA-LNP-based COVID-19 vaccines. The aim of the present study was to identify an effective premedication strategy capable of preventing or attenuating these reactions in hypersensitive subjects, using the hyperimmune porcine model. We compared the protective effects of individual pretreatment components; dexamethasone, famotidine, levocetirizine, acetaminophen, diclofenac, indomethacin, by analyzing hemodynamic endpoints (systemic and pulmonary arterial pressure, pulse pressure). All tested compounds modulated Comirnaty-induced anaphylactic responses; however, only cyclooxygenase (COX) inhibitors provided complete protection against anaphylaxis and other abnormal processes. This finding is consistent with the low incidence of infusion reactions to cancer nanomedicines at the Shaare Zedek Oncology Center in Israel which uses COX-inhibitors as premedication. Given that most currently used human infusion-reaction prevention protocols do not include COX inhibitors, and that steroid-containing regimens may potentially counteract vaccine efficacy, our results suggest that COX inhibitors may offer a clinically effective standalone option or form the basis of simplified premedication regimens for preventing this life-threatening condition.

immunology↗

bioRxiv2026

Hemoperfusion of pigs with a carbon-cellulose cartridge: a pilot study revealing a new animal model of extended anaphylactic shock

To investigate the immune mechanisms underlying extracorporeal circulation-associated anaphylactoid reactions, we inserted externally perfused cartridges into the venous circulation of pigs, including a cellulose-coated activated-charcoal adsorbent (Adsorba(R) 300C), a polysulfone hollow-fiber membrane hemofilter, and polypropylene hollow-fiber-based heart-lung machine gas-exchange oxygenators. Blood was circulated using a roller pump, and the animals were monitored for systemic and pulmonary arterial pressures (SAP, PAP) changes, blood levels of complement C3a, thromboxane B2, and hemoglobin, blood cell counts and hematocrit. None of the cartridges caused major changes in these endpoints except the Adsorba(R) 300C, which displayed a fulminant anaphylactoid reaction characterized by profound hypotension, maximal pulmonary hypertension, hemoconcentration, thrombocytopenia and a surge of C3a and thromboxane B2, i.e., hallmarks of complement activation-related pseudoallergy. Within 15 min, the reaction advanced to profound hemodynamic collapse, which was managed with norepinephrine and cardiopulmonary resuscitation. After brief rebound hypertension, shock recurred despite repeated rounds of resuscitation until death. Considering that major adverse reactions with overlapping symptoms have been reported in humans subjected to hemoperfusion with the same cartridge, this porcine model provides clinically relevant insights into the mechanisms of extracorporeal circulation-induced anaphylactoid responses. Furthermore, the Adsorba(R) 300C-induced physiological changes along the immune-cardiopulmonary axis represents a new animal model for irreversible cardiovascular collapse escalating into shock.

immunology↗

bioRxiv2025

Acute anaphylactic and multiorgan inflammatory effects of Comirnaty in pigs: evidence of spike protein mRNA transfection and paralleling inflammatory cytokine upregulation

Background and PurposeRare but serious adverse events (AEs) associated with mRNA-lipid nanoparticle (LNP) COVID-19 vaccines, such as Comirnaty and Spikevax, include anaphylaxis and acute multiorgan inflammatory syndrome. The mechanisms of these acute innate immune responses remain poorly understood. This study aimed to investigate these effects using an amplified porcine model. Experimental ApproachNaive and anti-PEG antibody-sensitized pigs were intravenously injected with Comirnaty. Acute anaphylactic responses were assessed through hemodynamic monitoring, hematological changes, and plasma inflammatory markers. Multiorgan inflammatory effects were evaluated by RT-qPCR detection of spike protein (SP) mRNA uptake and inflammatory cytokine gene expression in seven organs over 6 hours. Histopathology and immunohistochemistry were also performed. Key ResultsSevere cardiopulmonary distress developed within minutes of repeated intravenous injections of Comirnaty. RT-qPCR revealed predominant SP mRNA accumulation in liver and PBMCs, with spleen, kidney, lymph nodes, heart, and brain also affected in 40-90% of animals. Repetitive PBMC transfection showed reversible mRNA peaks at 15 minutes, followed by rapid decay. Expression of proinflammatory cytokines (IL-1RA, CXCL10, TNF-, CCL2) paralleled mRNA uptake, suggesting a causal relationship. Cytokine profiles varied by organ (e.g. IL-1RA in kidney, CCL2 in PBMCs). Histologic abnormalities and SP immunopositivity were noted in kidney, heart, and brain. Booster injections replicated PBMC transfection kinetics observed at first dose. Conclusions and ImplicationsThis porcine model reveals systemic anaphylactic reactivity and multiorgan SP mRNA transfection following intravenous injection of mRNA-LNPs, resulting in organ-specific inflammatory responses. These findings provide mechanistic insights into two rare vaccine-related acute AEs and may support future efforts to improve the safety of the mRNA-LNP platform technology.

immunology↗

bioRxiv2023

The COVID-19 mRNA vaccine Comirnaty induces anaphylactic shock in an anti-PEG hyperimmune large animal model: Role of complement in cardiovascular, hematological, and inflammatory mediator changes

BackgroundComirnaty, Pfizer-BioNTechs polyethylene-glycol (PEG)-containing Covid-19 vaccine, can cause hypersensitivity reactions (HSRs) in a small fraction of immunized people which can, very rarely, culminate in life-threatening anaphylaxis. A role of anti-PEG antibodies (Abs) has been proposed, but causality has not yet been proven in an animal model. This study aimed to provide such evidence using anti-PEG hyperimmune pigs (i.e., pigs displaying very high levels of anti-PEG Abs). We also sought to find evidence for the role of complement (C) activation and thromboxane A2 (TXA2) release in blood as contributing effects to anaphylaxis. MethodsPigs (n=6) were immunized with 0.1 mg/kg PEGylated liposome (Doxebo) i.v. the rise of anti-PEG IgG and IgM was measured in serial blood samples with ELISA. After 2-3 weeks, during the height of seroconversion, the animals were injected i.v. with 1/3 human vaccine dose (HVD) of Comirnaty, and the hemodynamic (PAP, SAP), cardiopulmonary (HR, EtCO2,), hematological parameters (WBC, granulocyte, lymphocyte, and platelet counts) and blood immune mediators (anti-PEG IgM and IgG Abs, C3a and TXA2) were measured as endpoints of HSRs. ResultsA week after immunization of 6 pigs with Doxebo, the level of anti-PEG IgM and IgG rose 5-10-thousands-fold in all animals, and they all developed anaphylactic shock to i.v. injection of 1/3 HVD of Comirnaty. The reaction, starting within 1 min, led to the abrupt decline of SAP along with maximal pulmonary hypertension, decreased pulse pressure amplitude, tachycardia, granulo- and thrombocytopenia, and paralleling rises of plasma C3a and TXB2 levels. These vaccine effects were not observed in non-immunized pigs. ConclusionsConsistent with previous studies with PEGylated nano-liposomes, these data show a causal role of anti-PEG Abs in the anaphylaxis to Comirnaty. The reaction involves C activation, and, hence, it represents C activation-related pseudo-allergy (CARPA). The setup provides the first large-animal model for mRNA-vaccine-induced anaphylaxis in humans.

pharmacology and toxicology↗

bioRxiv2023

Truncated titin is integrated into the human dilated cardiomyopathic sarcomere

Heterozygous (HET) truncating mutations in the TTN gene (TTNtv) encoding the giant titin protein are the most common genetic cause of dilated cardiomyopathy (DCM). However, the molecular mechanisms by which TTNtv mutations induce DCM are controversial. Here we investigated 127 clinically identified DCM human cardiac samples with next-generation sequencing (NGS), high-resolution gel electrophoresis, Western blot analysis and super-resolution microscopy in order to dissect the structural and functional consequences of TTNtv mutations. The occurrence of TTNtv was found to be 15% in the DCM cohort. Truncated titin proteins matching, by molecular weight, the gene-sequence predictions were detected in the majority of the TTNtv samples. The total amount of expressed titin, which includes the truncated fragments, was comparable in the TTNtv+ and TTNtv-samples, indicating that titin haploinsufficiency is not the leading cause of the molecular pathogenesis. Proteomic analysis of washed cardiac myofibrils and Stimulated Emission Depletion (STED) super-resolution microscopy of myocardial sarcomeres labeled with sequence-specific anti-titin antibodies revealed that truncated titin is structurally integrated in the sarcomere. Sarcomere lengthdependent anti-titin epitope position, shape and intensity analysis pointed at structural defects in the I/A junction and the M-band of TTNtv+ sarcomeres, which may contribute, via faulty mechanosensor function, to the development of manifest DCM.

biophysics↗

bioRxiv2022

Zymosan-induced leukocyte and cytokine changes in pigs: a new model for streamlined drug testing against severe COVID-19

Injection of 0.1 mg/kg zymosan in pigs i.v. elicited transient hemodynamic disturbance within minutes, without major blood cell changes. In contrast, infusion of 1 mg/kg zymosan triggered maximal pulmonary hypertension with tachycardia, lasting for 30 min. This change was followed by a transient granulopenia with a trough at 1 h, and then, up to about 6 h, a major granulocytosis, resulting in a 3-4-fold increase of neutrophil-to-lymphocyte ratio (NLR). In parallel with the changes in WBC differential, qRT-PCR and ELISA analyses showed increased transcription and/or release of inflammatory cytokines and chemokines into blood, including IL-6, TNF-, CCL-2, CXCL-10, and IL-1RA. The expression of IL-6 peaked at already 1.5-2.5 h, and we observed significant correlation between lymphopenia and IL-6 gene expression. While these changes are consistent with zymosans known stimulatory effect on both the humoral and cellular arms of the innate immune system, what gives novel clinical relevance to the co-manifestation of above hemodynamic, hematological, and immune changes is that they represent independent bad prognostic indicators in terminal COVID-19 and other diseases involving cytokine storm. Thus, within a 6 h experiment, the model enables consecutive reproduction of a symptom triad that is characteristic of late-stage COVID-19. Given the limitations of modeling cytokine storm in animals and effectively treating severe COVID-19, the presented relatively simple large animal model may advance the R&D of drugs against these conditions. One of these disease markers (NLR), obtained from a routine laboratory endpoint (WBC differential), may also enable streamlining the model for high throughput drug screening against innate immune overstimulation.

immunology↗