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

Abstract

BackgroundComirnaty, Pfizer-BioNTech’s 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.

mRNA-LNP COVID-19 vaccine lipids induce low level complement activation and production of proinflammatory cytokines: Mechanisms, effects of complement inhibitors, and relevance to adverse reactions

“…Human 77 and animal studies 44, 78, 109 have previously linked these HSRs to C activation by Doxil, while other studies have shown that Doxil and Doxebo are near equivalent in causing C activation 44 . Thus, despite the low level of C activation in vitro and low number of studied sera, the consistent finding of C activation by Comirnaty supports the implication of C activation in Comirnaty-induced HSRs and anaphylaxis 16, 17, 19 . The latter was listed in Comirnaty’s postmarketing survey, updated in Oct 2023, as the 3rd most frequent AE after the cardiac and gastrointestinal complications 110 .…”

“…Although Comirnaty also contains PEG, its surface density is lower than that in Doxebo (1.5% vs 5%), which may explain the small but consistent C4d rise in 3 of 5 sera in Figure 2C. In other experimental systems, e.g., anti-PEG hyperimmune pigs 19, 83 , or even humans with extremely high anti-PEG antibody levels in their blood 18 , the involvement of classical pathway in C activation by PEGylated nanoparticles may become more prominent.…”

“…anaphylatoxin/cytokine double hit) and start of symptoms can be reconciled. Examples for acute, subacute and chronic SAEs include the HSRs or anaphylaxis within minutes to hours [16][17][18][19] , heart inflammation [8][9][10][11][12][13][14][15] , coagulation disorders [21][22][23][24] , or skin diseases [25][26][27][28] can occur within days to months, and autoimmune phenomena 20 may arise without currently foreseeable time limit. A hypothesis that may explain these different latency periods postulates that the actions of effector immune cells, including the mast cells, basophil and neutrophil granulocytes, lymphocytes, macrophages and platelets, are discontinuous, graded in the sense that they manifest only after the activation state of their intracellular inflammatory signaling network reaches the reaction threshold.…”

“…We have previously reported C activation by Comirnaty in pig serum in vitro 17 and in pig blood in vivo, after i.v. injection of the vaccine in anti-PEG hyperimmune pigs 19 . The present reproduction of the phenomenon in human serum implies that it is not species-specific.…”

“…Table 1 lists the vaccine's reported AEs categorized according to the affected organ systems. Of note, myocarditis/pericarditis [8][9][10][11][12][13][14][15] , HSRs/anaphylaxis [16][17][18][19] , autoimmune diseases 20 , thrombosis, thrombocytopenia and other coagulation disorders [21][22][23][24] skin [25][26][27][28] and ocular inflammations [29][30][31] , Guillain-Barre syndrome [32][33][34][35][36][37][38] and other neurologic problems 39,40 can all be linked to acute or subacute inflammatory processes that are also characteristic of SARS-CoV-2 infections.…”