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\begin{document}

\title{The form of PEG matters: PEG conjugated with lipids and not PEG alone
could be the specific form involved in allergic reactions to COVID-19
vaccines}



\author[1]{Natalija Novak2, Cezmi A. Akdis3,4 Beatriz Cabanillas1*}%
\author[2]{Natalija Novak}%
\author[3]{Cezmi Akdis A}%
\affil[1]{Instituto de Investigacion Hospital 12 de Octubre}%
\affil[2]{Universitatsklinikum Bonn}%
\affil[3]{Universitat Zurich Schweizerisches Institut fur Allergie- und Asthmaforschung}%


\vspace{-1em}



  
  \date{May 21, 2024}


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\selectlanguage{english}
\begin{abstract}
Initial guidelines advised that sensitization to PEG should be taken
into consideration in suspected subjects before a recommendation on the
administration of vaccines for COVID-19 containing PEG or its
cross-reactive analogues. \textsuperscript{3} However, PEG shows an
important variability in terms of molecular weights and conjugation
forms. In that sense, although it is known that PEG-2000 (MW: 2000g/mol)
conjugated with lipids is the form contained in the vaccines for
COVID-19, there has been great variability in the PEG molecules used in
allergy tests to evaluate sensitization of suspected subjects in the
context of the current COVID-19 vaccination campaigns.
\textsuperscript{4} In this context, recent findings have shed light on
the specific form of PEG that could be responsible of the
hypersensitivity reactions to the mRNA vaccines for COVID-19.%
\end{abstract}%



\sloppy


\textbf{The form of PEG matters: PEG conjugated with lipids and not PEG
alone could be the specific form involved in allergic reactions to
COVID-19 vaccines}

Beatriz Cabanillas\textsuperscript{1*}, Natalija
Novak\textsuperscript{2}, Cezmi A. Akdis\textsuperscript{3,4}

1. Department of Allergy, Research Institute Hospital 12 de Octubre,
Avenida de C\selectlanguage{ngerman}órdoba s/n, 28041 Madrid, Spain

2. Department of Dermatology and Allergy, University Hospital, Bonn,
Venusberg Campus 1, 53127, Bonn, Germany

3. Swiss Institute of Allergy and Asthma Research (SIAF), University of
Zurich, Davos, Switzerland.

4. Christine Kühne-Center for Allergy Research and Education, Davos,
Switzerland

*Corresponding author: Dr. Beatriz Cabanillas. Department of Allergy,
Research Institute Hospital 12 de Octubre de Madrid, Avenida de Córdoba
s/n, 28041 Madrid, Spain. Phone: (+34) 913908763.
E-mail:\emph{bcabanillas.imas12@h12o.es}

\textbf{Keywords:} COVID-19; PEG; Polyethylene glycol; RNA Vaccine;
SARS-CoV-2

\textbf{To the Editor:}

The excipient polyethylene glycol (PEG) contained in the mRNA vaccines
for COVID-19 has been pointed out as one of the possible triggers of the
hypersensitivity reactions that have been described since the beginning
of the vaccine campaigns for COVID-19
protection.\textsuperscript{1}However, PEG is not present in the mRNA
vaccines in an isolated form but in conjugation with lipid-nanoparticles
thanks to a process called PEGylation, which could potentially alter its
immunogenic properties. More specifically, mRNA-1273 vaccine (produced
by Moderna Therapeutics) contains
1,2-dimyristoyl-rac-glycero-3-methoxy-polyethylene glycol-2000 (DMG-PEG
2000) which is formed by the PEGylation of the lipid dimyristoyl
glycerol. On the other hand, BNT162b2 vaccine (Comirnaty, produced by
Pfizer-BioNTech) contains 2-{[}(polyethylene glycol) 2000{]}
-N,N-ditetradecylacetamide (PEG-DTA also named as ALC-0159), which is
also a PEG/lipid conjugate.\textsuperscript{2}

Initial guidelines advised that sensitization to PEG should be taken
into consideration in suspected subjects before a recommendation on the
administration of vaccines for COVID-19 containing PEG or its
cross-reactive analogues.\textsuperscript{3} However, PEG shows an
important variability in terms of molecular weights and conjugation
forms. In that sense, although it is known that PEG-2000 (MW: 2000g/mol)
conjugated with lipids is the form contained in the vaccines for
COVID-19, there has been great variability in the PEG molecules used in
allergy tests to evaluate sensitization of suspected subjects in the
context of the current COVID-19 vaccination
campaigns.\textsuperscript{4} In this context, recent findings have shed
light on the specific form of PEG that could be responsible of the
hypersensitivity reactions to the mRNA vaccines for COVID-19.
Importantly, Troelnikov et al., found that BNT162b2 vaccine and
PEGylated liposomes but not PEG alone (200-6000 g/mol) without lipid
conjugation induced a robust basophil activation in a dose-dependent
manner in three patients with a history of PEG allergy. The results
suggested that during PEGylation process, possible changes in the
conformation and/or chemical structure of PEG covalently linked to the
surface of lipid nanoparticles may occur which could potentially change
and increase its immunogenicity\textsuperscript{5} (Figure 1). On
support of these findings that seem to indicate that PEG in its native
form could not be as immunoreactive as PEG/lipid conjugates, there is a
number of studies that have failed to demonstrate positive skin testing
results using PEG in its native form in patients with a history of
allergic reaction to mRNA vaccines for COVID-19, having skin testing
with PEG a poor sensitivity.\textsuperscript{4}

Furthermore, a recent study used the PEG/lipid conjugate DMG-PEG 2000
(which is the exact compound contained in mRNA-1273 vaccine) and not PEG
in its native form and found that 91 \% and 100 \% of patients with
anaphylactic reactions to mRNA COVID-19 vaccine (n=11) had positive BAT
results with DMG-PEG 2000 and with the administered mRNA vaccine,
respectively. The results were negative when DMG-PEG 2000 was assessed
in skin prick test (SPT), and only 1 out of 11 patients had a positive
SPT with the brand of mRNA vaccine which they reacted to, which
suggested that BAT performed with PEG/lipid conjugate and with the mRNA
vaccine itself could be a more robust experimental tool to assess
PEG-2000/lipid sensitization.\textsuperscript{6} In addition to direct
IgE-mediated degranulation reactions, it should be considered that IgG
to various PEGs may be playing a role in rapid complement activation
followed by mast cell and basophil
degranulation\textsuperscript{7,8}(Figure 1).

In light of these rapidly emerging new findings and due to the pressing
nature of the investigations on the adverse reactions to vaccines for
COVID-19, there is a need to reassess the initial recommendations on the
evaluation of sensitization to excipients contained in COVID-19
vaccines. In the case of PEG, and taking into consideration the new
findings, the choice of the PEG molecule to be tested should be based on
the closest characteristics to the specific molecule contained in the
vaccines for COVID-19, that is, PEG-2000/lipid conjugate or PEGylated
liposomes.

\textbf{References}

1. Cabanillas B, Akdis CA, Novak N. Allergic reactions to the first
COVID-19 vaccine: A potential role of polyethylene glycol?\emph{Allergy}
. 2021;76:1617-1618. doi: 10.1111/all.14711.

2. Klimek L, Novak N, Cabanillas B, Jutel M, Bousquet J, Akdis CA.
Allergenic components of the mRNA-1273 vaccine for COVID-19: Possible
involvement of polyethylene glycol and IgG-mediated complement
activation. \emph{Allergy} . 2021 Mar 3:10.1111/all.14794. doi:
10.1111/all.14794.

3. Sokolowska M, Eiwegger T, Ollert M, et al. EAACI statement on the
diagnosis, management and prevention of severe allergic reactions to
COVID-19 vaccines. \emph{Allergy} . 2021;76:1629-1639. doi:
10.1111/all.14739.

4. Greenhawt M, Abrams EM, Shaker M, et al. The Risk of Allergic
Reaction to SARS-CoV-2 Vaccines and Recommended Evaluation and
Management: A Systematic Review, Meta-Analysis, GRADE Assessment, and
International Consensus Approach. \emph{J Allergy Clin Immunol Pract} .
2021 Jun 18:S2213-2198(21)00671-1. doi: 10.1016/j.jaip.2021.06.006.

5. Troelnikov A, Perkins G, Yuson C, Ahamdie A, Balouch S, Hurtado PR,
Hissaria P. Basophil reactivity to BNT162b2 is mediated by PEGylated
lipid nanoparticles in patients with PEG allergy. \emph{J Allergy Clin
Immunol} . 2021;148:91-95. doi: 10.1016/j.jaci.2021.04.032. Epub 2021
May 12. PMID: 33991580.

6. Warren CM, Snow TT, Lee AS, et al. Assessment of Allergic and
Anaphylactic Reactions to mRNA COVID-19 Vaccines With Confirmatory
Testing in a US Regional Health System. \emph{JAMA Netw Open} .
2021;4:e2125524. doi: 10.1001/jamanetworkopen.2021.25524.

7. Elieh Ali Komi D, Shafaghat F, Kovanen PT, Meri S. Mast cells and
complement system: Ancient interactions between components of innate
immunity. \emph{Allergy} . 2020;75:2818-2828. doi: 10.1111/all.14413

8. Risma KA, Edwards KM, Hummell DS,et a. Potential mechanisms of
anaphylaxis to COVID-19 mRNA vaccines. \emph{J Allergy Clin Immunol} .
2021;147:2075-2082.e2. doi: 10.1016/j.jaci.2021.04.002.

\textbf{Conflict of interest}

The authors declare no conflict of interest

\textbf{Figure legend.}

\textbf{Figure 1.} Schematic representation of the lipid-nanoparticle
PEGylated with PEG-2000 contained in mRNA vaccines for COVID-19 (left
part). PEG-2000/lipid conjugate (individual unit) or PEGylated
nanoparticle could be involved in the allergic reactions to the mRNA
vaccines for COVID-19. The potential mechanisms involved (direct
IgE-mediated degranulation or CARPA) are depicted in the right-upper
part. PEG in its native form could not be as immunoreactive as
PEG-2000/lipid conjugates (right-lower part).\selectlanguage{english}
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\includegraphics[width=0.70\columnwidth]{figures/Figure-1/Figure-1}

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\end{figure}

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