Next generation vaccine platform: polymersomes as stable nanocarriers for a highly immunogenic and durable SARS-CoV-2 spike protein subunit vaccine

Abstract

Multiple successful vaccines against SARS-CoV-2 are urgently needed to address the ongoing Covid-19 pandemic. In the present work, we describe a subunit vaccine based on the SARS-CoV-2 spike protein co-administered with CpG adjuvant. To enhance the immunogenicity of our formulation, both antigen and adjuvant were encapsulated with our proprietary artificial cell membrane (ACM) polymersome technology. Structurally, ACM polymersomes are self-assembling nanoscale vesicles made up of an amphiphilic block copolymer comprising of polybutadiene-b-polyethylene glycol and a cationic lipid 1,2-dioleoyl-3-trimethylammonium-propane. Functionally, ACM polymersomes serve as delivery vehicles that are efficiently taken up by dendritic cells, which are key initiators of the adaptive immune response. Two doses of our formulation elicit robust neutralizing titers in C57BL/6 mice that persist at least 40 days. Furthermore, we confirm the presence of memory CD4⁺ and CD8⁺ T cells that produce Th1 cytokines. This study is an important step towards the development of an efficacious vaccine in humans.

Competing Interest Statement

The authors declare the following competing financial interests: D.E.A. and Y.J.T. developed the cPass kit; J.H.L, A.K.K., T.A.C., T.W.C., W.W.W.Y., and M.N. are employees of ACM Biolabs Pte Ltd; F.G. is part of the ACM SAB. The authors declare no non-financial competing interests.

Abstract

Multiple successful vaccines against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are urgently needed to address the ongoing coronavirus disease 2019 (Covid-19) pandemic. In the present work, we describe a subunit vaccine based on the SARS-CoV-2 spike protein coadministered with CpG adjuvant. To enhance the immunogenicity of our formulation, both antigen and adjuvant were encapsulated with our proprietary artificial cell membrane (ACM) polymersome technology. Structurally, ACM polymersomes are self-assembling nanoscale vesicles made up of an amphiphilic block copolymer comprising poly(butadiene)-b-poly(ethylene glycol) and a cationic lipid, 1,2-dioleoyl-3-trimethylammonium-propane. Functionally, ACM polymersomes serve as delivery vehicles that are efficiently taken up by dendritic cells (DC1 and DC2), which are key initiators of the adaptive immune response. Two doses of our formulation elicit robust neutralizing antibody titers in C57BL/6 mice that persist at least 40 days. Furthermore, we confirm the presence of functional memory CD4⁺ and CD8⁺ T cells that produce T helper type 1 cytokines. This study is an important step toward the development of an efficacious vaccine in humans.

Keywords: ACM; Covid-19; neutralizing antibody; polymersome; spike; vaccine.

Conflict of interest statement

The authors declare the following competing financial interest(s): D.E.A. developed the cPass kit; J.H.L, A.K.K., T.A.C., T.W.C., W.W.W.Y., S.V., and M.N. are employees of ACM Biolabs Pte Ltd; F.G. is part of the ACM SAB.

ACM Biosciences and Dr. Steve Pascolo, University Hospital Zurich awarded a prestigious Innosuisse grant to partner and develop stable mRNA COVID-19 vaccines

Basel, 27 May 2021 – ACM Biosciences AG, a Swiss biotechnology company focusing on the development of their proprietary polymersome-based vaccines, today announced that Innosuisse, the Swiss Innovation Agency, has awarded a grant for the development of a novel delivery system for mRNA COVD-19 vaccines. Dr. Steve Pascolo, global expert in mRNA vaccines and group leader at the University Hospital Zurich, and ACM Biosciences will join forces to develop a stable and novel carrier for mRNA with improved properties regarding storage at refrigerator temperature, logistics, and flexibility.

mRNA-based vaccines are one of the most important scientific breakthroughs arising from the COVID-19 pandemic. However, these vaccines are burdened with drawbacks that limit their widespread use. Specifically, they are unstable, requiring complex cooling solutions for transport and storage, and the manufacturing of the final product is complex and costly. With this project, ACM Biosciences aims to maximize the potential of mRNA vaccines by developing a novel vaccine carrier system to improve their efficacy, stability, and cost effectiveness. The proprietary Artificial Cell Membranes (ACMs) from ACM Biosciences are based on an innovative nanotechnology platform using non-immunogenic polymersomes as its stable carrier. In parallel to this project, the company is developing a sub-unit protein based COVID-19 vaccine candidate in clinical trials and is conducting an mRNA proof of concept stability and immunogenicity study.

Dr. Steve Pascolo, Principal Investigator at the University Hospital Zurich and co-founder of CureVac, a leading mRNA company, commented:

“A polymersome carrier would have a simpler structure than a lipid nanoparticle carrier, which is the current standard for mRNA vaccines. This could yield clear benefits such as higher stability with easier storage and handling, cheaper production and making global supply possible even in areas with poor infrastructure.”

“We are delighted to collaborate with Dr. Steve Pascolo with the support from Innosuisse to validate the polymersomes for mRNA delivery,” added Dr. Peter Moran, CEO of ACM Biosciences. “Through this public-private partnership, ACM Biosciences will push this platform as a stable mRNA vaccine closer to clinics. We are excited with this opportunity to strengthen our pipeline of polymersome-based vaccines as a highly effective and stable carrier.

About ACM
Biosciences ACM Biosciences was incorporated in Basel, Switzerland, in 2020 as the human infectious disease vaccine company of ACM Biolabs, which is based in Singapore, a leader in protein vaccines and novel nanoparticle delivery techniques in the oncology and veterinary fields. ACM Biosciences is dedicated to the development of infectious disease vaccines using the proprietary ACM polymersome platform technology. These artificial cell membranes (ACM) are nanoscale vesicles that are conceptually very similar to liposomes and have shown to have numerous advantages for both veterinary and human vaccines, including viral, bacterial, and oncological diseases. ACM Biosciences is now accelerating a COVID-19 vaccine into clinical trials. For further information, please visit: www.acmbiosciences.com

Basel, 7 April 2021 – ACM Biosciences AG, a Swiss biotechnology company focusing on the development of polymersome-based vaccines, today announced the closing of a first financing round to advance its human vaccines platform and a second-generation Covid-19 vaccine. ACM Biosciences secured the exclusive worldwide license to the proprietary polymersome platform for the development of human infectious disease vaccines from ACM Biolabs Pte Ltd in Singapore, which is a leader in protein vaccines and novel nanoparticle delivery techniques in the oncology and veterinary fields.

Dr Peter Moran, CEO of ACM Biosciences, commented:

“With the great results we have seen so far from our technology in animal health, this financing is a key step in our strategy and will provide the necessary financial resources to progress both the COVID-19 vaccine candidate into clinical trials and the mRNA proof of concept stability and immunogenicity study.”

Focus on fast, efficient development of clinical vaccine candidates

The proprietary Artificial Cell Membranes (ACMs) are based on an innovative nanotechnology platform using non-immunogenic polymersomes as its carrier. Through past developments by ACM Biolabs in Singapore, the ACM polymersome platform has been shown to produce a safe and efficacious veterinary vaccine against porcine epidemic diarrhea, a highly contagious and deadly coronavirus in pigs, for which there is no effective commercial vaccine. By working closely together, the Singapore and Swiss entities have developed a protein-based COVID-19 vaccine which shows an excellent immune response in preclinical trials. With the necessary financial resources secured, ACM Biosciences will now accelerate its development of the COVID-19 vaccine candidate and proceed with the running mRNA vaccine proof of concept stability and immunogenicity studies.

Prof Dr Daniel Paris, Medical Director and Head of the Department of Medicine at Swiss Tropical and Public Health Institute commented:

“ACM Biosciences’ technology has the potential to bring a step-change in manufacturability, and durability of vaccines, something Press Release ACM Biosciences AG, Steinenberg 1, 4051 Basel; www.acmbiosciences.com Page 2 of 2 which is urgently needed for a long-term solution to COVID-19, but also for other vaccine preventable diseases. Their preclinical efficacy data are really exciting, and their vaccine candidate should be taken into clinical trials as quickly as possible.”

Polymersome platform offers advantages in manufacturability and increases durability of vaccines

ACM Biosciences technology allows great variability because its polymersome platform is highly customizable and can be made compatible with different vaccine formats, including mRNA and protein antigens. A formulation with polymersomes also enables a vaccine to be delivered intranasally, which is not only a convenient route of administration but can reduce transmissibility by activating mucosal immunity. Furthermore, polymersomes do not suffer from vector neutralizing antibodies, are very stable for easy storage and shipping and do not need a complex cold chain. And they can be manufactured cost-effective and with scale. As such, the platform allows quick adjustability to new strains and is well suited for repetitive use and applications.

Prof Dr Onur Boyman, Professor and Chair of the Department of Immunology at the University of Zurich added:

“ACM Biosciences’ next-generation vaccines can readily be adapted to emerging mutant viruses, which is crucial to control infection with SARS-CoV-2 and with other viral diseases.”

About ACM Biosciences
ACM Biosciences was incorporated in Basel, Switzerland, in 2020 as the human infectious disease vaccine company of ACM Biolabs, which is based in Singapore, a leader in protein vaccines and novel nanoparticle delivery techniques in the oncology and veterinary fields. ACM Biosciences is dedicated to the development of infectious disease vaccines using the proprietary ACM polymersome platform technology. These artificial cell membranes (ACM) are nanoscale vesicles that are conceptually very similar to liposomes and have shown to have numerous advantages for both veterinary and human vaccines, including viral, bacterial, and oncological diseases. ACM Biosciences is now accelerating a COVID-19 vaccine into clinical trials. For further information, please visit: www.acmbiosciences.com

Abstract

Multicompartmentalized polymersomes are formed using block co-polymers PMOXA–PDMS–PMOXA and PS-PIAT, and are subsequently proven to be capable of selective encapsulation of biomacromolecules. This architecture mimics the compartmentalization found in cells and may serve as a simple, albeit robust, model system.

Abstract

G-protein coupled receptors (GPCRs) play a key role in physiological processes and are attractive drug targets. Their biophysical characterization is, however, highly challenging because of their innate instability outside a stabilizing membrane and the difficulty of finding a suitable expression system. We here show the cell-free expression of a GPCR, CXCR4, and its direct embedding in diblock copolymer membranes. The polymer-stabilized CXCR4 is readily immobilized onto biosensor chips for label-free binding analysis. Kinetic characterization using a conformationally sensitive antibody shows the receptor to exist in the correctly folded conformation, showing binding behaviour that is commensurate with heterologously expressed CXCR4.

Abstract

Compartmentalization, as a design principle, is a prerequisite for the functioning of eukaryotic cells. Although cell mimics in the form of single vesicular compartments such as liposomes or polymersomes have been tremendously successful, investigations of the corresponding higher-order architectures, in particular bilayer-based multicompartment vesicles, have only recently gained attention. We hereby demonstrate a multicompartment cell-mimetic nanocontainer, built-up from fully synthetic membranes, which features an inner compartment equipped with a channel protein and a semi-permeable outer compartment that allows passive diffusion of small molecules. The functionality of this multicompartment architecture is demonstrated by a cascade reaction between enzymes that are segregated in separate compartments. The unique architecture of polymersomes, which combines stability with a cell-membrane-mimetic environment, and their assembly into higher-order architectures could serve as a design principle for new generation drug-delivery vehicles, biosensors, and protocell models.

Abstract

The dopamine receptor D2 (DRD2), a G-protein coupled receptor is expressed into PBd₂₂-PEO₁₃ and PMOXA₂₀-PDMS₅₄-PMOXA₂₀ block copolymer vesicles (see scheme). The conformational integrity of the receptor is confirmed by antibody- and ligand-binding assays. Replacement of bound dopamine is demonstrated on surface-immobilized polymersomes, thus making this a promising platform for drug screening.

Abstract

To improve the stability of cell membrane mimics, there has been growing interest in the use of block copolymers. Here, we present an easy approach to create an array of planar polymeric matrices capable of hosting membrane proteins. The array of polymeric matrices was formed by the selective deposition of triblock copolymers onto an array of hydrophilic islands situated within a hydrophobic background. The thickness of these matrices corresponds to the length of a single polymer chain. These polymeric matrices were used to host cell-free expressed membrane proteins, and offers a prototype from which a membrane protein array can be created for diagnostics or drug discovery purposes.