Assembly of Immunogenic Protein Particles toward Advanced Synthetic Vaccines.

Immunogenic carrier proteins such as the non-toxic diphtheria toxin variant, cross-reacting material 197 (CRM197), are widely used in subunit vaccine formulations to boost immunogenicity of chemically conjugated antigens. Conjugate vaccines are inherently expensive due to laborious manufacturing steps. Here, this work develops a particulate vaccine platform based on using engineered Escherichia coli to assemble CRM197-antigen fusion proteins into discrete submicron-sized particles. This approach enables precise loading of diverse antigens and epitopes enhancing their immunogenicity. A cost-effective, high-yield, and scalable biomanufacturing process is developed. Purified particulate CRM197-antigen vaccines are ambient-temperature stable. CRM197 particles incorporating pathogen-specific antigens or epitopes from SARS-CoV-2, Streptococcus pyogenes (group A), and Mycobacterium tuberculosis induced cell-mediated and humoral immune responses mediating protective immunity in respective animal models of infection. The CRM197 particle vaccine platform is versatile, enabling co-delivery of selected antigens/epitopes together with immunogenic CRM197 as discrete stable particles avoiding laborious manufacture of soluble CRM197 and antigen followed by chemical conjugation.

Ambient Temperature Stable, Scalable COVID-19 Polymer Particle Vaccines Induce Protective Immunity (Adv. Healthcare Mater. 3/2022)

Sars-CoV-2 Vaccines In article number 2102089 by Bernd H. A. Rehm and co-workers, an ambient temperature-stable, scalable COVID-19 polymer particle vaccines are developed by engineering endotoxinfree bacterial cell factories to self-assemble biopolymer particles coated with immunogenic SARS-CoV-2 antigens. Polymer particle vaccines induce protective immunity in a hamster SARS-CoV-2 infection model reducing virus titers up to viral clearance in lungs post infection.

Ambient Temperature Stable, Scalable COVID-19 Polymer Particle Vaccines Induce Protective Immunity.

There is an unmet need for safe and effective severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccines that are stable and can be cost-effectively produced at large scale. Here, a biopolymer particle (BP) vaccine technology that can be quickly adapted to new and emerging variants of SARS-CoV-2 is used. Coronavirus antigen-coated BPs are described as vaccines against SARS-CoV-2. The spike protein subunit S1 or epitopes from S and M proteins (SM) plus/minus the nucleocapsid protein (N) are selected as antigens to either coat BPs during assembly inside engineered Escherichia coli or BPs are engineered to specifically ligate glycosylated spike protein (S1-ICC) produced by using baculovirus expression in insect cell culture (ICC). BP vaccines are safe and immunogenic in mice. BP vaccines, SM-BP-N and S1-ICC-BP induced protective immunity in the hamster SARS-CoV-2 infection model as shown by reduction of virus titers up to viral clearance in lungs post infection. The BP platform offers the possibility for rapid design and cost-effective large-scale manufacture of ambient temperature stable and globally available vaccines to combat the coronavirus disease 2019 (COVID-19) pandemic.

Antibodies to neutralising epitopes synergistically block the interaction of the receptor-binding domain of SARS-CoV-2 to ACE 2.

OBJECTIVES: A major COVID-19 vaccine strategy is to induce antibodies that prevent interaction between the Spike protein's receptor-binding domain (RBD) and angiotensin-converting enzyme 2 (ACE2). These vaccines will also induce T-cell responses. However, concerns were raised that aberrant vaccine-induced immune responses may exacerbate disease. We aimed to identify minimal epitopes on the RBD that would induce antibody responses that block the interaction of the RBD and ACE2 as a strategy leading to an effective vaccine with reduced risk of inducing immunopathology. METHODS: We procured a series of overlapping 20-amino acid peptides spanning the RBD and asked which were recognised by plasma from COVID-19 convalescent patients. Identified epitopes were conjugated to diphtheria-toxoid and used to vaccinate mice. Immune sera were tested for binding to the RBD and for their ability to block the interaction of the RBD and ACE2. RESULTS: Seven putative vaccine epitopes were identified. Memory B-cells (MBCs) specific for one of the epitopes were identified in the blood of convalescent patients. When used to vaccinate mice, six induced antibodies that bound recRBD and three induced antibodies that could partially block the interaction of the RBD and ACE2. However, when the sera were combined in pairs, we observed significantly enhanced inhibition of binding of RBD to ACE2. Two of the peptides were located in the main regions of the RBD known to contact ACE2. Of significant importance to vaccine development, two of the peptides were in regions that are invariant in the UK and South African strains. CONCLUSION: COVID-19 convalescent patients have SARS-CoV-2-specific antibodies and MBCs, the specificities of which can be defined with short peptides. Epitope-specific antibodies synergistically block RBD-ACE2 interaction.