Recent advances in veterinary applications of structural vaccinology

Global commercialization and research of veterinary vaccines against Pasteurella multocida: 2015-2022 technological surveillance

Background and Aim

Pasteurella multocida can infect a multitude of wild and domesticated animals, bacterial vaccines have become a crucial tool in combating antimicrobial resistance (AMR) in animal production. The study aimed to evaluate the current status and scientific trends related to veterinary vaccines against Pasteurella multocida during the 2015-2022 period.

Material and Methods

The characteristics of globally marketed vaccines were investigated based on the official websites of 22 pharmaceutical companies. VOSviewer® 1.6.18 was used to visualize networks of coauthorship and cooccurrence of keywords from papers published in English and available in Scopus.

Results

Current commercial vaccines are mostly inactivated (81.7%), adjuvanted in aluminum hydroxide (57.8%), and designed to immunize cattle (33.0%). Investigational vaccines prioritize the inclusion of attenuated strains, peptide fragments, recombinant proteins, DNA as antigens, aluminum compounds as adjuvants and poultry as the target species.

Conclusion

Despite advances in genetic engineering and biotechnology, there will be no changes in the commercial dominance of inactivated and aluminum hydroxide-adjuvanted vaccines in the short term (3-5 years). The future prospects for bacterial vaccines in animal production are promising, with advancements in vaccine formulation and genetic engineering, they have the potential to improve the sustainability of the industry. It is necessary to continue with the studies to improve the efficacy of the vaccines and their availability.

A gaps-and-needs analysis of vaccine R&D in Europe: Recommendations to improve the research infrastructure

The COVID-19 pandemic has brought into sharp focus the importance of strategies supporting vaccine development. During the pandemic, TRANSVAC, the European vaccine-research-infrastructure initiative, undertook an in-depth consultation of stakeholders to identify how best to position and sustain a European vaccine R&D infrastructure. The consultation included an online survey incorporating a gaps-and-needs analysis, follow-up interviews and focus-group meetings. Between October 2020 and June 2021, 53 organisations completed the online survey, including 24 research institutes and universities, and 9 pharmaceutical companies; 24 organisations participated in interviews, and 14 in focus-group meetings. The arising recommendations covered all aspects of the vaccine-development value chain: from preclinical development to financing and business development; and covered prophylactic and therapeutic vaccines, for both human and veterinary indications. Overall, the recommendations supported the expansion and elaboration of services including training programmes, and improved or more extensive access to expertise, technologies, partnerships, curated databases, and-data analysis tools. Funding and financing featured as critical elements requiring support throughout the vaccine-development programmes, notably for academics and small companies, and for vaccine programmes that address medical and veterinary needs without a great potential for commercial gain. Centralizing the access to these research infrastructures via a single on-line portal was considered advantageous.

Structure of P46, an immunodominant surface protein from Mycoplasma hyopneumoniae: interaction with a monoclonal antibody

Mycoplasma hyopneumoniae is a prokaryotic pathogen that colonizes the respiratory ciliated epithelial cells in swine. Infected animals suffer respiratory lesions, causing major economic losses in the porcine industry. Characterization of the immunodominant membrane-associated proteins from M. hyopneumoniae may be instrumental in the development of new therapeutic approaches. Here, the crystal structure of P46, one of the main surface-antigen proteins, from M. hyopneumoniae is presented and shows N- and C-terminal α/β domains connected by a hinge. The structures solved in this work include a ligand-free open form of P46 (3.1 Å resolution) and two ligand-bound structures of P46 with maltose (2.5 Å resolution) and xylose (3.5 Å resolution) in open and closed conformations, respectively. The ligand-binding site is buried in the cleft between the domains at the hinge region. The two domains of P46 can rotate with respect to each other, giving open or closed alternative conformations. In agreement with this structural information, sequence analyses show similarities to substrate-binding members of the ABC transporter superfamily, with P46 facing the extracellular side as a functional subunit. In the structure with xylose, P46 was also bound to a high-affinity (K_d = 29 nM) Fab fragment from a monoclonal antibody, allowing the characterization of a structural epitope in P46 that exclusively involves residues from the C-terminal domain. The Fab structure in the complex with P46 shows only small conformational rearrangements in the six complementarity-determining regions (CDRs) with respect to the unbound Fab (the structure of which is also determined in this work at 1.95 Å resolution). The structural information that is now available should contribute to a better understanding of sugar nutrient intake by M. hyopneumoniae. This information will also allow the design of protocols and strategies for the generation of new vaccines against this important swine pathogen.

Engineering a Rugged Nanoscaffold To Enhance Plug-and-Display Vaccination

Nanoscale organization is crucial to stimulating an immune response. Using self-assembling proteins as multimerization platforms provides a safe and immunogenic system to vaccinate against otherwise weakly immunogenic antigens. Such multimerization platforms are generally based on icosahedral viruses and have led to vaccines given to millions of people. It is unclear whether synthetic protein nanoassemblies would show similar potency. Here we take the computationally designed porous dodecahedral i301 60-mer and rationally engineer this particle, giving a mutated i301 (mi3) with improved particle uniformity and stability. To simplify the conjugation of this nanoparticle, we employ a SpyCatcher fusion of mi3, such that an antigen of interest linked to the SpyTag peptide can spontaneously couple through isopeptide bond formation (Plug-and-Display). SpyCatcher-mi3 expressed solubly to high yields in Escherichia coli, giving more than 10-fold greater yield than a comparable phage-derived icosahedral nanoparticle, SpyCatcher-AP205. SpyCatcher-mi3 nanoparticles showed high stability to temperature, freeze-thaw, lyophilization, and storage over time. We demonstrate approximately 95% efficiency coupling to different transmission-blocking and blood-stage malaria antigens. Plasmodium falciparum CyRPA was conjugated to SpyCatcher-mi3 nanoparticles and elicited a high avidity antibody response, comparable to phage-derived virus-like particles despite their higher valency and RNA cargo. The simple production, precise derivatization, and exceptional ruggedness of this nanoscaffold should facilitate broad application for nanobiotechnology and vaccine development.