Applications of platform technologies in veterinary vaccinology and the benefits for one health

A rapid human vaccine process development map outlining lessons learnt from ChAdOx1 nCoV-19 vaccine during the COVID-19 pandemic

In 2015 the UK Vaccine Network through its Working Group 3 began the creation of a website describing the conventional development of human and veterinary vaccines, which routinely takes several years to complete from concept through to licensure, in the form of process development maps. This website has proved to be a valuable resource for those involved in commercial vaccine development and it has also highlighted the potential bottlenecks within the processes. However, during the COVID-19 pandemic, vaccines were created, licenced and administered within 1 year of the SARS-CoV-2 virus sequence being made available to researchers globally, through the use of novel platform technologies, such as viral vectors and mRNA. The paper describes the updating of this vaccine process development website and the inclusion of a rapid development map with 14 Stages based knowledge gained during the development of the University of Oxford/Astra Zeneca ChAdOx-1 vectored COVID-19 vaccine. The map captures the key steps required to expedite human vaccine development in the face of a pandemic threat from pre-clinical discovery, vaccine platform development, regulatory review and approval through to the administration of the first dose in humans.

Opportunities and challenges for the adoption of novel platform technologies to develop veterinary bacterial vaccines

Vaccine platform technologies provide standardised vehicles for the delivery of diverse antigens to elicit specific immune responses. The deployment of these platforms for novel vaccine development is influenced by a wide range of factors that must meet end-user needs for uptake, which includes cost, frequency of delivery and dependency on cold-chain storage. These factors can be identified by constructing a vaccine target product profile (TPP) that helps to direct the research effort towards the desired goal. The COVID-19 pandemic has exemplified how viral vectored and nucleic acid-based platforms can be rapidly deployed for population disease control. While successful for viral vaccines, the applicability of these platforms for bacteria is less well defined. Bacteria present different challenges to vaccine design from viruses due to their diversity and complexity. Other platform technologies are under development to address these challenges. The more we understand about vaccine platforms, the more adaptable they become, particularly for deployment across species with benefits for One Health. A Workshop was held at the 13th International Veterinary Immunology Symposium (IVIS) in South Africa in November 2023 to discuss the opportunities and challenges in deploying novel platform technologies for vaccine development against bacteria, particularly those that are affordable to low-middle income countries (LMICs). We report here on the outcomes of the presentations and discussions at the Workshop, highlighting the gaps and potential solutions through collaborative global efforts.

Research publications and global manufacture of veterinary vaccines against avian influenza A (2019-2023)

The characteristics of the avian influenza virus and its worldwide spread have led to intense and unprecedented scientific activity and industrial production for preventive veterinary vaccines. However, knowledge gaps remain regarding the best strategies to prevent epidemiological events in the future. In this context, the present study aimed to provide a global analysis on the scientific and industrial production of avian influenza type A vaccines for farm animals and pets during the period 2019 2023. The Scopus database was used as the primary source of information (12,162 keywords, 2,437 scientific articles, 659 academic journals, and 46 countries) for the academic analysis, while technical information posted on official institutional websites (136 commercial formulations, 24 vaccines manufacturers, and 17 countries) was collected to conduct the industrial analysis. 3,045, 25.0%) exhibited the highest levels of co-occurrence in the sciences; the journal Vaccine was the most productive in terms of articles (11.8%, 288/2,437), and the countries with the most publications were the USA (25.5%, 622/2,437) and China (23.1%, 564/2,437). The most internationally marketed vaccines were inactivated (86.0%, 117/136), avian (47.1%, 64/136), and combined (52.2%, 71/136) vaccines as well as those containing Newcastle antigens (38.0%, 27/71). In conclusion, the study demonstrated the fundamental role of classical production methods (based on the use of the whole pathogen) in avian influenza A research and the production of veterinary vaccines.

Field Investigation Evaluating the Efficacy of Porcine Reproductive and Respiratory Syndrome Virus Type 2 (PRRSV-2) Modified Live Vaccines in Nursery Pigs Exposed to Multiple Heterologous PRRSV Strains

This study was conducted to evaluate the protective efficacy of modified live vaccines (MLVs) against porcine reproductive and respiratory syndrome (PRRS) in nursery pigs in a worst case scenario where MLV does not match the genetic profile of the field isolate, different MLVs are used for sows and piglets, and piglets are naturally exposed to genetically distinct heterologous PRRS virus (PRRSV) isolates. We divided 76,075, 2-week-old piglets from a seropositive sow herd vaccinated with US1-MLV into four groups. US1-MLV, US2-MLV, and US3-MLV groups were vaccinated with PRRSV-2 MLV including Ingelvac® PRRS MLV (Boehringer Ingelheim, Ingelheim am Rhein, Germany), HP-PRRSV-2 based MLV (Harbin Veterinary Research Institute, CAAS, Harbin, China), and Prime Pac® PRRS (MSD Animal Health, Rahway, NJ, USA), respectively. The NonVac group was left unvaccinated. At 0, 14, 28, and 56 days post-vaccination (DPV), sera were assayed for the presence of PRRSV-specific antibodies using ELISA and serum neutralization (SN), and PRRSV RNA using PCR. Average daily gain (ADG) and survival rates were compared between treatment groups. The results demonstrated vaccinated groups significantly improved in ADG compared to the non-vaccinated control group. Only US1-MLV and US3-MLV were able to significantly reduce mortality associated with field PRRSV infection in nursery pigs. Pigs vaccinated with US3-MLV displayed significantly lower mortality and higher ADG compared to all other groups. Field isolates were isolated and genetically compared to all three MLV vaccines at the start of the trial. The MLV with closest genetic similarity to the field isolate was US2-MLV by ORF5 gene comparison. This provided the lowest protection judging by ADG improvement and mortality reduction, as compared to US1-MLV and US3-MLV. Separately, strains of Thai PRRSV-2 isolates collected in 2017, 2019, and 2020 in the study area were investigated for evolutionary changes. Over time, we observed a shift in PRRSV-2 isolates from lineage 8.7 to lineage 1. The field isolates found shared 82.59-84.42%, 83.75-85.74%, and 84.25-85.90% nucleotide identity with the US1-MLV, US3-MLV and US2-MLV based vaccine, respectively. Our findings suggest genetic similarity between field viruses and vaccine strains should not be used as a predictor of field performance. We found that zootechnical performance of piglets was best in US3-MLV, despite sows being treated with a different vaccine The results also support that different MLVs can be used at different stages of production. Finally, we concluded that the shift from lineage 8.7 to lineage 1 was due to shifts in the worldwide prevalence of PRRSV isolates during that period of time and not due to vaccine recombination between isolates. Overall, MLV vaccine selection should be based on production performance and safety profile.

Lineage 7 Porcine Reproductive and Respiratory Syndrome Vaccine Demonstrates Cross-Protection Against Lineage 1 and Lineage 3 Strains

Background/Objectives: Porcine reproductive and respiratory syndrome virus (PRRSV) has a major impact on swine productivity. Modified-live vaccines (MLVs) are used to aid in control. We investigated the cross-protection provided by a lineage 7 PRRSV MLV against a lineage 1 isolate under laboratory conditions and a lineage 3 challenge under field conditions in Taiwan. Methods: In the first study, thirty PRRS antibody-negative conventional piglets were vaccinated via the intramuscular (IM) or the intradermal (ID) route, with the control group receiving a placebo. Four weeks after immunization, all groups were challenged with a Taiwanese lineage 1 strain. The standard protocol for detection of reversion to virulence was applied to the vaccine strain in the second study, using sixteen specific pathogen-free piglets. In the third study, on an infected pig farm in Taiwan (lineage 3 strain), three hundred piglets were randomly selected and divided into three groups, each injected with either the PrimePac® PRRS vaccine via the IM or the ID route, or a placebo. Results: In the first study, both vaccinated groups demonstrated reduced viraemia compared to the control group. The second study demonstrated that the MLV strain was stable. In the third study, piglet mortality, average daily weight gain, and pig stunting rate were significantly improved in the vaccinated groups compared to the control group. Conclusions: PrimePac® PRRS is safe to use in the field in the face of a heterologous challenge, successfully providing cross-protection against contemporary lineage 1 and lineage 3 PRRSV strains from Taiwan.

Platform Technology in Global Vaccine Regulation: Development, Applications, and Regulatory Strategies with Insights from China

The concept of "platform technology" gained prominence after the Ebola outbreak and since then has become essential to international vaccine (prophylactic vaccines against infectious disease) regulatory frameworks. Its significance was further amplified during the COVID-19 pandemic, where platform technology enabled the rapid development and approval of vaccines, optimizing regulatory processes, and enhancing global public health responses. As a transformative tool, platform technology streamlines product development, allowing for the reduction in the number of clinical trials or exemption from certain clinical trials and facilitating cross-referencing in regulatory submissions. Despite significant efforts to establish standardized regulatory procedures, challenges remain, particularly in achieving a unified definition and application of platform technology across regions. This paper explores the evolution, applications, and regulatory strategies of platform technology, with a focus on China's experience in this field. China's approach, encompassing risk assessment, and the expedited approval of emergency vaccines, offers valuable insights into global regulatory coordination. By analyzing China's regulatory contributions and international practices, this paper highlights the potential of platform technology to address future pandemics, including "Pathogen X", and underscores the importance of harmonizing global regulatory efforts to strengthen public health preparedness and response.

Revolutionizing Veterinary Health with Viral Vector-Based Vaccines

Vaccines signify one of the economical and reasonable means to prevent and eradicate the important infectious diseases. Conventional vaccines like live attenuated and inactivated vaccines comprise of whole pathogen either in attenuated or killed form. While, new generation vaccines have been designed to elicit immune response by genetically modifying only the nucleic acid portion of that pathogen. These new generation therapeutics include mRNA vaccines, DNA plasmid vaccines, chimeric vaccines and recombinant viral vector-based vaccines. Nucleic acid based vaccines use genetic material itself thus, they are highly stable and potent in nature to induce long-lasting immune response. Amongst these novel vaccine platforms, viral vector-based vaccines is one such emerging field which has proven to be extremely effective and potent. Nowadays, veterinary medicine has also accepted this innovative vectored vaccine platform to develop an effective control strategy against certain important viral diseases of animals. Viral vector-based vaccine uses various DNA and RNA viruses of human or animal origin to carry an immunogenic transgene of target pathogen. These vaccines enhance both humoral and cell mediated immune response without use of any accessory immune-stimulants. Till today, several viruses have been modified to be characterized as vaccine vectors. Currently, large number of research programs are going on to develop vectored vaccines and novel viral vector for veterinary use. In the present review, different kinds of viral vectored vaccines having veterinary importance have been discussed.

Potential of mRNA-based vaccines for the control of tick-borne pathogens in one health perspective

The One Health approach, which integrates the health of humans, animals, plants, and ecosystems at various levels, is crucial for addressing interconnected health threats. This is complemented by the advent of mRNA vaccines, which have revolutionized disease prevention. They offer broad-spectrum effectiveness and can be rapidly customized to target specific pathogens. Their utility extends beyond human medicine, showing potential in veterinary practices to control diseases and reduce the risk of zoonotic transmissions. This review place mRNA vaccines and One Health in the context of tick-borne diseases. The potential of these vaccines to confer cross-species immunity is significant, potentially disrupting zoonotic disease transmission cycles and protecting the health of both humans and animals, while reducing tick populations, infestations and circulation of pathogens. The development and application of mRNA vaccines for tick and tick-borne pathogens represent a comprehensive strategy in global health, fostering a healthier ecosystem for all species in our interconnected world.

Identifying major histocompatibility complex class II-DR molecules in bovine and swine peripheral blood monocyte-derived macrophages using mAb-L243

Major histocompatibility complex class II (MHC-II) molecules are involved in immune responses against pathogens and vaccine candidates' immunogenicity. Immunopeptidomics for identifying cancer and infection-related antigens and epitopes have benefited from advances in immunopurification methods and mass spectrometry analysis. The mouse anti-MHC-II-DR monoclonal antibody L243 (mAb-L243) has been effective in recognising MHC-II-DR in both human and non-human primates. It has also been shown to cross-react with other animal species, although it has not been tested in livestock. This study used mAb-L243 to identify Staphylococcus aureus and Salmonella enterica serovar Typhimurium peptides binding to cattle and swine macrophage MHC-II-DR molecules using flow cytometry, mass spectrometry and two immunopurification techniques. Antibody cross-reactivity led to identifying expressed MHC-II-DR molecules, together with 10 Staphylococcus aureus peptides in cattle and 13 S. enterica serovar Typhimurium peptides in swine. Such data demonstrates that MHC-II-DR expression and immunocapture approaches using L243 mAb represents a viable strategy for flow cytometry and immunopeptidomics analysis of bovine and swine antigen-presenting cells.

Efficiency of NHEJ-CRISPR/Cas9 and Cre-LoxP Engineered Recombinant Turkey Herpesvirus Expressing Pasteurella multocida OmpH Protein for Fowl Cholera Prevention in Ducks

Fowl cholera is caused by the bacterium Pasteurella multocida, a highly transmissible avian ailment with significant global implications, leading to substantial economic repercussions. The control of fowl cholera outbreaks primarily relies on vaccination using traditional vaccines that are still in use today despite their many limitations. In this research, we describe the development of a genetically engineered herpesvirus of turkeys (HVT) that carries the OmpH gene from P. multocida integrated into UL 45/46 intergenic region using CRISPR/Cas9-NHEJ and Cre-Lox system editing. The integration and expression of the foreign cassettes were confirmed using polymerase chain reaction (PCR), indirect immunofluorescence assays, and Western blot assays. The novel recombinant virus (rHVT-OmpH) demonstrated stable integration of the OmpH gene even after 15 consecutive in vitro passages, along with similar in vitro growth kinetics as the parent HVT virus. The protective efficacy of the rHVT-OmpH vaccine was evaluated in vaccinated ducks by examining the levels of P. multocida OmpH-specific antibodies in serum samples using ELISA. Groups of ducks that received the rHVT-OmpH vaccine or the rOmpH protein with Montanide™ (SEPPIC, Paris, France) adjuvant exhibited high levels of antibodies, in contrast to the negative control groups that received the parental HVT or PBS. The recombinant rHVT-OmpH vaccine also provided complete protection against exposure to virulent P. multocida X-73 seven days post-vaccination. This outcome not only demonstrates that the HVT vector possesses many characteristics of an ideal recombinant viral vaccine vector for protecting non-chicken hosts, such as ducks, but also represents significant research progress in identifying a modern, effective vaccine candidate for combatting ancient infectious diseases.

Omics tools enabling vaccine discovery against fasciolosis

In the past decade significant advances in our understanding of liver fluke biology have been made through in-depth interrogation and analysis of evolving Fasciola hepatica and Fasciola gigantica omics datasets. This information is crucial for developing novel control strategies, particularly vaccines necessitated by the global spread of anthelmintic resistance. Distilling them down to a manageable number of testable vaccines requires combined rational, empirical, and collaborative approaches. Despite a lack of clear outstanding vaccine candidate(s), we must continue to identify salient parasite-host interacting molecules, likely in the secretory products, tegument, or extracellular vesicles, and perform robust trials especially in livestock, using present and emerging vaccinology technologies to discover that elusive liver fluke vaccine. Omics tools are bringing this prospect ever closer.

Probiotics Surface-Delivering Fiber2 Protein of Fowl Adenovirus 4 Stimulate Protective Immunity Against Hepatitis-Hydropericardium Syndrome in Chickens

Background and Objectives

Hepatitis-hydropericardium syndrome (HHS) caused by Fowl adenoviruses serotype 4 (FAdV-4) leads to severe economic losses to the poultry industry. Although various vaccines are available, vaccines that effectively stimulate intestinal mucosal immunity are still deficient. In the present study, novel probiotics that surface-deliver Fiber2 protein, the major virulence determiner and efficient immunogen for FAdV-4, were explored to prevent this fecal–oral-transmitted virus, and the induced protective immunity was evaluated after oral immunization.

Methods

The probiotic Enterococcus faecalis strain MDXEF-1 and Lactococcus lactis NZ9000 were used as host strains to deliver surface-anchoring Fiber2 protein of FAdV-4. Then the constructed live recombinant bacteria were orally vaccinated thrice with chickens at intervals of 2 weeks. Following each immunization, immunoglobulin G (IgG) in sera, secretory immunoglobulin A (sIgA) in jejunum lavage, immune-related cytokines, and T-cell proliferation were detected. Following challenge with the highly virulent FAdV-4, the protective effects of the probiotics surface-delivering Fiber2 protein were evaluated by verifying inflammatory factors, viral load, liver function, and survival rate.

Results

The results demonstrated that probiotics surface-delivering Fiber2 protein stimulated humoral and intestinal mucosal immune responses in chickens, shown by high levels of sIgA and IgG antibodies, substantial rise in mRNA levels of cytokines, increased proliferative ability of T cells in peripheral blood, improved liver function, and reduced viral load in liver. Accordingly, adequate protection against homologous challenges and a significant increase in the overall survival rate were observed. Notably, chickens orally immunized with E. faecalis/DCpep-Fiber2-CWA were completely protected from the FAdV-4 challenge, which is better than L. lactis/DCpep-Fiber2-CWA.

Conclusion

The recombinant probiotics surface-expressing Fiber2 protein could evoke remarkable humoral and cellular immune responses, relieve injury, and functionally damage target organs. The current study indicates a promising method used for preventing FAdV-4 infection in chickens.