COVID-19 and Preparing Planetary Health for Future Ecological Crises: Hopes from Glycomics for Vaccine Innovation.

A key lesson emerging from COVID-19 is that pandemic proofing planetary health against future ecological crises calls for systems science and preventive medicine innovations. With greater proximity of the human and animal natural habitats in the 21st century, it is also noteworthy that zoonotic infections such as COVID-19 that jump from animals to humans are increasingly plausible in the coming decades. In this context, glycomics technologies and the third alphabet of life, the sugar code, offer veritable prospects to move omics systems science from discovery to diverse applications of relevance to global public health and preventive medicine. In this expert review, we discuss the science of glycomics, its importance in vaccine development, and the recent progress toward discoveries on the sugar code that can help prevent future infectious outbreaks that are looming on the horizon in the 21st century. Glycomics offers veritable prospects to boost planetary health, not to mention the global scientific capacity for vaccine innovation against novel and existing infectious agents.

The use of plants for the production of therapeutic human peptides.

Peptides have unique properties that make them useful drug candidates for diverse indications, including allergy, infectious disease and cancer. Some peptides are intrinsically bioactive, while others can be used to induce precise immune responses by defining a minimal immunogenic region. The limitations of peptides, such as metabolic instability, short half-life and low immunogenicity, can be addressed by strategies such as multimerization or fusion to carriers, to improve their pharmacological properties. The remaining major drawback is the cost of production using conventional chemical synthesis, which is also difficult to scale-up. Over the last 15 years, plants have been shown to produce bioactive and immunogenic peptides economically and with the potential for large-scale synthesis. The production of peptides in plants is usually achieved by the genetic fusion of the corresponding nucleotide sequence to that of a carrier protein, followed by stable nuclear or plastid transformation or transient expression using bacterial or viral vectors. Chimeric plant viruses or virus-like particles can also be used to display peptide antigens, allowing the production of polyvalent vaccine candidates. Here we review progress in the field of plant-derived peptides over the last 5 years, addressing new challenges for diverse pathologies.

Recombinant protein vaccines produced in insect cells.

The baculovirus-insect cell expression system is a well known tool for the production of complex proteins. The technology is also used for commercial manufacture of various veterinary and human vaccines. This review paper provides an overview of how this technology can be applied to produce a multitude of vaccine candidates. The key advantage of this recombinant protein manufacturing platform is that a universal "plug and play" process may be used for producing a broad range of protein-based prophylactic and therapeutic vaccines for both human and veterinary use while offering the potential for low manufacturing costs. Large scale mammalian cell culture facilities previously established for the manufacturing of monoclonal antibodies that have now become obsolete due to yield improvement could be deployed for the manufacturing of these vaccines. Alternatively, manufacturing capacity could be established in geographic regions that do not have any vaccine production capability. Dependent on health care priorities, different vaccines could be manufactured while maintaining the ability to rapidly convert to producing pandemic influenza vaccine when the need arises.

The future of cell culture-based influenza vaccine production.

Influenza vaccines have been prepared in embryonated chicken eggs and used for more than 60 years. Although this older technology is adequate to produce hundreds of millions of doses per year, most viral vaccines are now being produced in cell culture platforms. The question of whether egg-based influenza vaccines will continue to serve the needs of the growing influenza vaccine market is considered here. In 2006, the US government committed to support the development of cell-based influenza vaccines by funding advanced development and expansion of domestic manufacturing infrastructure. Funding has also been provided for other recombinant DNA approaches that do not depend on growth of influenza viruses. As the influenza vaccine industry expands over the next 5-10 years, it will be interesting to follow which of these various technologies are able to best meet the needs of a growing influenza vaccine market.

Recent progress in the development of plant derived vaccines.

Recombinant subunit vaccines have been with us for the last 30 years and they provide us with the unique opportunity to choose from the many available production systems that can be used for recombinant protein expression. Plants have become an attractive production platform for recombinant biopharmaceuticals and vaccines have been at the forefront of this new and expanding industry sector. The particular advantages of plant-based vaccines in terms of cost, safety and scalability are discussed in the light of recent successful clinical trials and the likely impact of plant systems on the vaccine industry is evaluated.

Plants as biofactories.

Cell substrates are a key component of successful vaccine development and throughout the last several decades there has been a dramatic increase in the types of cells available for vaccine production. Nevertheless, there is a continued demand for new and innovative approaches for vaccine development and manufacturing. Recent developments involving cells of insect and plant origin are attracting considerable scientific interest. Here we review vaccine antigen production in plant-based systems as was presented by Dr. Vidadi Yusibov of Fraunhofer USA Center for Molecular Biotechnology at the IABS International Scientific Workshop on NEW CELLS FOR NEW VACCINES II that was held in Wilmington, Delaware on September 17-19, 2007.

Production, quality control, stability and pharmacotoxicity of cGMP-produced Plasmodium falciparum AMA1 FVO strain ectodomain expressed in Pichia pastoris.

Plasmodium falciparum apical membrane antigen 1 (PfAMA1) is a leading asexual blood stage vaccine candidate for malaria. In preparation for clinical trials, PfAMA1 ectodomain (amino acid 25-545, FVO strain) was produced in Pichia pastoris by 35L scale fed batch fermentation under current Good Manufacturing Practice (cGMP). Fermentation was followed by a three-step chromatographic purification procedure resulting in a yield of 5.8g of purified protein. As judged by size exclusion chromatography, the cGMP-product comprised >95% PfAMA1 monomer, the remainder being predominantly PfAMA1 dimer. In SDS-PAGE two main bands of 68 and 70kDa and some minor bands were evident. Under reducing conditions a site of limited proteolytic cleavage within a disulphide bonded region became evident; less than 15% of the protein had this internal cleavage. By mass-spectrometric analysis, all bands analyzed in overloaded SDS-PAGE gels comprised PfAMA1 derived products. The protein was quantitatively bound by immobilized 4G2, a monoclonal antibody reactive with a reduction sensitive conformational determinant. The lyophilized product was stable for over 1 year. Immunopotency did not diminish, and storage did not lead to alterations in the behaviour of the protein upon formulation with adjuvants selected for Phase I clinical evaluation. These formulations also showed no pharmacotoxicity in rabbits. The final product conformed to preset criteria and was judged suitable for use in human clinical trials.

Plant-derived vaccines: a look back at the highlights and a view to the challenges on the road ahead.

The sobering reality is that each year, 33 million children remain unvaccinated for vaccine-preventable diseases. Universal childhood vaccination would have profound effects on leveling the health inequities in many parts of the world. As an alternative to administration of vaccines by needle and syringe, oral vaccines offer significant logistical advantages, as the polio eradication campaign has demonstrated. Over the past decade, the expression of subunit vaccine antigens in plants has emerged as a convenient, safe and potentially economical platform technology, with the potential to provide a novel biotechnological solution to vaccine production and delivery. As this technology has come of age, many improvements have been made on several fronts, as a growing number of research groups worldwide have extensively investigated plants as factories for vaccine production. This review attempts to highlight some of the achievements over the past 15 years, identify some of the potential problems and discuss the promises that this technology could fulfill.

The next 15 years: taking plant-made vaccines beyond proof of concept.

Significant potential advantages are associated with the production of vaccines in transgenic plants; however, no commercial product has emerged. An analysis of the strengths, weaknesses, opportunities and threats for plant-made vaccine technology is provided. The use of this technology for human vaccines will require significant investment and developmental efforts that cannot be supported entirely by the academic sector and is not currently supported financially by industry. A focus on downstream aspects to define potential products, conduct of additional basic clinical testing, and the incorporation of multidisciplinary strategic planning would accelerate the potential for commercialization in this field. Estimates of production cost per dose and volume of production are highly variable for a model vaccine produced in transgenic tomato, and can be influenced by the optimization of many factors. Commercialization of plant-made vaccine technology is likely to be led by the agricultural biotechnology sector rather than the pharmaceutical sector due to the disruptive nature of the technology and the complex intellectual property landscape. The next major milestones will be conduct of a phase II human clinical trial and demonstration of protection in humans. The achievement of these milestones would be accelerated by further basic investigation into mucosal immunity, the codevelopment of oral adjuvants, and the integration of quality control standards and good manufacturing practices for the production of preclinical and clinical batch materials.

Opportunities for recombinant antigen and antibody expression in transgenic plants--technology assessment.

Plants are now gaining widespread acceptance as a general platform for the large-scale production of recombinant proteins. The principle has been demonstrated by the success of a diverse repertoire of proteins, with therapeutic molecules showing the most potential for added value. Over the past 10 years, several efficient plant-based expression systems have emerged. However, a number of issues remain to be addressed before plant bioreactors can be accepted and adopted widely in preference to the established microbial and mammalian platforms. Overcoming bottlenecks imposed by low yields, poor and inconsistent product quality and difficulties with downstream processing are the most important goals for researchers working in this field. The achievement of these goals is conditional on the development of extraction and processing steps that comply with GMP standards, including extensive quality assurance and control procedures. Such rigorous and validated standards should be combined with measures applied earlier in production to ensure product sustainability and quality, such as the use of master seed banking procedures. Moreover, there are several further challenges concerning topics of environmental impact, biosafety and risk assessment, which reflect the release of transgenic plants, as well the safety of the plant-derived products themselves. We are facing a growing demand for protein diagnostics and therapeutics, but lack the capacity to meet those demands using established facilities. A shift to plant bioreactors may, therefore, become necessary within the next few years, making it more imperative that the technical and regulatory limitations are addressed and solved. The production of pharmaceutical proteins in plants will only realize its huge potential if the products are provided at consistent high quality levels, allowing the delivery of clinical grade proteins that will gain regulatory approval and which can be used routinely in clinical trials.

Plants as bioreactors for biopharmaceuticals: regulatory considerations.

Plants are one of several novel hosts that can be used for the production of recombinant biopharmaceuticals such as cytokines, hormones, monoclonal antibodies, enzymes and vaccines. The novelty of this technology and its wide range of potential applications require an assessment of possible regulatory concerns in the clinical development of plant-derived biopharmaceuticals. General principles extrapolated from experience gained with biotechnology products from other sources can serve as a foundation to develop scientifically sound strategies for the large-scale production and clinical development of safe and effective biopharmaceuticals in plant hosts.

Experience with veterinary vaccines in warm climates.

After a short description of the African laboratories manufacturing veterinary vaccines, the authors explain the main constraints for the use, in the field, of veterinary vaccines in warm climates. The need to respect the cold chain from the supplier of vaccines to the recipient animal is emphasised. In the Ivory Coast, during national vaccination campaigns, it has been proved that the quality of the rinderpest and contagious bovine pleuropneumonia vaccines is satisfactory when there is no disruption in the cold transport services. The data of this survey are exposed. In the framework of a project entitled "Thermostable rinderpest Vaccine, Transfer of Technology", a thermostable vaccine has been developed. It is manufactured in different African laboratories and integrated in some Pan African Rinderpest Campaign (PARC) vaccination programmes. On the other hand, the prospects offered by new thermotolerant attenuated vaccines against Newcastle disease are exposed. Finally, the authors present an outlook on the development of thermoresistant veterinary vaccines, such as those produced by genetic engineering, in particular with pox virus vectors.

Assessment of retrovirus-expressed nucleoprotein as a vaccine against lethal influenza virus infections of chickens.

Hemagglutinin-based influenza vaccines stimulate protection in chickens that is limited to the serotype of the expressed hemagglutinin. To evaluate whether a more highly conserved influenza virus protein might stimulate a broader protective response, the influenza virus nucleoprotein (NP) was introduced into a retroviral vector (mRCAS/NP). NP is an internal influenza virus protein that has been shown to stimulate cytotoxic T-cell responses in influenza-virus-infected mice. Cells infected with mRCAS/NP expressed approximately 10% of the level of NP observed in influenza-virus-infected chicken embryo fibroblasts. Immunocompetent chicks were vaccinated intramuscularly with approximately 1 x 10(5) NP-expressing units of mRCAS/NP. Four weeks later, chicks were bled and challenged with a highly pathogenic avian influenza virus (A/Chicken/Victoria/1/85). The NP-expressing vector stimulated an influenza-virus-specific response, as indicated by the presence of antibody to NP, but failed to protect against the lethal challenge.