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The São Paulo School of Advanced Sciences on Vaccines (SPSASV 2018) was held in the city of Santos, Brazil, from November 22nd to December 2nd 2018. The chosen venue was the elegant Hotel Mendes Plaza Hotel in Located in the heart of the Gonzaga, the most traditional neighborhood of Santos, one block from the beach. Attended by 80 PhD students, post-docs and independent researchers from 37 different countries, the SPSASV 2018 provided a critical and comprehensive view of the state of the art in vaccine research. During the 10 days, a variety of topics in immunization and vaccine development were discussed in more than 38 lectures, 54 oral-presentations and 2 days of poster sessions. Furthermore, the participants were encouraged to work in groups to propose and present a project for vaccine development, in a grant application model. This report highlights some of the knowledge shared at SPSASV 2018.
History of vaccination and its global impact
As properly addressed in the opening lecture by Dr. Oscar Bruna-Romero (Federal University of Santa Catarina, Brazil), vaccines along with sanitation and antibiotics have dramatically increased words life expectancy. Since its first documentations in the 15th century describing the attempts of Middle Eastern and Asian cultures to prevent small-pox infection, vaccination has evolved from an empirical to a rational and technological approach [1]. The first known vaccine trial was performed by Edward Jenner in the late 18th century, by taking cow-pox pustules from a milkmaid and inoculating an 8-year-old boy [2]. The procedure — named 'vaccination' from vacca, the Latin word for cow — became widespread and was used with few modifications until smallpox was fully eradicated [1]. Nearly a century after, another leap of knowledge was acquired when Louis Pasteur developed the rabies vaccine using the principle of attenuation [3]. This, combined with the ability to grow viruses in tissue culture was a crucial step in prevention of infectious diseases allowing the formulation of inactivated vaccines for multiple infectious diseases, including typhoid, plague and cholera [1]. The third phase of vaccines development occurred during the 1950s and 1960s with the ability to produce recombinant proteins, enabling the production of safer and cheaper vaccine candidates using specific antigens from various infectious agents [4]. Although, despite being safer, subunit vaccines demonstrated to be less immunogenic [5, 6]. That, led to the development of immunostimulatory molecules in the beginning of the 20th century, known as adjuvants [5]. Since their discovery, adjuvants play a crucial role in increasing the potency and efficacy of vaccines being widely incorporated in their formulations [6]. Nowadays, the use of reverse and structural vaccinology, combined with synthetic biology, resulted in a technological revolution in the field of vaccination, delivering novel and safer vaccines [1]. Further, the application of systems biology to vaccine development is allowing the identification of novel biomarkers that can be used to predict vaccine efficacy, thereby avoiding large-scale efficacy trials [7]. The more the vaccinology advances, more the infection-associated morbidity and mortality significantly decrease. At the present time, vaccines are responsible for 2.5 million deaths prevented annually [8] and this rate tends only to increase.
The Word Health Organization (WHO) priorities and challenges for new vaccines development
Despite all advances in the development of vaccines, several diseases remain not preventable through vaccination. And, for some diseases such as tuberculosis, the currently available vaccine, although very effective in children, leave adolescents and adults unprotected. Therefore, the need of novels, safe, widely applicable and more effective vaccines is undeniable. But, where to start? This issue was presented by Dr. Ricardo Palacios (Butantan Istitute, Brazil). WHO is the unanimous guidance when comes to the assessment of unmet public health need in vaccine development [9]. The identification of pathogens for which WHO will focus its resources undertake several candidates pipelines reviews and landscapes analyses [9]. The WHO R&D Blueprint works on the basis of a list of identified priority diseases that could cause outbreaks. For each disease an R&D roadmap is created, followed by target product profiles such as indication, target population, dosing regimen, duration of protection, route of administration, safety and efficacy requirements [10]. Despite potential outbreaks diseases, WHO also identifies research gaps of particular relevance to low- and middle-income countries, and provide guidance for new vaccines in these areas. Currently, among the priority diseases for vaccine developments are: Dengue, HIV, Influenza, Zika, RSV, Malaria, Meningitis, Tuberculosis and Group B Streptococcus [11]. Although needed, commercially viable vaccines and trials remain harder to conduct, typically taking more than 10 years. That, along with complex regulations and laws that vary from country to country can delay vaccines to be released. In an attempt to overcome these barriers, new models for funding vaccine developments, combining intergovernmental institutions, such as the WHO, governments, industry, academia and philanthropy institutions must occur. A good example of that is the Coalition for Epidemic Preparedness Innovations – CEPI, which finance and coordinate the development of new affordable vaccines, along with work with industry, regulators and other bodies, ensuring that any vaccines developed get licensed and reach the people who need them. Lastly, efforts in the vaccine research field must consider Dr. Palacios following advices: I- Learn about the target product profile for vaccines (check samples on WHO R&B Blueprint website, note differences in use i.e. preventive or outbreaks, compare with CEPIs calls); II- Learn about diseases (verify annual priority diseases, both short and long list provided by WHO R&B Blueprint); III- Learn about vaccines platforms to deliver antigens; IV- Learn about intellectual properties; and V- Learn about production process.
Antigen expressing systems
Vaccines production can demand huge amounts of recombinant proteins. When comes to protein production systems, chemical synthesis are expensive, demands lots of efforts and does not produce soluble active proteins. Extractions from living cells generally have low yield, require purification, presents bioethical issues and can consume a large amount of resources. Yet, recombinant protein expression in vivo highly depends on compatibility between host and cell protein, usually resulting in low success rates or low expression levels. Cell-free systems, such as E. coli, although low cost and well established, do not allow post‐translational modifications and have failed, in many cases, to express the proteins in full-length, or in soluble forms. So, as conventional systems of proteins production present lots of limitations, Dr. Takafumi Tsuboi (Ehime University, Japan) presented at SPSASV 2018 a new technology known as the ‘wheat germ cell free system’ (WGCFS). This eukaryotic expression system is suitable for the expression of bacteria, mammalian, plant, virus and parasites proteins. It is also a robust technique, presenting wide optimal experimental conditions and usually no requirement of codon optimization. Furthermore, it is flexible, allowing the production of multiple proteins or complexes, labeling and post-translational modifications. WGCFS instruments are fully automated, using pipetting robots in combination with reaction chamber, and can perform both small‐scale expression reactions on large throughput (384 reactions per run) or large‐scale protein production providing hundreds of milligrams of protein from re‐feeding experiments [12].
Mucosal immunity and vaccines
Mucosal immune responses are the first line of defense against potential injuries from the environment [13]. Therefore, immunizations of mucosal surfaces — that is, oral, nasal, sublingual, rectal and genital tract vaccines — can efficiently induce local protection against the majority of infectious agents. In addition, mucosal vaccines are also practical for mass vaccination due to its ease administration and better compliance. Currently only a few mucosal vaccines are commercially available. Dr. Denise Morais da Fonseca and Dr. Luís Carlos de Souza Ferreira (University of São Paulo, Brazil) addressed this issue during SPSASV 2018. The discrimination between non-dangerous and dangerous antigens by the mucosal immune system is crucial to avoid harmful inflammatory responses against food and to maintain a dynamic equilibrium with commensal bacterias [13]. Hence, in order to be effective, mucosal vaccines must overcome tolerance and induce proper immune response. For that, adjuvants or delivery systems are crucially needed [14]. Moreover, due to its size, the induction of protective immunity in the mucosal tissues is quite challenging. Mucosal vaccines can act mainly through the induction of antigen-specific secretory IgA (SIgA) production or through induction of effector T cells, especially Th17. The administration route usually induces a stronger immune response at the site of vaccine exposure and in anatomically adjacent mucosal sites; e.g. intranasal immunization efficiently stimulates a protective immune response in the lungs and upper respiratory tract but it is rather poor at stimulating distant sites as gut [15]. Despite the administration route, Dr. Denise also pointed out that the microbiome composition exerts a significant influence on mucosal immune regulation and, therefore, can be a factor in determining the effectiveness of mucosal vaccines. This field remains quite unexplored. The possibility to provide passive protection in infants through the maternal milk, using mucosal vaccination, were also addressed Dr. Luís Carlos. In an animal model, he demonstrated that vaccine-specific milk antibodies are protective against Escherichia coli in nursing pups [16]. This could lead to a new level of immunization possibilities, by vaccinating mothers to preventing neonates’ mortality. Lastly, although there are many particulate delivery systems being tested, new candidates remain needed in order to avoid antigen enzymatic degradations and assure potent activation of the immune system with long‐lasting immunological memory.
Cancer vaccines
Vaccinology is no longer a field directed only to prevent infectious diseases. Nowadays several groups are working on the development of vaccines against non-infectious diseases such as cancer, atherosclerosis, and diabetes. Named as ‘Therapeutic Vaccines’, this products aims not to prevent the establishment of those diseases, but to actively stimulate the immune system to target and properly fight them. The main challenge of this type of vaccination is that it must be able to overcome an immune system that has been restrained by tolerizing or polarizing mechanisms that sustain the established disease [17]. As addressed by Dr. José Alexandre M. Barbuto (University of São Paulo, Brazil), the knowledge that malignant cells express both self- and non-self-antigens generated interest in vaccination strategies that could induce immune responses specific to those tumor-antigens. DC are the most refined presenting cells in our body, their ability to connect innate and adaptive immune responses makes them crucial players in redirecting the immune system [18]. Hence, as they are able to orchestrate both cellular and antibody-mediated responses [18], many cancer therapeutic vaccines approaches attempt to engage the immune system to combat the tumor through DC inducement [19, 20]. The problem is that tumor environment can alters DC distributions, numbers, phenotypes and induce an impairment of activation [21]. The transfusion of DC obtained from healthy donors and simulated ex-vivo with tumor-antigens might be an alternative to bypass that problem [22]. Although stimulation can be done using many forms of tumor-antigens, including peptides, proteins, nucleic acids, vesicles or cells obtained from biopsies [22], Dr. Barbuto demonstrated in his studies that fusing dendritic cells with tumor cells, generate hybrids that induce tumor-specific immune responses more effectively than the simple mixture of dendritic and tumor-cells [23]. He also presented a case report describing the involution of metastatic lesions caused by renal cell carcinoma following therapy with hybrid dendritic-tumor cells [24]. Despite the promising results of these studies, the necessity to obtain cells donated from healthy individuals combined with the need of accessible tumors to generate the hybrid is a hurdle to this type of approach and many improvements are needed.
The reduction of antibiotic therapy by vaccination: a gap in fish farming field
Despite its role on preventing and treat human diseases, vaccination can also be important to animal health and to environment by reducing antibiotic therapy. Especially when comes to commercial large-scale animal breeding. It is worth noting that during SPSASV 2018 two projects were presented by attendants aiming to reduce antibiotic therapy in fish farming through vaccination. Currently there are only a few commercially available fish vaccines, and, besides that, vaccination must be performed individually by taking fishes out of their tanks, which can be laborious and stressful. Therefore, the development of new strategies and formulations to optimize the vaccination processes and coverage in this field are extremely necessary.
Beyond vaccinology: Innovation, Intellectual property and feasibility
The legal instrument that guarantees the interest of privet companies to investing in research and development for new vaccines are patents. Patents allow a 20-year monopoly of the vaccine developed, and due to that, Dr. Cesar Lopez Camacho (University of Oxford, UK), during a brief talk, advised scientists to consider applying for a patent before publish elsewhere. To him, new vaccines candidates’ studies must be suitable to patents and take into account the feasibility of a large scale production in order to have a chance to progress in clinical trials. Further, the process of reading patents already registered should be part of every new vaccine project. And, the more patents read, the better the chances to protect the intellectual property, and lower the chances of wasting time developing something that has been thought before.