5. Vaccine R&D
The consultation exercise on the key R&D needs covered both needs for prophylactic and therapeutic vaccines. The consultation was organised around three main areas of focus, for which short and medium term investment is considered key:
- Antigen selection and vaccine Design, encompassing more specifically host-pathogen interaction, B-cell & T-cell immunology, structural vaccine approach
- Novel technologies & Routes of Immunisation to enable innovation in the field mainly through adjuvants, vectors, alternative route of immunisation and prime-boost strategies
- Clinical studies and Data Interpretation with key topics being biomarkers of vaccine safety and efficacy and tools to facilitate data management and use.
One overarching gap identified as relevant across R&D has been the need for a multidisciplinary approach including microbiology, immunology, structural biology and bioinformatics. Scientific advances have enabled a paradigm shift from an empirical approach of ‘isolate, inactivate and inject’ to the more rational approach of ‘sequence, select and synthesise’. Participants highlighted the fact that such a rational approach inherently depends on a deep mechanistic understanding, which will rely on a continuous improvement in the underlying sciences, including highest quality novel immunology and pathogen biology, as well as, an optimised systems approach to data sharing and analysis. Here below are reported the main outcomes of the IPROVE consultation process for each of the sub-themes identified above and around which the stakeholder consultation was organised.
ANTIGEN SELECTION AND VACCINE DESIGN
Gaps and Challenges
The lack of full understanding of the pathogen and the host-pathogen interactions certainly represents a key challenge for vaccine developers. Infectious pathogens for which a vaccine still does not exist often present complex life cycles, and even though several antigens could be feasible targets of protective responses at distinct phases during the cycle, such antigens are often polymorphic. Traditional development approaches are thus not viable. A rational approach inherently depends on a better understanding of pathogens and the immunology of key antigens, as well as, host-pathogen interaction17 18 19. A clear understanding of the protective human immune response to infection is thus key to selecting and designing the right vaccine antigens. this calls for research investment and support to identify new generation assays for human b and t cell responses.
By using novel human B cell technologies, it is now possible to identify human monoclonal antibodies that inhibit pathogen infection or promote pathogen killing. These antibodies can be used to discover protective antigens for use in novel vaccines. In some cases, it has been possible to identify and isolate antibodies that broadly neutralise viral infections by targeting conserved sites present in viral protein antigens, such as influenza hemagglutinin or HIV gp120. The information derived from these antibodies can instruct the design of novel antigens focused on protective epitopes. However, little has been achieved in designing immunogens able to elicit antibodies with the same properties. More research on structural vaccinology and on the evolution of the antibody response starting from germline precursors is needed to design innovative antigens eliciting cross-reactive antibodies.
Recommendations for EU level action
- It is agreed among the expert community that the EU should support an integrated and multidisciplinary approach to antigen selection, adapted to the characteristics of the pathogen and target disease. This should include multi-disciplinary research programs, as well as training across expertise, notably training scientists in both biology and information technology in order to harness the potential of IT advances in the field
- In order to support a better understanding of pathogens and host-pathogen interaction, the stakeholder consultation pointed to the following priority areas for investment:
- Incentives and funding should specifically cover research into the knowledge base on host-pathogen interactions in vivo (e.g. representative strain collections, molecular epidemiology to define antigen variability and strain coverage, molecular modelling, high-throughput crystallography, high-throughput epitope mapping, particularly for therapeutic vaccines)
- Specific investment to refine animal models in order to maximise relevance to infections in humans
- As for the better understanding of human immune response, the consultation highlighted the need to further support research related to the following topics:
- New generation assays able to screen as rapidly as possible for antibody and T cell functions relevant to human infection
- Exploration of emergent in-vitro bioassay technologies (e.g. organ-on-a-chip and human tissue engineering and in-silico approaches)
- Improved in vitro assay for antibody functional screening (e.g. neutralisation, ADCC, complement dependent killing)
- Epitope selection and analyses are of particular relevance for all novel vaccine research, including therapeutic vaccines
- Support development of new bioinformatics tools applied to genomics, antigen diversity and antigen expression
- Finally, specific support for structural vaccinology is key, as to fully enable exploiting the knowledge derived from human immunology and molecular microbiology and translating it into more effective antigens.
NOVEL TECHNOLOGIES AND ROUTES OF IMMUNISATION
1. The need for novel adjuvants
Adjuvant expertise is high in Europe, yet there is an increasing need for novel adjuvants for preventive and therapeutic vaccines targeting infectious diseases for which conventional formulations have failed. New adjuvants are also needed to improve existing vaccines in different population groups for which the activity of current adjuvants may differ, e.g. the elderly, infants and chronically infected subjects that mount a suboptimal immune response to vaccination. For example, the expression of pattern recognition receptors is different in cells from new-borns and young adults, requiring adjuvants targeted for specific age groups. The development of more effective vaccines adapted to the pathogens and to the target population will require novel adjuvants, rationally designed and formulated based on the knowledge of their molecular mechanism of action.
Although several types of adjuvants have been identified and tested in different laboratory settings – be it in academia or industry – only very few have been approved by regulatory authorities. The mechanisms by which some traditional adjuvants approved for human use such as alum or emulsions, can induce an immunogenic response are still unclear and need to be further investigated to direct their rational use. A new generation of adjuvants would use compounds with well-known and characterised molecular and cellular targets that are optimised to enhance the nature,
quality and breadth of the immune response, using pharmacokinetic and pharmacodynamic properties that optimise impact whilst minimising reacto-genicity and safety concerns. More robust and reliable assays have emerged that can be successfully applied to the study of the immune response to adjuvanted vaccines using a systems biology approach. Traditional adjuvants enhancing vaccine’s immunogenicity may not be sufficient for effective therapeutic vaccines. The success of immunotherapy of cancer using monoclonal antibodies targeting checkpoint inhibitors such as CTLA4 and PD1 suggests that a combination of adjuvants and checkpoint inhibitors may represent an attractive strategy for therapeutic vaccines.
In addition, combinations of adjuvants which may increase vaccine efficacy and safety should be systemically investigated and the molecular and immunological mechanisms of action of these combinations should be characterised in detail. Their rational combination in heterologous prime-boost schedules should also be pursued. Finally, a particular need within adjuvants is the development of mucosal adjuvants enabling effective needle-free subunit vaccines. Several adjuvants have been efficiently tested in preclinical models, however none of them is currently available for humans, which makes the development of mucosal vaccines based on purified antigens very difficult.
2. The development of vaccine vectors needs to be accelerated
Viral vectors are attenuated or non-pathogenic viruses, genetically modified to express an inserted gene and generate strong antigen specific humoral and cellular responses. In particular, they can generate CD8 responses that are hard to induce with inactive or subunit vaccines, even in the presence of strong adjuvants. A broad spectrum of replicating and non- replicating vectors is available but their functioning mechanisms and risks require further investigation.
The area of vaccine vectors requires significant work to better understand the impact of pre-existing anti- vector immunity on efficacy (for instance Ad5 vector in the HIV trials20) and to address questions about safety raised by experiences. Another obstacle to be overcome is that many of the centres of excellence are specialised in only one vector or vector family. Innovation and development of heterologous prime- boost strategies would benefit from more collaboration between these groups, as shown in the context of the Ebola vaccine development to respond to the most recent outbreak.
The IPROVE consultation stressed the need for further research to better master the technology and secure its safe and appropriate use. It also identified a need to improve and develop new vectors as well as better defining their usage. One of the limitations of viral vectors is the interference of anti-vector immunity, which often decreases their potency and the ability to boost after a first dose. A potential solution is the use of fully synthetic nucleic acid vectors (e.g. nanocarriers, virosomes, ISCOMs, liposomes) based on DNA, messenger RNA or RNA replicons delivered to the cells by non-antigenic delivery systems or by electroporation. So far these vectors have been less potent in humans than viral vectors, however work aimed at improving their potency could have a strong impact in future development of effective CD8 vaccines. Another promising approach is the prime-boost strategy, based on priming the immune system to a target antigen delivered by a vector and then selectively boosting the secondary response by using a different vaccine formulation (e.g. a different vector or a recombinant protein). This approach is specifically aimed at the generation and enrichment of high avidity T cells and antibodies specific for the target antigen.
3. Alternative routes of immunisation are still needed
One of the major needs highlighted by the participants is the development of novel strategies for mucosal vaccination using purified subunit antigens. The low immunogenicity and weak stability of free protein antigens in the mucosal settings, requires an optimised vaccine formulation and delivery, suitable for the immunisation route selected. Adjuvants and/or delivery systems to be used for intranasal vaccination should induce the required immune responses, be safe and avoid reactogenicity. Other routes for inducing mucosal immunity include the sublingual, vaginal, rectal and transcutaneous routes. Sublingual administration is a promising approach that results in induction of mucosal and systemic T cell and antibody responses with a broad dissemination to different mucosae, including the gastrointestinal and respiratory tracts, and the genital mucosa. Many of these data, obtained in animal models, need to be confirmed in human studies. The development of topically administered vaccines, whether for mucosal or transcutaneous administration, requires efficient delivery devices, able to deliver the vaccine directly to the key immune cells. Needle-free technologies, like inhalers, nasal sprays, forced air injectors and patches, by virtue of their potential for improved efficacy and better patient compliance, are promising and effective vaccine delivery strategies need to be further researched and developed.
Recommendations for EU level action
The EU should support research and innovation activities for the rational development of novel immunisation technologies with a particular focus on vaccine adjuvants, novel delivery and prime-boost strategies. The Commission should support multidisciplinary R&D with the aim of addressing the above described unmet needs. The following set of specific recommendations for future research was formulated through the IPROVE consultation:
- Need for multidisciplinary research and innovation on vaccine adjuvants:
- Create a toolbox of adjuvants, with a well-defined profile to shape the immune response, which can be applied to vaccines against diverse pathogens
- Employ systems/omics analysis of the effect of vaccine adjuvants on the immune response to vaccines, to help define biomarkers of adjuvants’ activity both in animals and humans
- Head-to-head comparison of vaccine adjuvants
- Focussed research on vaccine adjuvants formulation
- Conduct cross species (rodents, NHP and humans) studies of vaccine adjuvants to pinpoint predictability of animal models for adjuvant research
- Develop toxicology research on adjuvant-induced inflammation: better animal models or human immunological investigations to evaluate local, regional and systemic effects, as well as, to understand mechanisms of adjuvant-induced inflammation
- Combine different adjuvants in prime-boost studies (i.e. using a different adjuvant for primary immunisation and boosters) to optimally direct the immune response
- Develop new adjuvants, new adjuvant formulations and adjuvant combinations to be used to improve vaccines adapted for the needs of specific target populations (i.e. elderly, infants, immune-compromised…)
- Develop vaccine adjuvants for mucosal administration
- Needs for research and innovation on vectors and novel routes of immunisation:
- Move towards a more evidence-based combination of vectors and other type of “carriers” (nanoparticles, nucleic acids), adjuvants, routes and schedule of immunisation
- Evidence-based development of heterologous prime- boost strategies for the induction of broad and long- lasting immunity
- Development of more potent synthetic vectors based on both conventional antigens and nucleic acids for rapid response to pathogens outbreaks
CLINICAL STUDIES AND DATA INTERPRETATION
Gaps and Challenges
The innovative design of clinical trials aims to allow for clinical studies’ acceleration and optimal use of the outcomes to demonstrate vaccines efficacy and safety. The gaps identified through the consultation mainly revolve around two aspects: finding the way forward to harmonise and standardise clinical data collection and analysis as well as finding better focused designs to reduce the size, lengths and costs of clinical trials.
There are few predictive biomarkers for vaccine safety beyond the common biologically predictable events. This makes large phase 2 & 3 clinical studies necessary. Equally, immunological biomarkers/predictors of vaccine efficacy are lacking for many disease targets. Identifying these biomarkers is challenging because they may be complex combinations of several biological responses. Further advances in this field require overcoming several challenges:
- Design clinical investigations around better and more clearly defined questions versus an ‘opportunistic’ approach
- Profile in-depth genetic background and baselines before vaccination of volunteers using systems biology approaches and conduct the investigation over a long run; and focus on outliers (non-responders, high reactogenic, high immune response, etc.)
- Develop new mathematical models and bioinformatics tools to extract biological knowledge from data sets: invest in new tools to compare biomarker data from recent clinical trials with data collected in the past on both licensed and failed vaccine candidates
- Allow for more collaborative work, which requires from the research community to better align the techniques and samples to be favoured for each purpose (e.g. muscle biopsy for reactogenicity analysis vs. blood samples for vaccines efficacy…)
- Anticipate and involve regulators early enough in such definitions, in order to accelerate clinical developments
Harmonisation and, to a certain degree, standardisation of data analysis frameworks is lacking, posing a big challenge to pooled data analysis. Different research groups use different analytical softwares, and data sets can be difficult to compare without pooling. The integration of different data sources has not sufficiently been addressed. In addition, there is a need for setting standards and norms for data collection, storage and analysis as well as ontologies and harmonisation of semantics, and a new language for adverse event coding. These will all facilitate data comparison and pooled analyses.
Recommendations for EU level action
- Enable access to “big data” at the micro and macro level through the following actions:
- European research should continue supporting projects to identify ways to simplify data collection and analysis. It should also enable comparability and developing capacity to extract biologically relevant knowledge from the data to generate innovation
- More efficient quality control on data collection, analysis, reporting and standardisation is key and the link between bioinformatics competencies and clinical and experimental data should be strengthened
- Clinical trials must be smartly designed around clear and specific questions to avoid informational pitfalls
- Create a framework to sustainably fund the structures/ institutions that will enable data to be aggregated at different levels and inclusive of data descriptors, pushing towards investment in the following areas:
- Semantics harmonisation, making available data on candidate vaccines, including abandoned projects to help learning and better understanding safety issues
- Explore different computational analyses and ways of visualising the data
- Establish a working group for concluding on biomarkers and harmonised processes
- Develop more research concentrated on identifying innovative design of clinical trials and methodologies to profile volunteers in advance. To do so, it will be essential to focus on outliers and have already from the onset the possibility of doing further in-depth studies and increase predictability of vaccination outcomes
- Rapidly develop multi-parametric technologies in cell biology as to provide deep insight in basic mechanisms, potentially identifying predictive markers and algorithms
- Develop expertise and support infrastructures for performing controlled challenges in humans
- Secure a European environment for clinical trials e.g. by having public operational Groups who can manage the tasks between idea and first human data
- Set up collaborative cost-sharing programmes in the EU and at international levels (transatlantic, Asia) to facilitate access to advanced technologies, large populations, rare outcomes, and avoid duplication in investments
R&D – Antigen selection
|GAPS & CHALLENGES||Recommendations|
|Lack of understanding of pathogen and host-pathogen interactions||
|Lack of understanding of the protective human immune response to infection||
|Successful application of structural vaccinology and design effective vaccine antigens||
R&D – novel technologies & routes of immunisation
|GAPS & CHALLENGES||Recommendations|
|Need for novel adjuvants:
|Needs for acceleration of vectors development
||Vectors & Routes of Immunisation:
|Needs for alternative routes of administration
R&D – clinical studies & data interpretation
|GAPS & CHALLENGES||Recommendations|
|Innovative design and harmonisation of clinical trials data and development of analyses frameworks||
|Lack of clear biomarkers of safety in vaccines, and correlates of protection and of efficacy||
18 Zielinski et al. (2011), Dissecting the human immunologic memory for pathogens
19 Aebischer (2014), Leishmania spp. Proteome data sets: a comprehensive resource for vaccine development to target visceral leishmaniasis
20 Delany et al. (2014) Vaccines for 21st century, EMBO Mol Med June 6(6); 708-720