Neglected tropical disease vaccines

The neglected tropical diseases or ‘NTDs’ represent the most common infections of the world's one billion poorest people. Unlike the better known acute or emerging infections, the NTDs are generally chronic and disabling (and often disfiguring) conditions. The long-term disability they cause has been revealed as a major reason why poor people in developing countries cannot escape the poverty trap. Because NTDs are associated with poverty, vaccines against these conditions are sometimes referred to as antipoverty vaccines. However, despite their global public health and economic importance, such vaccines have largely been ignored by industry and today are predominantly being produced through the activities of non-profit product development partnerships (PDPs). The Human Hookworm Vaccine Initiative based at the Sabin Vaccine Institute is one such PDP developing two antipoverty vaccines for hookworm and schistosomiasis, respectively. It has been proposed to combine these vaccines in order to target polyparasitic co-infections leading to severe anemia. Ultimately, to ensure global access of a multivalent anthelminthic vaccine, it may be linked to deworming programs through vaccine-linked chemotherapy. This would be an important step towards achieving the Millennium Development Goals for sustainable poverty reduction by 2015.     

Biotechnology to improve health in developing countries -- a review

The growing health disparities between the developing and the developed world call for urgent action from the scientific community. Science and technology have in the past played a vital role in improving public health. Today, with the tremendous potential of genomics and other advances in the life sciences, the contribution of science to improve public health and reduce global health disparities is more pertinent than ever before. Yet the benefits of modern medicine still have not reached millions of people in developing countries. It is crucial to recognize that science and technology can be used very effectively in partnership with public health practices in developing countries and can enhance their efficacy. The fight to improve global health needs, in addition to effective public health measures, requires rapid and efficient diagnostic tools; new vaccines and drugs, efficient delivery methods and novel approaches to therapeutics; and low-cost restoration of water, soil and other natural resources. In 2002, the University of Toronto published a report on the "Top 10 Biotechnologies for Improving Health in Developing Countries". Here we review these new and emerging biotechnologies and explore how they can be used to support the goals of developing countries in improving health.     

Easing the global burden of diarrhoeal disease: can synthetic biology help?

The Millennium Declaration committed the 193 member states of the United Nations to end poverty by 2015. Despite the efforts of the UN and World Health Organisation, and the G8 commitment to spend a fixed proportion of gross national income on overseas aid, more than 2.6 billion people still lack access to proper sanitation. The absence of effective public health strategies in developing countries results in significant health burdens following gastrointestinal infections. Diarrhoea associated with infections resulting from oral-faecal contamination is the second leading cause of death in children under 5 years of age, primarily in Africa and South Asia. Currently there are no appropriate vaccines that could be easily administered on a global scale to prevent these infections. Synthetic biology has the potential to contribute to development of such vaccines. Our work is directed at developing a range of multivalent oral vaccines against the most common diarrhoea-causing bacteria, e.g., Escherichia coli, Shigella and Salmonella. If synthetic biology is to avoid the suspicion and possible revulsion of the public, scientists need to demonstrate that this new field has something real to offer.     

Twenty-first century vaccinomics innovation systems: capacity building in the global South and the role of Product Development Partnerships (PDPs)

The availability of sequence information from publicly available complete genomes and data intensive sciences, together with next-generation sequencing technologies offer substantial promise for innovation in vaccinology and global public health in the beginning of the 21st century. This article presents an innovation analysis for the nascent field of vaccinomics by describing one of the major challenges in this endeavor: the need for capacities in "vaccinomics innovation systems" to support the developing countries involved in the creation and testing of new vaccines. In particular, we discuss the need for understanding how institutional frameworks can enhance capacities as intrinsic to a systems approach to health technology development. We focus our attention on the global South, meaning the technically less advanced and developing nations in Africa, Asia, and Latin America. This focus is timely and appropriate because the challenge for innovation in postgenomics medicine is markedly much greater in these regions where basic infrastructures are often underresourced and new or the anticipated institutional relationships can be fragile. Importantly, we examine the role of Product Development Partnerships (PDPs) as a 21st century organizational innovation that contributes to strengthening fragile institutions and capacity building. For vaccinomics innovation systems to stand the test of time in a context of global public health, local communities, knowledge, and cultures need to be collectively taken into account at all stages in programs for vaccinomics-guided vaccine development and delivery in the global South where the public health needs for rational vaccine development are urgent.     

Vaccines and global health

Vaccines have made a major contribution to global health in recent decades but they could do much more. In November 2011, a Royal Society discussion meeting, 'New vaccines for global health', was held in London to discuss the past contribution of vaccines to global health and to consider what more could be expected in the future. Papers presented at the meeting reviewed recent successes in the deployment of vaccines against major infections of childhood and the challenges faced in developing vaccines against some of the world's remaining major infectious diseases such as human immunodeficiency virus (HIV), malaria and tuberculosis. The important contribution that development of more effective veterinary vaccines could make to global health was also addressed. Some of the social and financial challenges to the development and deployment of new vaccines were reviewed. The latter issues were also discussed at a subsequent satellite meeting, 'Accelerating vaccine development', held at the Kavli Royal Society International Centre. Delegates at this meeting considered challenges to the more rapid development and deployment of both human and veterinary vaccines and how these might be addressed. Papers based on presentations at the discussion meeting and a summary of the main conclusions of the satellite meeting are included in this issue of Philosophical Transactions of the Royal Society B.     

Review of dengue virus and the development of a vaccine

Dengue viral infection has become an increasing global health concern with over two-fifths of the world's population at risk of infection. It is the most rapidly spreading vector borne disease, attributed to changing demographics, urbanization, environment, and global travel. It continues to be a threat in over 100 tropical and sub-tropical countries, affecting predominantly children. Dengue also carries a hefty financial burden on the health care systems in affected areas, as those infected seek care for their symptoms. The search for a suitable vaccine for dengue has been ongoing for the last sixty years, yet any effective treatment or vaccine remains elusive. A vaccine must be protective for all four serotypes of dengue and be cost-effective. Many approaches to developing candidate vaccines have been employed. The candidates include live attenuated tetravalent vaccines, chimeric tetravalent vaccines based on attenuated dengue virus or Yellow Fever 17D, and recombinant DNA vaccines based on flavivirus and non-flavivirus vectors. This review outlines the challenges involved in dengue vaccine development and presents the current stages of proposed vaccine candidate development.     

Red cell PMVs, plasma membrane-derived vesicles calling out for standards

Plasma membrane-derived vesicles (PMVs) or microparticles are vesicles (0.1-1 μm in diameter) released from the plasma membrane of all blood cell types under a variety of biochemical and pathological conditions. PMVs contain cytoskeletal elements and some surface markers from the parent cell but lack a nucleus and are unable to synthesise macromolecules. They are also defined on the basis that in most cases PMVs express varying amounts of the cytosolic leaflet lipid phosphatidylserine, which is externalised during activation on their surface. This marks the PMV as a biologically distinct entity from that of its parent cell, despite containing surface markers from the original cell, and also explains its role in events such as phagocytosis and thrombosis. There is currently a large amount of variation between investigators with regard to the pre-analytical steps employed in isolating red cell PMVs or RPMVs (which are slightly smaller than most PMVs), with key differences being centrifugation and sample storage conditions, which often leads to result variability. Unfortunately, standardization of preparation and detection methods has not yet been achieved. This review highlights and critically discusses the variables contributing to differences in results obtained by investigators, bringing to light numerous studies of which RPMVs have been analysed but have not yet been the subject of a review.     

Interactive learning and action: realizing the promise of synthetic biology for global health

The emerging field of synthetic biology has the potential to improve global health. For example, synthetic biology could contribute to efforts at vaccine development in a context in which vaccines and immunization have been identified by the international community as being crucial to international development efforts and, in particular, the millennium development goals. However, past experience with innovations shows that realizing a technology’s potential can be difficult and complex. To achieve better societal embedding of synthetic biology and to make sure it reaches its potential, science and technology development should be made more inclusive and interactive. Responsible research and innovation is based on the premise that a broad range of stakeholders with different views, needs and ideas should have a voice in the technological development and deployment process. The interactive learning and action (ILA) approach has been developed as a methodology to bring societal stakeholders into a science and technology development process. This paper proposes an ILA in five phases for an international effort, with national case studies, to develop socially robust applications of synthetic biology for global health, based on the example of vaccine development. The design is based on results of a recently initiated ILA project on synthetic biology; results from other interactive initiatives described in the literature; and examples of possible applications of synthetic biology for global health that are currently being developed.     

Molecular characterisation of plasma membrane-derived vesicles

Plasma membrane-derived vesicles (PMVs) are released into circulation in response to normal and stress/pathogenic conditions. They are of tremendous significance for the prediction, diagnosis, and observation of the therapeutic success of many diseases. Knowledge of their molecular characteristics and therefore functional properties would contribute to a better understanding of the pathological mechanisms leading to various diseases in which their levels are raised. The review aims at outlining and discussing the molecular characteristics of PMVs in order to bring to the fore some aspects/characteristics of PMVs that will assist the scientific community to properly understand the role of PMVs in various physiological and pathological processes. The review covers PMVs characterisation and discusses how distinct they are from exosomes and endosomes. Also, methods of PMVs analysis, importance of proper PMV level estimation/characterisation, PMVs and their constituents as well as their therapeutic significance are discussed. The review concludes by drawing attention to the importance of further study into the functions of the characteristics discussed which will lead to understanding the general role of PMVs both in health and in disease states.     

Do aluminum vaccine adjuvants contribute to the rising prevalence of autism?

Autism spectrum disorders (ASD) are serious multisystem developmental disorders and an urgent global public health concern. Dysfunctional immunity and impaired brain function are core deficits in ASD. Aluminum (Al), the most commonly used vaccine adjuvant, is a demonstrated neurotoxin and a strong immune stimulator. Hence, adjuvant Al has the potential to induce neuroimmune disorders. When assessing adjuvant toxicity in children, two key points ought to be considered: (i) children should not be viewed as “small adults” as their unique physiology makes them much more vulnerable to toxic insults; and (ii) if exposure to Al from only few vaccines can lead to cognitive impairment and autoimmunity in adults, is it unreasonable to question whether the current pediatric schedules, often containing 18 Al adjuvanted vaccines, are safe for children? By applying Hill's criteria for establishing causality between exposure and outcome we investigated whether exposure to Al from vaccines could be contributing to the rise in ASD prevalence in the Western world. Our results show that: (i) children from countries with the highest ASD prevalence appear to have the highest exposure to Al from vaccines; (ii) the increase in exposure to Al adjuvants significantly correlates with the increase in ASD prevalence in the United States observed over the last two decades (Pearson r = 0.92, p < 0.0001); and (iii) a significant correlation exists between the amounts of Al administered to preschool children and the current prevalence of ASD in seven Western countries, particularly at 3-4 months of age (Pearson r = 0.89-0.94, p = 0.0018-0.0248). The application of the Hill's criteria to these data indicates that the correlation between Al in vaccines and ASD may be causal. Because children represent a fraction of the population most at risk for complications following exposure to Al, a more rigorous evaluation of Al adjuvant safety seems warranted.     

Coronavirus and paramyxovirus in bats from Northwest Italy

Background

Bat-borne virus surveillance is necessary for determining inter-species transmission risks and is important due to the wide-range of bat species which may harbour potential pathogens. This study aimed to monitor coronaviruses (CoVs) and paramyxoviruses (PMVs) in bats roosting in northwest Italian regions. Our investigation was focused on CoVs and PMVs due to their proven ability to switch host and their zoonotic potential. Here we provide the phylogenetic characterization of the highly conserved polymerase gene fragments.

Results

Family-wide PCR screenings were used to test 302 bats belonging to 19 different bat species. Thirty-eight animals from 12 locations were confirmed as PCR positive, with an overall detection rate of 12.6% [95% CI: 9.3–16.8]. CoV RNA was found in 36 bats belonging to eight species, while PMV RNA in three Pipistrellus spp. Phylogenetic characterization have been obtained for 15 alpha- CoVs, 5 beta-CoVs and three PMVs; moreover one P. pipistrellus resulted co-infected with both CoV and PMV. A divergent alpha-CoV clade from Myotis nattereri SpA is also described. The compact cluster of beta-CoVs from R. ferrumequinum roosts expands the current viral sequence database, specifically for this species in Europe. To our knowledge this is the first report of CoVs in Plecotus auritus and M. oxygnathus, and of PMVs in P. kuhlii.

Conclusions

This study identified alpha and beta-CoVs in new bat species and in previously unsurveyed Italian regions. To our knowledge this represents the first and unique report of PMVs in Italy. The 23 new bat genetic sequences presented will expand the current molecular bat-borne virus databases. Considering the amount of novel bat-borne PMVs associated with the emergence of zoonotic infections in animals and humans in the last years, the definition of viral diversity within European bat species is needed. Performing surveillance studies within a specific geographic area can provide awareness of viral burden where bats roost in close proximity to spillover hosts, and form the basis for the appropriate control measures against potential threats for public health and optimal management of bats and their habitats.

     

Oxidized low-density lipoprotein-dependent platelet-derived microvesicles trigger procoagulant effects and amplify oxidative stress

The fundamental mechanisms that underlie platelet activation in atherothrombosis are still obscure. Oxidative stress is involved in central features of atherosclerosis. Platelet-derived microvesicles (PMVs) could be important mediators between oxidative stress and platelet activation. CD36 could be a receptor of PMVs, thus generating a PMV–CD36 complex. We aimed to investigate the detailed pathway by which oxidative damage contributes to platelet activation by the PMV–CD36 complex. We found that oxidized low-density lipoprotein stimulated the generation of PMVs. PMVs enhanced normal platelet activation, as assessed by the expression of integrin α_IIbβ₃, secretion of soluble P-selectin and platelet aggregation, but CD36-deficient platelets were not activated by PMVs. The function of the PMV–CD36 complex was mediated by the MKK4/JNK2 signaling axis. Meanwhile, PMVs increased the level of 8-iso-prostaglandin-F2α, a marker of oxidative stress, in a CD36- and phosphatidylserine-dependent manner. We concluded that PMVs are important mediators between oxidative stress and platelet activation. PMVs and CD36 may be effective targets for preventing platelet activation in cardiovascular diseases.     

Human plasma membrane-derived vesicles halt proliferation and induce differentiation of THP-1 acute monocytic leukemia cells

Plasma membrane-derived vesicles (PMVs) are small intact vesicles released from the cell surface that play a role in intercellular communication. We have examined the role of PMVs in the terminal differentiation of monocytes. The myeloid-differentiating agents all-trans retinoic acid/PMA and histamine, the inflammatory mediator that inhibits promonocyte proliferation, induced an intracellular Ca(2+)-mediated PMV (as opposed to exosome) release from THP-1 promonocytes. These PMVs cause THP-1 cells to enter G(0)-G(1) cell cycle arrest and induce terminal monocyte-to-macrophage differentiation. Use of the TGF-β receptor antagonist SB-431542 and anti-TGF-β1 Ab showed that this was due to TGF-β1 carried on PMVs. Although TGF-β1 levels have been shown to increase in cell culture supernatants during macrophage differentiation and dendritic cell maturation, the presence of TGF-β1 in PMVs is yet to be reported. In this study, to our knowledge we show for the first time that TGF-β1 is carried on the surface of PMVs, and we confirm the presence within PMVs of certain leaderless proteins, with reported roles in myeloid cell differentiation. Our in vitro findings support a model in which TGF-β1-bearing PMVs, released from promonocytic leukemia cells (THP-1) or primary peripheral blood monocytes on exposure to sublytic complement or after treatment with a differentiation therapy agent, such as all-trans retinoic acid, significantly reduce proliferation of THP-1 cells. Such PMVs also induce the terminal differentiation of primary peripheral blood monocytes as well as THP-1 monocytes.     

Risk analysis for plant-made vaccines

The production of vaccines in transgenic plants was first proposed in 1990 however no product has yet reached commercialization. There are several risks during the production and delivery stages of this technology, with potential impact on the environment and on human health. Risks to the environment include gene transfer and exposure to antigens or selectable marker proteins. Risks to human health include oral tolerance, allergenicity, inconsistent dosage, worker exposure and unintended exposure to antigens or selectable marker proteins in the food chain. These risks are controllable through appropriate regulatory measures at all stages of production and distribution of a potential plant-made vaccine. Successful use of this technology is highly dependant on stewardship and active risk management by the developers of this technology, and through quality standards for production, which will be set by regulatory agencies. Regulatory agencies can also negatively affect the future viability of this technology by requiring that all risks must be controlled, or by applying conventional regulations which are overly cumbersome for a plant production and oral delivery system. The value of new or replacement vaccines produced in plant cells and delivered orally must be considered alongside the probability and severity of potential risks in their production and use, and the cost of not deploying this technology – the risk of continuing with the status quo alternative.     

Melioidosis vaccines: a systematic review and appraisal of the potential to exploit biodefense vaccines for public health purposes

Background

Burkholderia pseudomallei is a Category B select agent and the cause of melioidosis. Research funding for vaccine development has largely considered protection within the biothreat context, but the resulting vaccines could be applicable to populations who are at risk of naturally acquired melioidosis. Here, we discuss target populations for vaccination, consider the cost-benefit of different vaccination strategies and review potential vaccine candidates.

Methods and Findings

Melioidosis is highly endemic in Thailand and northern Australia, where a biodefense vaccine might be adopted for public health purposes. A cost-effectiveness analysis model was developed, which showed that a vaccine could be a cost-effective intervention in Thailand, particularly if used in high-risk populations such as diabetics. Cost-effectiveness was observed in a model in which only partial immunity was assumed. The review systematically summarized all melioidosis vaccine candidates and studies in animal models that had evaluated their protectiveness. Possible candidates included live attenuated, whole cell killed, sub-unit, plasmid DNA and dendritic cell vaccines. Live attenuated vaccines were not considered favorably because of possible reversion to virulence and hypothetical risk of latent infection, while the other candidates need further development and evaluation. Melioidosis is acquired by skin inoculation, inhalation and ingestion, but routes of animal inoculation in most published studies to date do not reflect all of this. We found a lack of studies using diabetic models, which will be central to any evaluation of a melioidosis vaccine for natural infection since diabetes is the most important risk factor.

Conclusion

Vaccines could represent one strand of a public health initiative to reduce the global incidence of melioidosis.     

Accelerating introduction of new vaccines: barriers to introduction and lessons learned from the recent Haemophilus influenzae type B vaccine experience

Adoption of new vaccines in developing countries is critical to reducing child mortality and meeting Millennium Development Goal 4. However, such introduction has historically suffered from significant delays that can be attributed to various factors including (i) lack of recognition of the value of a vaccine, (ii) factors related to weak health systems, and (iii) policy considerations. Recently, the Global Alliance for Vaccines and Immunization (GAVI) supported efforts to accelerate the introduction of Haemophilus influenzae type b (Hib) vaccines in developing countries, which resulted in a significant surge in vaccine adoption by these countries. The experience with Hib vaccines, as well as similar efforts by GAVI to support the introduction of new pneumococcal and rotavirus vaccines, provides a strategy for new vaccine adoption that is reviewed in this paper, providing a useful model to help accelerate the uptake of other life-saving vaccines. This strategy addresses barriers for vaccine adoption by focusing on three major areas: (i) communications to increase awareness about the various factors needed for evidence-based decisions that meet a country's health goals; (ii) research activities to answer key questions that support vaccine introduction and long-term programme sustainability; and (iii) coordination with the various stakeholders at global, regional and country levels to ensure successful programme implementation.     

Exploiting virus-like particles as innovative vaccines against emerging viral infections

Emerging viruses pose a major threat to humans and livestock with global public health and economic burdens. Vaccination remains an effective tool to reduce this threat, and yet, the conventional cell culture often fails to produce sufficient vaccine dose. As an alternative to cell-culture based vaccine, virus-like particles (VLPs) are considered as a highpriority vaccine strategy against emerging viruses. VLPs represent highly ordered repetitive structures via macromolecular assemblies of viral proteins. The particulate nature allows efficient uptake into antigen presenting cells stimulating both innate and adaptive immune responses towards enhanced vaccine efficacy. Increasing research activity and translation opportunity necessitate the advances in the design of VLPs and new bioprocessing modalities for efficient and cost-effective production. Herein, we describe major achievements and challenges in this endeavor, with respect to designing strategies to harnessing the immunogenic potential, production platforms, downstream processes, and some exemplary cases in developing VLP-based vaccines.     

Designing the next generation of vaccines for global public health

Vaccine research and development are experiencing a renaissance of interest from the global scientific community. There are four major reasons for this: (1) the lack of efficacious treatment for many devastating infections; (2) the emergence of multidrug resistant bacteria; (3) the need for improving the safety of the more traditional licensed vaccines; and finally, (4) the great promise for innovative vaccine design and research with convergence of omics sciences, such as genomics, proteomics, immunomics, and vaccinology. Our first project based on omics was initiated in 2000 and was termed reverse vaccinology. At that time, antigen identification was mainly based on bioinformatic analysis of a singular genome. Since then, omics-guided approaches have been applied to its full potential in several proof-of-concept studies in the industry, with the first reverse vaccinology-derived vaccine now in late stage clinical trials and several vaccines developed by omics in preclinical studies. In the meantime, vaccine discovery and development has been further improved with the support of proteomics, functional genomics, comparative genomics, structural biology, and most recently vaccinomics. We illustrate in this review how omics biotechnologies and integrative biology are expected to accelerate the identification of vaccine candidates against difficult pathogens for which traditional vaccine development has thus far been failing, and how research will provide safer vaccines and improved formulations for immunocompromised patients in the near future. Finally, we present a discussion to situate omics-guided rational vaccine design in the broader context of global public health and how it can benefit citizens in both developed and developing countries.     

DNA vaccines: a ray of hope

Vaccines represent the most commonly employed immunologic intervention in medicine today. DNA vaccination or genetic immunization is a rapidly developing technology that offers new approaches for the prevention of disease. This method of vaccination provides a stable and long-lived source of the protein vaccine, and it is a simple, robust, and effective means of eliciting both antibody- and cell-mediated immune responses. Furthermore, DNA vaccines have a number of potential advantages such as they can address several diseases in one vaccine, they are cheap and easy to produce and have no special cold storage requirement because they are extremely stable. It has proven to be a generally applicable technology in various preclinical animal models of infectious and noninfectious diseases, and several DNA vaccines have now entered phase I/II, human clinical trials. There are several hurdles that need to be overcome on the road to the use of DNA vaccines widely. These include the technical challenges of improving delivery and/or potency so that low doses of DNA can achieve the efficacy of conventional vaccines.     

Phospholipase A2 Isolated from the Venom of Crotalus durissus terrificus Inactivates Dengue virus and Other Enveloped Viruses by Disrupting the Viral Envelope

The Flaviviridae family includes several virus pathogens associated with human diseases worldwide. Within this family, Dengue virus is the most serious threat to public health, especially in tropical and sub-tropical regions of the world. Currently, there are no vaccines or specific antiviral drugs against Dengue virus or against most of the viruses of this family. Therefore, the development of vaccines and the discovery of therapeutic compounds against the medically most important flaviviruses remain a global public health priority. We previously showed that phospholipase A₂ isolated from the venom of Crotalus durissus terrificus was able to inhibit Dengue virus and Yellow fever virus infection in Vero cells. Here, we present evidence that phospholipase A₂ has a direct effect on Dengue virus particles, inducing a partial exposure of genomic RNA, which strongly suggests inhibition via the cleavage of glycerophospholipids at the virus lipid bilayer envelope. This cleavage might induce a disruption of the lipid bilayer that causes a destabilization of the E proteins on the virus surface, resulting in inactivation. We show by computational analysis that phospholipase A₂ might gain access to the Dengue virus lipid bilayer through the pores found on each of the twenty 3-fold vertices of the E protein shell on the virus surface. In addition, phospholipase A₂ is able to inactivate other enveloped viruses, highlighting its potential as a natural product lead for developing broad-spectrum antiviral drugs.