Vaccines for the 21st century

Innovation Partnership for a Roadmap on Vaccines in Europe (IPROVE): A vision for the vaccines of tomorrow

A clear vision for vaccines research and development (R&D) is needed if Europe is to continue to lead the discovery of next generation vaccines. Innovation Partnership for a Roadmap on Vaccines in Europe (IPROVE) is a collaboration between leading vaccine experts to develop a roadmap setting out how Europe can best invest in the science and technology essential for vaccines innovation. This FP7 project, started in December 2013, brought together more than 130 key public and private stakeholders from academia, public health institutes, regulators, industry and small and medium-sized enterprises to determine and prioritise the gaps and challenges to be addressed to bolster innovation in vaccines and vaccination in Europe. The IPROVE consultation process was structured around seven themes: vaccine R&D, manufacturing and quality control, infrastructure, therapeutic vaccines, needs of small and medium-sized enterprises, vaccines acceptance and training needs. More than 80 recommendations were made by the consultation groups, mainly focused on the need for a multidisciplinary research approach to stimulate innovation, accelerated translation of scientific knowledge into technological innovation, and fostering of real collaboration within the European vaccine ecosystem. The consultation also reinforced the fact that vaccines are only as good as their vaccine implementation programmes, and that more must be done to understand and address vaccination hesitancy of both the general public and healthcare professionals. Bringing together a wide range of stakeholders to work on the IPROVE roadmap has increased mutual understanding of their different perspectives, needs and priorities. IPROVE is a first attempt to develop such a comprehensive view of the vaccine sector. This prioritisation effort, aims to help policy-makers and funders identify those vaccine-related areas and technologies where key investment is needed for short and medium-long term success.

Vaccine vectors based on Adenovirus 19a/64 exhibit broad cellular tropism and potently restimulate HCMV-specific T cell responses ex vivo

Human Cytomegalovirus (HCMV) remains a major health burden and the development of a vaccine is a global priority. We developed new viral vectors delivering the T cell immunogens IE-1 and pp65 based on Adenovirus 19a/64 (Ad19a/64), a member of subgroup D. In this ex vivo study, the novel vectors were compared side by side to Ad5 or modified Vaccinia Ankara (MVA) strains expressing the same transgenes. We found that unlike Ad5, Ad19a/64 vectors readily transduce a broad panel of immune cells, including monocytes, T cells, NK cells and monocyte-derived dendritic cells (moDCs). Both Ad19a/64- and MVA-transduced moDCs efficiently restimulated IE-1 or pp65-specific T cells but MVA induced a higher amount of cytotoxicity in this cell type. Ad5 and Ad19 induced upregulation of CD86 and HLA-DR in moDCs whereas expression of CD80 and CD83 was largely unaltered. By contrast, MVA transduction led to downregulation of all markers. Taken together, our data demonstrate that Ad19a/64 is a promising vector for the delivery of HCMV immunogens since it transduces dendritic cells with an efficiency that is comparable to MVA, but cytotoxicity and interference with dendritic cell maturation are less pronounced.

Photosensitizer-induced self-assembly of antigens as nanovaccines for cancer immunotherapy

Under near-infrared (NIR) laser irradiation, ICG–antigen conjugate-based nanovaccines enhanced the cross-presentation of antigens and induced cytotoxic T lymphocyte response.

Ebola virus - epidemiology, diagnosis, and control: threat to humans, lessons learnt, and preparedness plans - an update on its 40 year's journey

Ebola virus (EBOV) is an extremely contagious pathogen and causes lethal hemorrhagic fever disease in man and animals. The recently occurred Ebola virus disease (EVD) outbreaks in the West African countries have categorized it as an international health concern. For the virus maintenance and transmission, the non-human primates and reservoir hosts like fruit bats have played a vital role. For curbing the disease timely, we need effective therapeutics/prophylactics, however, in the absence of any approved vaccine, timely diagnosis and monitoring of EBOV remains of utmost importance. The technologically advanced vaccines like a viral-vectored vaccine, DNA vaccine and virus-like particles are underway for testing against EBOV. In the absence of any effective control measure, the adaptation of high standards of biosecurity measures, strict sanitary and hygienic practices, strengthening of surveillance and monitoring systems, imposing appropriate quarantine checks and vigilance on trade, transport, and movement of visitors from EVD endemic countries remains the answer of choice for tackling the EBOV spread. Herein, we converse with the current scenario of EBOV giving due emphasis on animal and veterinary perspectives along with advances in diagnosis and control strategies to be adopted, lessons learned from the recent outbreaks and the global preparedness plans. To retrieve the evolutionary information, we have analyzed a total of 56 genome sequences of various EBOV species submitted between 1976 and 2016 in public databases.

Modulating the immune system through nanotechnology

Nowadays, nanotechnology-based modulation of the immune system is presented as a cutting-edge strategy, which may lead to significant improvements in the treatment of severe diseases. In particular, efforts have been focused on the development of nanotechnology-based vaccines, which could be used for immunization or generation of tolerance. In this review, we highlight how different immune responses can be elicited by tuning nanosystems properties. In addition, we discuss specific formulation approaches designed for the development of anti-infectious and anti-autoimmune vaccines, as well as those intended to prevent the formation of antibodies against biologicals.

Immune Response of A Novel ATR-AP205-001 Conjugate Anti-hypertensive Vaccine

We developed a virus-like particle (VLP)-based therapeutic vaccine against angiotensin II receptor type 1, ATR-AP205-001, which could significantly reduce the blood pressure and protect target organs of hypertensive animals. In this study, we focused on the immunological effect and safety of the VLP-based vaccine. By comparing to the depolymerized dimeric vaccine ATR-Dimer-001, we found that ATR-AP205-001 reached subcapsular sinus of lymph node shortly after administration, followed by accumulation on follicle dendritic cells via follicle B cell transportation, while ATR-Dimer-001 vaccine showed no association with FDCs. ATR-AP205-001 vaccine strongly activated dendritic cells, which promoted T cells differentiation to follicular helper T cells. ATR-AP205-001 vaccine induced powerful germinal center reaction, which was translated to a boost of specific antibody production and long-lasting B cell memory, far superior to ATR-Dimer-001 vaccine. Moreover, neither cytotoxic T cells, nor Th1/Th17 cell-mediated inflammation was observed in ATR-AP205-001 vaccine, similar to ATR-Dimer-001 vaccine. We concluded that ATR-AP205-001 vaccine quickly induced potent humoral immunity through collaboration of B cells, follicular dendritic cells and follicular helper T cells, providing an effective and safe intervention for hypertension in the future clinical application.

Duck virus enteritis (duck plague) - a comprehensive update

Duck virus enteritis (DVE), also called duck plague, is one of the major contagious and fatal diseases of ducks, geese and swan. It is caused by duck enteritis virus (DEV)/Anatid herpesvirus-1 of the genus Mardivirus, family Herpesviridae, and subfamily Alpha-herpesvirinae. Of note, DVE has worldwide distribution, wherein migratory waterfowl plays a crucial role in its transmission within and between continents. Furthermore, horizontal and/ or vertical transmission plays a significant role in disease spread through oral-fecal discharges. Either of sexes from varying age groups of ducks is vulnerable to DVE. The disease is characterized by sudden death, vascular damage and subsequent internal hemorrhage, lesions in lymphoid organs, digestive mucosal eruptions, severe diarrhea and degenerative lesions in parenchymatous organs. Huge economic losses are connected with acute nature of the disease, increased morbidity and mortality (5%-100%), condemnations of carcasses, decreased egg production and hatchability. Although clinical manifestations and histopathology can provide preliminary diagnosis, the confirmatory diagnosis involves virus isolation and detection using serological and molecular tests. For prophylaxis, both live-attenuated and killed vaccines are being used in broiler and breeder ducks above 2 weeks of age. Since DEV is capable of becoming latent as well as shed intermittently, recombinant subunit and DNA vaccines either alone or in combination (polyvalent) are being targeted for its benign prevention. This review describes DEV, epidemiology, transmission, the disease (DVE), pathogenesis, and advances in diagnosis, vaccination and antiviral agents/therapies along with appropriate prevention and control strategies.

Maternal Immunization: New Perspectives on Its Application Against Non-Infectious Related Diseases in Newborns

The continuous evolution in preventive medicine has anointed vaccination a versatile, human-health improving tool, which has led to a steady decline in deaths in the developing world. Maternal immunization represents an incisive step forward for the field of vaccination as it provides protection against various life-threatening diseases in pregnant women and their children. A number of studies to improve prevention rates and expand protection against the largest possible number of infections are still in progress. The complex unicity of the mother-infant interaction, both during and after pregnancy and which involves immune system cells and molecules, is an able partner in the success of maternal immunization, as intended thus far. Interestingly, new studies have shed light on the versatility of maternal immunization in protecting infants from non-infectious related diseases, such as allergy, asthma and congenital metabolic disorders. However, barely any attempt at applying maternal immunization to the prevention of childhood cancer has been made. The most promising study reported in this new field is a recent proof of concept on the efficacy of maternal immunization in protecting cancer-prone offspring against mammary tumor progression. New investigations into the possibility of exploiting maternal immunization to prevent the onset and/or progression of neuroblastoma, one of the most common childhood malignancies, are therefore justified. Maternal immunization is presented in a new guise in this review. Attention will be focused on its versatility and potential applications in preventing tumor progression in neuroblastoma-prone offspring.

New approaches and omics tools for mining of vaccine candidates against vector-borne diseases

Vector-borne diseases (VBDs) present a major threat to human and animal health, as well as place a substantial burden on livestock production. As a way of sustainable VBD control, focus is set on vaccine development. Advances in genomics and other "omics" over the past two decades have given rise to a "third generation" of vaccines based on technologies such as reverse vaccinology, functional genomics, immunomics, structural vaccinology and the systems biology approach. The application of omics approaches is shortening the time required to develop the vaccines and increasing the probability of discovery of potential vaccine candidates. Herein, we review the development of new generation vaccines for VBDs, and discuss technological advancement and overall challenges in the vaccine development pipeline. Special emphasis is placed on the development of anti-tick vaccines that can quell both vectors and pathogens.

Protein Epitope Mimetics: From New Antibiotics to Supramolecular Synthetic Vaccines

Protein epitope mimetics provide powerful tools to study biomolecular recognition in many areas of chemical biology. They may also provide access to new biologically active molecules and potentially to new classes of drug and vaccine candidates. Here we highlight approaches for the design of folded, structurally defined epitope mimetics, by incorporating backbone and side chains of hot residues onto a stable constrained scaffold. Using robust synthetic methods, the structural, biological, and physical properties of epitope mimetics can be optimized, by variation of both side chain and backbone chemistry. To illustrate the potential of protein epitope mimetics in medicinal chemistry and biotechnology, we present studies in two areas of infectology; the discovery of new antibiotics targeting essential outer membrane (OM) proteins in Gram-negative bacteria and the design of supramolecular synthetic vaccines. The discovery of new antibiotics with novel mechanisms of action, in particular to combat infections caused by Gram-negative pathogens, represents a major challenge in medicinal chemistry. We were inspired by naturally occurring cationic antimicrobial peptides to design structurally related peptidomimetics and to optimize their antimicrobial properties through library synthesis and screening. Through these efforts, we could show that antimicrobial β-hairpin mimetics may have structures and properties that facilitate interactions with essential bacterial β-barrel OM proteins. One recently discovered family of antimicrobial peptidomimetics targets the β-barrel protein LptD in Pseudomonas spp. This protein plays a key role in lipopolysaccaride (LPS) transport to the cell surface during OM biogenesis. Through a highly selective interaction with LptD, the peptidomimetic blocks LPS transport, resulting in nanomolar antimicrobial activity against the important human pathogen P. aeruginosa. Epitope mimetics may also have great potential in the field of vaccinology, where structural information on complexes between neutralizing antibodies and their cognate epitopes can be taken as a starting point for B cell epitope mimetic design. In order to generate potent immune responses, an effective method of delivering epitope mimetics to relevant cells and tissues in the immune system is also required. For this, engineered synthetic nanoparticles (synthetic virus-like particles, SVLPs) prepared using supramolecular chemistry can be designed with optimal surface properties for efficient dendritic cell-mediated delivery of folded B-cell and linear T-cell epitopes, along with ligands for pattern recognition receptors, into lymphoid tissues. In this way, multivalent display of the epitope mimetics occurs over the surface of the nanoparticle, suitable for cross-linking B cell receptors. In this highly immunogenic format, strong epitope-specific humoral immune responses can be elicited that target infections caused by pathogenic microorganisms. Other potential applications of epitope mimetics in next-generation therapeutics are also discussed.

Use of adjuvants for immunotherapy

Cancer vaccines are designed to stimulate the body's immune system to kill tumor cells. To improve their immunogenicity, vaccine antigens must be combined with adjuvants which are able to stimulate the innate immunity and potentiate the adaptive immune response. In the last years a new generation of adjuvants mimicking the natural microbial ligands have been developed. In particular, several TLR ligands have been extensively explored as vaccine adjuvants and many preclinical and clinical studies have been conducted. However, the road to approval of such adjuvants for clinical use is still to go.

A New Adjuvant MTOM Mediates Mycobacterium tuberculosis Subunit Vaccine to Enhance Th1-Type T Cell Immune Responses and IL-2+ T Cells

The only licensed vaccine Mycobacterium bovis Bacillus Calmette–Guérin (BCG) cannot prevent the prevalence of tuberculosis (TB), which remains a major public health problem worldwide. A more effective TB vaccine than BCG is urgently needed. Subunit vaccine is a promising strategy, and suitable adjuvants will benefit the development of effective TB subunit vaccines. MTO, consisting of monophosphoryl lipid A (MPLA), trehalose-6,6′-dibehenate (TDB), and MF59, was developed as an adjuvant of TB vaccine because of its ability to evoke the Th1-type T cell responses, while it is insufficient to induce single and multifunctional IL-2⁺ T cells and has a limited ability to confer protection against Mycobacterium tuberculosis infection. Heat-killed Mycobacterium vaccae (Mv), which can evoke cytotoxic CD8⁺ and CD4⁺ T cell responses and has adjuvanticity, was, in this study, combined with MTO to produce a new adjuvant, called MTOM. The TB fusion protein Rv3407-PhoY2-Ag85A-Rv2626c-RpfB (WH121) was mixed with MTO, Mv, and MTOM to produce three subunit vaccines, and the protective efficacy and immune responses were compared in C57BL/6 mice. WH121/MTOM provided better protection against TB than the other two vaccines, matching the performance of BCG vaccine. MTOM showed stronger ability to increase single and multifunctional IL-2⁺ T cells and induce Th1-type responses than MTO or Mv. Therefore, MTOM might be a promising adjuvant that could contribute to the development of TB subunit vaccines.

CpG oligodeoxynucleotides augment antitumor efficacy of folate receptor α based DNA vaccine

Folate receptor α (FRα) is overexpressed in a variety of solid tumors and has become an attractive target antigen for immunotherapy purposes. A DNA vaccine was generated by ligation of FRα cDNA into the eukaryotic vector pcDNA3.1. Expression of FRα was confirmed in transiently transfected B16 cells. B16 cell lines that stably express FRα were set up by G418 selection. A total of 100 µg purified plasmid DNA alone or in combination with CpG oligodeoxynucleotides (CpG ODN) was injected intramuscularly in C57BL/6 mice four times at one week intervals. ELISA analysis confirmed that high titers of antibodies against FRα existed in the sera of the experimental animals. Specific cytotoxic T lymphocyte activity against FRα-expressing B16 cells was found and FRα specific lymphocyte proliferation was detected. Coinjection of CpG ODN increased both humoral and cellular immune responses. In the protective model, in which C57BL/6 mice were immunized with the FRα DNA vaccine four weeks before tumor cell inoculation, the growth of tumor was significantly inhibited, and the presence of CpG ODN further increased the inhibitory effect. FRα DNA vaccine alone did not show a significant inhibitory effect in the therapeutic model, in which the DNA vaccine was immediately injected after tumor inoculation. However, FRα DNA vaccine plus CpG ODN showed a significant inhibitory effect in tumor growth. Survival curves for both animal experiments confirmed that mice immunized with pcDNA3.1/FRα plus CpG ODN had a significantly prolonged survival period than that of the pcDNA3.1 control group, the CpG ODN group or the pcDNA3.1/FRα group. The above showed that human FRα based DNA vaccination with CpG ODN as an adjuvant was effective in growth inhibition of a FRα expressing tumor in mice and deserves further evaluation as a possible immunotherapy.

Phage-displayed peptides that mimic epitopes of hepatitis E virus capsid

Hepatitis E is an emerging zoonotic infection of increasing public health threat for the UK, especially for immunosuppressed individuals. A human recombinant vaccine has been licensed only in China and is not clear whether it protects against hepatitis E virus (HEV) genotype 3, the most prevalent in Europe. The aim of this study was to use phage display technology as a tool to identify peptides that mimic epitopes of HEV capsid (mimotopes). We identified putative linear and conformational mimotopes using sera from Scottish blood donors that have the immunological imprint of past HEV infection. Four mimotopes did not have homology with the primary sequence of HEV ORF2 capsid but competed effectively with a commercial HEV antigen for binding to anti-HEV reference serum. When the reactivity profile of each mimotope was compared with Wantai HEV-IgG ELISA, the most sensitive HEV immunoassay, mimotopes showed 95.2-100% sensitivity while the specificity ranged from 81.5 to 95.8%. PepSurf algorithm was used to map affinity-selected peptides onto the ORF2 crystal structure of HEV genotype 3, which predicted that these four mimototopes are clustered in the P domain of ORF2 capsid, near conformational epitopes of anti-HEV neutralising monoclonal antibodies. These HEV mimotopes may have potential applications in the design of structural vaccines and the development of new diagnostic tests.

Biotechnology approaches to produce potent, self-adjuvanting antigen-adjuvant fusion protein subunit vaccines

Traditional vaccination approaches (e.g. live attenuated or killed microorganisms) are among the most effective means to prevent the spread of infectious diseases. These approaches, nevertheless, have failed to yield successful vaccines against many important pathogens. To overcome this problem, methods have been developed to identify microbial components, against which protective immune responses can be elicited. Subunit antigens identified by these approaches enable the production of defined vaccines, with improved safety profiles. However, they are generally poorly immunogenic, necessitating their administration with potent immunostimulatory adjuvants. Since few safe and effective adjuvants are currently used in vaccines approved for human use, with those available displaying poor potency, or an inability to stimulate the types of immune responses required for vaccines against specific diseases (e.g. cytotoxic lymphocytes (CTLs) to treat cancers), the development of new vaccines will be aided by the availability of characterized platforms of new adjuvants, improving our capacity to rationally select adjuvants for different applications. One such approach, involves the addition of microbial components (pathogen-associated molecular patterns; PAMPs), that can stimulate strong immune responses, into subunit vaccine formulations. The conjugation of PAMPs to subunit antigens provides a means to greatly increase vaccine potency, by targeting immunostimulation and antigen to the same antigen presenting cell. Thus, methods that enable the efficient, and inexpensive production of antigen-adjuvant fusions represent an exciting mean to improve immunity towards subunit antigens. Herein we review four protein-based adjuvants (flagellin, bacterial lipoproteins, the extra domain A of fibronectin (EDA), and heat shock proteins (Hsps)), which can be genetically fused to antigens to enable recombinant production of antigen-adjuvant fusion proteins, with a focus on their mechanisms of action, structural or sequence requirements for activity, sequence modifications to enhance their activity or simplify production, adverse effects, and examples of vaccines in preclinical or human clinical trials.

Assessment of the adjuvant activity of mesoporous silica nanoparticles in recombinant Mycoplasma hyopneumoniae antigen vaccines

The adjuvant potential of two mesoporous silica nanoparticles (MSNs), SBa-15 and SBa-16, was assessed in combination with a recombinant HSP70 surface polypeptide domain from Mycoplasma hyopneumoniae, the etiological agent of porcine enzootic pneumonia (PEP). The recombinant antigen (HSP70_212-600), previously shown as immunogenic in formulation with classic adjuvants, was used to immunize BALB/c mice in combination with SBa-15 or SBa-16 MSNs, and the effects obtained with these formulations were compared to those obtained with alum, the adjuvant traditionally used in anti-PEP bacterins. The HSP70_212-600 + SBa-15 vaccine elicited a strong humoral immune response, with high serum total IgG levels, comparable to those obtained using HSP70_212-600 + alum. The HSP70_212-600 + SBa-16 vaccine elicited a moderate humoral immune response, with lower levels of total IgG. The cellular immune response was assessed by the detection of IFN-γ, IL-4 and IL-10 in splenocyte culture supernatants. The HSP70_212-600 + SBa-15 vaccine increased IFN-γ, IL-4 and IL-10 levels, while no stimulation was detected with the HSP70_212-600 + SBa-16 vaccine. The HSP70_212-600 + SBa-15 vaccine induced a mixed Th1/Th2-type response, with an additional IL-10 mediated anti-inflammatory effect, both of relevance for an anti-PEP vaccine. Alum adjuvant controls stimulated an unspecific cellular immune response, with similar levels of cytokines detected in mice immunized either with HSP70_212-600 + alum or with the adjuvant alone. The better humoral and cellular immune responses elicited in mice indicated that SBa-15 has adjuvant potential, and can be considered as an alternative to the use of alum in veterinary vaccines. The use of SBa-15 with HSP70_212-600 is also promising as a potential anti-PEP subunit vaccine formulation.

Immunological effects of a novel RNA-based adjuvant in liver cancer patients

Evaluation of biological effects of adjuvants on immune cells has been assessed in a limited number of studies. Moreover, no data are available on samples derived from cancer patients who may have a severe immune impairment. The effects of a novel RNA-based adjuvant (RNAdjuvant® developed by CureVac) were assessed in an ex vivo setting on PBMCs obtained from 8 healthy volunteers and 17 HCC patients, using a multiparametric approach to analyze network dynamics of early immune responses. Evaluation of CD80, CD86 and HLA-DR expression, cytokine production as well as gene expression was performed. Moreover, the downstream effect on CD4+ T cell phenotyping was evaluated. Treatment with RNAdjuvant® showed comparable effects on PBMCs of both HCC and healthy subjects. In particular, CD80, CD86 and HLA-DR expression was found up-regulated in circulating dendritic cells, which promoted a CD4+ T cell differentiation toward an effector phenotype. A mixed Th1/Th2 cytokine pattern was induced, although a more predominant production of TNFα and IFNγ was observed in HCC patients versus healthy controls. The cytokine profile was further confirmed by gene transcriptional analysis, which showed up-regulation of several genes involved in innate and adaptive immune-related pathways. The present study is the first demonstration that HCC patients and healthy subjects are equally responsive to an adjuvant. This may suggest that the same vaccine formulation including the RNAdjuvant® might have similar potency in healthy subjects and cancer patients.

Cytomegalovirus (CMV) Infection Causes Degeneration of Cochlear Vasculature and Hearing Loss in a Mouse Model

Cytomegalovirus (CMV) infection is one of the most common causes of congenital hearing loss in children. We have used a murine model of CMV infection to reveal functional and structural cochlear pathogenesis. The cerebral cortex of Balb/c mice (Mus musculus) was inoculated with 2000 pfu (plaque forming units) of murine CMV on postnatal day 3. At 6 weeks of age, cochlear function was monitored using auditory brainstem response (ABR) and distortion product otoacoustic emission (DPOAE) measures. Histological assessment of cochlear vasculature using a corrosion cast technique was made at 8 weeks. Vascular casts of mCMV-damaged cochleas, and those of untreated control animals, were examined using scanning electron microscopy. We find very large variations in the degree of vascular damage in animals given identical viral injections (2000 pfu). The primary lesion caused by CMV infection is to the stria vascularis and to the adjacent spiral limbus capillary network. Capillary beds of the spiral ligament are generally less affected. The initial vascular damage is found in the mid-apical turn and appears to progress to more basal cochlear regions. After viral migration to the inner ear, the stria vascularis is the primary affected structure. We suggest that initial auditory threshold losses may relate to the poor development or maintenance of the endocochlear potential caused by strial dysfunction. Our increased understanding of the pathogenesis of CMV-related hearing loss is important for defining methods for early detection and treatment.

Conserved Molecular Superlattices in a Series of Homologous Synthetic Mycobacterial Cell-Wall Lipids Forming Interdigitated Bilayers

Synthetic analogues of the cell-wall lipid monomycoloyl glycerol (MMG) are promising as next-generation vaccine adjuvants. In the present study, the thermotropic phase behavior of an array of synthetic MMG analogues was examined by using simultaneous small- and wide-angle X-ray scattering under excess water conditions. The MMG analogues differed in the alkyl chain lengths and in the stereochemistry of the polar glycerol headgroup or of the lipid tails (native-like versus alternative compounds). All MMG analogues formed poorly hydrated lamellar phases at low temperatures and inverse hexagonal (H₂) phases at higher temperatures prior to melting. MMG analogues with a native-like lipid acid configuration self-assembled into noninterdigitated bilayers whereas the analogues displaying an alternative lipid acid configuration formed interdigitated bilayers in a subgel (L_c') state. This is in contrast to previously described interdigitated phases for other lipids, which are usually in a gel (L_β) state. All investigated MMG analogues displayed an abrupt direct temperature-induced phase transition from L_c' to H₂. This transition is ultimately driven by the lipid chain melting and the accompanying change in molecular shape. No intermediate structures were found, but the entire array of MMG analogues displayed phase coexistence during the lamellar to H₂ transition. The structural data also showed that the headgroups of the MMG analogues adopting the alternative lipid acid configuration were ordered and formed a two-dimensional molecular superlattice, which was conserved regardless of the lipid tail length. To our knowledge, the MMG analogues with an alternative lipid acid configuration represent the first example of a lipid system showing both interdigitation and superlattice formation, and as such could serve as an interesting model system for future studies. The MMG analogues are also relevant from a subunit vaccine perspective because they are well-tolerated and display promising immunopotentiating activity. The structural characterization described here will serve as a prerequisite for the rational design of nanoparticulate adjuvants with specific and tailored structural features.

The assessment of Hantaan virus-specific antibody responses after the immunization program for hemorrhagic fever with renal syndrome in northwest China

Xianyang city is one of the main hemorrhagic fever with renal syndrome (HFRS) epidemic areas in northwest China. Although the HFRS immunity program has been provided in this city, HFRS is still occurred every year. In order to implement the vaccination program effectively and to control HFRS, the analysis of antibody responses specific to Hantaan virus (HTNV) in individuals after vaccination is essential. In this study, a total of 100 subjects were divided into 5 groups: unvaccinated, 1, 3, 29 and 33 months after boost vaccination. The levels and the positive rates of HTNV-NP-specific IgM and IgG antibodies as well as HTNV neutralizing antibodies were significantly increased in the serum of the vaccinated individuals. The positive rates and levels of HTNV-NP-specific IgG and HTNV neutralizing antibody reached their highest values at 3 months respectively and could be sustained up to 33 months after vaccination. Moreover, the titres of HTNV-NP-specific IgM or IgG antibody and the titres of HTNV neutralizing antibody at 1 month after vaccination have a positive correlation. The level of HTNV-NP-specific IgG antibody was much higher than that of HTNV-NP-specific IgM antibody or HTNV neutralizing antibody. In addition, the strongest responses of antibody-secreting cells were observed at 3 months after vaccination, which was consistent with the serum results. Therefore, the HFRS immunization program is effective to induce humoral immunity in the population of northwest China.

Biomaterials-Based Vaccination Strategies for the Induction of CD8+T Cell Responses

Natural and synthetic biomaterials are increasingly being used for the development of vaccines and immunotherapies as alternatives to traditional live-attenuated formulations due to their improved safety profiles and no risk of reversion to virulence. Polymeric materials in particular enjoy attention due to the ease of fabrication, control over physicochemical properties, and their wide range of immunogenicity. While the majority of studies focus on inducing protective antibody responses, in recent years, materials-based strategies for the delivery of antigens and immunomodulators to improve CD8⁺T cell immunity against infectious and non-infectious diseases have gained momentum. Notably, platforms based on polymeric nanoparticles, liposomes, micelles, virus-like particles, self-assembling peptides and peptidomimetics, and multilayer thin films show considerable promise in preclinical studies. In this Review, we first introduce the concepts of CD8⁺T cell activation, effector and memory functions, and cytotoxic activity, followed by vaccine design for eliciting robust and protective long-lived CD8⁺T cell immunity. We then discuss different materials-based vaccines developed in the past decade to elicit CD8⁺T cell responses based on molecular composition or fabrication methods and conclude with a summary and glimpse at the future trends in this area.

International Consensus (ICON): allergic reactions to vaccines

BACKGROUND

Routine immunization, one of the most effective public health interventions, has effectively reduced death and morbidity due to a variety of infectious diseases. However, allergic reactions to vaccines occur very rarely and can be life threatening. Given the large numbers of vaccines administered worldwide, there is a need for an international consensus regarding the evaluation and management of allergic reactions to vaccines.

METHODS

Following a review of the literature, and with the active participation of representatives from the World Allergy Organization (WAO), the European Academy of Allergy and Clinical Immunology (EAACI), the American Academy of Allergy, Asthma, and Immunology (AAAAI), and the American College of Allergy, Asthma, and Immunology (ACAAI), the final committee was formed with the purpose of having members who represented a wide-range of countries, had previously worked on vaccine safety, and included both allergist/immunologists as well as vaccinologists.

RESULTS

Consensus was reached on a variety of topics, including: definition of immediate allergic reactions, including anaphylaxis, approaches to distinguish association from causality, approaches to patients with a history of an allergic reaction to a previous vaccine, and approaches to patients with a history of an allergic reaction to components of vaccines.

CONCLUSIONS

This document provides comprehensive and internationally accepted guidelines and access to on-line documents to help practitioners around the world identify allergic reactions following immunization. It also provides a framework for the evaluation and further management of patients who present either following an allergic reaction to a vaccine or with a history of allergy to a component of vaccines.

Successful completion of a semi-automated enzyme-free cloning method

Nowadays, in scientific fields such as Structural Biology or Vaccinology, there is an increasing need of fast, effective and reproducible gene cloning and expression processes. Consequently, the implementation of robotic platforms enabling the automation of protocols is becoming a pressing demand. The main goal of our study was to set up a robotic platform devoted to the high-throughput automation of the polymerase incomplete primer extension cloning method, and to evaluate its efficiency compared to that achieved manually, by selecting a set of bacterial genes that were processed either in the automated platform (330) or manually (94). Here we show that we successfully set up a platform able to complete, with high efficiency, a wide range of molecular biology and biochemical steps. 329 gene targets (99 %) were effectively amplified using the automated procedure and 286 (87 %) of these PCR products were successfully cloned in expression vectors, with cloning success rates being higher for the automated protocols respect to the manual procedure (93.6 and 74.5 %, respectively).

Nano-Self-Assemblies Based on Synthetic Analogues of Mycobacterial Monomycoloyl Glycerol and DDA: Supramolecular Structure and Adjuvant Efficacy

The mycobacterial cell-wall lipid monomycoloyl glycerol (MMG) is a potent immunostimulator, and cationic liposomes composed of a shorter synthetic analogue (MMG-1) and dimethyldioctadecylammonium (DDA) bromide represent a promising adjuvant that induces strong antigen-specific Th1 and Th17 responses. In the present study, we investigated the supramolecular structure and in vivo adjuvant activity of dispersions based on binary mixtures of DDA and an array of synthetic MMG-1 analogues (MMG-2/3/5/6) displaying longer (MMG-2) or shorter (MMG-3) alkyl chain lengths, or variations in stereochemistry of the polar headgroup (MMG-5) or of the hydrophobic moiety (MMG-6). Synchrotron small-angle X-ray scattering experiments and cryo transmission electron microscopy revealed that DDA:MMG-1/2/5/6 dispersions consisted of unilamellar and multilamellar vesicles (ULVs/MLVs), whereas a coexistence of both ULVs and hexosomes was observed for DDA:MMG-3, depending on the DDA:MMG molar ratio. The studies also showed that ULVs were formed, regardless of the structural characteristics of the neat MMG analogues in excess buffer [lamellar (MMG-1/2/5) or inverse hexagonal (MMG-3/6) phases]. Immunization of mice with a chlamydia antigen surface-adsorbed to DDA:MMG-1/3/6 dispersions revealed that all tested adjuvants were immunoactive and induced strong Th1 and Th17 responses with a potential for a central effector memory profile. The MMG-1 and MMG-6 analogues were equally immunoactive in vivo upon incorporation into DDA liposomes, despite the reported highly different immunostimulatory properties of the neat analogues in vitro, which were attributed to the different nanostructural characteristics. This clearly demonstrates that optimal formulation and delivery of MMG analogues to the immune system is of major importance and challenges the use of in vitro screening assays with nondispersed compounds to identify potential new vaccine adjuvants.

Priming Vaccination With Influenza Virus H5 Hemagglutinin Antigen Significantly Increases the Duration of T cell Responses Induced by a Heterologous H5 Booster Vaccination

BACKGROUND

Influenza A(H5N1) virus and other avian influenza virus strains represent major pandemic threats. Like all influenza A virus strains, A(H5N1) viruses evolve rapidly. Innovative immunization strategies are needed to induce cross-protective immunity.

METHODS

Subjects primed with clade 1 H5 antigen, with or without adjuvant, and H5-naive individuals were boosted with clade 2 H5 antigen. The impact of priming on T cells capable of both proliferation and cytokine production after antigen restimulation was assessed.

RESULTS

Subjects previously vaccinated with clade 1 H5 antigen developed significantly enhanced clade 2 H5 cross-reactive T cell responses detectable 6 months after vaccination with clade 2 H5 antigen. Priming dose (15 µg vs 45 or 90 µg) had no effect on magnitude of heterotypic H5 T cell responses. In contrast, age at priming negatively modulated both the magnitude and duration of heterotypic H5 T cell responses. Elderly subjects developed significantly less heterotypic H5 T cell boosting, predominantly for T cells capable of cytokine production. Adjuvant had a positive albeit weaker effect than age. The magnitude of CD4(+) interferon-γ producing T cells correlated with H5 antibody responses.

CONCLUSIONS

H5 heterotypic priming prior to onset of an A(H5N1) pandemic may increase magnitude and duration of immunity against a newly drifted pandemic H5 virus.

Hyaluronic Acid-Modified Cationic Lipid-PLGA Hybrid Nanoparticles as a Nanovaccine Induce Robust Humoral and Cellular Immune Responses

Here, we investigated the use of hyaluronic acid (HA)-decorated cationic lipid-poly(lactide-co-glycolide) acid (PLGA) hybrid nanoparticles (HA-DOTAP-PLGA NPs) as vaccine delivery vehicles, which were originally developed for the cytosolic delivery of genes. Our results demonstrated that after the NPs uptake by dendritic cells (DCs), some of the antigens that were encapsulated in HA-DOTAP-PLGA NPs escaped to the cytosolic compartment, and whereas some of the antigens remained in the endosomal/lysosomal compartment, where both MHC-I and MHC-II antigen presentation occurred. Moreover, HA-DOTAP-PLGA NPs led to the up-regulation of MHC, costimulatory molecules, and cytokines. In vivo experiments further revealed that more powerful immune responses were induced from mice immunized with HA-DOTAP-PLGA NPs when compared with cationic lipid-PLGA nanoparticles and free ovalbumin (OVA); the responses included antigen-specific CD4(+) and CD8(+) T-cell responses, the production of antigen-specific IgG antibodies and the generation of memory CD4(+) and CD8(+) T cells. Overall, these data demonstrate the high potential of HA-DOTAP-PLGA NPs for use as vaccine delivery vehicles to elevate cellular and humoral immune responses.

Systems immunology: Beyond antibody titers

Despite the evident success of currently available vaccines to prevent infectious diseases, we still lack a full understanding of the mechanisms by which vaccines induce protective immune responses. Systems immunology applies multifaceted analytical tools to better understand the immune responses to vaccines by deep characterization of the cellular components, regulatory pathways, antibody responses and immune gene profiles with the ultimate goal of identifying the complex cellular, genetic and regulatory factors and mechanisms that contribute to effective and protective immune responses.

Streptococcus pneumoniae fructose-1,6-bisphosphate aldolase, a protein vaccine candidate, elicits Th1/Th2/Th17-type cytokine responses in mice

Streptococcus pneumoniae (S. pneumoniae) is a major pathogen worldwide. The currently available polysaccharide-based vaccines significantly reduce morbidity and mortality. However, the inherent disadvantages of the currently available polysaccharide-based vaccines have motivated the search for other bacterial immunogens capable of eliciting a protective immune response against S. pneumoniae. Fructose-1,6-bisphosphate aldolase (FBA) is a glycolytic enzyme, which was found to localize to the bacterial surface, where it functions as an adhesin. Previously, immunizing mice with recombinant FBA (rFBA) in the presence of alum elicited a protective immune response against a lethal challenge with S. pneumoniae. Thus, the aim of the present study was to determine the cytokine responses that are indicative of protective immunity following immunization with rFBA. The protective effects against pneumococcal challenge in mice immunized with rFBA with complete Freund's adjuvant (CFA) in the initial immunization and with incomplete Freund's adjuvant (IFA) in booster immunizations surpassed the protective effects observed following immunization with either rFBA + alum or pVACfba. CD4+ T-cells obtained from the rFBA/CFA/IFA/IFA-immunized mice co-cultured with rFBA-pulsed antigen-presenting cells (APCs), exhibited a significantly greater proliferative ability than CD4+ T-cells obtained from the adjuvant-immunized mice co-cultured with rFBA‑pulsed APCs. The levels of the Th1-type cytokines, interferon (IFN)-γ, interleukin (IL)-2, tumor necrosis factor (TNF)-α and IL-12, the Th2-type cytokines, IL-4, IL-5 and IL-10, and the Th17-type cytokine, IL-17A, significantly increased within 72 h of the initiation of co-culture with CD4+ T-cells obtained from the rFBA‑immunized mice, in comparison with the co-cultures with CD4+ T-cells obtained from the adjuvant-immunized mice. Immunizing mice with rFBA resulted in an IgG1/IgG2 ratio of 41, indicating a Th2 response with substantial Th1 involvement. In addition, rabbit and mouse anti-rFBA antisera significantly protected the mice against a lethal S. pneumoniae challenge in comparison with preimmune sera. Our results emphasize the mixed involvement of the Th1, Th2 and Th17 arms of the immune system in response to immunization with pneumococcal rFBA, a potential vaccine candidate.

Deciphering Antigenic Determinants of Streptococcus pneumoniae Serotype 4 Capsular Polysaccharide using Synthetic Oligosaccharides

Streptococcus pneumoniae is a major cause of mortality and morbidity worldwide. More than 90 S. pneumoniae serotypes are distinguished based on the structure of their primary targets to the human immune system, the capsular polysaccharides (CPSs). The CPS of the prevalent serotype 4 (ST4) is composed of tetrasaccharide repeating units and is included in existing pneumococcal vaccines. Still, the structural antigenic determinants that are essential for protective immunity, including the role of the rare and labile cyclic trans-(2,3) pyruvate ketal modification, remain largely unknown. Molecular insights will support the design of synthetic subunit oligosaccharide vaccines. Here, we identified the key antigenic determinants of ST4 CPS with the help of pyruvated and nonpyruvated synthetic repeating unit glycans. Glycan arrays revealed oligosaccharide antigens recognized by antibodies in the human reference serum. Selected depyruvated ST4 oligosaccharides were used to formulate neoglycoconjugates and immunologically evaluated in mice. These oligosaccharides were highly immunogenic, but the resulting antiglycan antibodies showed only limited binding to the natural CPS present on the bacterial surface. Glycan array and surface plasmon resonance analysis of murine polyclonal serum antibodies as well as monoclonal antibodies revealed that terminal sugars are important in directing the immune responses. The pyruvate modification on the oligosaccharide is needed for cross-reactivity with the native CPS. These findings are an important step toward the design of oligosaccharide-based vaccines against S. pneumoniae ST4.

Cell Wall Anchoring of the Campylobacter Antigens to Lactococcus lactis

Campylobacter jejuni is the most frequent cause of human food-borne gastroenteritis and chicken meat is the main source of infection. Recent studies showed that broiler chicken immunization against Campylobacter should be the most efficient way to lower the number of human infections by this pathogen. Induction of the mucosal immune system after oral antigen administration should provide protective immunity to chickens. In this work we tested the usefulness of Lactococcus lactis, the most extensively studied lactic acid bacterium, as a delivery vector for Campylobacter antigens. First we constructed hybrid protein - CjaA antigen presenting CjaD peptide epitopes on its surface. We showed that specific rabbit anti-rCjaAD serum reacted strongly with both CjaA and CjaD produced by a wild type C. jejuni strain. Next, rCjaAD and CjaA were fused to the C-terminus of the L. lactis YndF containing the LPTXG motif. The genes expressing these proteins were transcribed under control of the L. lactis Usp45 promoter and their products contain the Usp45 signal sequences. This strategy ensures a cell surface location of both analyzed proteins, which was confirmed by immunofluorescence assay. In order to evaluate the impact of antigen location on vaccine prototype efficacy, a L. lactis strain producing cytoplasm-located rCjaAD was also generated. Animal experiments showed a decrease of Campylobacter cecal load in vaccinated birds as compared with the control group and showed that the L. lactis harboring the surface-exposed rCjaAD antigen afforded greater protection than the L. lactis producing cytoplasm-located rCjaAD. To the best of our knowledge, this is the first attempt to employ Lactic Acid Bacteria (LAB) strains as a mucosal delivery vehicle for chicken immunization. Although the observed reduction of chicken colonization by Campylobacter resulting from vaccination was rather moderate, the experiments showed that LAB strains can be considered as an alternative vector to deliver heterologous antigens to the bird immune system. Additionally, the analysis of the structure and immunogenicity of the generated rCjaAD hybrid protein showed that the CjaA antigen can be considered as a starting point to construct multiepitope anti-Campylobacter vaccines.

Can follicular helper T cells be targeted to improve vaccine efficacy?

The success of most vaccines relies on the generation of antibodies to provide protection against subsequent infection; this in turn depends on a robust germinal centre (GC) response that culminates in the production of long-lived antibody-secreting plasma cells. The size and quality of the GC response are directed by a specialised subset of CD4 ⁺ T cells: T follicular helper (Tfh) cells. Tfh cells provide growth and differentiation signals to GC B cells and mediate positive selection of high-affinity B cell clones in the GC, thereby determining which B cells exit the GC as plasma cells and memory B cells. Because of their central role in the production of long-lasting humoral immunity, Tfh cells represent an interesting target for rational vaccine design.

Targeting soluble proteins to exosomes using a ubiquitin tag

As "natural" antigen carriers in the body, exosomes are potential vaccine vectors. A number of animal studies indicate that antigen-containing exosomes can induce a specific immune response which can protect against tumor progression or various infections. Exosomes that carry the protective antigens can be purified from cells that release them including tumor cells, dendritic cells, and macrophages. However, this strategy is restricted to proteins that are naturally targeted to exosomes and is therefore limited in the number of antigens present within exosomes. Therefore, with the goal of developing an exosome-based vaccine that is more flexible in its antigen composition and has the potential to be scalable, we have developed a new approach where recombinant soluble proteins can be packaged into exosomes and released from a transformed cell line. In this study, we determined that a C-terminal fusion of ubiquitin to EGFP, tumor antigenic protein nHer2 and Mycobacterium tuberculosis proteins Ag85B and ESAT6 served as an efficient delivery sequence into exosomes when expressed in a human embryonic kidney (HEK 293) cell line, a cell line widely used in industrial recombinant protein production. Two stably transgenic HEK293 cell lines were generated using a retroviral vector to express the Ag85B-ESAT6 fusion protein either alone or tagged at the C-terminus with ubiquitin. Both transformants released exosomes containing the fusion proteins. However, the concentration of Ag85B and ESAT6 in exosomes was increased approximately 10-fold when they were coupled to ubiquitin. Moreover, when the exosomes were used for immunization, there was a direct correlation between the amount of fusion protein within the exosomes and the number of Ag85B and ESAT6 specific INFɣ-secreting T lymphocytes in the lung and spleen. This suggests that exosomes containing recombinant antigen can be used to elicit a T cell response. In summary our data indicates that a ubiquitin-based exosomal protein delivery strategy could represent a unique approach to generate antigen-specific exosomes with the potential to be used as novel vaccines. Biotechnol. Bioeng. 2016;113: 1315-1324. © 2015 Wiley Periodicals, Inc.

Successive site translocating inoculation potentiates DNA/recombinant vaccinia vaccination

DNA vaccines have advantages over traditional vaccine modalities; however the relatively low immunogenicity restrains its translation into clinical use. Further optimizations are needed to get the immunogenicity of DNA vaccine closer to the level required for human use. Here we show that intramuscularly inoculating into a different limb each time significantly improves the immunogenicities of both DNA and recombinant vaccinia vaccines during multiple vaccinations, compared to repeated vaccination on the same limb. We term this strategy successive site translocating inoculation (SSTI). SSTI could work in synergy with genetic adjuvant and DNA prime-recombinant vaccinia boost regimen. By comparing in vivo antigen expression, we found that SSTI avoided the specific inhibition of in vivo antigen expression, which was observed in the limbs being repeatedly inoculated. Employing in vivo T cell depletion and passive IgG transfer, we delineated that the inhibition was not mediated by CD8⁺ T cells but by specific antibodies. Finally, by using C3^−/− mouse model and in vivo NK cells depletion, we identified that specific antibodies negatively regulated the in vivo antigen expression primarily in a complement depended way.

Recent advances in vaccine delivery

The field of vaccination is moving from the use of attenuated or inactivated pathogens to safer but less immunogenic protein and peptide antigens, which require stronger adjuvant compositions. Antigen delivery carriers appear to play an important role in vaccine development, providing not only antigen protection and controlled release but also an intrinsic adjuvant potential. Among them, carriers based on polymers and lipids are the most representative ones. Patent applications in this area have disclosed, either the design and preparation methods for new biocompatible antigen delivery systems or the application of the previously developed systems for the delivery of novel antigens. Some of them have also reported the use of these technologies for modern therapeutic vaccination approaches.

Anti-Infectious Human Vaccination in Historical Perspective

A brief history of vaccination is presented since the Jenner's observation, through the first golden age of vaccinology (from Pasteur's era to 1938), the second golden age (from 1940 to 1970), until the current period. In the first golden age, live, such as Bacille Calmette Guérin (BCG), and yellow fever, inactivated, such as typhoid, cholera, plague, and influenza, and subunit vaccines, such as tetanus and diphtheria toxoids, have been developed. In the second golden age, the cell culture technology enabled polio, measles, mumps, and rubella vaccines be developed. In the era of modern vaccines, in addition to the conjugate polysaccharide, hepatitis A, oral typhoid, and varicella vaccines, the advent of molecular biology enabled to develop hepatitis B, acellular pertussis, papillomavirus, and rotavirus recombinant vaccines. Great successes have been achieved in the fight against infectious diseases, including the smallpox global eradication, the nearly disappearance of polio, the control of tetanus, diphtheria, measles, rubella, yellow fever, and rabies. However, much work should still be done for improving old vaccines, such as BCG, anthrax, smallpox, plague, or for developing effective vaccines against old or emerging infectious threats, such as human-immunodeficiency-virus, malaria, hepatitis C, dengue, respiratory-syncytial-virus, cytomegalovirus, multiresistant bacteria, Clostridium difficile, Ebola virus. In addition to search for innovative and effective vaccines and global infant coverage, even risk categories should adequately be protected. Despite patients under immunosuppressive therapy are globally increasing, their vaccine coverage is lower than recommended, even in developed and affluent countries.

MF59- and Al(OH)3-Adjuvanted Staphylococcus aureus (4C-Staph) Vaccines Induce Sustained Protective Humoral and Cellular Immune Responses, with a Critical Role for Effector CD4 T Cells at Low Antibody Titers

Staphylococcus aureus (S. aureus) is an important opportunistic pathogen that may cause invasive life-threatening infections, like sepsis and pneumonia. Due to the increasing antibiotic resistance, the development of an effective vaccine against S. aureus is needed. Although a correlate of protection against staphylococcal diseases is not yet established, several findings suggest that both antibodies and CD4 T cells might contribute to optimal immunity. In this study, we show that adjuvanting a multivalent vaccine (4C-Staph) with MF59, an oil-in-water emulsion licensed in human vaccines, further potentiated antigen-specific IgG titers and CD4 T-cell responses compared to alum and conferred protection in the peritonitis model of S. aureus infection. Moreover, we showed that MF59- and alum-adjuvanted 4C-Staph vaccines induced persistent antigen-specific humoral and T-cell responses, and protected mice from infection up to 4 months after immunization. Furthermore, 4C-Staph formulated with MF59 was used to investigate which immune compartment is involved in vaccine-induced protection. Using CD4 T cell-depleted mice or B cell-deficient mice, we demonstrated that both T and B-cell responses contributed to 4C-Staph vaccine-mediated protective immunity. However, the role of CD4 T cells seemed more evident in the presence of low-antibody responses. This study provides preclinical data further supporting the use of the adjuvanted 4C-Staph vaccines against S. aureus diseases, and provides critical insights on the correlates of protective immunity necessary to combat this pathogen.

New Vaccines for the World's Poorest People

The 2000 Millennium Development Goals helped stimulate the development of life-saving childhood vaccines for pneumococcal and rotavirus infections while greatly expanding coverage of existing vaccines. However, there remains an urgent need to develop new vaccines for HIV/AIDS, malaria, and tuberculosis, as well as for respiratory syncytial virus and those chronic and debilitating (mostly parasitic) infections known as neglected tropical diseases (NTDs). The NTDs represent the most common diseases of people living in extreme poverty and are the subject of this review. The development of NTD vaccines, including those for hookworm infection, schistosomiasis, leishmaniasis, and Chagas disease, is being led by nonprofit product development partnerships (PDPs) working in consortia of academic and industrial partners, including vaccine manufacturers in developing countries. NTD vaccines face unique challenges with respect to their product development and manufacture, as well as their preclinical and clinical testing. We emphasize global efforts to accelerate the development of NTD vaccines and some of the hurdles to ensuring their availability to the world's poorest people.

[Development of new vaccines]

Recent and important advances in the fields of immunology, genomics, functional genomics, immunogenetics, immunogenomics, bioinformatics, microbiology, genetic engineering, systems biology, synthetic biochemistry, proteomics, metabolomics and nanotechnology, among others, have led to new approaches in the development of vaccines. The better identification of ideal epitopes, the strengthening of the immune response due to new adjuvants, and the search of new routes of vaccine administration, are good examples of advances that are already a reality and that will favour the development of more vaccines, their use in indicated population groups, or its production at a lower cost. There are currently more than 130 vaccines are under development against the more wished (malaria or HIV), difficult to get (CMV or RSV), severe re-emerging (Dengue or Ebola), increasing importance (Chagas disease or Leishmania), and nosocomial emerging (Clostridium difficile or Staphylococcus aureus) infectious diseases.