Vaccines, new opportunities for a new society

Synthesis of Multicomponent Peptide-Based Vaccine Candidates against Group A Streptococcus

Group A streptococcus (GAS; Streptococcus pyogenes), known as the ‘flesh-eating bacterium’, is a human bacterial pathogen that normally causes benign infections (e.g. sore throat and pyoderma), but is also responsible for severe invasive infections (e.g. ‘flesh-eating’ disease and toxic shock syndrome), heart disease, and kidney failure. A safe commercial GAS vaccine is yet to be developed. Individual GAS antigens demonstrate potential universal expression across all GAS serotypes (>200 known), with dramatically reduced concern for autoimmune complications, and compelling efficacy in preclinical testing in mice. In this study, we developed a stepwise conjugation strategy, copper-catalysed alkyne–azide cycloaddition reaction (CuAAC), followed by mercapto–maleimide conjugation, to synthesise a multiantigenic, self-adjuvanting, peptide-based vaccine candidate against GAS. This multiantigenic vaccine includes two GAS antigens, J8 and NS1, a T-helper epitope, PADRE, and a self-adjuvanting moiety, dipalmitoyl serine.

Molecular-Level Interactions of Polyphosphazene Immunoadjuvants and Their Potential Role in Antigen Presentation and Cell Stimulation

Two macromolecular immunoadjuvants, poly[di(carboxylatophenoxy)phosphazene], PCPP, and poly[di(carboxylatoethylphenoxy)phosphazene], PCEP, have been investigated for their molecular interactions with model and biopharmaceutically important proteins in solutions, as well as for their TLR stimulatory effects and pH-dependent membrane disruptive activity in cellular assays. Solution interactions between polyphosphazenes and proteins, including antigens and soluble immune receptor proteins, have been studied using Asymmetric Flow Field Flow Fractionation (AF4) and Dynamic Light Scattering (DLS) at near physiological conditions: phosphate buffered saline, pH 7.4. Polyphosphazenes demonstrated selectivity in their molecular interactions with various proteins, but displayed strong binding with all vaccine antigens tested in the present study. It was found that both PCPP and PCEP showed strong avidity to soluble immune receptor proteins, such as Mannose Receptor (MR) and certain Toll-Like Receptor (TLR) proteins. Studies on TLR stimulation in vitro using HEK293 cells with overexpressed human TLRs revealed activation of TLR7, TLR8, and TLR9 signaling pathways, albeit with some nonspecific stimulation, for PCPP and the same pathways plus TLR3 for PCEP. Finally, PCEP, but not PCPP, demonstrated pH-dependent membrane disruptive activity in the pH range corresponding to the pH environment of early endosomes, which may play a role in a cross-presentation of antigenic proteins.

Scoring and psychometric validation of the 'Determinants of Intentions to Vaccinate' (DIVA©) questionnaire

Background

Primary care physicians (PCPs) play a key role regarding vaccination in France. The aims of the present study were to define the scoring rules and to assess the measurement properties of the ‘Determinants of Intentions to Vaccinate’ (DIVA^©) questionnaire that aims to assess PCPs’ attitudes and beliefs toward vaccination.

Methods

The DIVA questionnaire was derived from a literature review and PCPs focus groups. Scoring and early validation of the DIVA questionnaire were determined during a cross-sectional study conducted in France. During the study, PCPs had to complete the DIVA questionnaire for any of the six vaccine-preventable diseases (VPDs) to which they were randomly assigned (measles, pertussis, pneumococcus infection, seasonal influenza, human papillomavirus -HPV- infection and tetanus). Descriptive analyses of items and the analysis of the grouping of items into domains were conducted. Internal consistency reliability and construct validity was assessed according to each VPD.

Results

The DIVA questionnaire was completed by 1,069 PCPs and was well accepted. The ‘Commitment of the PCP to the vaccination approach’ score showed very good internal consistency reliability (Cronbach’s alpha >0.70 overall and for each VPD). The construct validity of the DIVA questionnaire was confirmed.

Conclusions

The DIVA questionnaire is a valid and reliable measure of PCPs’ attitudes and beliefs toward vaccination.

Electronic supplementary material

The online version of this article (doi:10.1186/s12875-016-0539-3) contains supplementary material, which is available to authorized users.

New vaccines: challenges of discovery

Vaccines have been a major component of preventing and controlling infectious diseases. The basis for discovery of what protects is reviewed as well as new attempts in utilizing Reverse Vaccinology, RNA-RNA methods and proteome analysis are adding significantly to our knowledge. The challenge of how to define protective and defined components of microbes is still hampering efforts to discover new vaccines. Recent excitement about immunotherapy of cancer opens the way to develop vaccines against multiple malignancies.

Biologics to treat substance use disorders: Current status and new directions

Biologics (vaccines, monoclonal antibodies (mAb), and genetically modified enzymes) offer a promising class of therapeutics to treat substance use disorders (SUD) involving abuse of opioids and stimulants such as nicotine, cocaine, and methamphetamine. In contrast to small molecule medications targeting brain receptors, biologics for SUD are larger molecules that do not cross the blood-brain barrier (BBB), but target the drug itself, preventing its distribution to the brain and blunting its effects on the central nervous system (CNS). Active and passive immunization approaches rely on antibodies (Ab) that bind drugs of abuse in serum and block their distribution to the brain, preventing the rewarding effects of drugs and addiction-related behaviors. Alternatives to vaccines and anti-drug mAb are genetically engineered human or bacterial enzymes that metabolize drugs of abuse, lowering the concentration of free active drug. Pre-clinical and clinical data support development of effective biologics for SUD.

Dendrimer-RNA nanoparticles generate protective immunity against lethal Ebola, H1N1 influenza, and Toxoplasma gondii challenges with a single dose

Vaccines have had broad medical impact, but existing vaccine technologies and production methods are limited in their ability to respond rapidly to evolving and emerging pathogens, or sudden outbreaks. Here, we develop a rapid-response, fully synthetic, single-dose, adjuvant-free dendrimer nanoparticle vaccine platform wherein antigens are encoded by encapsulated mRNA replicons. To our knowledge, this system is the first capable of generating protective immunity against a broad spectrum of lethal pathogen challenges, including H1N1 influenza, Toxoplasma gondii, and Ebola virus. The vaccine can be formed with multiple antigen-expressing replicons, and is capable of eliciting both CD8(+) T-cell and antibody responses. The ability to generate viable, contaminant-free vaccines within days, to single or multiple antigens, may have broad utility for a range of diseases.

Recommended immunization schedules for adults: Clinical practice guidelines by the Escmid Vaccine Study Group (EVASG), European Geriatric Medicine Society (EUGMS) and the World Association for Infectious Diseases and Immunological Disorders (WAidid)

Rapid population aging has become a major challenge in the industrialized world and progressive aging is a key reason for making improvement in vaccination a cornerstone of public health strategy. An increase in age-related disorders and conditions is likely to be seen in the near future, and these are risk factors for the occurrence of a number of vaccine-preventable diseases. An improvement in infectious diseases prevention specifically aimed at adults and the elderly can therefore also decrease the burden of these chronic conditions by reducing morbidity, disability, hospital admissions, health costs, mortality rates and, perhaps most importantly, by improving the quality of life. Among adults, it is necessary to identify groups at increased risk of vaccine-preventable diseases and highlight the epidemiological impact and benefits of vaccinations using an evidence-based approach. This document provides clinical practice guidance on immunization for adults in order to provide recommendations for decision makers and healthcare workers in Europe. Although immunization is considered one of the most impactful and cost-effective public health measures that can be undertaken, vaccination coverage rates among adults are largely lower than the stated goal of ≥ 95% among adults, and stronger efforts are needed to increase coverage in this population. Active surveillance of adult vaccine-preventable diseases, determining the effectiveness of the vaccines approved for marketing in the last 5 y, the efficacy and safety of vaccines in immunocompromised patients, as well as in pregnant women, represent the priorities for future research.

Antigenic variability: Obstacles on the road to vaccines against traditionally difficult targets

Despite the impressive impact of vaccines on public health, the success of vaccines targeting many important pathogens and cancers has to date been limited. The burden of infectious diseases today is mainly caused by antigenically variable pathogens (AVPs), which escape immune responses induced by prior infection or vaccination through changes in molecular structures recognized by antibodies or T cells. Extensive genetic and antigenic variability is the major obstacle for the development of new or improved vaccines against "difficult" targets. Alternative, qualitatively new approaches leading to the generation of disease- and patient-specific vaccine immunogens that incorporate complex permanently changing epitope landscapes of intended targets accompanied by appropriate immunomodulators are urgently needed. In this review, we highlight some of the most critical common issues related to the development of vaccines against many pathogens and cancers that escape protective immune responses owing to antigenic variation, and discuss recent efforts to overcome the obstacles by applying alternative approaches for the rational design of new types of immunogens.

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.

Genome-Wide Analysis of Human Metapneumovirus Evolution

Human metapneumovirus (HMPV) has been described as an important etiologic agent of upper and lower respiratory tract infections, especially in young children and the elderly. Most of school-aged children might be introduced to HMPVs, and exacerbation with other viral or bacterial super-infection is common. However, our understanding of the molecular evolution of HMPVs remains limited. To address the comprehensive evolutionary dynamics of HMPVs, we report a genome-wide analysis of the eight genes (N, P, M, F, M2, SH, G, and L) using 103 complete genome sequences. Phylogenetic reconstruction revealed that the eight genes from one HMPV strain grouped into the same genetic group among the five distinct lineages (A1, A2a, A2b, B1, and B2). A few exceptions of phylogenetic incongruence might suggest past recombination events, and we detected possible recombination breakpoints in the F, SH, and G coding regions. The five genetic lineages of HMPVs shared quite remote common ancestors ranging more than 220 to 470 years of age with the most recent origins for the A2b sublineage. Purifying selection was common, but most protein genes except the F and M2-2 coding regions also appeared to experience episodic diversifying selection. Taken together, these suggest that the five lineages of HMPVs maintain their individual evolutionary dynamics and that recombination and selection forces might work on shaping the genetic diversity of HMPVs.

Cell culture-based influenza vaccines: A necessary and indispensable investment for the future

The traditional platform of using embryonated chicken eggs for the production of influenza vaccines has several drawbacks including the inability to meet the volume of required doses in the case of widespread epidemics and pandemics. Cell culture platforms have therefore been explored in the last 2 decades, and have attracted further attention following the H1N1 pandemic outbreak. This platform, while not the most economical for large-scale production, has several advantages, and can supplement the vaccine requirement when needed. Recent developments in production technologies have contributed greatly to fine-tuning this platform. In combination with other technologies such as live attenuated and recombinant protein or virus-like particle vaccines, and different adjuvants and delivery systems, cell culture-based influenza vaccine platform can be used both for production of seasonal vaccine, and to mitigate vaccine shortages in pandemic situations.

Development of a custom pentaplex sandwich immunoassay using Protein-G coupled beads for the Luminex® xMAP® platform

Multiplex bead-based assays have many advantages over ELISA, particularly for the analyses of large quantities of samples and/or precious samples of limited volume. Although many commercial arrays covering multitudes of biologically significant analytes are available, occasionally the development of custom arrays is necessary. Here, the development of a custom pentaplex sandwich immunoassay using Protein G-coupled beads, for analysis using the Luminex® xMAP® platform, is described. This array was required for the measurement of candidate biomarkers of vaccine safety in small volumes of mouse sera. Optimisation of this assay required a stepwise approach: testing cross-reactivity of the antibody pairs, the development of an in-house serum diluent buffer as well as heat-inactivation of serum samples to prevent interference from matrix effects. We then demonstrate the use of this array to analyse inflammatory mediators in mouse serum after immunisation. The work described here exemplifies how Protein G-coupled beads offer a flexible and robust approach to develop custom multiplex immunoassays, which can be applied to a range of analytes from multiple species.

Different human vaccine adjuvants promote distinct antigen-independent immunological signatures tailored to different pathogens

The majority of vaccine candidates in clinical development are highly purified proteins and peptides relying on adjuvants to enhance and/or direct immune responses. Despite the acknowledged need for novel adjuvants, there are still very few adjuvants in licensed human vaccines. A vast number of adjuvants have been tested pre-clinically using different experimental conditions, rendering it impossible to directly compare their activity. We performed a head-to-head comparison of five different adjuvants Alum, MF59®, GLA-SE, IC31® and CAF01 in mice and combined these with antigens from M. tuberculosis, influenza, and chlamydia to test immune-profiles and efficacy in infection models using standardized protocols. Regardless of antigen, each adjuvant had a unique immunological signature suggesting that the adjuvants have potential for different disease targets. Alum increased antibody titers; MF59® induced strong antibody and IL-5 responses; GLA-SE induced antibodies and Th1; CAF01 showed a mixed Th1/Th17 profile and IC31® induced strong Th1 responses. MF59® and GLA-SE were strong inducers of influenza HI titers while CAF01, GLA-SE and IC31® enhanced protection to TB and chlamydia. Importantly, this is the first extensive attempt to categorize clinical-grade adjuvants based on their immune profiles and protective efficacy to inform a rational development of next generation vaccines for human use.

Double conjugation strategy to incorporate lipid adjuvants into multiantigenic vaccines

Conjugation of multiple peptides by their N-termini is a promising technique to produce branched multiantigenic vaccines.

Conjugation of multiple peptides by their N-termini is a promising technique to produce branched multiantigenic vaccines. We established a double conjugation strategy that combines a mercapto-acryloyl Michael addition and a copper-catalysed alkyne-azide 1,3-dipolar cycloaddition (CuAAC) reaction to synthesise self-adjuvanting branched multiantigenic vaccine candidates. These vaccine candidates aim to treat cervical cancer and include two HPV-16 derived epitopes and a novel self-adjuvanting moiety. This is the first report of mercapto-acryloyl conjugation applied to the hetero conjugation of two unprotected peptides by their N-termini followed by a CuAAC reaction to conjugate a novel synthetic lipoalkyne self-adjuvanting moiety. In vivo experiments showed that the most promising vaccine candidate completely eradicated tumours in 46% of the mice (6 out of 13 mice).

Future Challenges for Vaccinologists

Vaccination is one of the cheapest health-care interventions that have saved more lives than any other drugs or therapies. Due to successful immunization programs we rarely hear about some of the common diseases of the early twentieth century including small pox and polio. Vaccination programs have also helped to increase food production notably poultry, cattle, and milk production due to lower incidence of infectious diseases in farm animals. Though vaccination programs have eradicated several diseases and increased the quality of life there are several diseases that have no effective vaccines. Currently there are no vaccines for cancer, neurodegenerative diseases, autoimmune diseases, as well as infectious diseases like tuberculosis, AIDS, and parasitic diseases including malaria. Abuse of antibiotics has resulted in the generation of several antibiotic-resistant bacterial strains; hence there is a need to develop novel vaccines for antibiotic-resistant microorganisms. Changes in climate is another concern for vaccinologists. Climate change could lead to generation of new strains of infectious microorganisms that would require development of novel vaccines. Use of conventional vaccination strategies to develop vaccines has severe limitations; hence innovative strategies are essential in the development of novel and effective vaccines.

Enhancing Vaccine Safety Capacity Globally: A Lifecycle Perspective

Major vaccine safety controversies have arisen in several countries beginning in the last decades of 20th century. Such periodic vaccine safety controversies are unlikely to go away in the near future as more national immunization programs mature with near elimination of target vaccine-preventable diseases that result in relative greater prominence of adverse events following immunizations, both true reactions and temporally coincidental events. There are several ways in which vaccine safety capacity can be improved to potentially mitigate the impact of future vaccine safety controversies. This paper aims to take a "lifecycle" approach, examining some potential pre- and post-licensure opportunities to improve vaccine safety, in both developed (specifically U.S. and Europe) and low- and middle-income countries.

Enhancing vaccine safety capacity globally: A lifecycle perspective

Major vaccine safety controversies have arisen in several countries beginning in the last decades of 20th century. Such periodic vaccine safety controversies are unlikely to go away in the near future as more national immunization programs mature with near elimination of target vaccine-preventable diseases that result in relative greater prominence of adverse events following immunizations, both true reactions and temporally coincidental events. There are several ways in which vaccine safety capacity can be improved to potentially mitigate the impact of future vaccine safety controversies. This paper aims to take a "lifecycle" approach, examining some potential pre- and post-licensure opportunities to improve vaccine safety, in both developed (specifically U.S. and Europe) and low- and middle-income countries.

Self-assembling protein nanoparticles in the design of vaccines

For over 100 years, vaccines have been one of the most effective medical interventions for reducing infectious disease, and are estimated to save millions of lives globally each year. Nevertheless, many diseases are not yet preventable by vaccination. This large unmet medical need demands further research and the development of novel vaccines with high efficacy and safety. Compared to the 19th and early 20th century vaccines that were made of killed, inactivated, or live-attenuated pathogens, modern vaccines containing isolated, highly purified antigenic protein subunits are safer but tend to induce lower levels of protective immunity. One strategy to overcome the latter is to design antigen nanoparticles: assemblies of polypeptides that present multiple copies of subunit antigens in well-ordered arrays with defined orientations that can potentially mimic the repetitiveness, geometry, size, and shape of the natural host-pathogen surface interactions. Such nanoparticles offer a collective strength of multiple binding sites (avidity) and can provide improved antigen stability and immunogenicity. Several exciting advances have emerged lately, including preclinical evidence that this strategy may be applicable for the development of innovative new vaccines, for example, protecting against influenza, human immunodeficiency virus, and respiratory syncytial virus. Here, we provide a concise review of a critical selection of data that demonstrate the potential of this field. In addition, we highlight how the use of self-assembling protein nanoparticles can be effectively combined with the emerging discipline of structural vaccinology for maximum impact in the rational design of vaccine antigens.

[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.

The re-emergency and persistence of vaccine preventable diseases

The introduction of vaccination worldwide dramatically reduced the incidence of pathogenic bacterial and viral diseases. Despite the highly successful vaccination strategies, the number of cases among vaccine preventable diseases has increased in the last decade and several of those diseases are still endemic in different countries. Here we discuss some epidemiological aspects and possible arguments that may explain why ancient diseases such as, measles, polio, pertussis, diphtheria and tuberculosis are still with us.

Delivering vaccines to the people who need them most

Thanks to the Global Alliance for Vaccines and Immunization (GAVI), the Vaccine Fund and the Bill & Melinda Gates Foundation, the global health community has made enormous progress in providing already existing vaccines to developing countries. However, there still exists a gap to develop vaccines for which there is no market in the Western world, owing to low economic incentives for the private sector to justify the investments necessary for vaccine development. In many cases, industry has the technologies, but lacks the impetus to direct resources to develop these vaccine products. The present emergency with the Ebola vaccine provides us an excellent example where a vaccine was feasible several years ago, but the global health community waited for a humanitarian disaster to direct efforts and resources to develop this vaccine. In the beginning of 2015, the first large-scale trials of two experimental vaccines against Ebola virus disease have begun in West Africa. During the past few years, several institutions have dedicated efforts to the development of vaccines against diseases present only in low-income countries. These include the International Vaccine Institute, the Novartis Vaccines Institute for Global Health, the Hilleman Institute, the Sabin Vaccine Institute and the Infectious Disease Research Institute. Nevertheless, solving this problem requires a more significant global effort than that currently invested. These efforts include a clear policy, global coordination of funds dedicated to the development of neglected disease and an agreement on regulatory strategies and incentives for the private sector.

The frequency of naive and early-activated hapten-specific B cell subsets dictates the efficacy of a therapeutic vaccine against prescription opioid abuse

Translation of therapeutic vaccines for addiction, cancer, or other chronic noncommunicable diseases has been slow because only a small subset of immunized subjects achieved effective Ab levels. We hypothesize that individual variability in the number of naive and early-activated hapten-specific B cells determines postvaccination serum Ab levels and vaccine efficacy. Using a model vaccine against the highly abused prescription opioid oxycodone, the polyclonal B cell population specific for an oxycodone-based hapten (6OXY) was analyzed by flow cytometry paired with Ag-based magnetic enrichment. A higher frequency of 6OXY-specific B cells in either spleen biopsies or blood, before and after immunization, correlated to subsequent greater oxycodone-specific serum Ab titers and their efficacy in blocking oxycodone distribution to the brain and oxycodone-induced behavior in mice. The magnitude of 6OXY-specific B cell activation and vaccine efficacy was tightly correlated to the size of the CD4(+) T cell population. The frequency of enriched 6OXY-specific B cells was consistent across various mouse tissues. These data provide novel evidence that variations in the frequency of naive or early-activated vaccine-specific B and T cells can account for individual responses to vaccines and may predict the clinical efficacy of a therapeutic vaccine.

Reaching for the Holy Grail: insights from infection/cure models on the prospects for vaccines for Trypanosoma cruzi infection

Prevention of Trypanosoma cruzi infection in mammals likely depends on either prevention of the invading trypomastigotes from infecting host cells or the rapid recognition and killing of the newly infected cells by T. cruzi-specific T cells. We show here that multiple rounds of infection and cure (by drug therapy) fails to protect mice from reinfection, despite the generation of potent T cell responses. This disappointing result is similar to that obtained with many other vaccine protocols used in attempts to protect animals from T. cruzi infection. We have previously shown that immune recognition of T. cruzi infection is significantly delayed both at the systemic level and at the level of the infected host cell. The systemic delay appears to be the result of a stealth infection process that fails to trigger substantial innate recognition mechanisms while the delay at the cellular level is related to the immunodominance of highly variable gene family proteins, in particular those of the trans-sialidase family. Here we discuss how these previous studies and the new findings herein impact our thoughts on the potential of prophylactic vaccination to serve a productive role in the prevention of T. cruzi infection and Chagas disease.

Hematopoietic cancer cell lines can support replication of Sabin poliovirus type 1

Viral vaccines can be produced in adherent or in suspension cells. The objective of this work was to screen human suspension cell lines for the capacity to support viral replication. As the first step, it was investigated whether poliovirus can replicate in such cell lines. Sabin poliovirus type 1 was serially passaged on five human cell lines, HL60, K562, KG1, THP-1, and U937. Sabin type 1 was capable of efficiently replicating in three cell lines (K562, KG1, and U937), yielding high viral titers after replication. Expression of CD155, the poliovirus receptor, did not explain susceptibility to replication, since all cell lines expressed CD155. Furthermore, we showed that passaged virus replicated more efficiently than parental virus in KG1 cells, yielding higher virus titers in the supernatant early after infection. Infection of cell lines at an MOI of 0.01 resulted in high viral titers in the supernatant at day 4. Infection of K562 with passaged Sabin type 1 in a bioreactor system yielded high viral titers in the supernatant. Altogether, these data suggest that K562, KG1, and U937 cell lines are useful for propagation of poliovirus.

Progress in vaccine development

Vaccination has a proven record as one of the most effective medical approaches to prevent the spread of infectious diseases. Traditional vaccine approaches involve the administration of whole killed or weakened microorganisms to stimulate protective immune responses. Such approaches deliver many microbial components, some of which contribute to protective immunity, and assist in guiding the type of immune response that is elicited. Despite their impeccable record, these approaches have failed to yield vaccines for many important infectious organisms. This has prompted a move towards more defined vaccines ('subunit vaccines'), where individual protective components are administered. This unit provides an overview of the components that are used for the development of modern vaccines including: an introduction to different vaccine types (whole organism, protein/peptide, polysaccharide, conjugate, and DNA vaccines); techniques for identifying subunit antigens; vaccine delivery systems; and immunostimulatory agents ('adjuvants'), which are fundamental for the development of effective subunit vaccines.

Polyionic vaccine adjuvants: another look at aluminum salts and polyelectrolytes

Adjuvants improve the adaptive immune response to a vaccine antigen by modulating innate immunity or facilitating transport and presentation. The selection of an appropriate adjuvant has become vital as new vaccines trend toward narrower composition, expanded application, and improved safety. Functionally, adjuvants act directly or indirectly on antigen presenting cells (APCs) including dendritic cells (DCs) and are perceived as having molecular patterns associated either with pathogen invasion or endogenous cell damage (known as pathogen associated molecular patterns [PAMPs] and damage associated molecular patterns [DAMPs]), thereby initiating sensing and response pathways. PAMP-type adjuvants are ligands for toll-like receptors (TLRs) and can directly affect DCs to alter the strength, potency, speed, duration, bias, breadth, and scope of adaptive immunity. DAMP-type adjuvants signal via proinflammatory pathways and promote immune cell infiltration, antigen presentation, and effector cell maturation. This class of adjuvants includes mineral salts, oil emulsions, nanoparticles, and polyelectrolytes and comprises colloids and molecular assemblies exhibiting complex, heterogeneous structures. Today innovation in adjuvant technology is driven by rapidly expanding knowledge in immunology, cross-fertilization from other areas including systems biology and materials sciences, and regulatory requirements for quality, safety, efficacy and understanding as part of the vaccine product. Standardizations will aid efforts to better define and compare the structure, function and safety of adjuvants. This article briefly surveys the genesis of adjuvant technology and then re-examines polyionic macromolecules and polyelectrolyte materials, adjuvants currently not known to employ TLR. Specific updates are provided for aluminum-based formulations and polyelectrolytes as examples of improvements to the oldest and emerging classes of vaccine adjuvants in use.