Vaccine technologies: From whole organisms to rationally designed protein assemblies

Vaccines have been the single most significant advancement in public health, preventing morbidity and mortality in millions of people annually. Vaccine development has traditionally focused on whole organism vaccines, either live attenuated or inactivated vaccines. While successful for many different infectious diseases whole organisms are expensive to produce, require culture of the infectious agent, and have the potential to cause vaccine associated disease in hosts. With advancing technology and a desire to develop safe, cost effective vaccine candidates, the field began to focus on the development of recombinantly expressed antigens known as subunit vaccines. While more tolerable, subunit vaccines tend to be less immunogenic. Attempts have been made to increase immunogenicity with the addition of adjuvants, either immunostimulatory molecules or an antigen delivery system that increases immune responses to vaccines. An area of extreme interest has been the application of nanotechnology to vaccine development, which allows for antigens to be expressed on a particulate delivery system. One of the most exciting examples of nanovaccines are rationally designed protein nanoparticles. These nanoparticles use some of the basic tenants of structural biology, biophysical chemistry, and vaccinology to develop protective, safe, and easily manufactured vaccines. Rationally developed nanoparticle vaccines are one of the most promising candidates for the future of vaccine development.

Aluminum in Vaccines: Addressing Parents' Concerns

With myriad frightening stories on the Internet about vaccines, parents are frequently presenting to the pediatrician with questions about the safety of vaccine ingredients, and pediatricians need to be ready to listen to families with a kind ear. Pediatricians must also feel prepared to offer thoughtful, knowledgeable advice, appreciating the parent's concerns and educating them about the irrefutable benefits as well as the potential risks of vaccination. [Pediatr Ann. 2016;45(7):e231-e233.].

[Vaccines: history and stories between reality and imagination]

Vaccinations and the controversy around them always go in parallel. We identified four categories blending in various amounts of truth and imagination: history, myths, shams and frauds. Over the years, they have alternated and sometimes transformed into one another. This sharp separation into categories is certainly academic and forced. In fact, the line between these aspects is not clear enough to allow a rigid and well-defined division. Our work starts from the category containing the most truthfulness: history, and goes on to analyze two categories that add fantasy to facts: myths and shams (or better, "old wives' tales"). The history deals with the topics of variolation and the first anti-vaccine activists' disputes. Myths that arose around immunization include immune overload, homeoprophylaxis, and excessive hygiene. In this context, immunization itself risked becoming a myth, being considered not amenable to improvements. In the category of old wives' tales we find rumors about the presence in the vaccines of considerable quantities of supposedly toxic components such as aluminum, squalene, Thimerosal and nanoparticles, as well as the existence of secret techniques of vaccine preparation that involve unethical procedures. The last category, fraud, is the poorest in both truth and fantasy but it is still hard to confront. The most famous fraud is the supposed link between vaccines and autism. In this frame, disinformation is certainly a fertile substrate for the emergence both of elements close to reality and of very imaginative ones. Vaccine hesitancy is believed to be responsible for decreasing vaccine coverage and increasing the risk of vaccine-preventable disease outbreaks and epidemics. The role of communication in immunization is essential to its success, especially taking into account the deep transformations the world of information is going through. The great multitude of voices seem to carry the same weight, but it is not so in science. Web searches are influenced by the filter bubble phenomenon, which contributes to the radicalization of people's opinion through cognitive isolation. A new, more effective strategy of communication is required in order to regain the trust of populations in immunization in a context characterized by the presence of groups impervious to scientific evidence.

Polymer-Encapsulated Aβ Peptide Fragments as an Oligomeric-Specific Vaccine for Alzheimer's Disease

Vaccination is regarded as one of the most cost-effective and reliable methods for combating disease. We have developed a new method for an oligomeric Aβ-specific AD vaccination using polymer micelle-encapsulated peptide fragments, which overcome many problems of vaccination associated with the direct use of the Aβ1–42 peptide. We studied different encapsulated forms of shortened Aβ peptides with and without the entire T cell epitope in an APP/PS1 mouse model. After two inoculations with encapsulated Aβ fragments, antibodies were produced in all mice with antibody titer greater than 1:12,800. No anti-polymer antibodies were detected after five inoculations, and none of the injected mice showed any adverse effects throughout experimentation. Anti-Aβ antibodies from our polymer-encapsulated vaccine were able to bind to A plaques in the brain of our mice, and were able to specifically recognize oligomeric Aβ. Our results suggest that the safety and efficacy issues previously encountered in other Aβ vaccination trials may be successfully addressed by using micelle-encapsulated peptides. These shorter Aβ fragments are also easier to synthesize and more cost-effective than the highly hydrophobic full-length Aβ1–42 peptide.

Advanced Nanobiomaterials: Vaccines, Diagnosis and Treatment of Infectious Diseases

The use of nanoparticles has contributed to many advances due to their important properties such as, size, shape or biocompatibility. The use of nanotechnology in medicine has great potential, especially in medical microbiology. Promising data show the possibility of shaping immune responses and fighting severe infections using synthetic materials. Different studies have suggested that the addition of synthetic nanoparticles in vaccines and immunotherapy will have a great impact on public health. On the other hand, antibiotic resistance is one of the major concerns worldwide; a recent report of the World Health Organization (WHO) states that antibiotic resistance could cause 300 million deaths by 2050. Nanomedicine offers an innovative tool for combating the high rates of resistance that we are fighting nowadays, by the development of both alternative therapeutic and prophylaxis approaches and also novel diagnosis methods. Early detection of infectious diseases is the key to a successful treatment and the new developed applications based on nanotechnology offer an increased sensibility and efficiency of the diagnosis. The aim of this review is to reveal and discuss the main advances made on the science of nanomaterials for the prevention, diagnosis and treatment of infectious diseases. Highlighting innovative approaches utilized to: (i) increasing the efficiency of vaccines; (ii) obtaining shuttle systems that require lower antibiotic concentrations; (iii) developing coating devices that inhibit microbial colonization and biofilm formation.

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.

Novel Ricin Subunit Antigens With Enhanced Capacity to Elicit Toxin-Neutralizing Antibody Responses in Mice

RiVax is a candidate ricin toxin subunit vaccine antigen that has proven to be safe in human phase I clinical trials. In this study, we introduced double and triple cavity-filling point mutations into the RiVax antigen with the expectation that stability-enhancing modifications would have a beneficial effect on overall immunogenicity of the recombinant proteins. We demonstrate that 2 RiVax triple mutant derivatives, RB (V81L/C171L/V204I) and RC (V81I/C171L/V204I), when adsorbed to aluminum salts adjuvant and tested in a mouse prime-boost-boost regimen were 5- to 10-fold more effective than RiVax at eliciting toxin-neutralizing serum IgG antibody titers. Increased toxin neutralizing antibody values and seroconversion rates were evident at different antigen dosages and within 7 days after the first booster. Quantitative stability/flexibility relationships analysis revealed that the RB and RC mutations affect rigidification of regions spanning residues 98-103, which constitutes a known immunodominant neutralizing B-cell epitope. A more detailed understanding of the immunogenic nature of RB and RC may provide insight into the fundamental relationship between local protein stability and antibody reactivity.

Spontaneous Protein Adsorption on Graphene Oxide Nanosheets Allowing Efficient Intracellular Vaccine Protein Delivery

Nanomaterials hold potential of altering the interaction between therapeutic molecules and target cells or tissues. High aspect ratio nanomaterials in particular have been reported to possess unprecedented properties and are intensively investigated for their interaction with biological systems. Graphene oxide (GOx) is a water-soluble graphene derivative that combines high aspect ratio dimension with functional groups that can be exploited for bioconjugation. Here, we demonstrate that GOx nanosheets can spontaneously adsorb proteins by a combination of interactions. This property is then explored for intracellular protein vaccine delivery, in view of the potential of GOx nanosheets to destabilize lipid membranes such as those of intracellular vesicles. Using a series of in vitro experiments, we show that GOx nanosheet adsorbed proteins are efficiently internalized by dendritic cells (DCs: the most potent class of antigen presenting cells of the immune system) and promote antigen cross-presentation to CD8 T cells. The latter is a hallmark in the induction of potent cellular antigen-specific immune responses against intracellular pathogens and cancer.

The Use of Microwave-Assisted Solid-Phase Peptide Synthesis and Click Chemistry for the Synthesis of Vaccine Candidates Against Hookworm Infection

A protein-based vaccine approach against hookworm infection has failed to deliver the expected outcome, due to a problem with an allergic response in the patient or difficulties in the proteins' production. This implication could be overcome by using a chemically synthesized peptide-based vaccine approach. This approach utilizes minimal pathogenic components that are necessary for the stimulation of the immune response without triggering adverse side effects. To boost the peptide's immunogenicity, a lipid core peptide (LCP) system can be utilized as a carrier molecule/immunostimulant. This chapter describes in detail the synthesizing of protected lipoamino acid, the self-adjuvanting moiety (LCP core), the peptide epitope, and the final vaccine candidate. The subunit peptide and the LCP core were synthesized using microwave-assisted solid-phase peptide synthesis (SPPS). Then the final hookworm vaccine construct was assembled using the copper-catalyzed azide-alkyne cycloaddition, or "click," reaction.

Applications of an Automated and Quantitative CE-Based Size and Charge Western Blot for Therapeutic Proteins and Vaccines

Capillary Electrophoresis (CE) is a versatile and indispensable analytical tool that can be applied to characterize proteins. In recent years, labor-intensive SDS-PAGE and IEF slab gels have been replaced with CE-SDS (CGE) and CE-IEF methods, respectively, in the biopharmaceutical industry. These two CE-based methods are now an industry standard and are an expectation of the regulatory agencies for biologics characterization. Another important and traditional slab gel technique is the western blot, which detects proteins using immuno-specific reagents after SDS-PAGE separation. This technique is widely used across industrial and academic laboratories, but it is very laborious, manual, time-consuming, and only semi-quantitative. Here, we describe the applications of a relatively new CE-based western blot technology which is automated, fast, and quantitative. We have used this technology for both charge- and size-based CE westerns to analyze biotherapeutic and vaccine products. The size-based capillary western can be used for fast antibody screening, clone selection, product titer, identity, and degradation while the charge-based capillary western can be used to study product charge heterogeneity. Examples using this technology for monoclonal antibody (mAb), Enbrel, CRM197, and Clostridium difficile (C. difficile) vaccine proteins are presented here to demonstrate the utility of the capillary western techniques. Details of sample preparation and experimental conditions for each capillary western mode are described in this chapter.

Identification and evaluation of vaccine candidate antigens from the poultry red mite (Dermanyssus gallinae)

•

Ten poultry red mite vaccine candidate antigens were identified and recombinant versions produced.

•

Mite mortality was monitored after feeding on the blood from vaccinated hens.

•

A ⩾1.6-fold increased risk of mite death was observed with four of the vaccine candidates (P < 0.001).

•

Best candidates include: a serpin, vitellogenin, hemelipoglycoprotein and a novel protein.

An aqueous extract of the haematophagous poultry ectoparasite, Dermanyssus gallinae, was subfractionated using anion exchange chromatography. Six of these subfractions were used to immunise hens and the blood from these hens was fed, in vitro, to poultry red mites. Mite mortality following these feeds was indicative of protective antigens in two of the subfractions, with the risks of mites dying being 3.1 and 3.7 times higher than in the control group (P < 0.001). A combination of two-dimensional immunoblotting and immunoaffinity chromatography, using IgY from hens immunised with these subfractions, was used in concert with proteomic analyses to identify the strongest immunogenic proteins in each of these subfractions. Ten of the immunoreactive proteins were selected for assessment as vaccine candidates using the following criteria: intensity of immune recognition; likelihood of exposure of the antigen to the antibodies in a blood meal; proposed function and known vaccine potential of orthologous molecules. Recombinant versions of each of these 10 proteins were produced in Escherichia coli and were used to immunise hens. Subsequent in vitro feeding of mites on blood from these birds indicated that immunisation with Deg-SRP-1 (serpin), Deg-VIT-1 (vitellogenin), Deg-HGP-1 (hemelipoglycoprotein) or Deg-PUF-1 (a protein of unknown function) resulted in significantly increased risk of mite death (1.7–2.8 times higher than in mites fed blood from control hens immunised with adjuvant only, P < 0.001). The potential for using these antigens in a recombinant vaccine is discussed.

Nanoengineering of vaccines using natural polysaccharides

Currently, there are over 70 licensed vaccines, which prevent the pathogenesis of around 30 viruses and bacteria. Nevertheless, there are still important challenges in this area, which include the development of more active, non-invasive, and thermo-resistant vaccines. Important biotechnological advances have led to safer subunit antigens, such as proteins, peptides, and nucleic acids. However, their limited immunogenicity has demanded potent adjuvants that can strengthen the immune response. Particulate nanocarriers hold a high potential as adjuvants in vaccination. Due to their pathogen-like size and structure, they can enhance immune responses by mimicking the natural infection process. Additionally, they can be tailored for non-invasive mucosal administration (needle-free vaccination), and control the delivery of the associated antigens to a specific location and for prolonged times, opening room for single-dose vaccination. Moreover, they allow co-association of immunostimulatory molecules to improve the overall adjuvant capacity.

The natural and ubiquitous character of polysaccharides, together with their intrinsic immunomodulating properties, their biocompatibility, and biodegradability, justify their interest in the engineering of nanovaccines. In this review, we aim to provide a state-of-the-art overview regarding the application of nanotechnology in vaccine delivery, with a focus on the most recent advances in the development and application of polysaccharide-based antigen nanocarriers.

Discovering protective CD8 T cell epitopes--no single immunologic property predicts it!

Once a burgeoning field of study, over the past decade or so, T cell epitope discovery has lost some luster. The contributory factors perchance are the general notion that any newly discovered epitope will reveal very little about an immune response and that knowledge of epitopes are less critical for vaccine design. Despite these notions, the breadth and depth of T cell epitopes derived from clinically important microbial agents of human diseases largely remain ill defined. We review here a flurry of recent reports that have rebirthed the field. These reports reveal that epitope discovery is an essential step toward rational vaccine design and critical for monitoring vaccination efficacy. The new findings also indicate that neither immunogenicity nor immunodominance predict protective immunity. Hence, an immunogenic epitope is but a peptide unless proven protective against disease.

Immunopotentiator-Loaded Polymeric Microparticles as Robust Adjuvant to Improve Vaccine Efficacy

PURPOSE

Adjuvants are required to ensure the efficacy of subunit vaccines. Incorporating molecular immunopotentiators within particles could overcome drawbacks of molecular adjuvants (such as solubility and toxicity), and improve adjuvanticity of particles, achieving stronger adjuvant activity. Aim of this study is to evaluate the adjuvanticity of immunopotentiator-loaded polymeric particles for subunit vaccine.

METHODS

PLGA microparticles (PMPs) and imiquimod (TLR-7 ligand)-loaded PLGA microparticles (IPMPs) were prepared by SPG premix membrane emulsification. In vitro and in vivo studies were performed to their adjuvant activity, using ovalbumin and H5N1 influenza split vaccine as antigens.

RESULTS

Incorporating imiquimod into microparticles significantly improved the efficacy of PLGA microparticles in activating BMDCs and pMΦs, and antigen uptake by pMΦs was also promoted. IPMPs showed stronger adjuvanticity to augment OVA-specific immune responses than PMPs. IgG subclass profiles and cytokine secretion levels by splenocytes indicated that IPMPs elicited more Th1-polarized immune response, compared to PMPs. In vivo study using H5N1 influenza split vaccine as antigen also confirmed the effects of IPMPs on antigen-specific cellular immunity.

CONCLUSIONS

Considering adjuvanticity and safety profiles (PLGA and IMQ, both approved by FDA), we conclude that IMQ-loaded PLGA microparticles are promising robust adjuvant for subunit vaccines.

Guiding principles in the design of molecular bioconjugates for vaccine applications

Antigen- and adjuvant-based bioconjugates that can stimulate the immune system play an important role in vaccine applications. Bioconjugates have demonstrated unique physicochemical and biological properties, enabling vaccines to be delivered to key immune cells, to target specific intracellular pathways, or to mimic immunogenic properties of natural pathogens. In this Review we highlight recent advances in such molecular immunomodulators, with an emphasis on the structure-function relationships that provide the foundation for rational design of safe and effective vaccines and immunotherapies.

In planta production of flock house virus transencapsidated RNA and its potential use as a vaccine

We have developed a transencapsidated vaccine delivery system based on the insect virus, Flock House virus (FHV). FHV is attractive due to its small genome size, simple organization, and nonpathogenic characteristics. With the insertion of a Tobacco mosaic virus (TMV) origin of assembly (Oa), the independently replicating FHV RNA1 can be transencapsidated by TMV coat protein. In this study, we demonstrated that the Oa-adapted FHV RNA1 transencapsidation process can take place in planta, by using a bipartite plant expression vector system, where TMV coat protein is expressed by another plant virus vector, Foxtail mosaic virus (FoMV). Dual infection in the same cell by both FHV and FoMV was observed. Though an apparent classical coat protein-mediated resistance repressed FHV expression, this was overcome by delaying inoculation of the TMV coat protein vector by 3 days after FHV vector inoculation. Expression of the transgene marker in animals by these in vivo-generated transencapsidated nanoparticles was confirmed by mouse vaccination, which also showed an improved vaccine response compared to similar in vitro-produced vaccines.

Phospholipid bilayer-coated aluminum nanoparticles as an effective vaccine adjuvant-delivery system

The phospholipid bilayer-coated aluminum nanoparticles (PLANs), formed via chemisorption, were prepared by reverse ethanol injection-lyophilization (REIL) utilizing the phosphophilicity of aluminum. The anhydrous antigen-loaded PLANs obtained by REIL proved stable, satisfying using the controlled-temperature-chain instead of the integrated cold-chain for distribution, and could be rehydrated to reconstitute instantly an aqueous suspension of the antigen-PLANs, which were more readily taken up by antigen-presenting cells and, when given subcutaneously to mice, induced more robust antigen-specific humoral and cellular immunoresponses but less local inflammation than the antigen-alum. Thus, the PLANs are a useful vaccine adjuvant-delivery system with advantages over the widely used naked alum.

Computational peptide vaccinology

Immunoinformatics focuses on modeling immune responses for better understanding of the immune system and in many cases for proposing agents able to modify the immune system. The most classical of these agents are vaccines derived from living organisms such as smallpox or polio. More modern vaccines comprise recombinant proteins, protein domains, and in some cases peptides. Generating a vaccine from peptides however requires technologies and concepts very different from classical vaccinology. Immunoinformatics therefore provides the computational tools to propose peptides suitable for formulation into vaccines. This chapter introduces the essential biological concepts affecting design and efficacy of peptide vaccines and discusses current methods and workflows applied to design successful peptide vaccines using computers.

Sociological Environmental Causes are Insufficient to Explain Autism Changepoints of Incidence

The Environmental Protection Agency (EPA) recently published a study analyzing time trends in the cumulative incidence of autistic disorder (AD) in the U.S., Denmark, and worldwide. A birth year changepoint (CP) around 1988 was identified. It has been argued that the epidemic rise in autism over the past three decades is partly due to a combination of sociologic factors along with the potential contribution of thimerosal containing vaccines. Our work conducted an expanded analysis of AD changepoints in CA and U.S., and determined whether changepoints in time trends of AD rates temporally coincide with changepoints for the proposed causative sociologic and environmental factors. Birth year changepoints were identified for 1980.9 [95% CI, 1978.6-1983.1], 1988.4 [95% CI, 1987.8-1989.0] and 1995.6 [95% CI, 1994.6-1996.6] for CA and U.S. data, confirming and expanding the EPA results. AD birth year changepoints significantly precede the changepoints calculated for indicators of increased social awareness of AD. Furthermore, the 1981 and 1996 AD birth year changepoints don't coincide with any predicted changepoints based on altered thimerosal content in vaccines nor on revised editions of the Diagnostic and Statistical Manual of Mental Disorders (DSM).

Synthesis and immunological effects of heroin vaccines

Three haptens have been synthesized with linkers for attachment to carrier macromolecules at either the piperidino-nitrogen or via an introduced 3-amino group. Two of the haptens, with a 2-oxopropyl functionality at either C6, or at both the C3 and C6 positions on the 4,5-epoxymorphinan framework, as well as the third hapten (DiAmHap) with diamido moieties at both the C3 and C6 positions, should be much more stable in solution, or in vivo in a vaccine, than a hapten with an ester in one of those positions, as found in many heroin-based haptens. A "classical" opioid synthetic scheme enabled the formation of a 3-amino-4,5-epoxymorphinan which could not be obtained using palladium chemistry. Our vaccines are aimed at the reduction of the abuse of heroin and, as well, at the reduction of the effects of its predominant metabolites, 6-acetylmorphine and morphine. One of the haptens, DiAmHap, has given interesting results in a heroin vaccine and is clearly more suited for the purpose than the other two haptens.

Hydrogels and scaffolds for immunomodulation

For over two decades, immunologists and biomaterials scientists have co-existed in parallel world with the rationale of understanding the molecular profile of immune responses to vaccination, implantation, and treating incurable diseases. Much of the field of biomaterial-based immunotherapy has relied on evaluating model antigens such as chicken egg ovalbumin in mouse models but their relevance to humans has been point of much discussion. Nevertheless, such model antigens have provided important insights into the mechanisms of immune regulation and served as a proof-of-concept for plethora of biomaterial-based vaccines. After years of extensive development of numerous biomaterials for immunomodulation, it is only recently that an experimental scaffold vaccine implanted beneath the skin has begun to use the human model to study the immune responses to cancer vaccination by co-delivering patient-derived tumor lysates and immunomodulatory proteins. If successful, this scaffold vaccine will change the way we approached untreatable cancers, but more importantly, will allow a faster and more rational translation of therapeutic regimes to other cancers, chronic infections, and autoimmune diseases. Most materials reviews have focused on immunomodulatory adjuvants and micro-nano-particles. Here we provide an insight into emerging hydrogel and scaffold based immunomodulatory approaches that continue to demonstrate efficacy against immune associated diseases.

Characterization and optimization of heroin hapten-BSA conjugates: method development for the synthesis of reproducible hapten-based vaccines

A potential new treatment for drug addiction is immunization with vaccines that induce antibodies that can abrogate the addictive effects of the drug of abuse. One of the challenges in the development of a vaccine against drugs of abuse is the availability of an optimum procedure that gives reproducible and high yielding hapten-protein conjugates. In this study, a heroin/morphine surrogate hapten (MorHap) was coupled to bovine serum albumin (BSA) using maleimide-thiol chemistry. MorHap-BSA conjugates with 3, 5, 10, 15, 22, 28, and 34 haptens were obtained using different linker and hapten ratios. Using this optimized procedure, MorHap-BSA conjugates were synthesized with highly reproducible results and in high yields. The number of haptens attached to BSA was compared by 2,4,6-trinitrobenzenesulfonic acid (TNBS) assay, modified Ellman's test and matrix assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS). Among the three methods, MALDI-TOF MS discriminated subtle differences in hapten density. The effect of hapten density on enzyme-linked immunosorbent assay (ELISA) performance was evaluated with seven MorHap-BSA conjugates of varying hapten densities, which were used as coating antigens. The highest antibody binding was obtained with MorHap-BSA conjugates containing 3-5 haptens. This is the first report that rigorously analyzes, optimizes and characterizes the conjugation of haptens to proteins that can be used for vaccines against drugs of abuse. The effect of hapten density on the ELISA detection of antibodies against haptens demonstrates the importance of careful characterization of the hapten density by the analytical techniques described.

Gradated assembly of multiple proteins into supramolecular nanomaterials

Biomaterials exhibiting precise ratios of different bioactive protein components are critical for applications ranging from vaccines to regenerative medicine, but their design is often hindered by limited choices and cross-reactivity of protein conjugation chemistries. Here, we describe a strategy for inducing multiple different expressed proteins of choice to assemble into nanofibres and gels with exceptional compositional control. The strategy employs 'βTail' tags, which allow for good protein expression in bacteriological cultures, yet can be induced to co-assemble into nanomaterials when mixed with additional β-sheet fibrillizing peptides. Multiple different βTail fusion proteins could be inserted into peptide nanofibres alone or in combination at predictable, smoothly gradated concentrations, providing a simple yet versatile route to install precise combinations of proteins into nanomaterials. The technology is illustrated by achieving precisely targeted hues using mixtures of fluorescent proteins, by creating nanofibres bearing enzymatic activity, and by adjusting antigenic dominance in vaccines.

Nanoporous polyelectrolyte vaccine microcarriers. A formulation platform for enhancing humoral and cellular immune responses

In this paper we report on the design, characterization and immuno-biological evaluation of nanoporous polyelectrolyte microparticles as vaccine carrier. Relative to soluble antigen, formulation of antigen as a sub-10 μm particle can strongly enhance antigen-specific cellular immune responses. The latter is crucial to confer protective immunity against intracellular pathogens and for anti-cancer vaccines. However, a major bottleneck in microparticulate vaccine formulation is the development of generic strategies that afford antigen encapsulation under benign and scalable conditions. Our strategy is based on spray drying of a dilute aqueous solution of antigen, oppositely charged polyelectrolytes and mannitol as a pore-forming component. The obtained solid microparticles can be redispersed in aqueous medium, leading to leaching out of the mannitol, thereby creating a highly porous internal structure. This porous structure enhances enzymatic processing of encapsulated proteins. After optimizing the conditions to process these microparticles we demonstrate that they strongly enhance cross-presentation in vitro by dendritic cells to CD8 T cells. In vivo experiments in mice confirm that this vaccine formulation technology is capable of enhancing cellular immune responses.