Guiding principles in the design of molecular bioconjugates for vaccine applications

Computational Development of Transmission-Blocking Vaccine Candidates Based on Fused Antigens of Pre- and Post-fertilization Gametocytes Against Plasmodium falciparum

Plasmodium falciparum is the most fatal species of malaria parasites in humans. Attempts at developing vaccines against the malaria parasites have not been very successful even after the approval of the RTS, S/AS01 vaccine. There is a continuous need for more effective vaccines including sexual-stage antigens that could block the transmission of malaria parasites between mosquitoes and humans. Low immunogenicity, expression, and stability are some of the challenges of transmission-blocking vaccine (TBV). This study was designed to computationally identify TBV candidates based on fused antigens by combining highly antigenic peptides from prefertilization (Pfs230, Pfs48/45) and postfertilization (Pfs25, Pfs28) gametocytes. The peptides were selected based on their antigenicity, nonallergenicity, and lack of similarity with the human proteome. Two fused antigens vaccine candidates (FAVCs) were constructed using Flagellin Salmonella enterica (FAVC-FSE) and Cholera toxin B (FAVC-CTB) as adjuvants. The constructs were evaluated for their physicochemical properties, structural stability, immunogenicity, and potential to elicit cross-protection across multiple Plasmodium species. The results yielded antigenic peptides, with antigenicity scores between 0.7589 and 1.1821. The structural analysis of FAVC-FSE and FAVC-CTB showed a Z-score of -6.70 and -4.79, a Ramachandran plot of 96.94% and 94.86% with overall quality of 94.20% and 89.85%, respectively. The FAVCs contained CD8+, CD4+, and linear B-cell epitopes with antigenicity scores between 1.2089 and 2.8623, 0.5663 and 2.4132, and 1.5196 and 2.2212, respectively. Each FAVC generated 6 conformational B-cells. High population coverage values were recorded for the FAVCs. The ability of the FAVCs to trigger immune response was evaluated through an in silico immune stimulation. The low-binding interaction energy that resulted from molecular docking and dynamics simulations showed a strong affinity of FAVCs to Toll-like receptor 5 (TLR5). The results indicate that the FAVC-FSE vaccine candidate is more promising to interrupt P falciparum transmission and provides a baseline for experimental validation.

Innovative translational platforms for rapid developing clinical vaccines against COVID-19 and other infectious disease

A vaccine is a biological preparation that contains the antigen capable of stimulating the immune system to form the defense against pathogens. Vaccine development often confronts big challenges, including time/energy-consuming, low efficacy, lag to pathogen emergence and mutation, and even safety concern. However, these seem now mostly conquerable through constructing the advanced translational platforms that can make innovative vaccines, sometimes, potentiated with a distinct multifunctional VADS (vaccine adjuvant delivery system), as evidenced by the development of various vaccines against the covid-19 pandemic at warp speed. Particularly, several covid-19 vaccines, such as the viral-vectored vaccines, mRNA vaccines and DNA vaccines, regarded as the innovative ones that are rapidly made via the high technology-based translational platforms. These products have manifested powerful efficacy while showing no unacceptable safety profile in clinics, allowing them to be approved for massive vaccination at also warp speed. Now, the proprietary translational platforms integrated with the state-of-the-art biotechnologies, and even the artificial intelligence (AI), represent an efficient mode for rapid making innovative clinical vaccines against infections, thus increasingly attracting interests of vaccine research and development. Herein, the advanced translational platforms for making innovative vaccines, together with their design principles and immunostimulatory efficacies, are comprehensively elaborated.

Novel sialoglycan linkage for constructing adjuvant-protein conjugate as potent vaccine for COVID-19

Self-adjuvanting protein vaccines have been proved to be highly immunogenic with efficient codelivery of adjuvant and antigen. Current protein vaccines with built-in adjuvants are all modified at the peptide backbone of antigen protein, which could not achieve minor epitope interference and adjuvant multivalency at the same time. Herein, we developed a new conjugate strategy to construct effective adjuvant-protein vaccine with adjuvant cluster effect and minimal epitope interference. The toll-like receptor 7 agonist (TLR7a) is covalently conjugated on the terminal sialoglycans of SARS-CoV-2-S1 protein, leading to intracellular release of the small-molecule stimulators with greatly reduced risks of systemic toxicity. The resulting TLR7a-S1 conjugate elicited strong activation of immune cells in vitro, and potent antibody and cellular responses with a significantly enhanced Th1-bias in vivo. TLR7a-S1-induced antibody also effectively cross-neutralized all variants of concern. This sialoglycoconjugation approach to construct protein conjugate vaccines will have more applications to combat SARS-CoV-2 and other diseases.

Molecular DNA dendron vaccines

A foundational principle of rational vaccinology is that vaccine structure plays a critical role in determining therapeutic efficacy, but in order to establish fundamental, effective, and translatable vaccine design parameters, a highly modular and well-defined platform is required. Herein, we report a DNA dendron vaccine, a molecular nanostructure that consists of an adjuvant DNA strand that splits into multiple DNA branches with a varied number of conjugated peptide antigens that is capable of dendritic cell uptake, immune activation, and potent cancer killing. We leveraged the well-defined architecture and chemical modularity of the DNA dendron to study structure-function relationships that dictate molecular vaccine efficacy, particularly regarding the delivery of immune-activating DNA sequences and antigenic peptides on a single chemical construct. We investigated how adjuvant and antigen placement and number impact dendron cellular uptake and immune activation, in vitro. These parameters also played a significant role in raising a potent and specific immune response against target cancer cells. By gaining this structural understanding of molecular vaccines, DNA dendrons successfully treated a mouse cervical human papillomavirus TC-1 cancer model, in vivo, where the vaccine structure defined its efficacy; the top-performing design effectively reduced tumor burden (<150 mm³ through day 30) and maintained 100% survival through 44 d after tumor inoculation.

Effect of carrier molecular weight on physicochemical properties and the in vitro immune-stimulatory activity of the CpG-dextran conjugates

The effect of dextran molecular weight on the in vitro physicochemical and immune properties of cytosine-phosphate-guanine (CpG) oligodeoxynucleotide-amino-dextran conjugates is investigated. CpG-1668 was conjugated at the 3'-end to amino-dextran of differing molecular weight (20, 40, 70 or 110-kDa) via a stable bis-aryl hydrazone linkage. Conjugate formation was confirmed by agarose gel electrophoresis and dynamic light scattering measured the size and surface charge of conjugates. Uptake and immune-stimulatory activity of CpG-dextran by antigen-presenting cells was evaluated by flow cytometry and confocal microscopy. Degradation by DNase I was monitored by loss of the fluorescent signal from labelled CpG and changes in size and zeta potential. Hydrazone bond formation (UV 354 nm) showed on average four CpG molecules conjugated per polymer. CpG-dextran prepared from 20 or 40-kDa dextran had a size of 17 nm while 70 or 110-kDa was 30 nm. CpG-dextran was preferentially taken up by dendritic cells, followed by macrophages and then B-cells. Only the 20-kDa dextran conjugate significantly enhanced uptake by bone-marrow derived dendritic cells (BMDCs) compared to free CpG. Confocal microscopy showed that CpG and CpG-dextran accumulates in the endo-lysosomal compartment of BMDCs at 24 h. All conjugates upregulated activation markers (CD40, CD80 or CD86) of BMDCs to a similar level as for free CpG. CpG-dextran 40-kDa produced highest levels of cytokines (TNF-α, IL-6, and IL-12p70) secreted by BMDCs. Enzymatic protection assays showed that the conjugate made from dextran 20-kDa provided no protection for CpG while the higher molecular weight conjugates reduced degradation by DNase I. The 40-kDa dextran conjugate produced the greatest in vitro immune activity, this was due to the conjugate being relatively small in size for cell uptake while sufficiently large enough to protect CpG from nuclease attack. These in vitro studies identify the need to consider the molecular weight of the carrier in bioconjugate design.

Designing a Multi-Epitope Vaccine against Toxoplasma gondii: An Immunoinformatics Approach

Infection with the intracellular apicomplexan parasite Toxoplasma gondii causes serious clinical outcomes in both human and veterinary settings worldwide. Although approximately one-third of the world’s population is infected with T. gondii, an effective human vaccine for this disease remains unavailable. We aimed to design a potential T. gondii vaccine candidate that consisted of the B- and T-lymphocyte epitopes of three parasite immunogenic antigens. Firstly, the immunodominant epitopes expressed within the ROP2, MIC3, and GRA7 proteins of T. gondii were identified. Subsequently, six B-cell epitopes, five CTL epitopes, and five HTL epitopes were combined to generate a multi-epitope vaccine, and the 50S ribosomal protein L7/L12 was added as an adjuvant to boost the vaccine’s immunogenicity. All these epitopes were found to be antigenic, nonallergenic, nontoxic, and nonhuman homologs. The designed vaccine construct has a molecular weight of 51 kDa, an antigenicity score of 0.6182, and a solubility of 0.903461. Likewise, the candidate vaccine was immunogenic, nonallergenic, and stable. Molecular docking analysis revealed stable interactions between the vaccine construct and the TLR-4 immune receptor. Meanwhile, the stability of the developed vaccine was validated using molecular dynamics simulation. In silico, the vaccine construct was able to trigger primary immune responses. However, further laboratory-based assessments are needed to confirm its efficacy and safety.

Reverse vaccinology approach to design a multi-epitope vaccine construct based on the Mycobacterium tuberculosis biomarker PE_PGRS17

Mycobacterium tuberculosis (Mtb) is responsible for high mortality rates in many low- and middle-income countries. This infectious disease remains accountable for around 1.4 million deaths yearly. Finding effective control measures against Mtb has become imperative. Vaccination has been regarded as the safe and lasting control measure to curtail the impact of Mtb. This study used the Mtb protein biomarker PE_PGRS17 to design a multi-epitope vaccine. A previous study predicted a strong antigenic property of PE_PGRS17. Immunogenic properties such as antigenicity, toxicity, and allergenicity were predicted for the PE_PGRS17 biomarker, specific B- and T-cell epitope sequences, and the final multiple epitope vaccine (MEV) construct. Algorithmic tools predicted the T- and B-cell epitopes and those that met the immunogenic properties were selected to construct the MEV candidate for predicted vaccine development. The epitopes were joined via linkers and an adjuvant was attached to the terminals of the entire vaccine construct. Immunogenic properties, and physicochemical and structural predictions gave insight into the MEV construct. The assembled vaccine candidate was docked with a receptor and validated using web-based tools. An immune simulation was performed to imitate the immune response after exposure to a dosed administrated predicted MEV subunit. An in silico cloning and codon optimisation gave insight into optimal expression conditions regarding the MEV candidate. In conclusion, the generated MEV construct may potentially emit both cellular and humoral responses which are vital in the development of a peptide-based vaccine against Mtb; nonetheless, further experimental validation is still required.

Calix[n]arene-based immunogens: A new non-proteic strategy for anti-cocaine vaccine

Introduction

Cocaine use disorder is a significant public health issue without a current specific approved treatment. Among different approaches to this disorder, it is possible to highlight a promising immunologic strategy in which an immunogenic agent may reduce the reinforcing effects of the drug if they are able to yield sufficient specific antibodies capable to bind cocaine and/or its psychoactive metabolites before entering into the brain. Several carriers have been investigated in the anti-cocaine vaccine development; however, they generally present a very complex chemical structure, which potentially hampers the proper assessment of the coupling efficiency between the hapten units and the protein structure.

Objectives

The present study reports the design, synthesis and preclinical evaluation of two novel calix[n]arene-based anti-cocaine immunogens (herein named as V4N2 and V8N2) by the tethering of the hydrolysis-tolerant hapten GNE (15) on calix[4]arene and calix[8]arene moieties.

Methods

The preclinical assessment corresponded to the immunogenicity and dose-response evaluation of V4N2 and V8N2. The potential of the produced antibodies to reduce the passage of cocaine analogue through the blood-brain-barrier (BBB), modifying its biodistribution was also investigated.

Results

Both calix[n]arene-based immunogens elicited high titers of cocaine antibodies that modified the biodistribution of a cocaine radiolabeled analogue (99mTc-TRODAT-1) and decreased cocaine-induced behavior, according to an animal model.

Conclusion

The present results demonstrate the potential of V4N2 and V8N2 as immunogens for the treatment of cocaine use disorder.

Hybrid Membrane Nanovaccines Combined with Immune Checkpoint Blockade to Enhance Cancer Immunotherapy

Purpose

Cancer vaccines are a promising therapeutic approach in cancer immunotherapy and can inhibit tumor growth and prevent tumor recurrence and metastasis by activating a sustained antitumor immunoprotective effect. However, the therapeutic effect of cancer vaccines is severely weakened by the low immunogenicity of cancer antigens and the immunosuppressive microenvironment in tumor tissues.

Methods

Here, we report a novel hybrid membrane nanovaccine, composed of mesoporous silica nanoparticle as a delivery carrier, hybrid cell membranes obtained from dendritic cells and cancer cells, and R837 as an immune adjuvant (R837@HM-NPs). We investigated the anti-tumor, tumor recurrence and metastasis prevention abilities of R837@HM-NPs and their mechanisms of action through a series of in vivo and ex vivo experiments.

Results

R837@HM-NPs not only provide effective antigenic stimulation but are also a durable supply of the immune adjuvant R837. In addition, R837@HM-NPs promote antigen endocytosis into dendritic cells via various receptor-mediated pathways. Compared with HM-NPs or R837@HM-NPs, R837@HM-NPs in combination with an immune checkpoint blockade showed stronger antitumor immune responses in inhibiting tumor growth, thus eliminating established tumors, and rejecting re-challenged tumors by regulating the immunosuppressive microenvironment and immunological memory effect.

Conclusion

These findings suggest that the hybrid membrane nanovaccine in combination with immune checkpoint blockade is a powerful strategy to enhance antitumor immunotherapy without concerns of systemic toxicity.

Safety Evaluation of Nanotechnology Products

Nanomaterials are now being used in a wide variety of biomedical applications. Medical and health-related issues, however, have raised major concerns, in view of the potential risks of these materials against tissue, cells, and/or organs and these are still poorly understood. These particles are able to interact with the body in countless ways, and they can cause unexpected and hazardous toxicities, especially at cellular levels. Therefore, undertaking in vitro and in vivo experiments is vital to establish their toxicity with natural tissues. In this review, we discuss the underlying mechanisms of nanotoxicity and provide an overview on in vitro characterizations and cytotoxicity assays, as well as in vivo studies that emphasize blood circulation and the in vivo fate of nanomaterials. Our focus is on understanding the role that the physicochemical properties of nanomaterials play in determining their toxicity.

Subtractive Proteomics and Immuno-informatics Approaches for Multi-peptide Vaccine Prediction Against Klebsiella oxytoca and Validation Through In Silico Expression

Klebsiella oxytoca is a gram-negative bacterium. It is opportunistic in nature and causes hospital acquired infections. Subtractive proteomics and reverse vaccinology approaches were employed to screen out the best proteins for vaccine designing. Whole proteome of K. oxytoca strain ATCC 8724, consisting of 5483 proteins, was used for designing the vaccine. Total 1670 cytotoxic T lymphocyte (CTL) epitope were predicted through NetCTL while 1270 helper T lymphocyte (HTL) epitopes were predicted through IEDB server. The epitopes were screened for non-toxicity, allergenicity, antigenicity and water solubility. After epitope screening 300 CTL and 250 HTL epitopes were submitted to IFN-γ epitope server to predict their Interferon-γ induction response. The selected IFN-γ positive epitopes were tested for their binding affinity with MHCI-DRB1 by MHCPred. The 15 CTL and 13 HTL epitopes were joined by linkers AAY and GPGPG respectively in vaccine construct. Chain C of Pam3CSK4 (PDB ID; 2Z7X) was linked to the vaccine construct as an adjuvant. A 450aa long vaccine construct was submitted to I-TASSER server for 3D structure prediction. Thirteen Linear B cells were predicted by ABCPred server and 10 sets of discontinues epitopes for 3D vaccine structure were predicted by DiscoTope server. The modeled 3D vaccine construct was docked with human Toll-like receptor 2 (PDB ID: 6NIG) by PatchDock. The docked complexes were refined by FireDock. The selected docked complex showed five hydrogen bonds and one salt bridge. The vaccine sequence was reverse transcribed to get nucleotide sequence for In silico cloning. The reverse transcribed sequence strand was cloned in pET28a(+) expression vector. A clone containing 6586 bp was constructed including the 450 bp of query gene sequence.

An immunoinformatics approach to design a multi-epitope vaccine against Mycobacterium tuberculosis exploiting secreted exosome proteins

Tuberculosis is one the oldest known affliction of mankind caused by the pathogen Mycobacterium tuberculosis. Till date, there is no absolute single treatment available to deal with the pathogen, which has acquired a great potential to develop drug resistance rapidly. BCG is the only anti-tuberculosis vaccine available till date which displays limited global efficacy due to genetic variation and concurrent pathogen infections. Extracellular vesicles or exosomes vesicle (EVs) lie at the frontier cellular talk between pathogen and the host, and therefore play a significant role in establishing pathogenesis. In the present study, an in-silico approach has been adopted to construct a multi-epitope vaccine from selected immunogenic EVs proteins to elicit a cellular as well as a humoral immune response. Our designed vaccine has wide population coverage and can effectively compensate for the genetic variation among different populations. For maximum efficacy and minimum adverse effects possibilities the antigenic, non-allergenic and non-toxic B-cell, HTL and CTL epitopes from experimentally proven EVs proteins were selected for the vaccine construct. TLR4 agonist RpfE served as an adjuvant for the vaccine construct. The vaccine construct structure was modelled, refined and docked on TLR4 immune receptor. The designed vaccine construct displayed safe usage and exhibits a high probability to elicit the critical immune regulators, like B cells, T-cells and memory cells as displayed by the in-silico immunization assays. Therefore, it can be further corroborated using in vitro and in vivo assays to fulfil the global need for a more efficacious anti-tuberculosis vaccine.

Chemical Conjugation Strategies for the Development of Protein-Based Subunit Nanovaccines

The production of subunit nanovaccines relies heavily on the development of a vaccine delivery system that is safe and efficient at delivering antigens to the target site. Nanoparticles have been extensively investigated for vaccine delivery over the years, as they often possess self-adjuvanting properties. The conjugation of antigens to nanoparticles by covalent bonds ensures co-delivery of these components to the same subset of immune cells in order to trigger the desired immune responses. Herein, we review covalent conjugation strategies for grafting protein or peptide antigens onto other molecules or nanoparticles to obtain subunit nanovaccines. We also discuss the advantages of chemical conjugation in developing these vaccines.

Immuno-informatics design of a multimeric epitope peptide based vaccine targeting SARS-CoV-2 spike glycoprotein

Developing an efficacious vaccine for SARS-CoV-2 infection is critical to stemming COVID-19 fatalities and providing the global community with immune protection. We have used a bioinformatic approach to aid in designing an epitope peptide-based vaccine against the spike protein of the virus. Five antigenic B cell epitopes with viable antigenicity and a total of 27 discontinuous B cell epitopes were mapped out structurally in the spike protein for antibody recognition. We identified eight CD8+ T cell 9-mers and 12 CD4+ T cell 14-15-mer as promising candidate epitopes putatively restricted by a large number of MHC I and II alleles, respectively. We used this information to construct an in silico chimeric peptide vaccine whose translational rate was highly expressed when cloned in pET28a (+) vector. With our In silico test, the vaccine construct was predicted to elicit high antigenicity and cell-mediated immunity when given as a homologous prime-boost, triggering of toll-like receptor 5 by the adjuvant linker. The vaccine was also characterized by an increase in IgM and IgG and an array of Th1 and Th2 cytokines. Upon in silico challenge with SARS-CoV-2, there was a decrease in antigen levels using our immune simulations. We, therefore, propose that potential vaccine designs consider this approach.

Mining of Ebola virus genome for the construction of multi-epitope vaccine to combat its infection

Ebola virus is the primary causative agent of viral hemorrhagic fever that is an epidemic disease and responsible for the massive premature deaths in humans. Despite knowing the molecular mechanism of its pathogenesis, to date, no commercial or FDA approved multiepitope vaccine is available against Ebola infection. The current study focuses on designing a multi-epitope subunit vaccine for Ebola using a novel immunoinformatic approach. The best predicted antigenic epitopes of Cytotoxic-T cell (CTL), Helper-T cells (HTL), and B-cell epitopes (BCL) joined by various linkers were selected for the multi-epitope vaccine designing. For the enhanced immune response, two adjuvants were also added to the construct. Further analysis showed the vaccine to be immunogenic and non-allergenic, forming a stable and energetically favorable structure. The stability of the unbound vaccine construct and vaccine/TLR4 was elucidated via atomistic molecular dynamics simulations. The binding free energy analysis (ΔG_Bind = -194.2 ± 0.5 kcal/mol) via the molecular mechanics Poisson-Boltzmann docking scheme revealed a strong association and thus can initiate the maximal immune response. Next, for the optimal expression of the vaccine construct, its gene construct was cloned in the pET28a + vector system. In summary, the Ebola viral proteome was screened to identify the most potential HTLs, CTLs, and BCL epitopes. Along with various linkers and adjuvants, a multi-epitope vaccine is constructed that showed a high binding affinity with the immune receptor, TLR4. Thus, the current study provides a highly immunogenic multi-epitope subunit vaccine construct that may induce humoral and cellular immune responses against the Ebola infection.Communicated by Ramaswamy H. Sarma.

Designing a conserved peptide-based subunit vaccine against SARS-CoV-2 using immunoinformatics approach

The widespread of coronavirus (COVID-19) is a new global health crisis that poses a threat to the world. The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) originated in bats and was discovered first in Wuhan, Hubei province, China in December 2019. Immunoinformatics and bioinformatics tools were employed for the construction of a multi-epitope subunit vaccine to prevent the diseases. The antigenicity, toxicity and allergenicity of all epitopes used in the construction of the vaccine were predicted and then conjugated with adjuvants and linkers. Vaccine Toll-Like Receptors (2, 3, 4, 8 and 9) complex was also evaluated. The vaccine construct was antigenic, non-toxic and non-allergic, which indicates the vaccines ability to induce antibodies in the host, making it an effective vaccine candidate.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40203-020-00062-x.

Peptide-Protein Conjugation and Characterization to Develop Vaccines for Group A Streptococcus

Peptide conjugates have been widely used for developing vaccines that prevent common bacterial infections for which peptides alone are either ineffective or provide only short-term protection. Among several carrier proteins, diphtheria toxoid and CRM₁₉₇ (a genetically detoxified diphtheria toxin) are considered safe and have been used in several licensed vaccines. For developing a vaccine against group A streptococcus (GAS), antigens from conserved region of M protein and the IL-8 protease, SpyCEP, have been identified. In this chapter, we describe a method for producing peptide-conjugate subunit GAS vaccines, which involves maleimide conjugation of peptides to a carrier protein and their subsequent characterization.

Self-Adjuvanting Cancer Vaccines from Conjugation-Ready Lipid A Analogues and Synthetic Long Peptides

Self-adjuvanting vaccines, wherein an antigenic peptide is covalently bound to an immunostimulating agent, have been shown to be promising tools for immunotherapy. Synthetic Toll-like receptor (TLR) ligands are ideal adjuvants for covalent linking to peptides or proteins. We here introduce a conjugation-ready TLR4 ligand, CRX-527, a potent powerful lipid A analogue, in the generation of novel conjugate-vaccine modalities. Effective chemistry has been developed for the synthesis of the conjugation-ready ligand as well as the connection of it to the peptide antigen. Different linker systems and connection modes to a model peptide were explored, and in vitro evaluation of the conjugates showed them to be powerful immune-activating agents, significantly more effective than the separate components. Mounting the CRX-527 ligand at the N-terminus of the model peptide antigen delivered a vaccine modality that proved to be potent in activation of dendritic cells, in facilitating antigen presentation, and in initiating specific CD8⁺ T-cell-mediated killing of antigen-loaded target cells in vivo. Synthetic TLR4 ligands thus show great promise in potentiating the conjugate vaccine platform for application in cancer vaccination.

A systematic mutational analysis identifies a 5-residue proline tag that enhances the in vivo immunogenicity of a non-immunogenic model protein

Poor immunogenicity of small proteins is a major hurdle in developing vaccines or producing antibodies for biopharmaceutical usage. Here, we systematically analyzed the effects of 10 solubility controlling peptide tags (SCP‐tags) on the immunogenicity of a non‐immunogenic model protein, bovine pancreatic trypsin inhibitor (BPTI‐19A; 6 kDa). CD, fluorescence, DLS, SLS, and AUC measurements indicated that the SCP‐tags did not change the secondary structure content nor the tertiary structures of the protein nor its monomeric state. ELISA results indicated that the 5‐proline (C5P) and 5‐arginine (C5R) tags unexpectedly increased the IgG level of BPTI‐19A by 240‐ and 73‐fold, respectively, suggesting that non‐oligomerizing SCP‐tags may provide a novel method for increasing the immunogenicity of a protein in a highly specific manner.

Biodegradable PLGA-b-PEG Nanoparticles Induce T Helper 2 (Th2) Immune Responses and Sustained Antibody Titers via TLR9 Stimulation

Sustained immune responses, particularly antibody responses, are key for protection against many endemic infectious diseases. Antibody responses are often accompanied by T helper (Th) cell immunity. Herein we study small biodegradable poly (ethylene glycol)-b-poly (lactic-co-glycolic acid) nanoparticles (PEG-b-PLGA NPs, 25-50 nm) as antigen- or adjuvant-carriers. The antigen carrier function of PEG-b-PLGA NPs was compared against an experimental benchmark polystyrene nanoparticles (PS NPs, 40-50 nm), both conjugated with the model antigen ovalbumin (OVA-PS NPs, and OVA-PEG-b-PLGA NPs). The OVA-PEG-b-PLGA NPs induced sustained antibody responses to Day 120 after two immunizations. The OVA-PEG-b-PLGA NPs as a self-adjuvanting vaccine further induced IL-4 producing T-helper cells (Th2), but not IFN-γ producing T-cells (Th1). The PEG-b-PLGA NPs as a carrier for CpG adjuvant (CpG-PEG-b-PLGA NPs) were also tested as mix-in vaccine adjuvants comparatively for protein antigens, or for protein-conjugated to PS NPs or to PEG-b-PLGA NPs. While the addition of this adjuvant NP did not further increase T-cell responses, it improved the consistency of antibody responses across all immunization groups. Together these data support further development of PEG-b-PLGA NPs as a vaccine carrier, particularly where it is desired to induce Th2 immunity and achieve sustained antibody titers in the absence of affecting Th1 immunity.

Carbohydrate Conjugates in Vaccine Developments

Vaccines are powerful tools that can activate the immune system for protection against various diseases. As carbohydrates can play important roles in immune recognition, they have been widely applied in vaccine development. Carbohydrate antigens have been investigated in vaccines against various pathogenic microbes and cancer. Polysaccharides such as dextran and β-glucan can serve as smart vaccine carriers for efficient antigen delivery to immune cells. Some glycolipids, such as galactosylceramide and monophosphoryl lipid A, are strong immune stimulators, which have been studied as vaccine adjuvants. In this review, we focus on the current advances in applying carbohydrates as vaccine delivery carriers and adjuvants. We will discuss the examples that involve chemical modifications of the carbohydrates for effective antigen delivery, as well as covalent antigen-carbohydrate conjugates for enhanced immune responses.

Protein and Peptide Biomaterials for Engineered Subunit Vaccines and Immunotherapeutic Applications

Although vaccines have been the primary defense against widespread infectious disease for decades, there is a critical need for improvement to combat complex and variable diseases. More control and specificity over the immune response can be achieved by using only subunit components in vaccines. However, these often lack sufficient immunogenicity to fully protect, and conjugation or carrier materials are required. A variety of protein and peptide biomaterials have improved effectiveness and delivery of subunit vaccines for infectious, cancer, and autoimmune diseases. They are biodegradable and have control over both material structure and immune function. Many of these materials are built from naturally occurring self-assembling proteins, which have been engineered for incorporation of vaccine components. In contrast, others are de novo designs of structures with immune function. In this review, protein biomaterial design, engineering, and immune functionality as vaccines or immunotherapies are discussed.

Physical and chemical profiles of nanoparticles for lymphatic targeting

Nanoparticles (NPs) have been gaining prominence as delivery vehicles for modulating immune responses to improve treatments against cancer and autoimmune diseases, enhancing tissue regeneration capacity, and potentiating vaccination efficacy. Various engineering approaches have been extensively explored to control the NP physical and chemical properties including particle size, shape, surface charge, hydrophobicity, rigidity and surface targeting ligands to modulate immune responses. This review examines a specific set of physical and chemical characteristics of NPs that enable efficient delivery targeted to secondary lymphoid tissues, specifically the lymph nodes and immune cells. A critical analysis of the structure-property-function relationship will facilitate further efforts to engineer new NPs with unique functionalities, identify novel utilities, and improve the clinical translation of NP formulations for immunotherapy.

Liposomes used as a vaccine adjuvant-delivery system: From basics to clinical immunization

Liposomes are widely utilized as a carrier to improve therapeutic efficacy of agents thanks to their merits of high loading capacity, targeting delivery, reliable protection of agents, good biocompatibility, versatile structure modification and adjustable characteristics, such as size, surface charge, membrane flexibility and the agent loading mode. In particular, in recent years, through modification with immunopotentiators and targeting molecules, and in combination with innovative immunization devices, liposomes are rapidly developed as a multifunctional vaccine adjuvant-delivery system (VADS) that has a high capability in inducing desired immunoresponses, as they can target immune cells and even cellular organelles, engender lysosome escape, and promote Ag cross-presentation, thus enormously enhancing vaccination efficacy. Moreover, after decades of development, several products developed on liposome VADS have already been authorized for clinical immunization and are showing great advantages over conventional vaccines. This article describes in depth some critical issues relevant to the development of liposomes as a VADS, including principles underlying immunization, physicochemical properties of liposomes as the immunity-influencing factors, functional material modification to enhance immunostimulatory functions, the state-of-the-art liposome VADSs, as well as the marketed vaccines based on a liposome VADS. Therefore, this article provides a comprehensive reference to the development of novel liposome vaccines.

Cationic polymer modified PLGA nanoparticles encapsulating Alhagi honey polysaccharides as a vaccine delivery system for ovalbumin to improve immune responses

Background: Poly (lactic-co-glycolic acid) (PLGA) nanoparticles and surface modified PLGA nanoparticles have been widely studied as antigens or drugs carriers due to their controlled release characteristics and biocompatibility. However, most PLGA nanoparticles have lower antigens loading efficiency and adjuvanticity.

Purpose: The aim of this study was to improve the antigen loading efficiency and adjuvant activity of PLGA nanoparticles.

Materials and methods: Surface cationic polymer modification can improve the antigens loading efficiency of PLGA nanoparticles by surface adsorption. Therefore, in this study, chitosan modified PLGA nanoparticles (CS-AHPP/OVA), polyethyleneimine modified PLGA nanoparticles (PEI-AHPP/OVA), and ε-Poly-L-lysine modified PLGA nanoparticles (εPL-AHPP/OVA) were prepared as antigen delivery carriers to investigate the characterization and stability of these nanoparticles. These nanoparticles were evaluated for their efficacies as adjuvants pre- and post-modification.

Results: The AHP and OVA-loaded PLGA nanoparticles (AHPP/OVA) were positively charged after surface cationic polymers modification, and their structural integrity was maintained. Their antigen loading capacity and stability of nanoparticles were improved by the surface cationic polymers modification. Increased positive surface charge resulted in greater OVA adsorption capacity. Among AHPP/OVA and the three surface cationic polymers synthesized from modified PLGA nanoparticles, PEI-AHPP/OVA showed the highest antigen loading efficiency and good stability. AHPP/OVA, CS-AHPP/OVA PEI-AHPP/OVA, and εPL-AHPP/OVA formulations significantly enhanced lymphocyte proliferation and improved the ratio of CD4+/CD8+ T cells. In addition, AHPP/OVA, PEI-AHPP/OVA and εPL-AHPP/OVA formulations induced secretion of cytokines (TNF-α, IFN-γ, IL-4, and IL-6), antibodies (IgG) and antibody subtypes (IgG1 and IgG2a) in immunized mice. These results demonstrate that these formulations generated a strong Th1-biased immune response. Among them, PEI-AHPP/OVA induced the strongest Th1-biased immune response.

Conclusion: In conclusion, PEI-AHPP/OVA nanoparticles may be a potential antigen delivery system for the induction of strong immune responses.

The Content of CpG-DNA in Antigen-CpG Conjugate Vaccines Determines Their Cross-Presentation Activity

Cross-presentation, the process that facilitates display of exogenous antigens on MHC-I molecules, is a crucial step in the cascade of CD8 T cell activation. Potentiation of cross-presentation therefore represents an essential design criterion for development of subunit vaccines that target the induction of CD8 T cell immunity. Covalent conjugation of CpG-DNA to antigenic proteins has shown the potential to promote cross-presentation and has attracted great interest as a promising approach for vaccine development. However, heterogeneous product mixtures that result from typical conjugation schemes precluded identification of active conjugate species and impeded optimization of cross-presentation activity. In this report, we explore the effect of molecular composition of antigen-CpG conjugates on their cross-presentation activity using model Ovalbumin (OVA)-CpG conjugates. We developed a method to generate antigen-CpG conjugates with defined molecular compositions and leveraged this method to produce a series of OVA-CpG conjugates with one, two, and three CpG molecules linked to OVA. We observed that conjugates containing one CpG per OVA enhanced cross-presentation by 4-fold compared to native OVA, while conjugates with higher contents of CpG provided no cross-presentation enhancement. These differences are likely due to enhanced aggregation propensity observed for conjugates that carry more than one CpG per OVA. Our findings suggest that tuning molecular composition of antigen-CpG conjugates to maintain physical stability may be essential for achieving potent cross-presentation activity. Our method to generate defined conjugates could facilitate such molecular tuning and may be useful for continued development of antigen-CpG vaccines.

Recent Advances in Polymeric Nanomedicines for Cancer Immunotherapy

Immunotherapy has emerged as a promising approach to treat cancer, since it facilitates eradication of cancer by enhancing innate and/or adaptive immunity without using cytotoxic drugs. Of the immunotherapeutic approaches, significant clinical potentials are shown in cancer vaccination, immune checkpoint therapy, and adoptive cell transfer. Nevertheless, conventional immunotherapies often involve immune-related adverse effects, such as liver dysfunction, hypophysitis, type I diabetes, and neuropathy. In an attempt to address these issues, polymeric nanomedicines are extensively investigated in recent years. In this review, recent advances in polymeric nanomedicines for cancer immunotherapy are highlighted and thoroughly discussed in terms of 1) antigen presentation, 2) activation of antigen-presenting cells and T cells, and 3) promotion of effector cells. Also, the future perspectives to develop ideal nanomedicines for cancer immunotherapy are provided.

Cancer Immunotherapy of TLR4 Agonist-Antigen Constructs Enhanced with Pathogen-Mimicking Magnetite Nanoparticles and Checkpoint Blockade of PD-L1

Despite the tremendous potential of Toll-like receptor 4 (TLR4) agonists in vaccines, their efficacy as monotherapy to treat cancer has been limited. Only some lipopolysaccharides (LPS) isolated from particular bacterial strains or structures like monophosphoryl lipid A (MPLA) derived from lipooligosaccharide (LOS), avoid toxic overactivation of innate immune responses while retaining adequate immunogenicity to act as adjuvants. Here, different LOS structures are incorporated into nanoparticle-filled phospholipid micelles for efficient vaccine delivery and more potent cancer immunotherapy. The structurally unique LOS of the plant pathogen Xcc is incorporated into phospholipid micelles encapsulating iron oxide nanoparticles, producing stable pathogen-mimicking nanostructures suitable for targeting antigen presenting cells in the lymph nodes. The antigen is conjugated via a hydrazone bond, enabling rapid, easy-to-monitor and high-yield antigen ligation at low concentrations. The protective effect of these constructs is investigated against a highly aggressive model for tumor immunotherapy. The results show that the nanovaccines lead to a higher-level antigen-specific cytotoxic T lymphocyte (CTL) effector and memory responses, which when combined with abrogation of the immunosuppressive programmed death-ligand 1 (PD-L1), provide 100% long-term protection against repeated tumor challenge. This nanovaccine platform in combination with checkpoint inhibition of PD-L1 represents a promising approach to improve the cancer immunotherapy of TLR4 agonists.

Artificial bioconjugates with naturally occurring linkages: the use of phosphodiester

Artificial orthogonal bond formations such as the alkyne–azide cycloaddition have enabled selective bioconjugations under mild conditions, yet naturally occurring linkages between native functional groups would be more straightforward to elaborate bioconjugates. Herein, we describe the use of a phosphodiester bond as a versatile option to access various bioconjugates. An opposite activation strategy, involving 5’-phosphitylation of the supported oligonucleotides, has allowed several biomolecules that possess an unactivated alcohol to be directly conjugated. It should be noted that there is no need to pre-install artificial functional groups and undesired and unpredictable perturbations possibly caused by bioconjugation can be minimized.

Recent Advances in Toll Like Receptor-Targeting Glycoconjugate Vaccines

Many malignant cell surface carbohydrates resulting from abnormal glycosylation patterns of certain diseases can serve as antigens for the development of vaccines against these diseases. However, carbohydrate antigens are usually poorly immunogenic by themselves, thus they need to be covalently coupled with immunologically active carrier molecules to be functional. The most well established and commonly used carriers are proteins. In recent years, the use of toll-like receptor (TLR) ligands to formulate glycoconjugate vaccines has gained significant attention because TLR ligands can serve not only as carrier molecules but also as built-in adjuvants to form fully synthetic and self-adjuvanting conjugate vaccines, which have several advantages over carbohydrate-protein conjugates and formulated mixtures with external adjuvants. This article reviews recent progresses in the development of conjugate vaccines based on TLR ligands. Two major classes of TLR ligands, lipopeptides and lipid A derivatives will be covered with more focus on monophosohoryl lipid A (MPLA) and related analogs, which are TLR4 ligands demonstrated to be able to provoke T cell-dependent, adaptive immune responses. Corresponding conjugate vaccines have shown promising application potentials to multiple diseases including cancer.

Designing B- and T-cell multi-epitope based subunit vaccine using immunoinformatics approach to control Zika virus infection

The Zika virus is a rapidly spreading Aedes mosquito-borne sickness, which creates an unanticipated linkage birth deformity and neurological turmoil. This study represents the use of the combinatorial immunoinformatics approach to develop a multiepitope subunit vaccine using the structural and nonstructural proteins of the Zika virus. The designed subunit vaccine consists of cytotoxic T-lymphocyte and helper T-lymphocyte epitopes accompanied by suitable adjuvant and linkers. The presence of humoral immune response specific B-cell epitopes was also confirmed by B-cell epitope mapping among vaccine protein. Further, the vaccine protein was characterized for its allergenicity, antigenicity, and physiochemical parameters and found to be safe and immunogenic. Molecular docking and molecular dynamics studies of the vaccine protein with the toll-like receptor-3 were performed to ensure the binding affinity and stability of their complex. Finally, in silico cloning was performed for the effective expression of vaccine construct in the microbial system (Escherichia coli K12 strain). Aforementioned approaches result in the multiepitope subunit vaccine which may have the ability to induce cellular as well as humoral immune response. Moreover, this study needs the experimental validation to prove the immunogenic and protective behavior of the developed subunit vaccine.

Induction of necrotic cell death and activation of STING in the tumor microenvironment via cationic silica nanoparticles leading to enhanced antitumor immunity

Nanotechnology has demonstrated tremendous clinical utility, with potential applications in cancer immunotherapy. Although nanoparticles with intrinsic cytotoxicity are often considered unsuitable for clinical applications, such toxicity may be harnessed in the fight against cancer. Nanoparticle-associated toxicity can induce acute necrotic cell death, releasing tumor-associated antigens which may be captured by antigen-presenting cells to initiate or amplify tumor immunity. To test this hypothesis, cytotoxic cationic silica nanoparticles (CSiNPs) were directly administered into B16F10 melanoma implanted in C57BL/6 mice. CSiNPs caused plasma membrane rupture and oxidative stress of tumor cells, inducing local inflammation, tumor cell death and the release of tumor-associated antigens. The CSiNPs were further complexed with bis-(3'-5')-cyclic dimeric guanosine monophosphate (c-di-GMP), a molecular adjuvant which activates the stimulator of interferon genes (STING) in antigen-presenting cells. Compared with unformulated c-di-GMP, the delivery of c-di-GMP with CSiNPs markedly prolonged its local retention within the tumor microenvironment and activated tumor-infiltrating antigen-presenting cells. The combination of CSiNPs and a STING agonist showed dramatically increased expansion of antigen-specific CD8+ T cells, and potent tumor growth inhibition in murine melanoma. These results demonstrate that cationic nanoparticles can be used as an effective in situ vaccine platform which simultaneously causes tumor destruction and immune activation.

Potent anti-viral vaccine adjuvant based on pH-degradable nanogels with covalently linked small molecule imidazoquinoline TLR7/8 agonist

Improving the immunogenicity of subunit vaccines, in particular skewing of the immune response towards Th1 type immunity, is crucial for the development of effective vaccines against intracellular infections and for the development of anti-cancer vaccines. Small molecule TLR7/8 agonist hold high potential for this purpose, but suffer from an undesirable pharmacokinetic profile, resulting in systemic inflammatory responses. An effective solution to this problem is covalent ligation to a larger carrier. Here, a degradable nanogel carrier containing a covalently linked imidazoquinoline (IMDQ) TLR7/8 agonist is explored as adjuvant for vaccination against the respiratory syncytial virus (RSV). In vitro and in vivo experiments in mice provide a solid rational base for preferring nanogels over soluble polymers as IMDQ carrier in terms of cellular uptake and lymph node accumulation.

Site-Selective Functionalization of Flagellin by Steric Self-Protection: A Strategy To Facilitate Flagellin as a Self-Adjuvanting Carrier in Conjugate Vaccine

Flagellin (FliC) can act as a carrier protein in the preparation of conjugate vaccines to elicit a T-cell-dependent immune response and as an intrinsic adjuvant to activate the toll-like receptor 5 (TLR5) to enhance vaccine potency. To enable the use of FliC as a self-adjuvanting carrier, an effective method for site-selective modification (SSM) of pertinent amino-acid residues in the D2 and D3 domains of FliC is explored without excessive modification of the D0 and D1 domains, which are responsible for activating and binding with TLR5. In highly concentrated Na₂ SO₄ solution, FliC monomers form flagellar filaments, in which the D0 and D1 domains are situated inside the tubular structure. Thus, the lysine residues (K219, K224, K324, and K331) in the D2 and D3 domains of flagellin are selectively modified by a diazo-transfer reaction with imidazole-1-sulfonyl azide. The sites with azido modification are confirmed by MALDI-TOF-MS, ESI-TOF-MS, and LC-MS/MS analyses along with label-free quantitation. The azido-modified filament dissolves to give FliC monomers, which can conjugate with alkyne-hinged saccharides by the click reaction. Transmission electron microscopy imaging, dynamic light scattering measurements, and the secreted embryonic alkaline phosphatase reporter assay indicate that the modified FliC monomers retain the ability either to bind with TLR5 or to reassemble into filaments. Overall, this study establishes a feasible method for the SSM of FliC by steric self-protection of the D0 and D1 domains.

Targeting Suppressive Oligonucleotide to Lymph Nodes Inhibits Toll-like Receptor-9-Mediated Activation of Adaptive Immunity

PURPOSE

This paper aims to investigate the immunoinhibitory properties of a lymph nodes-targeting suppressive oligonucleotide (ODN) for the potential treatment of autoimmune diseases or chronic inflammation.

METHODS

Synthetic suppressive ODN engineered with an albumin-binding diacyl lipid at the 5'-terminal (lipo-ODN) was synthesized. In vitro and in vivo experiments were designed to compare the immune suppressive properties of lipo-ODN and unmodified ODN. Cellular uptake and distribution, inhibition of Toll-like receptor (TLR) activation, lymph nodes (LN) draining, and the suppression of antigen-specific immune responses in an ovalbumin protein model was investigated.

RESULTS

Compared to unmodified ODN, lipid functionalized suppressive ODN demonstrated enhanced cellular uptake and TLR-9 specific immune suppression in TLR reporter cells. Additionally, injection of a low dose of lipid-modified suppressive ODN, but not the unconjugated ODN, accumulated in the draining LNs and exhibited potent inhibition of antigen-specific CD8⁺ T cell and B cell responses in vivo.

CONCLUSIONS

Targeting suppressive ODN to antigen presenting cells (APCs) in the local LNs is an effective approach to amplify the immune modulation mediated by ODN containing repetitive TTAGGG motif. This approach might be broadly applicable to target molecular adjuvants to the key immune cells in the LNs draining from disease site, providing a simple strategy to improve the efficacy of many molecular immune modulators.

The use of gold nanorods as a new vaccine platform against schistosomiasis

Schistosomiasis is an important parasitic disease affecting >207 million people in 76 countries around the world and causing approximately 250,000 deaths per year. At present, the main strategy adopted for the control of schistosomiasis is the use of safe chemotherapy, such as praziquantel. However, the high rates of reinfection after treatment restrict the use of this treatment approach and assume the need for other forms of control such as vaccination. Sm29 is a protein that is localized in the Schistosoma mansoni tegument of adult worms and schistosomula and is considered a powerful vaccine candidate. Because of the chemical, physical and immunological characteristics of nanoparticles, nanocarriers have received increasing attention. In the field of nanotechnology, gold nanorods are considered potential vaccine carriers. In this study, we bound S. mansoni rSm29 protein to gold nanorods either directly or by cysteamine functionalization. When the worm burden was evaluated, the AuNRs-NH₂-rSm29 group of immunized mice showed the best protection level (34%). Following AuNRs-NH₂-rSm29 immunization, we observed a Th1 immunological response in mice with higher production of IFN-γ, mainly by CD4⁺ and CD8⁺ T cells. Furthermore, AuNRs-NH₂-rSm29 could activate dendritic cells in vitro, enhancing MHCII and MHCI expression and the production of IL-1β in a NLRP3-, ASC- and Caspase-1-dependent manner. In summary, our findings support the use of nanorods as an immunization strategy in vaccine development against infectious diseases.

Co-Spray Dried Mannitol/Poly(amidoamine)-Doxorubicin Dry-Powder Inhaler Formulations for Lung Adenocarcinoma: Morphology, In Vitro Evaluation, and Aerodynamic Performance

nhaled chemotherapeutics have emerged as a promising regimen to combat lung cancer as they maximize local drug concentration while significantly reduce systemic exposure. However, the poor lung/systemic safety profiles and lack of clinically efficient formulations restrict the applicability of inhaled chemotherapeutics. This work developed a dry-powder inhaler (DPI) formulation that dispersed a pH-responsive poly(amidoamine) dendrimer-doxorubicin conjugate (G4-12DOX) into mannitol microparticles. The dendrimer conjugate only releases cytotoxic agents in response to intracellular pH drop, leading to reduced systemic and local toxicity. This work investigated the effect of G4-12DOX content on the microparticle size and morphology, redispersibility, in vitro cytotoxicity, and aerosol properties of the formulations. The spray-dried G4-12DOX/mannitol microparticles showed smooth and spherical morphology with 1-4 μm in diameter. As the content of the G4-12DOX conjugate in the microparticles increased, the size, and degree of aggregation of microparticles increased dramatically. The G4-12DOX/mannitol microparticles were readily redispersed in the aqueous environment, reverting to nanoscale dendrimer conjugates to escape alveolar phagocytosis. All DPI formulations demonstrated the similar cytotoxicity as the original conjugate against a lung adenocarcinoma cell line. The emitted dose (ED) and fine particle fraction (FPF) of the DPI formulations decreased as the content of G4-12DOX increased, but EDs and FPFs of all formulations fell within the range of 85-60% and 60-40%, which were higher than those of commercial products (EDs = 40-60%; FPFs = 12-40%). Therefore, the spray-dried dendrimer/mannitol microparticle is an efficient and practical DPI formulation for direct delivery of large dose of chemotherapeutics to lung tumors.

Simple and Green Strategy for the Synthesis of "Pathogen-Mimetic" Glycoadjuvant@AuNPs by Combination of Photoinduced RAFT and Bioinspired Dopamine Chemistry

Innate immune responses recognizing pathogen associated molecular patterns (PAMPs) play a crucial role in adaptive immunity. Toll-like receptors (TLRs) and C-type lectin receptors (CLRs) contribute to antigen capture, uptake, presentation and activation of immune responses. In this contribution, metal-free reversible addition-fragmentation chain transfer (RAFT) polymerization of N-3,4-dihydroxybenzenethyl methacrylamide (DMA) and 2-(methacrylamido) glucopyranose (MAG) under sunlight irradiation using 2-cyanoprop-2-yl-α-dithionaphthalate (CPDN) as iniferter agent, can be employed to fabricate the multivalent glycopolymer containing bioresponsive sugar group and multifunctional catechol functionalities. The polymerization behavior is investigated and it presents controlled features. Moreover, bioinspired dopamine chemistry can be successfully utilized to form in situ glycopolymer-coated gold nanoparticles (AuNPs) without the need of additional reducing reagent, design "pathogen-mimetic" glycoadjuvant recognized by both CLRs and TLRs. The synthetic glycoadjuvant is found to enhance the adjuvant activity as "infected signals" in vitro.

Peptide Amphiphile Micelles for Vaccine Delivery

Peptide subunit vaccines enable the specific activation of an immune response without the shortcomings of killed or attenuated pathogens. However, peptide subunit vaccines tend to be less immunogenic than those based on whole organisms. To improve peptide immunogenicity, biomaterials-based platforms have been developed. One such platform, the peptide amphiphile micelle platform, has displayed a unique ability to dramatically improve observed immune responses. Here we describe the design, synthesis, characterization, and application of peptide amphiphile micelles to elicit a robust immune response.

Toward Personalized Peptide-Based Cancer Nanovaccines: A Facile and Versatile Synthetic Approach

Personalized cancer vaccines (PCVs) are receiving attention as an avenue for cancer immunotherapy. PCVs employ immunogenic peptide epitopes capable of stimulating the immune system to destroy cancer cells with great specificity. Challenges associated with effective delivery of these peptides include poor solubility of hydrophobic sequences, rapid clearance, and poor immunogenicity, among others. The incorporation of peptides into nanoparticles has the potential to overcome these challenges, but the broad range of functionalities found in amino acids presents a challenge to conjugation due to possible interferences and lack of reaction specificity. Herein, a facile and versatile approach to generating nanosized PCVs under mild nonstringent conditions is reported. Following a simple two-step semibatch synthetic approach, amphiphilic hyperbranched polymer-peptide conjugates were prepared by the conjugation of melanoma antigen peptides, either TRP2 (hydrophobic) or MUT30 (hydrophilic), to an alkyne functionalized core via strain-promoted azide-alkyne click chemistry. Self-assembly of the amphiphiles gave spherical nanovaccines (by transmission electron microscopy) with sizes in the range of 10-30 nm (by dynamic light scattering). Fluorescently labeled nanovaccines were prepared to investigate the cellular uptake by antigen presenting cells (dendritic cells), and uptake was confirmed by flow cytometry and microscopy. The TRP2 nanovaccine was taken up the most followed by MUT30 nanoparticles and, finally, nanoparticles without peptide. The nanovaccines showed good biocompatibility against B16-F10 cells, yet the TRP2 peptide showed signs of toxicity, possibly due to its hydrophobicity. A test for immunogenicity revealed that the nanovaccines were poorly immunogenic, implying the need for an adjuvant when administered in vivo. Treatment of mice with melanoma tumors showed that in combination with adjuvant, CpG, groups with the peptide nanovaccines slowed tumor growth and improved survival (up to 24 days, TRP2) compared to the untreated group (14 days).

Targeted antigen delivery by an anti-class II MHC VHH elicits focused αMUC1(Tn) immunity

Unusual patterns of glycosylation on the surface of transformed cells contribute to immune modulation and metastasis of malignant tumors. Active immunization against them requires effective antigen presentation, which is complicated by a lack of access to tumor-specific posttranslational modifications through standard genetic approaches and by the low efficiency of passive antigen sampling. We found that antigen targeted to antigen presenting cells via class II MHC products can elicit a robust immune response against MUC1(Tn) bearing a defined tumor-associated glycoform, Tn. The two-component vaccine construct was prepared by sortase-mediated protein ligation of a synthetic MUC1(Tn) fragment to a class II MHC-binding single-domain antibody fragment (VHH7) as targeting moiety. We show that VHH7 targets antigen presenting cells in vivo, and when conjugated to MUC1(Tn) can elicit a strong αMUC1(Tn) immune response in mice. The resulting sera preferentially recognized the MUC1 epitope with the tumor-associated carbohydrate antigen Tn and were capable of killing cancer cells in a complement-mediated cytotoxicity assay. Immunoglobulin isotype analysis and cytokine release assays suggested a favorable Th1 response. A single boost 12 months after primary immunization triggered a recall response of the same quality, suggesting that long-term αMUC1(Tn) memory had been achieved.