Polyionic vaccine adjuvants: another look at aluminum salts and polyelectrolytes

Picrasidine S Induces cGAS-Mediated Cellular Immune Response as a Novel Vaccine Adjuvant

New adjuvants that trigger cellular immune responses are urgently needed for the effective development of cancer and virus vaccines. Motivated by recent discoveries that show activation of type I interferon (IFN-I) signaling boosts T cell immunity, this study proposes that targeting this pathway can be a strategic approach to identify novel vaccine adjuvants. Consequently, a comprehensive chemical screening of 6,800 small molecules is performed, which results in the discovery of the natural compound picrasidine S (PS) as an IFN-I inducer. Further analysis reveals that PS acts as a powerful adjuvant, significantly enhancing both humoral and cellular immune responses. At the molecular level, PS initiates the activation of the cGAS-IFN-I pathway, leading to an enhanced T cell response. PS vaccination notably increases the population of CD8+ central memory (TCM)-like cells and boosts the CD8+ T cell-mediated anti-tumor immune response. Thus, this study identifies PS as a promising candidate for developing vaccine adjuvants in cancer prevention.

Immunomodulatory chitosan nanoparticles for Toxoplasma gondii infection: Novel application of chitosan in complex propranolol-hydrochloride as an adjuvant in vaccine delivery

The study aimed to investigate the immunomodulatory effects of propranolol hydrochloride (PRO) in combination with chitosan nanoparticles (CS NPs) as an adjuvant to develop an effective vaccine against T. gondii. A total of 105 BALB/c mice were randomly divided into seven equal groups including PBS alone, CS NPs, SAG1 (Surface antigen 1), CS-SAG1 NPs, CS-PRO NPs, SAG1-PRO, and CS-SAG1-PRO NPs. The immunostimulatory effect of each adjuvant used for vaccine delivery was evaluated in a mice immunization model. The results showed that the mice immunized with CS-SAG1-PRO NPs exhibited the highest lymphocyte proliferation rate, along with increased secretion of IFN-γ, TNF-α, IL-6, IL-12, IL-17, and IL-23, as well as elevated levels of protective cytokines such as TGF-β, IL-27, and IL-10. Although, the CS-SAG1-PRO NPs immunized mice showed the highest level of T. gondii specific IgG compared to the other groups, a significant production of IgG2a and IgG1 was observed in the sera of mice immunized with the CS-SAG1-PRO NPs compared to the other group (p <0.001). The higher IgG2a/IgG1 ratio observed in the CS-SAG1-PRO NPs group indicates a bias towards Th1 cell polarization, suggesting the promotion of Th1 cell-mediated immune responses. Considering the combination of the highest lymphocyte proliferation and survival rates, IgG2a/IgG1 ratio, and cytokine levels in the mice immunized with CS-SAG1-PRO NPs, this approach holds promise for immunostimulation and vaccine delivery against T. gondii infection.

Monitoring Protein Complexation with Polyphosphazene Polyelectrolyte Using Automated Dynamic Light Scattering Titration and Asymmetric Flow Field Flow Fractionation and Protein Recognition Immunoassay

Polyphosphazenes represent a class of intrinsically flexible polyelectrolytes with potent immunoadjuvant activity, which is enabled through non-covalent self-assembly with antigenic proteins by charge complexation. The formation of supramolecular complexes between polyphosphazene adjuvant, poly[di(carboxylatophenoxy)phosphazene] (PCPP), and a model vaccine antigen, hen egg lysozyme, was studied under physiological conditions using automated dynamic light scattering titration, asymmetric flow field flow fractionation (AF4), enzyme-linked immunosorbent assay (ELISA), and fluorescent quenching methods. Three regimes of self-assembly were observed covering complexation of PCPP with lysozyme in the nano-scale range, multi-chain complexes, and larger aggregates with complexes characterized by a maximum loading of over six hundred protein molecules per PCPP chain and dissociation constant in the micromolar range (Kd = 7 × 10-6 mol/L). The antigenicity of PCPP bound lysozyme, when compared to equivalent lysozyme solutions, was largely retained for all complexes, but observed a dramatic reduction for heavily aggregated systems. Routes to control the complexation regimes with elevated NaCl or KCl salt concentrations indicate ion-specific effects, such that more smaller-size complexes are present at higher NaCl, counterintuitive with respect to PCPP solubility arguments. While the order of mixing shows a prominent effect at lower stoichiometries of mixing, higher NaCl salt reduces the effect all together.

Addressing practical issues in the smooth implementation of revised guidelines for non-clinical studies of vaccines for infectious disease prevention

Herein, we investigated possible practical issues for the smooth implementation of the revised Japanese Guidelines for Non-clinical Studies of Vaccines for the Prevention of Infectious Diseases, which were raised in response to public comments on the proposed guideline revision and a gap analysis of the World Health Organization and European Medicines Agency guidelines. We identified main issues such as the non-clinical safety studies of adjuvants and evaluation of local cumulative tolerance in toxicity studies. The revised Japanese Pharmaceuticals and Medical Devices Agency (PMDA)/Ministry of Health, Labour and Welfare (MHLW) guidelines require non-clinical safety studies for vaccines containing new adjuvants, but additional safety pharmacology studies or safety studies in two animal species may be required if non-clinical safety studies raise any concerns (i.e., systemic distribution). Adjuvant biodistribution studies may aid in understanding vaccine characteristics. The evaluation of local cumulative tolerance in non-clinical studies, which was the focus of the Japanese review, can be omitted by including a warning in the package insert to avoid injection to the same site. The study's findings will be reflected in a Q&A to be released by the Japanese MHLW. We hope that this study will contribute to the global and harmonized development of vaccines.

An ELISA-based assay for determining haemagglutinin potency in egg, cell, or recombinant protein derived influenza vaccines

Background

The current compendial assay for haemagglutinin antigen potency in influenza vaccine is the single radial immunodiffusion (SRID) which is time consuming and can lead to delays in release of vaccine. We previously described an alternate capture and detection enzyme linked immunoassay (ELISA) that utilizes sub-type specific, sub-clade cross-reactive monoclonal antibodies (mAbs) that are haemagglutination inhibiting (HAI) and correlate with SRID. The aim of this study is to determine the applicability of ELISA across current platforms for quantitation of seasonal quadrivalent vaccine.

Methods

A single mAb capture and detection ELISA was employed to quantitate hemagglutinin (HA) derived from different vaccine platforms and host organisms and compared to SRID and a polyclonal antibody based ELISA.

Results

We selected mAbs that displayed appropriate characteristics for a stability indicating potency assay which reacted to avian, insect and mammalian derived HA. Qualification of the homologous mAb assay against egg and cell derived HA demonstrated performance similar to that of the SRID however, superiority in sensitivity and specificity against strains from both influenza B/Victoria and B/Yamagata lineages. Analysis of drifted strains across multiple seasons demonstrated continued utility of this approach, reducing the need to develop reagents each season. With modification of the assay, we were able to accurately measure HA from different platforms and process stages using a single calibrated reference standard. We demonstrated the accuracy of ELISA when testing vaccine formulations containing selected adjuvants at standard and higher concentrations. Accelerated stability analysis indicated a strong correlation in the rate of degradation between the homologous mAb ELISA and SRID but not with ELISA utilizing polyclonal antisera. Further, we demonstrated specificity was restricted to the trimeric and oligomeric forms of HA but not monomeric HA.

Conclusion

We believe this homologous mAb ELISA is a suitable replacement for the SRID compendial assay for HA antigen quantitation and stability assessment. Identification of suitable mAbs that are applicable across multiple vaccine platforms with extended sub-type reactivity across a number of influenza seasons, indicate that this assay has broad applicability, leading to earlier availability of seasonal and pandemic vaccines without frequent replacement of polyclonal antisera that is required with SRID.

Viral delivery of a peptide-based immunomodulator enhances T cell priming during vaccination

Modern, subunit-based vaccines have so far failed to induce significant T cell responses, contributing to ineffective vaccination against many pathogens. Importantly, while today's adjuvants are designed to trigger innate and non-specific immune responses, they fail to directly stimulate the adaptive immune compartment. Programmed cell death 1 (PD-1) partly regulates naïve-to-antigen-specific effector T cell transition and differentiation by suppressing the magnitude of activation. Indeed, we previously reported on a microbial-derived, peptide-based PD-1 checkpoint inhibitor, LD01, which showed potent T cell-stimulating activity when combined with a vaccine. Here we sought to improve the potency of LD01 by designing and testing new LD01 derivatives. Accordingly, we found that a modified version of an 18-amino acid metabolite of LD01, LD10da, improved T cell activation capability in a malaria vaccine model. Specifically, LD10da demonstrates improved antigen-specific CD8⁺ T cell expansion when combined prophylactically with an adenovirus-based malaria vaccine. A single dose of LD10da at the time of vaccination is sufficient to increase antigen-specific CD8⁺ T cell expansion in wild-type mice. Further, we show that LD10 can be encoded and delivered by a Modified Vaccinia Ankara viral vector and can enhance antigen-specific CD8⁺ T cell expansion comparable to that of synthetic peptide administration. Therefore, LD10da represents a promising biologic-based immunomodulator that can be genetically encoded and delivered, along with the antigen, by viral or other nucleic acid vectors to improve the efficacy and delivery of vaccines for ineradicable and emerging infectious diseases.

Improving safety of oil adjuvant-based vaccines

High adjuvant reactogenicity is the main limitation for increasing the effectiveness of vaccine therapy. The aim was to reduce the immunotoxicity effects of complete Freunds adjuvant (CFA) in warm-blooded animals. Materials and methods. The study examined Wistar rats by dividing animals into negative control (solvents); positive control (single subcutaneous CFA injection of 0.1 ml/200 g body weight (b.w.)); the minimum and maximum (per os administration of 1:4 citric and succinic acids in ratio of 17 and 88 mg/kg b.w. during 4 weeks after immunization of CFA) experiment. Body weight, hematological (complete blood count) and biochemical (hydroperoxides, malondialdehyde, catalase activity, mitochondrial dehydrogenase activity) parameters were dynamically investigated. At the end of the experiment, necropsy was performed and the relative internal organ mass coefficients were calculated. The spleen and connective tissue (knee joint) were examined histologically. The median, C25C75 quartiles, MannWhitney U-test were calculated. Results and discussion. it was found that parameters examined were within normal range in animals of negative control group. Immunization of warm-blooded animals with CFA was accompanied by transition of acute-to- chronic inflammatory reaction (week 3 and week 7, respectively). The total leukocyte count increased from 12.5 109 (negative control) up to 26.6 109/L (P = 0.01) on week 3 followed by its decline down to 19.2 109/L (P = 0.01) by week 7. Platelet count also increased significantly: from 506 109 (negative control) up to 656 109/L (P = 0.01, week 3) followed by decrease down to 610 109/L by week 7 (P = 0.01). Activation of lipid peroxidation was manifested by malondialdehyde (MDA) level elevated by 55.861.8% (P = 0.01); the general CFA-related toxic effect resulted in 11.7% weight loss (P = 0.01), spleen swelling and thymus reduction. Administration of antioxidant acids led to a dose-dependent decline in inflammation (leukocyte count at the minimum dosage 19.6 10920.9 109/L; at the maximum 16.6 10916.0 109/L), as well as normalized the platelet/leukocyte index up to 29.536.3 (positive control 24.6, negative control 40.5). The acid-related protective effect was also manifested as maintained body weight, activated catalase and inhibited lipid peroxidation. The therapeutic effect in alleviated degenerative changes in the spleen and connective tissue were revealed: reduced hemorrhagic focuses and swelling as well as preserved histoarchitectonics. Conclusion. The use of citric and succinic acids contributes to profoundly lowered CFA toxicity due to increased total antioxidant status, inhibited lipid peroxidation, improved mitochondrial metabolic activity, which ultimately lead to a decline in general systemic inflammation and allows to recommend such acids as immunoprotectors from oil adjuvant-coupled effects.

Chitosan Nanoparticles: A Versatile Platform for Biomedical Applications

Chitosan is a biodegradable and biocompatible natural polymer that has been extensively explored in recent decades. The Food and Drug Administration has approved chitosan for wound treatment and nutritional use. Furthermore, chitosan has paved the way for advancements in different biomedical applications including as a nanocarrier and tissue-engineering scaffold. Its antibacterial, antioxidant, and haemostatic properties make it an excellent option for wound dressings. Because of its hydrophilic nature, chitosan is an ideal starting material for biocompatible and biodegradable hydrogels. To suit specific application demands, chitosan can be combined with fillers, such as hydroxyapatite, to modify the mechanical characteristics of pH-sensitive hydrogels. Furthermore, the cationic characteristics of chitosan have made it a popular choice for gene delivery and cancer therapy. Thus, the use of chitosan nanoparticles in developing novel drug delivery systems has received special attention. This review aims to provide an overview of chitosan-based nanoparticles, focusing on their versatile properties and different applications in biomedical sciences and engineering.

Advances in Infectious Disease Vaccine Adjuvants

Vaccines are one of the most significant medical interventions in the fight against infectious diseases. Since their discovery by Edward Jenner in 1796, vaccines have reduced the worldwide transmission to eradication levels of infectious diseases, including smallpox, diphtheria, hepatitis, malaria, and influenza. However, the complexity of developing safe and effective vaccines remains a barrier for combating many more infectious diseases. Immune stimulants (or adjuvants) are an indispensable factor in vaccine development, especially for inactivated and subunit-based vaccines due to their decreased immunogenicity compared to whole pathogen vaccines. Adjuvants are widely diverse in structure; however, their overall function in vaccine constructs is the same: to enhance and/or prolong an immunological response. The potential for adverse effects as a result of adjuvant use, though, must be acknowledged and carefully managed. Understanding the specific mechanisms of adjuvant efficacy and safety is a key prerequisite for adjuvant use in vaccination. Therefore, rigorous pre-clinical and clinical research into adjuvant development is essential. Overall, the incorporation of adjuvants allows for greater opportunities in advancing vaccine development and the importance of immune stimulants drives the emergence of novel and more effective adjuvants. This article highlights recent advances in vaccine adjuvant development and provides detailed data from pre-clinical and clinical studies specific to infectious diseases. Future perspectives into vaccine adjuvant development are also highlighted.

Comparison of adjuvant properties of chitosan during oral and subcutaneous immunization of mice with BSA

Vaccination is the best method to prevent the spread of infectious diseases, its disadvantages are side effects. Potentially safe DNA, RNA or protein molecules possess antigenic properties, but are low-immunogenic and therefore require conjugation with an adjuvant. The aim of the research was to evaluate Chitosan (CS) potency as an adjuvant and compare its effectiveness depending on the route of drug administration. The experiments were carried out on 3 groups of BALB/c mice. Mice of the first group were injected subcutaneously with 20 µl of a mixture of CS (3.3 mg/kg) and BSA (1.7 mg/kg). The mixture of CS and BSA at the same doses and volume was administered orally to mice of the second experimental group. The third group – control – unvaccinated mice. Anti-BSA antibody levels were measured by ELISA. Aspartate aminotransferase, alanine aminotransferase activity and cholesterol, creatinine and urea levels were determined in the serum. It was found that both subcutaneous and mucosal immunizations provided a 2-fold increase in anti-BSA antibody titers against the background of maintaining all biochemical blood parameters at the level of the physiological norm. However, AST activity in the serum of oral-immunized mice was elevated as compared to subcutaneous-immunized mice. Serum cholesterol level in the group of subcutaneously immunized mice and creatinine and urea levels in both experimental groups were reduced compared to the control. It is concluded that oral immunization with CS is the optimal route for antigen-specific IgG antibody response induction.

Safety and Efficacy of the Bordetella bronchiseptica Vaccine Combined with a Vegetable Oil Adjuvant and Multi-Omics Analysis of Its Potential Role in the Protective Response of Rabbits

Infectious respiratory diseases caused by Bordetella bronchiseptica (Bb) are seriously endangering the development of the rabbit industry in China. Unfortunately, no licensed vaccines are available for this pathogen. The present study was designed to determine whether the inactivated Bb antigen formulated with vegetable oil adjuvant (named E515) which contains soybean oil, vitamin E, and ginseng saponins, functions as a safe and effective vaccine (E515-Bb) against Bb infection in rabbits. Based on local and systemic reactions, both the E515 adjuvant alone and the E515-Bb vaccine exhibited good safety in rabbits. Immune response analysis implies that rabbits immunized with the E515-Bb vaccine produced significantly higher, earlier, and longer-lasting specific antibody responses and activated Th1/Th2/Th17 cell responses than those immunized with the aluminum hydroxide (Alum)-adjuvanted Bb vaccine (Alum-Bb) or Bb antigen alone. Moreover, the E515-Bb vaccine effectively protected rabbits from Bb infection. Additionally, integrated multi-omics analysis revealed that the immunoprotective effect of the E515-Bb vaccine was achieved through upregulation of the complement and coagulation cascades and cell adhesion molecule (CAM) pathways, and the downregulation of the P53 pathway. Overall, these results indicate that the E515-Bb vaccine is safe, elicits an efficient immune response and provides good protection against Bb infection in rabbits. Thus, the E515-adjuvanted Bb vaccine can be considered a promising candidate vaccine for preventing Bb infection.

Rational Vaccinology: Harnessing Nanoscale Chemical Design for Cancer Immunotherapy

Cancer immunotherapy is a powerful treatment strategy that mobilizes the immune system to fight disease. Cancer vaccination is one form of cancer immunotherapy, where spatiotemporal control of the delivery of tumor-specific antigens, adjuvants, and/or cytokines has been key to successfully activating the immune system. Nanoscale materials that take advantage of chemistry to control the nanoscale structural arrangement, composition, and release of immunostimulatory components have shown significant promise in this regard. In this Outlook, we examine how the nanoscale structure, chemistry, and composition of immunostimulatory compounds can be modulated to maximize immune response and mitigate off-target effects, focusing on spherical nucleic acids as a model system. Furthermore, we emphasize how chemistry and materials science are driving the rational design and development of next-generation cancer vaccines. Finally, we identify gaps in the field that should be addressed moving forward and outline future directions to galvanize researchers from multiple disciplines to help realize the full potential of this form of cancer immunotherapy through chemistry and rational vaccinology.

Novel naltrexone hydrochloride nanovaccine based on chitosan nanoparticles promotes induction of Th1 and Th17 immune responses resulting in protection against Toxoplasma gondii tachyzoites in a mouse model

This study was aimed to encapsulate and construct the Toxoplasma gondii surface antigen (SAG1) and naltrexone hydrochloride (NLT-HCL) as an adjuvant within chitosan nanoparticles (CS-NPs) to develop efficacious vaccine against T. gondii. Seven groups of BALB/c mice were immunized with SAG1, chitosan (CS), NLT-SAG1, CS-SAG1, CS-SAG1-NLT, CS-NLT and PBS. The efficiency of each approach was detected in vivo mouse immunization. Moreover, the immuno-induction effect of SAG1 recombinant protein and CS-NPs-based NLT-HCL as an adjuvant in a vaccine delivery was evaluated. Experimentally, Th1/Th17 biased cellular and humoral immune responses were activated in the mice immunized with CS-SAG1-NLT nanoparticles that were accompanied by considerable increased production of IFN-γ, IL-17, IL-12, IL-4, IFN-γ/IL-4 ratio, IgG, IgG2a. This group of mice also showed significantly increased survival time post-challenging. The successful encapsulated SAG1 recombinant protein and NLT-HCL, as an adjuvant, within CS-NPs can induce immune responses against toxoplasmosis. We could incorporate NLT-HCL adjuvant into the CS-NPs based delivery systems, which makes CS-NPs attractive as a colloidal carrier system for NLT-HCL as secondary adjuvant. This new approach or the simultaneous use of CS and NLT demonstrated that the co-administration of CS-NPs and NLT-HCL induce production of IL-17 cytokine. This approach can be used for vaccination purposes, in which Th17 and Th1 cellular immune are considered the key of the successful immune response.

Promotion of trained innate immunity by nanoparticles

The dogma that immunological memory is an exclusive trait of adaptive immunity has been recently challenged by studies showing that priming of innate cells can also result in modified long-term responsiveness to secondary stimuli, once the cells have returned to a non-activated state. This phenomenon is known as 'innate immune memory', 'trained immunity' or 'innate training'. While the main known triggers of trained immunity are microbial-derived molecules such as β-glucan, endogenous particles such as oxidized low-density lipoprotein and monosodium urate crystals can also induce trained phenotypes in innate cells. Whether exogenous particles can induce trained immunity has been overlooked. Our exposure to particulates has dramatically increased in recent decades as a result of the broad medical use of particle-based drug carriers, theragnostics, adjuvants, prosthetics and an increase in environmental pollution. We recently showed that pristine graphene can induce trained immunity in macrophages, enhancing their inflammatory response to TLR agonists, proving that exogenous nanomaterials can affect the long-term response of innate cells. The consequences of trained immunity can be beneficial, for instance, enhancing protection against unrelated pathogens; however, they can also be deleterious if they enhance inflammatory disorders. Therefore, studying the ability of particulates and biomaterials to induce innate trained phenotypes in cells is warranted. Here we analyse the mechanisms whereby particles can induce trained immunity and discuss how physicochemical characteristics of particulates could influence the induction of innate memory. We review the implications of trained immunity in the context of particulate adjuvants, nanocarriers and nanovaccines and their potential applications in medicine. Finally, we reflect on the unanswered questions and the future of the field.

Current approaches to HIV vaccine development: a narrative review

INTRODUCTION

The development of an effective vaccine to protect against HIV is a longstanding global health need complicated by challenges inherent to HIV biology and to the execution of vaccine efficacy testing in the context of evolving biomedical prevention interventions. This review describes lessons learnt from previous efficacy trials, highlights unanswered questions, and surveys new approaches in vaccine development addressing these gaps.

METHODS

We conducted a targeted peer-reviewed literature search of articles and conference abstracts from 1989 through 2021 for HIV vaccine studies and clinical trials. The US National Library of Medicine's Clinical Trials database was accessed to further identify clinical trials involving HIV vaccines. The content of the review was also informed by the authors' own experience and engagement with collaborators in HIV vaccine research.

DISCUSSION

The HIV vaccine field has successfully developed multiple vaccine platforms through advanced clinical studies; however, the modest efficacy signal of the RV144 Thai trial remains the only demonstration of HIV vaccine protection in humans. Current vaccine strategies include prime-boost strategies to improve elicitation of immune correlates derived from RV144, combination mosaic antigens, novel viral vectors, antigens designed to elicit broadly neutralizing antibody, new nucleic acid platforms and potent adjuvants to enhance immunogenicity across multiple classes of emerging vaccine candidates.

CONCLUSIONS

HIV vaccine developers have applied lessons learnt from previous successes and failures to innovative vaccine design approaches. These strategies have yielded novel mosaic antigen constructs now in efficacy testing, produced a diverse pipeline of early-stage immunogens and novel adjuvants, and advanced the field towards a globally effective HIV vaccine.

Reviewing the biological activity of chitosan in the mucosa: Focus on intestinal immunity

Chitosan is a polymer derived from the partial deacetylation of chitin with particular characteristics, such as mucoadhesiveness, tolerability, biocompatibility and biodegradability. Biomedical uses of chitosan cover a wide spectrum of applications as dietary fiber, immunoadjuvant and regulator of the intestinal microbiota or delivery agent. Chemical modification of chitosan is feasible because its reactive amino and hydroxyl groups can be modified by a diverse array of ligands, functional groups and molecules. This gives rise to numerous derivatives that allow different formulation types influencing their activity. Considering the multiple events resulting from the interaction with mucosal tissues, chitosan is a singular candidate for strategies targeting immune stimulation (i.e., tolerance induction, vaccination). Its role as a prebiotic and probiotic carrier represents an effective option to manage intestinal dysbiosis. In the intestinal scenario where the exposure of the immune system to a wide variety of antigens is permanent, chitosan increases IgA levels and favors a tolerogenic environment, thus becoming a key ally for host homeostasis.

Azoximer Bromide: Mystery, Serendipity, and Promise

Azoximer bromide (AZB) was identified as an immunomodulator, and was initially developed and currently successfully indicated as one of several natural polyelectrolytes, a vaccine adjuvant, and an effective agent for the treatment of infectious and inflammatory diseases of viral, bacterial, and fungal origin. AZB has the potential to increase an individual's resistance to local and general infection and is indicated for the treatment of viral infections, and has also demonstrated clinical efficacy in the treatment of a variety of secondary immunodeficiencies. However, AZB may offer long-term promise beyond use against infection. Multiple clinical trials and research studies in cancer patients have reported favourable outcomes with AZB as well as an optimal safety and tolerability profile. The findings raise the possibility of direct antitumor properties. This literature review analyses the novel mechanisms that mediate the AZB direct anticancer effects. Overall, the evidence suggests that AZB has the hallmark of an agent that could be used to support existing cancer treatments at different stages of disease.

Improvement of RG1-VLP vaccine performance in BALB/c mice by substitution of alhydrogel with the next generation polyphosphazene adjuvant PCEP

Current human papillomavirus (HPV) vaccines provide substantial protection against the most common HPV types responsible for oral and anogenital cancers, but many circulating cancer-causing types remain for which vaccine coverage is lacking. In addition, all current HPV vaccines rely on aluminum salt-based adjuvant formulations that function through unclear mechanisms with few substitutes available. In an effort to expand the toolbox of available adjuvants suitable for HPV vaccines, we compared the immunogenicity of the RG1-VLP (virus-like particle) vaccine in BALB/c mice when formulated with either the aluminum hydroxide adjuvant Alhydrogel or the novel polyphosphazene macromolecular adjuvant poly[di (carboxylatoethylphenoxy) phosphazene] (PCEP). PCEP-formulated RG1-VLPs routinely outperformed VLP/Alhydrogel in several measurements of VLP-specific humoral immunity, including consistent improvements in the magnitude of antibody (Ab) responses to both HPV16-L1 and the L2 RG1 epitope as well as neutralizing titers to HPV16 and cross-neutralization of pseudovirion (PsV) types HPV18 and HPV39. Dose-sparing studies indicated that RG1-VLPs could be reduced in dose by 75% and the presence of PCEP ensured activity comparable to a full VLP dose adjuvanted by Alhydrogel. In addition, levels of HPV16-L1 and -L2-specific Abs were achieved after two vaccinations with PCEP as adjuvant that were equivalent to or greater than levels achieved with three vaccinations with Alhydrogel alone, indicating that the presence of PCEP resulted in accelerated immune responses that could allow for a decreased dose schedule. Given the extensive clinical track record of polyphosphazenes, these data suggest that substitution of alum-based adjuvants with PCEP for the RG1-VLP vaccine could lead to rapid seropositivity requiring fewer boosts, the dose-sparing of commercial VLP-based vaccines, and the establishment of longer-lasting humoral responses to HPV.

Immunological Mechanism and Clinical Application of PAMP Adjuvants

BACKGROUND

The host innate immune system can recognize Pathogen-Associated Molecular Patterns (PAMPs) through Pattern Recognition Receptors (PRRs), thereby initiating innate immune responses and subsequent adaptive immune responses. PAMPs can be developed as a vaccine adjuvant for modulating and optimizing antigen-specific immune responses, especially in combating viral infections and tumor therapy. Although several PAMP adjuvants have been successfully developed they are still lacking in general, and many of them are in the preclinical exploration stage.

OBJECTIVE

This review summarizes the research progress and development direction of PAMP adjuvants, focusing on their immune mechanisms and clinical applications.

METHODS

PubMed, Scopus, and Google Scholar were screened for this information. We highlight the immune mechanisms and clinical applications of PAMP adjuvants.

RESULTS

Because of the differences in receptor positions, specific immune cells targets, and signaling pathways, the detailed molecular mechanism and pharmacokinetic properties of one agonist cannot be fully generalized to another agonist, and each PAMP should be studied separately. In addition, combination therapy and effective integration of different adjuvants can increase the additional efficacy of innate and adaptive immune responses.

CONCLUSION

The mechanisms by which PAMPs exert adjuvant functions are diverse. With continuous discovery in the future, constant adjustments should be made to build new understandings. At present, the goal of therapeutic vaccination is to induce T cells that can specifically recognize and eliminate tumor cells and establish long-term immune memory. Following immune checkpoint modulation therapy, cancer treatment vaccines may be an option worthy of clinical testing.

Adsorption of protein antigen to the cationic liposome adjuvant CAF®01 is required for induction of Th1 and Th17 responses but not for antibody induction

The degree of antigen adsorption to adjuvants in subunit vaccines may significantly influence the immune responses they induce upon vaccination. Commonly used approaches for studying how the level of adsorption affects the induction of antigen-specific immune responses include (i) using adjuvants with different abilities to adsorb antigens, and (ii) comparing different antigens selected based on their ability to adsorb to the adjuvant. A weakness of these approaches is that not only the antigen adsorption level is varied, but also other important functional factors such as adjuvant composition and/or the B/T cell epitopes, which may affect immunogenicity. Hence, we investigated how changing the adsorption capabilities of a single antigen to an adjuvant influenced the vaccine-induced immune responses. The model antigen lysozyme, which displays a positive net charge at physiological pH due to an isoelectric point (pI) of 11, was succinylated to different extents, resulting in a reduction of the pI value to 4.4–5.9, depending on the degree of succinylation. A pronounced inverse correlation was found between the pI value of the succinylated lysozyme analogues and the degree of adsorption to a cationic liposomal adjuvant consisting of dimethyldioctadecylammonium bromide (DDA) and trehalose dibehenate (TDB) (CAF®01). Furthermore, increased adsorption to this adjuvant correlated directly with the magnitude of lysozyme-specific Th1/Th17 immune responses induced by the vaccine in mice, while there was an inverse correlation with antibody induction. However, high lysozyme-specific antibody titers were induced with an increased antigen dose, even upon vaccination with a strongly adsorbed succinylated lysozyme analogue. Hence, these data illustrate that the degree of lysozyme adsorption to CAF®01 strongly affects the quality of the resulting immune responses.

Comparative Immunomodulatory Evaluation of the Receptor Binding Domain of the SARS-CoV-2 Spike Protein; a Potential Vaccine Candidate Which Imparts Potent Humoral and Th1 Type Immune Response in a Mouse Model

The newly emerged novel coronavirus, SARS-CoV-2, the causative agent of COVID-19 has proven to be a threat to the human race globally, thus, vaccine development against SARS-CoV-2 is an unmet need driving mass vaccination efforts. The receptor binding domain of the spike protein of this coronavirus has multiple neutralizing epitopes and is associated with viral entry. Here we have designed and characterized the SARS-CoV-2 spike protein fragment 330-526 as receptor binding domain 330-526 (RBD330-526) with two native glycosylation sites (N331 and N343); as a potential subunit vaccine candidate. We initially characterized RBD330-526 biochemically and investigated its thermal stability, humoral and T cell immune response of various RBD protein formulations (with or without adjuvant) to evaluate the inherent immunogenicity and immunomodulatory effect. Our result showed that the purified RBD immunogen is stable up to 72 h, without any apparent loss in affinity or specificity of interaction with the ACE2 receptor. Upon immunization in mice, RBD generates a high titer humoral response, elevated IFN-γ producing CD4+ cells, cytotoxic T cells, and robust neutralizing antibodies against live SARS-CoV-2 virus. Our results collectively support the potential of RBD330-526 as a promising vaccine candidate against SARS-CoV-2.

Next generation polyphosphazene immunoadjuvant: Synthesis, self-assembly and in vivo potency with human papillomavirus VLPs-based vaccine

Poly[di(carboxylatomethylphenoxy)phosphazene] (PCMP), a new member of polyphosphazene immunoadjuvant family, is synthesized. In vitro assessment of a new macromolecule revealed hydrolytic degradation profile and immunostimulatory activity comparable to its clinical stage homologue PCPP; however, PCMP was characterized by a beneficial reduced sensitivity to the ionic environment. In vivo evaluation of PCMP potency was conducted with human papillomavirus (HPV) virus-like particles (VLPs) based RG1-VLPs vaccine. In contrast with previously reported self-assembly of polyphosphazene adjuvants with proteins, which typically results in the formation of complexes with multimeric display of antigens, PCMP surface modified VLPs in a composition dependent pattern, which at a high polymer-to VLPs ratio led to stabilization of antigenic particles. Immunization experiments in mice demonstrated that PCMP adjuvanted RG1-VLPs vaccine induced potent humoral immune responses, in particular, on the level of highly desirable protective cross-neutralizing antibodies, and outperformed PCPP and Alhydrogel adjuvanted formulations.

Pyridine-pyrazole based Al(iii) 'turn on' sensor for MCF7 cancer cell imaging and detection of picric acid

We report herein the development of a new pyridine-pyrazole based bis-bidentate asymmetric chemosensor that shows excellent turn-on chelation-enhanced Al3+-responsive fluorescence. The presence of two 'hard' phenolic hydroxyl groups plays a pivotal role in switching-on the sensing through coordination to the 'hard' Al3+ ion, while the mechanism can be interpreted by the chelation-enhanced fluorescence (CHEF) process. The X-ray single structure show a planar conjugated structure of the ligand, which was further stabilized by extensive H-bonding and π-π stacking. The photophysical studies related to the sensing behavior of the titular ligand toward aluminum was investigated in detail using various spectroscopic techniques like UV-Vis, photoluminescence, fluorescence and time-correlated single-photon count (TCSPC) and time-resolved NMR. The spectroscopic methods also confirm the selective detection of Al3+ ion in the presence of other metal ions. The theoretical calculations using Density Functional Theory (DFT) and the Time Dependent Density Functional Theory (TD-DFT) provide further insight on the mechanistic aspects of the turn-on sensing behavior including the electronic spectra of both the ligand and the complex. Interestingly, the as-synthesized H2DPC-Al complex can also be utilized as a fluorescence-based sensor for various nitroaromatics including picric acid, for which an INHIBIT logic gate can also be constructed. The as synthesized complex was subsequently used as a fluorescent probe for imaging of human breast adenocarcinoma (MCF7) cells using live cell confocal microscopic techniques.

In Vivo and In Vitro Potency of Polyphosphazene Immunoadjuvants with Hepatitis C Virus Antigen and the Role of Their Supramolecular Assembly

Two well-defined synthetic polyphosphazene immunoadjuvants, PCPP and PCEP, were studied for their ability to potentiate the immune response to the hepatitis C virus (HCV) E2 glycoprotein antigen in vivo. We report that PCEP induced significantly higher serum neutralization and HCV-specific IgG titers in mice compared to other adjuvants used in the study: PCPP, Alum, and Addavax. PCEP also shifted the response toward the desirable balanced Th1/Th2 immunity, as evaluated by the antibody isotype ratio (IgG2a/IgG1). The in vivo results were analyzed in the context of antigen-adjuvant molecular interactions in the system and in vitro immunostimulatory activity of formulations. Asymmetric flow field flow fractionation (AF4) and dynamic light scattering (DLS) analysis showed that both PCPP and PCEP spontaneously self-assemble with the E2 glycoprotein with the formation of multimeric water-soluble complexes, which demonstrates the role of polyphosphazene macromolecules as vaccine delivery vehicles. Intrinsic in vitro immunostimulatory activity of polyphosphazene adjuvants, which was assessed using a mouse macrophage cell line, revealed comparable activities of both polymers and did not provide an explanation of their in vivo performance. However, PCEP complexes with E2 displayed greater stability against agglomeration and improved in vitro immunostimulatory activity compared to those of PCPP, which is in line with superior in vivo performance of PCEP. The results emphasize the importance of often neglected antigen-polyphosphazene self-assembly mechanisms in formulations, which can provide important insights on their in vivo behavior and facilitate the establishment of a structure-activity relationship for this important class of immunoadjuvants.

A novel vaccine adjuvant based on straight polyacrylate potentiates vaccine-induced humoral and cellular immunity in cynomolgus macaques

Adjuvants are central to the efficacy of subunit vaccines. Although several new adjuvants have been approved in human vaccines over the last decade, the panel of adjuvants in licensed human vaccines remains small. There is still a need for novel adjuvants that can be safely used in humans, easy to source and to formulate with a wide range of antigens and would be broadly applicable to a wide range of vaccines. In this article, using the Respiratory Syncytial Virus (RSV) nanoparticulate prefusion F model antigen developed by Sanofi, we demonstrate in the macaque model that the polyacrylate (PAA)-based adjuvant SPA09 is well tolerated and increases vaccine antigen-specific humoral immunity (sustained neutralizing antibodies, memory B cells and mucosal immunity) and elicits strong T_H1-type responses (based on IFNγ and IL-2 ELISpots) in a dose-dependent manner. These data warrant further development of the SPA09 adjuvant for evaluation in clinical trials.

Highly selective and sensitive chemosensor for Al(III) based on isoquinoline Schiff base

As a colorimetric and fluorescent turn-on sensor to Al³⁺, N'-(2-hydroxybenzylidene)isoquinoline-3-carbohydrazide (HL) has been easily synthesized. The fluorescence intensity increases by 273 times in the presence of Al³⁺ at 458 nm. Meanwhile, the experiment data indicate that the limit of detection for Al³⁺ is 1.11 × 10^-9 M. Remarkably, the blue fluorescence signal of HL-Al³⁺ could be specially observed by the naked eye under UV light and is significantly different from those of other metal ions. Fluorescence switch based on the control of Al³⁺ and EDTA proved HL could act as a reversible chemosensor. According to ESI-MS result and the Job's plots, the 2:1 coordination complex formed by HL and Al³⁺ could be produced. Density functional theory calculations were performed to illustrate the structures of HL and complex. The cell imaging experiment indicates that HL can be applied for monitoring intracellular Al³⁺ levels in cells.

Anionic Polyelectrolyte Hydrogel as an Adjuvant for Vaccine Development

Vaccination is one of the main methods for the specific prevention of infectious diseases. The disadvantage of vaccination is the use of pathogens (live or attenuated viruses and bacteria) that can lead to the development of a disease. Recombinant technologies are capable of producing specific DNA or protein molecules that possess antigenic properties and do not cause disease. However, individual antigen molecules are low-immunogenic, and therefore, require conjugation with a compound possessing stronger immunogenic properties. In this study, we examined the immunogenic properties of the new anionic copolymer consisting of glycidyl methacrylate, butyl acrylate, triethylene glycol dimethacrylate, and acrylic acid, in mice. The experimental polymer induced a stronger immunogenic response than aluminum hydroxide. The histological studies have established that immunization both with aluminum hydroxide and the polymer studied does not cause damage to the liver, kidneys, or the spleen. No negative side effects were observed. It has been concluded that the new synthetic anionic polyelectrolyte hydrogel (PHG) has a potential as an adjuvant for vaccine development.

Self-Assembled Cationic-Covered Nanoemulsion as A Novel Biocompatible Immunoadjuvant for Antiserum Production Against Tityus serrulatus Scorpion Venom

This study assesses the efficacy of different nanoemulsion formulations as new and innovative adjuvants for improving the in vivo immunization against the Tityus serrulatus scorpion venom. Nanoemulsions were designed testing key-variables such as surfactants, co-solvents, and the influence of the temperature, which would be able to induce the phase transition from a liquid crystal to a stable nanoemulsion, assessed for four months. Additionally, cationic-covered nanoemulsion with hyper-branched poly(ethyleneimine) was prepared and its performance was compared to the non-cationic ones. The physicochemical properties of the selected nanoemulsions and the interactions among their involved formulation compounds were carefully monitored. The cytotoxicity studies in murine macrophages (RAW 264.7) and red blood cells were used to compare different formulations. Moreover, the performance of the nanoemulsion systems as biocompatible adjuvants was evaluated using mice immunization protocol. The FTIR shifts and the zeta potential changes (from -18.3 ± 1.0 to + 8.4 ± 1.4) corroborated with the expected supramolecular anchoring of venom proteins on the surface of the nanoemulsion droplets. Cell culture assays demonstrated the non-toxicity of the formulations at concentrations less than 1.0 mg/mL, which were able to inhibit the hemolytic effect of the scorpion venom. The cationic-covered nanoemulsion has shown superior adjuvant activity, revealing the highest IgG titer in the immunized animals compared to both the non-cationic counterpart and the traditional aluminum adjuvant. In this approach, we demonstrate the incredible potential application of nanoemulsions as adjuvants, using a nanotechnology platform for antigen delivery system on immune cells. Additionally, the functionalization with hyper-branched poly(ethyleneimine) enhances this recognition and improves its action in immunization.

Low-dose influenza vaccine Grippol Quadrivalent with adjuvant Polyoxidonium induces a T helper-2 mediated humoral immune response and increases NK cell activity

The influenza vaccine Grippol® Quadrivalent (GQ) is a new vaccine, containing the adjuvant Polyoxidonium® and recombinant hemagglutinins from 4 strains of the influenza virus in amount of 5-6 μg of each hemagglutinin per human dose. These doses of antigens are about 3 times less than the standard dose recommended by WHO. We sought to characterize the immune response to the GQ vaccine and to determine the contribution of the adjuvant in this response. BALB/c mice were vaccinated with GQ or with adjuvant-free antigen mixtures (AGs). Then, the antibody response, the number of memory T cells in the spleen, and the functional properties of splenocytes were determined. The vaccine GQ has been shown to induce antibodies to all 4 influenza hemagglutinins. The vaccination with GQ caused a strong increase in the AG-induced proliferation and production of Th2 cytokines ex vivo. These effects were equal to effect achieved by standard dose of antigens. Vaccination also caused the accumulation of CD4⁺ large lymphocytes with the phenotype of central and effector memory T cells in the spleen. The GQ vaccine enhanced the cytolytic activity of natural killer (NK) cells, whereas the adjuvant-free mixture of AGs in lowered and standard doses did not affect NK activity. We did not find a noticeable response of Th1 and CD8⁺ T cells to vaccination. In vitro, the GQ vaccine stimulated the maturation of human monocyte-derived dendritic cells (DCs) enhancing the expression of HLA-DR, CD80, CD83, CD86 and ICOSL molecules. Polyoxidonium without AGs also induced expression of ICOSL, which plays an important role in T-dependent humoral immune response. In summary, the low-dose influenza vaccine GQ with Polyoxidonium adjuvant is immunogenic, induces a Th2-polarized T-cell response and CD4⁺ memory T cells maturation, activates the production of antibodies to influenza hemagglutinins, and increases the activity of NK cells.

A potent novel vaccine adjuvant based on straight polyacrylate

A structure-activity study was conducted to identify the structural characteristics underlying the adjuvant activity of straight (i.e. non-crosslinked) polyacrylate polymers (PAAs) in order to select a new PAA adjuvant candidate for future clinical development. The study revealed that the adjuvant effect of PAA was mainly influenced by polymer size (Mw) and dose. Maximal effects were obtained with large PAAs above 350 kDa and doses above 100 μg in mice. Small PAAs below 10 kDa had virtually no adjuvant effect. HPSEC analysis revealed that PAA polydispersity index and ramification had less impact on adjuvanticity. Heat stability studies indicated that residual persulfate could be detrimental to PAA stability. Hence, this impurity was systematically eliminated by diafiltration along with small Mw PAAs and residual acrylic acid that could potentially affect product safety, potency and stability. The selected PAA, termed SPA09, displayed an adjuvant effect that was superior to that of a standard emulsion adjuvant when tested with CMV-gB in mice, even in the absence of binding to the antigen. The induced immune response was dominated by strong IFNγ, IgG2c and virus neutralizing titers. The activity of SPA09 was then confirmed on human cells via the innate immune module of the human MIMIC® system.

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Straight polyacrylate (350 kDa < Mw < 650 kDa; termed SPA09) is a strong adjuvant easy to formulate with vaccine antigens

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SPA09 induces Th-1 type immune responses in mice, dominated by strong IFN-γ, IgG2c and virus neutralizing titers

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SPA09 can activate human antigen presenting cells when tested via the innate immune module (PTE) of the human MIMIC® system

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SPA09 constitutes a straightforward new adjuvant candidate for future clinical development

An insight into the epitope-based peptide vaccine design strategy and studies against COVID-19

SARS-CoV-2 is a new member of the coronavirus family and caused the pandemic of coronavirus disease 2019 (COVID-19) in 2020. It is crucial to design and produce an effective vaccine for the prevention of rapid transmission and possible deaths wcaused by the disease. Although intensive work and research are being carried out all over the world to develop a vaccine, an effective and approved formulation that can prevent the infection and limit the outbreak has not been announced yet. Among all types of vaccines, epitope-based peptide vaccines outshine with their low-cost production, easy modification in the structure, and safety. In this review, vaccine studies against COVID-19 have been summarized and detailed information about the epitope-based peptide vaccines against COVID-19 has been provided. We have not only compared the peptide vaccine with other types of vaccines but also presented comprehensive literature information about development steps for an effective and protective formulation to give an insight into on-going peptide vaccine studies against SARS-CoV-2.

Use of DAMPs and SAMPs as Therapeutic Targets or Therapeutics: A Note of Caution

This opinion article discusses the increasing attention paid to the role of activating damage-associated molecular patterns (DAMPs) in initiation of inflammatory diseases and suppressing/inhibiting DAMPs (SAMPs) in resolution of inflammatory diseases and, consequently, to the future roles of these novel biomarkers as therapeutic targets and therapeutics. Since controlled production of DAMPs and SAMPs is needed to achieve full homeostatic restoration and repair from tissue injury, only their pathological, not their homeostatic, concentrations should be therapeutically tackled. Therefore, distinct caveats are proposed regarding choosing DAMPs and SAMPs for therapeutic purposes. For example, we discuss the need to a priori identify and define a context-dependent “homeostatic DAMP:SAMP ratio” in each case and a “homeostatic window” of DAMP and SAMP concentrations to guarantee a safe treatment modality to patients. Finally, a few clinical examples of how DAMPs and SAMPs might be used as therapeutic targets or therapeutics in the future are discussed, including inhibition of DAMPs in hyperinflammatory processes (e.g., systemic inflammatory response syndrome, as currently observed in Covid-19), administration of SAMPs in chronic inflammatory diseases, inhibition of SAMPs in hyperresolving processes (e.g., compensatory anti-inflammatory response syndrome), and administration/induction of DAMPs in vaccination procedures and anti-cancer therapy.

Supramolecular assembly of Toll-like receptor 7/8 agonist into multimeric water-soluble constructs enables superior immune stimulation in vitro and in vivo

Resiquimod or R848 (RSQD) is a Toll-like receptor (TLR) 7/8 agonist which shows promise as vaccine adjuvant due to its potential to promote highly desirable cellular immunity. The development of this small molecule in the field to date has been largely impeded by its rapid in vivo clearance and lack of association with vaccine antigens. Here, we report a multimeric TLR 7/8 construct of nano-scale size, which results from a spontaneous self-assembly of RSQD with a water-soluble clinical-stage polymer - poly[di(carboxylatophenoxy)phosphazene] (PCPP). The formation of ionically paired construct (PCPP-R) and a ternary complex, which also includes Hepatitis C virus (HCV) antigen, has been demonstrated by dynamic lights scattering (DLS), turbidimetry, fluorescence spectroscopy, asymmetric flow field flow fractionation (AF4), and ¹H NMR spectroscopy methods. The resulting supramolecular assembly PCPP-R enabled superior immunostimulation in cellular assays (mouse macrophage reporter cell line) and displayed improved in vitro hemocompatibility (human erythrocytes). In vivo studies demonstrated that PCPP-R adjuvanted HCV formulation induced higher serum neutralization titers in BALB/c mice and shifted the response towards desirable cellular immunity, as evaluated by antibody isotype ratio (IgG2a/IgG1) and ex vivo analysis of cytokine secreting splenocytes (higher levels of interferon gamma (IFN-γ) single and tumor necrosis factor alpha (TNF-α)/IFN-γ double producing cells). The non-covalent multimerization approach stands in contrast to previously suggested RSQD delivery methods, which involve covalent conjugation or encapsulation, and offers a flexible methodology that can be potentially integrated with other parenterally administered drugs.

Novel Peptide-Based PD1 Immunomodulators Demonstrate Efficacy in Infectious Disease Vaccines and Therapeutics

Many pathogens use the same immune evasion mechanisms as cancer cells. Patients with chronic infections have elevated levels of checkpoint receptors (e.g., programed cell death 1, PD1) on T cells. Monoclonal antibody (mAb)-based inhibitors to checkpoint receptors have also been shown to enhance T-cell responses in models of chronic infection. Therefore, inhibitors have the potential to act as a vaccine “adjuvant” by facilitating the expansion of vaccine antigen-specific T-cell repertoires. Here, we report the discovery and characterization of a peptide-based class of PD1 checkpoint inhibitors, which have a potent adaptive immunity adjuvant capability for vaccines against infectious diseases. Briefly, after identifying peptides that bind to the recombinant human PD1, we screened for in vitro efficacy in reporter assays and human peripheral blood mononuclear cells (PBMC) readouts. We first found the baseline in vivo performance of the peptides in a standard mouse oncology model that demonstrated equivalent efficacy compared to mAbs against the PD1 checkpoint. Subsequently, two strategies were used to demonstrate the utility of our peptides in infectious disease indications: (1) as a therapeutic in a bacteria-induced lethal sepsis model in which our peptides were found to increase survival with enhanced bacterial clearance and increased macrophage function; and (2) as an adjuvant in combination with a prophylactic malaria vaccine in which our peptides increased T-cell immunogenicity and the protective efficacy of the vaccine. Therefore, our peptides are promising as both a therapeutic agent and a vaccine adjuvant for infectious disease with a potentially safer and more cost-effective target product profile compared to mAbs. These findings are essential for deploying a new immunomodulatory regimen in infectious disease primary and clinical care settings.

Protein-loaded soluble and nanoparticulate formulations of ionic polyphosphazenes and their interactions on molecular and cellular levels

Nanoparticulate and water-soluble formulations of ionic polyphosphazenes and protein cargo - lysozyme (LYZ) were prepared by their self-assembly in aqueous solutions at near physiological pH (pH 7.4) in the presence and absence of an ionic cross-linker - spermine tetrahydrochloride. Efficiency of LYZ encapsulation, physico-chemical characteristics of formulations, and the effect of reaction parameters were investigated using asymmetric flow field flow fractionation (AF4) and dynamic light scattering (DLS) methods. The effect of both polymer formulations on encapsulated LYZ was evaluated using soluble oligosaccharide substrate, whereas their ability to present the protein to cellular surfaces was assessed by measuring enzymatic activity of encapsulated LYZ against Micrococcus lysodeikticus cells. It was found that both soluble and cross-linked polymer matrices reduce lysis of bacterial cells by LYZ, whereas activity of encapsulated protein against oligosaccharide substrate remained practically unchanged indicating no adverse effect of polyphosphazene on protein integrity. Moreover, nanoparticulate formulations display distinctly different behavior in cellular assays when compared to their soluble counterparts. LYZ encapsulated in polyphosphazene nanoparticles shows approximately 2.5-fold higher activity in its ability to lyse cells as compared with water-soluble LYZ-PCPP formulations. A new approach to PEGylation of polyphosphazene nanoparticles was also developed. The method utilizes a new ionic polyphosphazene derivative, which contains graft (polyethylene glycol) chains. PEGylation allows for an improved control over the size of nanoparticles and broader modulation of their cross-linking density, while still permitting for protein presentation to cellular substrates.

Polyoxidonium® Activates Cytotoxic Lymphocyte Responses Through Dendritic Cell Maturation: Clinical Effects in Breast Cancer

Immunotherapy, which is seen as a major tool for cancer treatment, requires, in some cases, the presence of several agents to maximize its effects. Adjuvants can enhance the effect of other agents. However, despite their long-time use, only a few adjuvants are licensed today, and their use in cancer treatment is rare. Azoximer bromide, marketed under the trade name Polyoxidonium® (PO), is a copolymer of N-oxidized 1,4-ethylenepiperazine and (N-carboxyethyl)-1,4-ethylene piperazinium bromide. It has been described as an immune adjuvant and immunomodulator that is clinically used with excellent tolerance. PO is used in the treatment and prophylaxis of diseases connected with damage to the immune system, and there is interest in testing it in antitumor therapy. We show here that PO treatment for 1 week induced positive pathological changes in 6 out of 20 patients with breast cancer, including complete response in a triple-negative patient. This correlated with an increased tumor CD4⁺ T-lymphocyte infiltration. The immune effects of PO are associated with myeloid cell activation, and little is known about the action of PO on lymphocyte lineages, such as natural killer (NK) and T cells. We reveal that PO increases T-cell proliferation in vitro without negative effects on any activation marker. PO does not affect dendritic cell (DC) viability and increases the expansion of immature DC (iDC) and mature DC (mDC) at 100 μg/ml, and it stimulates expression of several DC co-stimulatory molecules, inducing the proliferation of allogeneic T cells. In contrast, PO decreases DC viability when added at day 5 post-expansion. PO is not toxic for NK cells at doses up to 100 μM and does not affect their activation, maturation, and cytotoxicity but tends to increase degranulation. This could be beneficial against target cells that show low sensitivity to NK cells, e.g., solid tumor cells. Finally, we have found great variability in PO response between donors. In summary, our in vitro results show that PO increases the number of costimulatory molecules on DC that prime T cells, favoring the production of effector T cells. This may support the future clinical development of PO in cancer treatment.

Adjuvants: What a Difference 15 Years Makes!

Vaccination is a critical tool in modern animal production and key to maintaining animal health. Adjuvants affect the immune response by increasing the rate, quantity, or quality of the protective response generated by the target antigens. Although adjuvant technology dates back to the nineteenth century, there was relatively little improvement in adjuvant technology before the late twentieth century. With the discovery of molecular pathways that regulate the timing, quantity, and quality of the immune response, new technologies are focused on bringing safer, more effective, and inexpensive adjuvants to commercial use.

Vaccine Adjuvants Derived from Marine Organisms

Vaccine adjuvants help to enhance the immunogenicity of weak antigens. The adjuvant effect of certain substances was noted long ago (the 40s of the last century), and since then a large number of adjuvants belonging to different groups of chemicals have been studied. This review presents research data on the nonspecific action of substances originated from marine organisms, their derivatives and complexes, united by the name 'adjuvants'. There are covered the mechanisms of their action, safety, as well as the practical use of adjuvants derived from marine hydrobionts in medical immunology and veterinary medicine to create modern vaccines that should be non-toxic and efficient. The present review is intended to briefly describe some important achievements in the use of marine resources to solve this important problem.

Chemical and Immunological Characteristics of Aluminum-Based, Oil-Water Emulsion, and Bacterial-Origin Adjuvants

Adjuvants are a diverse family of substances whose main objective is to increase the strength, quality, and duration of the immune response caused by vaccines. The most commonly used adjuvants are aluminum-based, oil-water emulsion, and bacterial-origin adjuvants. In this paper, we will discuss how the election of adjuvants is important for the adjuvant-mediated induction of immunity for different types of vaccines. Aluminum-based adjuvants are the most commonly used, the safest, and have the best efficacy, due to the triggering of a strong humoral response, albeit generating a weak induction of cell-mediated immune response. Freund's adjuvant is the most widely used oil-water emulsion adjuvant in animal trials; it stimulates inflammation and causes aggregation and precipitation of soluble protein antigens that facilitate the uptake by antigen-presenting cells (APCs). Adjuvants of bacterial origin, such as flagellin, E. coli membranes, and monophosphoryl lipid A (MLA), are known to potentiate immune responses, but their safety and risks are the main concern of their clinical use. This minireview summarizes the mechanisms that classic and novel adjuvants produce to stimulate immune responses.

Nanomedicines for the Delivery of Biologics

A special symposium of the Academy of Pharmaceutical Sciences Nanomedicines Focus Group reviewed the current status of the use of nanomedicines for the delivery of biologics drugs. This meeting was particularly timely with the recent approval of the first siRNA-containing product Onpattro™ (patisiran), which is formulated as a lipid nanoparticle for intravenous infusion, and the increasing interest in the use of nanomedicines for the oral delivery of biologics. The challenges in delivering such molecules were discussed with specific emphasis on the delivery both across and into cells. The latest developments in Molecular Envelope Technology® (Nanomerics Ltd, London, UK), liposomal drug delivery (both from an academic and industrial perspective), opportunities offered by the endocytic pathway, delivery using genetically engineered viral vectors (PsiOxus Technologies Ltd, Abingdon, UK), Transint™ technology (Applied Molecular Transport Inc., South San Francisco, CA, USA), which has the potential to deliver a wide range of macromolecules, and AstraZeneca's initiatives in mRNA delivery were covered with a focus on their uses in difficult to treat diseases, including cancers. Preclinical data were presented for each of the technologies and where sufficiently advanced, plans for clinical studies as well as early clinical data. The meeting covered the work in progress in this exciting area and highlighted some key technologies to look out for in the future.

Immunotherapy with interferon-α-induced dendritic cells for chronic HCV infection (the results of pilot clinical trial)

The key role of T cells in hepatitis C virus (HCV) elimination and the ability of dendritic cells (DCs) to induce antiviral T cell responses suggest that DC vaccines could be a promising approach in the treatment of chronic HCV infection. The aim of our study was to evaluate, whether immunotherapy with DCs is safe and elicits anti-HCV T cell responses. Ten patients with HCV (genotype 1) were vaccinated with monocyte-derived DCs, generated in the presence of IFN-α (IFN-DCs) and pulsed with recombinant HCV Core and NS3 proteins. Treatment schedule included four subcutaneous vaccinations with 1 week interval and six vaccinations with month interval. No serious adverse events or an increase in hepatitis C biochemical activity were registered after vaccination. Using ex vivo assays for the detection of proliferative responses, IFN-γ production and CD8⁺ degranulation have shown that immunotherapy elicited antigen-specific responses in all patients although individual heterogeneity existed within their types, magnitude, and timing. Core/NS3-specific proliferative response and CD8⁺ T cell degranulation have already been registered after the first course of vaccination. Of note, Core-specific responses had higher magnitude. The appearance of antigen-specific IFN-γ responses was registered after the second vaccination course. Vaccination did not cause Th2 response and expansion of the CD4⁺CD25⁺CD127^- regulatory T cells. Generated immune responses failed to provide virus elimination. Nevertheless, there were inverse correlations between viral load and NS3-specific proliferation (R _S = 0.62; p = 0.05) and IFN-γ secretion (R _S = - 0.82; p = 0.001) at 6-month post-treatment period. Immunotherapy with IFN-DCs was safe and elicited HCV-specific T cell responses which were insufficient to eliminate viruses but could be implicated in the restriction of viral replication.

The Biologics Revolution and Endotoxin Test Concerns

The advent of “at will” production of biologics in lieu of harvesting animal proteins (i.e. insulin) or human cadaver proteins (i.e. growth hormone) has revolutionized the treatment of disease. While the fruits of the biotechnology revolution are widely acknowledged, the realization of the differences in the means of production and changes in the manner of control of potential impurities and contaminants in regard to the new versus the old are less widely appreciated. This chapter is an overview of the biologics revolution in terms of the rigors of manufacturing required to produce them, their mechanism of action, and caveats of endotoxin control. It is a continulation of the previous chapter that established a basic background knowledge of adaptive immune principles necessary to understand the mode of action of both disease causation and biologics therapeutic treatment via immune modulation.