A chitosan-mediated inhalable nanovaccine against SARS-CoV-2

Harnessing the immunomodulatory potential of chitosan and its derivatives for advanced biomedical applications

The success of biomaterial applications in medicine, particularly in tissue engineering, relies on achieving a balance between promoting tissue regeneration and controlling the immune response. Due to its natural origin, high biocompatibility, and versatility, chitosan has emerged as a promising biomaterial especially for immunomodulation purposes. Immunomodulation, refers to the deliberate alteration of the immune system's activity to achieve a desired therapeutic effect either by enhancing or suppressing the function of specific immune cells, signaling pathways, or cytokine production. This modulation opens up the unlimited possibilities for the use of biomaterials, especially about the use of natural polymers such as chitosan. Although numerous chitosan-based immunoregulatory strategies have been demonstrated over the past two decades, the lack of in-depth exploration hinders the full potential of strategies that include chitosan and its derivatives in biomedical applications. Thus, in this review, the possible immunomodulatory effects of chitosan, chitosan derivatives and their potential combined with various agents and therapies are investigated in detail. Moreover, this report includes agents for localized immune response control, chitosan-based strategies with complementary immunomodulatory properties to create synergistic effects that will influence the success of cell therapies for enhanced tissue acceptance and regeneration. Finally, the challenges and outlook of chitosan-based therapies as a powerful tool for improving immunomodulatory applications are discussed for paving the way for further studies.

The development of a human Brucella mucosal vaccine: What should be considered?

Brucellosis is a chronic infectious disease that is zoonotic in nature. Brucella can infect humans through interactions with livestock, primarily via the digestive tract, respiratory tract, and oral cavity. This bacterium has the potential to be utilized as a biological weapon and is classified as a Category B pathogen by the Centers for Disease Control and Prevention. Currently, there is no approved vaccine for humans against Brucella, highlighting an urgent need for the development of a vaccine to mitigate the risks posed by this pathogen. Brucella primarily infects its host by adhering to and penetrating mucosal surfaces. Mucosal immunity plays a vital role in preventing local infections, clearing microorganisms from mucosal surfaces, and inhibiting the spread of pathogens. As mucosal vaccine strategies continue to evolve, the development of a safe and effective mucosal vaccine against Brucella appears promising.This paper reviews the immune mechanism of mucosal vaccines, the infection mechanism of Brucella, successful Brucella mucosal vaccines in animals, and mucosal adjuvants. Additionally, it elucidates targeting and optimization strategies for mucosal vaccines to facilitate the development of human vaccines against Brucella.

A General Strategy toward Self-assembled Nanovaccine Based on Cationic Lentinan to Induce Potent Humoral and Cellular Immune Responses

Adjuvants play a critical role in the induction of effective immune responses by vaccines. Here, a self-assembling nanovaccine platform that integrates adjuvant functions into the delivery vehicle is prepared. Cationic Lentinan (CLNT) is mixed with ovalbumin (OVA) to obtain a self-assembling nanovaccine (CLNTO nanovaccine), which induces the uptake and maturation of bone marrow dendritic cells (BMDCs) via the toll-like receptors 2/4 (TLR2/4) to produce effective antigen cross-presentation. CLNTO nanovaccines target lymph nodes (LNs) and induce a robust OVA-specific immune response via TLR and tumor necrosis factor (TNF) signaling pathways, retinoic acid-inducible gene I (RIG-I) receptor, and cytokine-cytokine receptor interactions. In addition, CLNTO nanovaccines are found that promote the activation of follicular helper T (Tfh) cells and induce the differentiation of germinal center (GC) B cells into memory B cells and plasma cells, thereby enhancing the immune response. Vaccination with CLNTO nanovaccine significantly inhibits the growth of ovalbumin (OVA)-expressing B16 melanoma cell (B16-OVA) tumors, indicating its great potential for cancer immunotherapy. Therefore, this study presents a simple, safe, and effective self-assembling nanovaccine that induces helper T cell 1 (Th1) and helper T cell (Th2) immune responses, making it an effective vaccine delivery system.

Pyroptosis: Induction and inhibition strategies for immunotherapy of diseases

Cell death is a central process for organismal health. Pyroptosis, namely pyroptotic cell death, is recognized as a critical type that disrupts membrane and triggers pro-inflammatory cytokine secretion via gasdermins, providing a robust form of cytolysis. Meanwhile, along with the thorough research, a great deal of evidence has demonstrated the dual effects of pyroptosis in host defense and inflammatory diseases. More importantly, the recent identification of abundant gasdermin-like proteins in bacteria and fungi suggests an ancient origin of pyroptosis-based regulated cell death in the life evolution. In this review, we bring a general overview of pyroptosis pathways focusing on gasdermin structural biology, regulatory mechanisms, and recent progress in induction and inhibition strategies for disease treatment. We look forward to providing an insightful perspective for readers to comprehend the frame and challenges of the pyroptosis field, and to accelerating its clinical application.

Applications of Chitosan in Prevention and Treatment Strategies of Infectious Diseases

Chitosan is the most commonly investigated functional cationic biopolymer in a wide range of medical applications due to its promising properties such as biocompatibility, biodegradability, and bioadhesivity, as well as its numerous bioactive properties. Within the last three decades, chitosan and its derivatives have been investigated as biomaterials for drug and vaccine delivery systems, besides for their bioactive properties. Due to the functional groups in its structure, it is possible to tailor the delivery systems with desired properties. There has been a great interest in the application of chitosan-based systems also for the prevention and treatment of infectious diseases, specifically due to their antimicrobial, antiviral, and immunostimulatory effects. In this review, recent applications of chitosan in the prevention and treatment of infectious diseases are reviewed, and possibilities and limitations with regards to technical and regulatory aspects are discussed. Finally, the future perspectives on utilization of chitosan as a biomaterial are discussed.

Recent Developments in Aerosol Pulmonary Drug Delivery: New Technologies, New Cargos, and New Targets

There is nothing like a global pandemic to motivate the need for improved respiratory treatments and mucosal vaccines. Stimulated by the COVID-19 pandemic, pulmonary aerosol drug delivery has seen a flourish of activity, building on the prior decades of innovation in particle engineering, inhaler device technologies, and clinical understanding. As such, the field has expanded into new directions and is working toward the efficient delivery of increasingly complex cargos to address a wider range of respiratory diseases. This review seeks to highlight recent innovations in approaches to personalize inhalation drug delivery, deliver complex cargos, and diversify the targets treated and prevented through pulmonary drug delivery. We aim to inform readers of the emerging efforts within the field and predict where future breakthroughs are expected to impact the treatment of respiratory diseases.

Engineering customized nanovaccines for enhanced cancer immunotherapy

Nanovaccines have gathered significant attention for their potential to elicit tumor-specific immunological responses. Despite notable progress in tumor immunotherapy, nanovaccines still encounter considerable challenges such as low delivery efficiency, limited targeting ability, and suboptimal efficacy. With an aim of addressing these issues, engineering customized nanovaccines through modification or functionalization has emerged as a promising approach. These tailored nanovaccines not only enhance antigen presentation, but also effectively modulate immunosuppression within the tumor microenvironment. Specifically, they are distinguished by their diverse sizes, shapes, charges, structures, and unique physicochemical properties, along with targeting ligands. These features of nanovaccines facilitate lymph node accumulation and activation/regulation of immune cells. This overview of bespoke nanovaccines underscores their potential in both prophylactic and therapeutic applications, offering insights into their future development and role in cancer immunotherapy.

Nanotechnology of inhalable vaccines for enhancing mucosal immunity

Vaccines are the cornerstone of world health. The majority of vaccines are formulated as injectable products, facing the drawbacks of cold chain transportation, needle-stick injuries, and primary systemic immunity. Inhalable vaccines exhibited unique advantages due to their small dose, easy to use, quick effect, and simultaneous induction of mucosal and systemic responses. Facing global pandemics, especially the coronavirus disease 2019 (COVID-19), a majority of inhalable vaccines are in preclinical or clinical trials. A better understanding of advanced delivery technologies of inhalable vaccines may provide new scientific insights for developing inhalable vaccines. In this review article, detailed immune mechanisms involving mucosal, cellular, and humoral immunity were described. The preparation methods of inhalable vaccines were then introduced. Advanced nanotechnologies of inhalable vaccines containing inhalable nucleic acid vaccines, inhalable adenovirus vector vaccines, novel adjuvant-assisted inhalable vaccines, and biomaterials for inhalable vaccine delivery were emphatically discussed. Meanwhile, the latest clinical progress in inhalable vaccines for COVID-19 and tuberculosis was discussed.

The Application of Nanovaccines in Autoimmune Diseases

Autoimmune diseases are diseases caused by the body's chronic immune responses to self-antigens and attacks on the host's own cells, tissues and organs. The dysfunction of innate immunity and adaptive immunity leads to the destruction of autoimmune tolerance, which is the most basic factor leading to pathogenesis. The optimal strategy for autoimmune diseases is to modify the host immune system to restore tolerance. The ideal effect of therapeutic autoimmune diseases is to eliminate the autoantigen-specific spontaneous immune response without interfering with the immune response against other antigens. Therapeutic nanovaccines that produce immune tolerance conform to this principle. Nanomaterials provide a platform for antigen loading and modification due to their unique physical and chemical properties. Nanovaccines based on nanomaterial technology can simultaneously enable antigens and adjuvants to be absorbed by immune cells and induce rapid and durable immunity. Nanovaccines have the advantages of being able to be designed and loaded and of better protecting antigens from premature degradation. Nanovaccines also have the ability to target specific tissues or cells through optimized design. We review the latest research progress of nanovaccines for autoimmune diseases and the design strategies of nanovaccines to promote the development of more effective nanovaccines for autoimmune diseases.

Nanoparticles and Antiviral Vaccines

Viruses have threatened human lives for decades, causing both chronic and acute infections accompanied by mild to severe symptoms. During the long journey of confrontation, humans have developed intricate immune systems to combat viral infections. In parallel, vaccines are invented and administrated to induce strong protective immunity while generating few adverse effects. With advancements in biochemistry and biophysics, different kinds of vaccines in versatile forms have been utilized to prevent virus infections, although the safety and effectiveness of these vaccines are diverse from each other. In this review, we first listed and described major pathogenic viruses and their pandemics that emerged in the past two centuries. Furthermore, we summarized the distinctive characteristics of different antiviral vaccines and adjuvants. Subsequently, in the main body, we reviewed recent advances of nanoparticles in the development of next-generation vaccines against influenza viruses, coronaviruses, HIV, hepatitis viruses, and many others. Specifically, we described applications of self-assembling protein polymers, virus-like particles, nano-carriers, and nano-adjuvants in antiviral vaccines. We also discussed the therapeutic potential of nanoparticles in developing safe and effective mucosal vaccines. Nanoparticle techniques could be promising platforms for developing broad-spectrum, preventive, or therapeutic antiviral vaccines.

Recent advances in nano- and micro-scale carrier systems for controlled delivery of vaccines

Vaccines provide substantial safety against infectious diseases, saving millions of lives each year. The recent COVID-19 pandemic highlighted the importance of vaccination in providing mass-scale immunization against outbreaks. However, the delivery of vaccines imposes a unique set of challenges due to their large molecular size and low room temperature stability. Advanced biomaterials and delivery systems such as nano- and mciro-scale carriers are becoming critical components for successful vaccine development. In this review, we provide an updated overview of recent advances in the development of nano- and micro-scale carriers for controlled delivery of vaccines, focusing on carriers compatible with nucleic acid-based vaccines and therapeutics that emerged amid the recent pandemic. We start by detailing nano-scale delivery systems, focusing on nanoparticles, then move on to microscale systems including hydrogels, microparticles, and 3D printed microneedle patches. Additionally, we delve into emerging methods that move beyond traditional needle-based applications utilizing innovative delivery systems. Future challenges for clinical translation and manufacturing in this rapidly advancing field are also discussed.

Exosomes-based particles as inhalable COVID-19 vaccines

Coronavirus disease 2019 (COVID-19), a severely spreading pandemic, has dramatically brought physiological and economical burdens to people. Although the injectable vaccines have some achievements for coronavirus defense, they still generate accompanied pain, untoward reaction and cannot take part in mucosal immunity. Inhalable vaccines, as a safe, facile and efficient strategy, have been presented to protect body from virus by inducing robust mucosal immunity. Here, we give a perspective of an inhalable COVID-19 vaccine composed of lung-derived exosomes (a type of virus-like particle) conjugated with viral receptor-binding domain. The lung-derived exosomes act as carriers, such inhalable particles successfully reach at lung and reveal wider distribution and longer retention on respiratory mucosa. In addition, such vaccines induce the high production of specific antibodies and T cells in lung, significantly protecting host against coronavirus invasion. It is conceived that inhalable virus-like particles with long-term stability wound open a new avenue for vaccines delivery and further achieve vaccine popularization to against with COVID-19 pandemic.

Nanovaccines: A game changing approach in the fight against infectious diseases

The field of nanotechnology has revolutionised global attempts to prevent, treat, and eradicate infectious diseases in the foreseen future. Nanovaccines have proven to be a valuable pawn in this novel technology. Nanovaccines are made up of nanoparticles that are associated with or prepared with components that can stimulate the host's immune system. In addition to their delivery capabilities, the nanocarriers have been demonstrated to possess intrinsic adjuvant properties, working as immune cell stimulators. Thus, nanovaccines have the potential to promote rapid as well as long-lasting humoral and cellular immunity. The nanovaccines have several possible benefits, including site-specific antigen delivery, increased antigen bioavailability, and a diminished adverse effect profile. To avail these benefits, several nanoparticle-based vaccines are being developed, including virus-like particles, liposomes, polymeric nanoparticles, nanogels, lipid nanoparticles, emulsion vaccines, exomes, and inorganic nanoparticles. Inspired by their distinctive properties, researchers are working on the development of nanovaccines for a variety of applications, such as cancer immunotherapy and infectious diseases. Although a few challenges still need to be overcome, such as modulation of the nanoparticle pharmacokinetics to avoid rapid elimination from the bloodstream by the reticuloendothelial system, The future prospects of this technology are also assuring, with multiple options such as personalised vaccines, needle-free formulations, and combination nanovaccines with several promising candidates.

N-dihydrogalactochitosan reduces mortality in a lethal mouse model of SARS-CoV-2

The rapid emergence and global dissemination of SARS-CoV-2 that causes COVID-19 continues to cause an unprecedented global health burden resulting in nearly 7 million deaths. While multiple vaccine countermeasures have been approved for emergency use, additional treatments are still needed due to sluggish vaccine rollout, vaccine hesitancy, and inefficient vaccine-mediated protection. Immunoadjuvant compounds delivered intranasally can guide non-specific innate immune responses during the critical early stages of viral replication, reducing morbidity and mortality. N-dihydrogalactochitosan (GC) is a novel mucoadhesive immunostimulatory polymer of β-0-4-linked N-acetylglucosamine that is solubilized by the conjugation of galactose glycans with current applications as a cancer immunotherapeutic. We tested GC as a potential countermeasure for COVID-19. GC was well-tolerated and did not produce histopathologic lesions in the mouse lung. GC administered intranasally before and after SARS-CoV-2 exposure diminished morbidity and mortality in humanized ACE2 receptor expressing mice by up to 75% and reduced infectious virus levels in the upper airway. Fluorescent labeling of GC shows that it is confined to the lumen or superficial mucosa of the nasal cavity, without involvement of adjacent or deeper tissues. Our findings demonstrate a new application for soluble immunoadjuvants such as GC for preventing disease associated with SARS-CoV-2 and may be particularly attractive to persons who are needle-averse.

Efficiency of Chitosan Nanocarriers in Vaccinology for Mucosal Immunization

The mucosal barrier constitutes a huge surface area, close to 40 m2 in humans, located mostly in the respiratory, gastrointestinal and urogenital tracts and ocular cavities. It plays a crucial role in tissue interactions with the microbiome, dietary antigens and other environmental materials. Effective vaccinations to achieve highly protective mucosal immunity are evolving strategies to counteract several serious diseases including tuberculosis, diphtheria, influenzae B, severe acute respiratory syndrome, Human Papilloma Virus infection and Acquired Immune Deficiency Syndrome. Interestingly, one of the reasons behind the rapid spread of severe acute respiratory syndrome coronavirus 2 variants has been the weakness of local immunization at the level of the respiratory mucosa. Mucosal vaccines can outperform parenteral vaccination as they specifically elicit protective mucosal immune responses blocking infection and transmission. In this scenario, chitosan-based nanovaccines are promising adjuvants-carrier systems that rely on the ability of chitosan to cross tight junctions and enhance particle uptake due to chitosan-specific mucoadhesive properties. Indeed, chitosan not only improves the adhesion of antigens to the mucosa promoting their absorption but also shows intrinsic immunostimulant abilities. Furthermore, by finely tuning the colloidal properties of chitosan, it can provide sustained antigen release to strongly activate the humoral defense. In the present review, we agnostically discuss the potential reasons why chitosan-based vaccine carriers, that efficiently elicit strong immune responses in experimental setups and in some pre-clinical/clinical studies, are still poorly considered for therapeutic formulations.

Adjuvant-Free COVID-19 Vaccine with Glycoprotein Antigen Oxidized by Periodate Rapidly Elicits Potent Immune Responses

Modification of antigens to improve their immunogenicity represents a promising direction for the development of protein vaccine. Here, we designed facilely prepared adjuvant-free vaccines in which the N-glycan of SARS-CoV-2 receptor-binding domain (RBD) glycoprotein was oxidized by sodium periodate. This strategy only minimally modifies the glycans and does not interfere with the epitope peptides. The RBD glycoprotein oxidized by high concentrations of periodate (RBDHO) significantly enhanced antigen uptake mediated by scavenger receptors and promoted the activation of antigen-presenting cells. Without any external adjuvant, two doses of RBDHO elicited 324- and 27-fold increases in IgG antibody titers and neutralizing antibody titers, respectively, compared to the unmodified RBD antigen. Meanwhile, the RBDHO vaccine could cross-neutralize all of the SARS-CoV-2 variants of concern. In addition, RBDHO effectively enhanced cellular immune responses. This study provides a new insight for the development of adjuvant-free protein vaccines.

SARS-CoV-2 Vaccines, Vaccine Development Technologies, and Significant Efforts in Vaccine Development during the Pandemic: The Lessons Learned Might Help to Fight against the Next Pandemic

We are currently approaching three years since the beginning of the coronavirus disease 2019 (COVID-19) pandemic. SARS-CoV-2 has caused extensive disruptions in everyday life, public health, and the global economy. Thus far, the vaccine has worked better than expected against the virus. During the pandemic, we experienced several things, such as the virus and its pathogenesis, clinical manifestations, and treatments; emerging variants; different vaccines; and the vaccine development processes. This review describes how each vaccine has been developed and approved with the help of modern technology. We also discuss critical milestones during the vaccine development process. Several lessons were learned from different countries during the two years of vaccine research, development, clinical trials, and vaccination. The lessons learned during the vaccine development process will help to fight the next pandemic.

Natural Polymeric Composites Derived from Animals, Plants, and Microbes for Vaccine Delivery and Adjuvant Applications: A Review

A key element in ensuring successful immunization is the efficient delivery of vaccines. However, poor immunogenicity and adverse inflammatory immunogenic reactions make the establishment of an efficient vaccine delivery method a challenging task. The delivery of vaccines has been performed via a variety of delivery methods, including natural-polymer-based carriers that are relatively biocompatible and have low toxicity. The incorporation of adjuvants or antigens into biomaterial-based immunizations has demonstrated better immune response than formulations that just contain the antigen. This system may enable antigen-mediated immunogenicity and shelter and transport the cargo vaccine or antigen to the appropriate target organ. In this regard, this work reviews the recent applications of natural polymer composites from different sources, such as animals, plants, and microbes, in vaccine delivery systems.

Recent advances in respiratory immunization: A focus on COVID-19 vaccines

The development of vaccines has always been an essential task worldwide since vaccines are regarded as powerful weapons in protecting the global population. Although the vast majority of currently authorized human vaccinations are administered intramuscularly or subcutaneously, exploring novel routes of immunization has been a prominent area of study in recent years. This is particularly relevant in the face of pandemic diseases, such as COVID-19, where respiratory immunization offers distinct advantages, such as inducing systemic and mucosal responses to prevent viral infections in both the upper and lower respiratory tracts and also leading to higher patient compliance. However, the development of respiratory vaccines confronts challenges due to the physiological barriers of the respiratory tract, with most of these vaccines still in the research and development stage. In this review, we detail the structure of the respiratory tract and the mechanisms of mucosal immunity, as well as the obstacles to respiratory vaccination. We also examine the considerations necessary in constructing a COVID-19 respiratory vaccine, including the dosage form of the vaccines, potential excipients and mucosal adjuvants, and delivery systems and devices for respiratory vaccines. Finally, we present a comprehensive overview of the COVID-19 respiratory vaccines currently under clinical investigation. We hope this review can provide valuable insights and inspiration for the future development of respiratory vaccinations.

Current status of mucosal vaccines against SARS-CoV2: a hope for protective immunity

INTRODUCTION

The current vaccines used to fight against COVID-19 are effective, however the induction of protective immunity is a pending goal required to prevent viral transmission, prevent the generation of new variants, and ultimately eradicate SARS-CoV-2. Mucosal immunization stands as a promising approach to achieve protective immunity against SARS-CoV-2; therefore, it is imperative to innovate the current vaccines by developing mucosal candidates, focusing not only on their ability to prevent severe COVID-19 but to neutralize the virus before invasion of the respiratory system and other mucosal compartments.

AREAS COVERED

This review covers the current advances on the development of anti-COVID-19 mucosal vaccines. Biomedical literature, including PubMed and clinicaltrials.gov website, was analyzed to identify the state of the art for this field. The achievements in preclinical and clinical evaluations are presented and critically analyzed.

EXPERT OPINION

There is a significant advance on the development of mucosal vaccines against SARSCoV-2, which is a promise to increase the efficacy of immunization against this pathogen. Both preclinical and clinical evaluation for several candidates have been performed. The challenges in this road (e.g. low immunogenicity, a reduced number of adjuvants available, and inaccurate dosage) are identified and also critical perspectives for the field are provided.

Self-Adjuvanting Protein Vaccine Conjugated with a Novel Synthetic TLR4 Agonist on Virus-Like Liposome Induces Potent Immunity against SARS-CoV-2

Exploring potent adjuvants and new vaccine strategies is crucial for the development of protein vaccines. In this work, we synthesized a new TLR4 agonist, structurally simplified lipid A analogue GAP112, as a potent built-in adjuvant to improve the immunogenicity of SARS-CoV-2 spike RBD protein. The new TLR4 agonist GAP112 was site-selectively conjugated on the N-terminus of RBD to construct an adjuvant-protein conjugate vaccine in a liposomal formulation. It is the first time that a TLR4 agonist is site-specifically and quantitatively conjugated to a protein antigen. Compared with an unconjugated mixture of GAP112/RBD, a two-dose immunization of the GAP112-RBD conjugate vaccine strongly activated innate immune cells, elicited a 223-fold increase in RBD-specific antibodies, and markedly enhanced T-cell responses. Antibodies induced by GAP112-RBD also effectively cross-neutralized SARS-CoV-2 variants (Delta/B.1.617.2 and Omicron/B.1.1.529). This conjugate strategy provides an effective method to greatly enhance the immunogenicity of antigen in protein vaccines against SARS-CoV-2 and other diseases.

Biomaterials for intranasal and inhaled vaccine delivery

Delivery of vaccines by nasal sprays may enable more robust, protective mucosal immune responses against infectious diseases, such as COVID-19, compared with intramuscular injection. In this Comment, we highlight how biomaterials can be designed to allow intranasal and inhaled vaccination.

Rational Design of T-Cell- and B-Cell-Based Therapeutic Cancer Vaccines

Cancer vaccines provide an efficient strategy to enhance tumor-specific immune responses by redeploying immune systems. Despite the approval of the first cancer vaccine (Sipuleucel-T) by the U.S. Food and Drug Administration in 2010, most therapeutic cancer vaccines fail in clinical trials. Basically, tumor-specific immune responses rely on not only T-cell but also B-cell immunity, which indicates that cancer vaccines should leverage both arms of the adaptive immune system. For example, CD8⁺ T cells activated by antigen-presenting cells (APCs) recognize and directly kill tumor cells via peptide-bound major histocompatibility complex (pMHC). B cells recognize antigen with no need of pMHC and require CD4⁺ T cells for sufficient activation and antibody generation, enabling antibody-mediated nondirect killing on tumor cells. Considering the different mechanisms of T-cell and B-cell activation, the rational design of therapeutic cancer vaccines should consider several factors, including antigen selection and recognition, immune activation, vaccine delivery, and repeatable vaccination, which can be advanced by chemical strategies.In this Account, we summarize our recent contributions to the development of effective T-cell- and B-cell-based therapeutic cancer vaccines. For T-cell-based vaccines, we focus on adjuvants as the key component for controllable APC activation and T-cell priming. Not only synthetic molecular agonists of pattern recognition receptors (PRRs) but also adjuvant nanomaterials were explored to satisfy diversiform vaccine designs. For example, a type of natural cyclic dinucleotide (CDN) that was chemically modified with fluorination and ipsilateral phosphorothioation to activate the stimulator of interferon gene (STING) was found to mediate antitumor responses. It retains structural similarity to the parent CDN scaffold but possesses increased stability, cellular uptake, and immune activation for antitumor treatment. It also facilitates facile conjugation with other agonists, which not only enhances APC-targeting delivery but also balances cellular and humoral antitumor responses. We also explored the intrinsic properties of nanomaterials that allow them to serve as adjuvants. A black phosphorus nanosheet-based nanovaccine was constructed and found to strongly potentiate antigen-specific T-cell antitumor immune responses through multiple immune-potentiating properties, leading to a highly integrated nanomaterial-based adjuvant design. For B-cell-based vaccines, multicomponent and multivalent strategies were applied to improve the immunogenicity. A multicomponent linear vaccine conjugate coordinates helper T (Th) cells and APCs to proliferate and differentiates B cells for enhanced antitumor immunoglobulin G antibody responses. To further improve antigen recognition, clustered designs on a multivalent epitope were applied by generating various structures, including branched lysine-based peptides, natural multivalent scaffold molecules, and self-assembled nanofibers. We also engineered nano- and microvaccine systems to optimize systemic and localized vaccination. A multilayer-assembled nanovaccine successfully integrated antigens and multiple agonists to modulate APC activation. A DNA hydrogel contributed to the control of APC's immune behaviors, including cell recruitment, activation, and migration, and induced robust antitumor responses as an all-in-one designable platform. In this Account, by summarizing strategies for both T-cell- and B-cell-based vaccine design, we not only compare the differences but also address the intrinsic uniformity between such vaccine designs and further discuss the potential of a combined T-cell- and B-cell-based vaccine, which highlights the applicability and feasibility of chemical strategies.

Tailorable antibacterial and cytotoxic chitosan derivatives by introducing quaternary ammonium salt and sulfobetaine

Chitosan (CS) derivatives with improved water solubility, antibacterial activity and adequate biocompatibility are attracting increasingly interest in medical application. Herein, we have successfully synthesized isocyanate terminated quaternary ammonium salt (IQAS) and sulfopropylbetaine (ISB) to be readily covalently bounded to CS skeleton by selective reaction with amino and hydroxyl groups. And their molecular structures and crystallinity were confirmed by Fourier transform infrared spectroscopy, proton nuclear magnetic resonance, and X-ray diffraction. The effect of the substitution degree, carbon chain length, content ratio of IQAS/ISB on their water solubility, antibacterial activity and cytotoxicity were systematically investigated, which shows that those properties of the CS derivatives can be tailored by adjusting the grafted antibacterial agents and their additive amount. The structure-property relationship of these CS derivatives may provide a solid guidance on the development of CS derivatives for more efficient practical applications.

Biodegradable Imiquimod-Loaded Mesoporous Organosilica as a Nanocarrier and Adjuvant for Enhanced and Prolonged Immunity against Foot-and-Mouth Disease Virus in Mice

Foot-and-mouth disease (FMD), a serious, fast-spreading, and virulent disease, has led to huge economic losses to people all over the world. Vaccines are the most effective way to control FMD. However, the weak immunogenicity of inactivated FMD virus (FMDV) requires the addition of adjuvants to enhance the immune effectiveness of the vaccines. Herein, we formulated and fabricated biodegradable dendritic mesoporous tetrasulfide-doped organosilica nanoparticles SOMSN with imiquimod complex (SOMSN-IMQ) and used it as a platform for FMD vaccine delivery and as an adjuvant. SOMSN-IMQ demonstrated excellent stability for 6 months when stored in PBS, while it could be completely degraded within 42 days in SBF at room temperature. Biosafety experiments such as cell toxicity, hemolysis, and histology indicated that the as-prepared SOMSN-IMQ showed nontoxicity and good biocompatibility. Furthermore, SOMSN-IMQ exhibited a maximum adsorption capacity of 1000 μg/mg for inactivated FMDV antigens. Our results showed that SOMSN-IMQ can be effectively engulfed by RAW264.7 cells in a dose-dependent manner. After immunization, SOMSN-IMQ@FMDV can elicit persistent higher antibody levels, higher IgG2a/IgG1 ratio, and cytokine expression, which indicated that SOMSN-IMQ@FMDV triggered superior humoral and cellular immune responses. Moreover, SOMSN-IMQ could provoke maturation and activation of dendritic cells in lymph nodes (LDCs) as well as the proliferation of lymphocytes in vivo. Thus, SOMSN-IMQ could promote effective and potent immunity and provide a promising adjuvant platform for FMDV vaccination with acceptable safety.

Biodegradation and Prospect of Polysaccharide from Crustaceans

Marine crustacean waste has not been fully utilized and is a rich source of chitin. Enzymatic degradation has attracted the wide attention of researchers due to its unique biocatalytic ability to protect the environment. Chitosan (CTS) and its derivative chitosan oligosaccharides (COSs) with various biological activities can be obtained by the enzymatic degradation of chitin. Many studies have shown that chitosan and its derivatives, chitosan oligosaccharides (COSs), have beneficial properties, including lipid-lowering, anti-inflammatory and antitumor activities, and have important application value in the medical treatment field, the food industry and agriculture. In this review, we describe the classification, biochemical characteristics and catalytic mechanisms of the major degrading enzymes: chitinases, chitin deacetylases (CDAs) and chitosanases. We also introduced the technology for enzymatic design and modification and proposed the current problems and development trends of enzymatic degradation of chitin polysaccharides. The discussion on the characteristics and catalytic mechanism of chitosan-degrading enzymes will help to develop new types of hydrolases by various biotechnology methods and promote their application in chitosan.