Vaccine Delivery and Immune Response Basics

Spider minor ampullate silk protein nanoparticles: an effective protein delivery system capable of enhancing systemic immune responses

Spider silk proteins (spidroins) are particularly attractive due to their excellent biocompatibility. Spider can produce up to seven different types of spidroins, each with unique properties and functions. Spider minor ampullate silk protein (MiSp) might be particularly interesting for biomedical applications, as the constituent silk is mechanically strong and does not super-contract in water, attributed to its amino acid composition. In this study, we evaluate the potential of recombinant nanoparticles derived from Araneus ventricosus MiSp as a protein delivery carrier. The MiSp-based nanoparticles were able to serve as an effective delivery system, achieving nearly 100% efficiency in loading the model protein lysozyme, and displayed a sustained release profile at physiological pH. These nanoparticles could significantly improve the delivery efficacy of the model proteins through different administration routes. Furthermore, nanoparticles loaded with model protein antigen lysozyme after subcutaneous or intramuscular administration could enhance antigen-specific immune responses in mouse models, through a mechanism involving antigen-depot effects at the injection site, long-term antigen persistence, and efficient uptake by dendritic cells as well as internalization by lymph nodes. These findings highlight the transnational potential of MiSp-based nanoparticle system for protein drug and vaccine delivery.

Noncoding RNAs in hepatitis: Unraveling the apoptotic pathways

Hepatitis is a worldwide health issue that causes inflammation of the liver and is frequently brought on by viral infections, specifically those caused by the hepatitis B and C viruses. Although the pathophysiological causes of hepatitis are complex, recent research indicates that noncoding RNAs (ncRNAs) play a crucial role in regulating apoptosis, an essential process for maintaining liver homeostasis and advancing the illness. Noncoding RNAs have been linked to several biological processes, including apoptosis. These RNAs include microRNAs (miRNAs), long noncoding RNAs (lncRNAs), and circular RNAs (circRNAs). Distinct expression patterns characterising different stages of the disease have been discovered, indicating dysregulation of these non-coding RNAs in liver tissues infected with hepatitis. The complex interplay that exists between these noncoding RNAs and apoptotic effectors, including caspases and members of the Bcl-2 family, plays a role in the precarious equilibrium that regulates cell survival and death during hepatitis. The purpose of this review is to provide an overview of ncRNA-mediated apoptosis in hepatitis, as well as insights into possible therapeutic targets and diagnostic indicators.

Development and efficacy evaluation of a novel water-in-oil-in-water adjuvant for an inactivated foot-and-mouth disease vaccine

To develop a novel water-in-oil-in-water (W/O/W) adjuvant and evaluate the effect on foot-and-mouth disease (FMD) inactivated vaccine, in this study, we prepared the novel nano-emulsion adjuvant based on QS-21 (BEA) which is composed of the mixture of mineral oil Marcol52, surfactant Tween80, oleate polyoxyethylene ether ester, polyoxyethylene palmitic acid ester and span80, cosurfactant polyethylene glycol and QS-21. The two-step emulsification method formed the W/O/W nano-emulsion with two films and three-phase structures. The effective particle diameter of the BEA was about 184 nm, and it has good thermal stability. Then, BEA was emulsified as an adjuvant to prepare for the inactivated FMDV vaccine, and BALB/c mice and pigs were immunized to evaluate its safety and immunization effect. The results showed that the inactivated BEA-FMDV vaccine significantly increased BALB/c mice and pigs' antibodies and cytokine IFN-γ in serum. Meanwhile, the pig-neutralizing antibodies were higher than control group. Safety tests found no symptoms of FMD or significant toxic reactions. After 28 days of immunization, the protection rate can reach 93.3%. The BEA vaccine had good stability at 4 °C, no stratification after 180 days, and the content of 146S in the vaccine did not decrease. In conclusion, the BEA prepared in this study is suitable for FMDV inactivated vaccine and is an effective adjuvant.

Rationally Designed Self-Assembling Nanovaccines Elicit Robust Mucosal and Systemic Immunity against Rhabdovirus

Viral diseases have constantly caused great threats to global public health, resulting in an urgent need for effective vaccines. However, the current viral vaccines often show low immunogenicity. To counter this, we report a smart strategy of a well-designed modular nanoparticle (LSG-TDH) that recapitulates the dominant antigen SG, low-molecular-weight protamine, and tetralysine-modified H-chain apoferritin (TDH). The constructed LSG-TDH nanovaccine could self-assemble into a nanocage structure, which confers excellent mucus-penetrating, cellular affinity, and uptake ability. Studies demonstrate that the LSG-TDH nanovaccine could strongly activate both mucosal and systemic immune responses. Importantly, by immunizing wild-type and TLR2 knockout (TLR2-KO) zebrafish, we found that TLR2 could mediate LSG-TDH-induced adaptive mucosal and systemic immune responses by activating antigen-presenting cells. Collectively, our findings offer new insights into rational viral vaccine design and provide additional evidence of the vital role of TLR2 in regulating adaptive immunity.

Circular RNA: A promising new star of vaccine

Circular RNAs (circRNAs) are a class of single-stranded RNAs with covalently closed structures. Owing to their not having 3' or 5' ends, circRNAs are highly durable and insusceptible to exonuclease-mediated degradation. Moreover, some circRNAs with certain structures are translatable, making them novel vaccines. Vaccines are efficient tools for immunotherapy, such as for the prevention of infectious diseases and cancer treatment. The immune system is activated during immunotherapy to fight against abnormal allies or invaders. CircRNA vaccines represent a potential new avenue in the vaccine era. Recently, several circRNA vaccines have been synthesized and tested in vitro and in vivo. Our review briefly introduces the current understanding of the biology and function of translatable circRNAs, molecular biology, synthetic methods, delivery of circRNA, and current circRNA vaccines. We also discussed the challenges and future directions in the field by summarizing the developments in circRNA vaccines in the past few years.

BCEDB: a linear B-cell epitopes database for SARS-CoV-2

The 2019 Novel Coronavirus (SARS-CoV-2) has infected millions of people worldwide and caused millions of deaths. The virus has gone numerous mutations to replicate faster, which can overwhelm the immune system of the host. Linear B-cell epitopes are becoming promising in prevention of various deadly infectious diseases, breaking the general idea of their low immunogenicity and partial protection. However, there is still no public repository to host the linear B-cell epitopes for facilitating the development vaccines against SARS-CoV-2. Therefore, we developed BCEDB, a linear B-cell epitopes database specifically designed for hosting, exploring and visualizing linear B-cell epitopes and their features. The database provides a comprehensive repository of computationally predicted linear B-cell epitopes from Spike protein; a systematic annotation of epitopes including sequence, antigenicity score, genomic locations of epitopes, mutations in different virus lineages, mutation sites on the 3D structure of Spike protein and a genome browser to visualize them in an interactive manner. It represents a valuable resource for peptide-based vaccine development. Database URL: http://www.oncoimmunobank.cn/bcedbindex.

An updated review on oral protein-based antigen vaccines efficiency and delivery approaches: a special attention to infectious diseases

Various infectious agents affect human health via the oral entrance. The majority of pathogens lack approved vaccines. Oral vaccination is a convenient, safe and cost-effective approach with the potential of provoking mucosal and systemic immunity and maintaining individual satisfaction. However, vaccines should overcome the intricate environment of the gastrointestinal tract (GIT). Oral protein-based antigen vaccines (OPAVs) are easier to administer than injectable vaccines and do not require trained healthcare professionals. Additionally, the risk of needle-related injuries, pain, and discomfort is eliminated. However, OPAVs stability at environmental and GIT conditions should be considered to enhance their stability and facilitate their transport and storage. These vaccines elicit the local immunity, protecting GIT, genital tract and respiratory epithelial surfaces, where numerous pathogens penetrate the body. OPAVs can also be manipulated (such as using specific incorporated ligand and receptors) to elicit targeted immune response. However, low bioavailability of OPAVs necessitates development of proper protein carriers and formulations to enhance their stability and efficacy. There are several strategies to improve their efficacy or protective effects, such as incorporation of adjuvants, enzyme inhibitors, mucoadhesive or penetrating devices and permeation enhancers. Hence, efficient delivery of OPAVs into GIT require proper delivery systems mainly including smart target systems, probiotics, muco-adhesive carriers, lipid- and plant-based delivery systems and nano- and microparticles.

Tetrahedral-Framework Nucleic Acid Loaded with MicroRNA-155 Enhances Immunocompetence in Cyclophosphamide-Induced Immunosuppressed Mice by Modulating Dendritic Cells and Macrophages

Nanomaterials are often used as immunomodulators because they can be tailored by a controllable process. In this work, a complex based on a tetrahedral framework nucleic acid delivery system and MicroRNA-155, known as T-155, is synthesized for the modulation of immunosuppression. In vivo, T-155 ameliorated spleen and thymus damage and hematopoiesis suppression in cyclophosphamide-induced immunosuppressed mice by promoting T-cell proliferation to resist oxidative stress. In vitro, T-155 induced immature dendritic cells (DCs) to differentiate into mature DCs by the ERK1/2 pathway and converted M0 macrophages (Mφ) into the M1 type by the NF-κB pathway to enhance the surveillance capabilities of antigen-presenting cells. The experimental results suggest that T-155 has therapeutic potential as an immunomodulator for immunosuppression.

Protein-Based Adjuvants for Vaccines as Immunomodulators of the Innate and Adaptive Immune Response: Current Knowledge, Challenges, and Future Opportunities

New-generation vaccines, formulated with subunits or nucleic acids, are less immunogenic than classical vaccines formulated with live-attenuated or inactivated pathogens. This difference has led to an intensified search for additional potent vaccine adjuvants that meet safety and efficacy criteria and confer long-term protection. This review provides an overview of protein-based adjuvants (PBAs) obtained from different organisms, including bacteria, mollusks, plants, and humans. Notably, despite structural differences, all PBAs show significant immunostimulatory properties, eliciting B-cell- and T-cell-mediated immune responses to administered antigens, providing advantages over many currently adopted adjuvant approaches. Furthermore, PBAs are natural biocompatible and biodegradable substances that induce minimal reactogenicity and toxicity and interact with innate immune receptors, enhancing their endocytosis and modulating subsequent adaptive immune responses. We propose that PBAs can contribute to the development of vaccines against complex pathogens, including intracellular pathogens such as Mycobacterium tuberculosis, those with complex life cycles such as Plasmodium falciparum, those that induce host immune dysfunction such as HIV, those that target immunocompromised individuals such as fungi, those with a latent disease phase such as Herpes, those that are antigenically variable such as SARS-CoV-2 and those that undergo continuous evolution, to reduce the likelihood of outbreaks.

Conjugation with 8-arm PEG and CRM197 enhances the immunogenicity of SARS-CoV-2 ORF8 protein

Safe and effective vaccines are urgently needed to combat the COVID-19 pandemic. However, the SARS-CoV-2 variants raise concerns about the effectiveness of vaccines. As a SARS-CoV-2 antigen target, ORF8 strongly inhibits the IFN-β and NF-κB-responsive promoter, and can be potentially used for the development of SARS-CoV-2 vaccine. However, it is necessary to improve the immunogenicity of ORF8 by adjuvants or delivery systems. CRM₁₉₇ was a carrier protein with the ability to activate T helper cells for antigens. Eight-arm PEG could conjugate multiple antigen molecules in one entity with inherent adjuvant effect. In the present study, ORF8 was conjugated with CRM₁₉₇ and 8-arm PEG, respectively. The cellular and humoral immune responses to the conjugates (ORF8-CRM and ORF8-PEG) were evaluated in the BALB/c mice. As compared with ORF8-CRM and ORF8 administrated with aluminum adjuvant (ORF8/AL), ORF8-PEG induced a higher ORF8-specific IgG titer (2.6 × 10⁴), higher levels of cytokines (IFN-γ, TNF-α, IFN-β, and IL-5), stronger splenocyte proliferation. Thus, conjugation with 8-arm PEG was an effective method to improve the immune response to ORF8. Moreover, ORF8-PEG did not lead to apparent toxicity to the cardiac, liver and renal functions. ORF8-PEG was expected to act as an effective vaccine to provide the immune protection against SARS-CoV-2.

The important role of non-covalent drug-protein interactions in drug hypersensitivity reactions

Drug hypersensitivity reactions (DHR) are heterogeneous and unusual immune reactions with rather unique clinical presentations. Accumulating evidence indicates that certain non‐covalent drug‐protein interactions are able to elicit exclusively effector functions of antibody reactions or complete T‐cell reactions which contribute substantially to DHR. Here, we discuss three key interactions; (a) mimicry: whereby soluble, non‐covalent drug‐protein complexes (“fake antigens”) mimic covalent drug‐protein adducts; (b) increased antibody affinity: for example, in quinine‐type immune thrombocytopenia where the drug gets trapped between antibody and membrane‐bound glycoprotein; and (c) p‐i‐stimulation: where naïve and memory T cells are activated by direct binding of drugs to the human leukocyte antigen and/or T‐cell receptors. This transient drug‐immune receptor interaction initiates a polyclonal T‐cell response with mild‐to‐severe DHR symptoms. Notable complications arising from p‐i DHR can include viral reactivations, autoimmunity, and multiple drug hypersensitivity. In conclusion, DHR is characterized by abnormal immune stimulation driven by non‐covalent drug‐protein interactions. This contrasts DHR from “normal” immunity, which relies on antigen‐formation by covalent hapten‐protein adducts and predominantly results in asymptomatic immunity.