Single-injection subunit vaccine for rabies prevention using lentinan as adjuvant

Sequential release of vascular endothelial growth factor and platelet-derived growth factor at the appropriate time for improved angiogenesis

Sequential release of vascular endothelial growth factor (VEGF) and platelet-derived growth factor (PDGF) was proposed to enhance therapeutic angiogenesis, however, it remains a challenge to accomplish distinct sequential release of the two proteins. More importantly, the appropriate timing of PDGF release remains an open question. Herein to solve these problems, a new time-controlled release system was designed in which tannic acid/Pluronic F127 (TA/F127) layer-by-layer (LBL) films were used as erodible coatings. The hydrogen-bonded TA/F127 films disintegrate in water at a constant rate. Therefore this system can not only achieve distinct sequential release of two proteins, but can finely control the lag time of the second protein by the TA/F127 coating thickness. In this way drug carriers for sequential release of VEGF and PDGF were prepared. Their angiogenic effects were evaluated using a mouse model of lower limb ischemia. Improved therapeutic efficiency was observed when VEGF and PDGF were sequentially released. More importantly, it was observed that the therapeutic efficiency first increased with increasing TA/F127 film thickness, reached a maximum, and then dropped with further increased TA/F127 film thickness. The results demonstrated that it is important to release PDGF at the appropriate time point to further improve angiogenesis. For the first time, the appropriate timing for PDGF application was determined to be 5-7 days after the application of VEGF. STATEMENT OF SIGNIFICANCE: It remains a challenge to accomplish distinct sequential release of VEGF and PDGF to enhance therapeutic angiogenesis. The appropriate timing for PDGF release is also an open question. In this study, a new time-controlled release system using a TA/F127 layer-by-layer film as an erodible coating was designed. Not only can distinct sequential release of VEGF and PDGF be achieved, but the lag time of PDGF release can also be finely controlled by the coating thickness. In this way, the appropriate timing for PDGF application was successfully determined.

Application prospect of polysaccharide in the development of vaccine adjuvants

Vaccination is an effective strategy for preventing infectious diseases. Subunit vaccines offer more precise targeting and safer protection compared with traditional inactivated virus vaccines. However, due to their poor immunogenicity, subunit vaccines necessitate the use of adjuvants to stimulate the immune system. Adjuvants have long been incorporated into vaccines to enhance the body's immune response, allowing for reduced dosage and lower production costs. Despite the development of numerous vaccine adjuvants, few exhibit the necessary potency and low toxicity for clinical use, often due to limited efficacy or adverse side effects. This underscores the urgent need for novel human vaccine adjuvants that are safe, effective, and cost-efficient. Recent studies have identified certain natural polysaccharides as promising human vaccine adjuvants due to their immunostimulatory properties, low toxicity, and high safety profiles, which enhance both humoral and cellular immunity. These natural polysaccharides are primarily derived from traditional Chinese medicine (TCM) plants, bacteria, and yeast. This review comprehensively analyzes several promising polysaccharide adjuvants, discussing their clinical applications, market potential, and immunoregulatory activities. In summary, the future prospects of polysaccharides provide valuable insights for the application and development of vaccine adjuvants.

Infection and Prevention of Rabies Viruses

Rabies is a fatal zoonotic disease and causes about 59,000 human deaths globally every year. Especially, its mortality is almost 100% in cases where the rabies virus has transmitted to the central nervous system. The special virus life cycle and pathogenic mechanism make it difficult for the host immune system to combat rabies viruses. Vaccination including pre-exposure and post-exposure prophylaxis is an effective strategy for rabies prevention. The pre-exposure vaccination is mainly applied for animals and the post-exposure vaccination is the most application for humans. Although rabies vaccines are widely used and seem to be safe and effective, there are some disadvantages, limitations, or challenges affecting vaccine promotion and distribution. Therefore, more effective, convenient, safer, and cheaper rabies vaccines have been developed or are being developed. The development of novel human rabies vaccine is mainly focusing on vaccines based on a purified Vero cell-cultured freeze-dried rabies vaccine (PVRV). PVRV has been demonstrated to be promising to make the rabies vaccine more effective and secure in animal studies or clinical trials. Moreover, mRNA-based vaccines have been shown to have the potential to enhance the safety and efficacy of rabies vaccines for both animal and human uses.

Progress and prospect of polysaccharides as adjuvants in vaccine development

Vaccines are an effective approach to confer immunity against infectious diseases. Modern subunit vaccines offer more precise target and safe protection compared to traditional whole-pathogen vaccines. However, subunit vaccines require adjuvants to stimulate the immune system due to the less immunogenicity. Adjuvants strengthen immunogenicity by enhancing, modulating, and prolonging the immune response. Unfortunately, few adjuvants have sufficient potency and low enough toxicity for clinical use, highlighting the urgent need for new vaccine adjuvants with the characteristics of safety, efficacy, and cost-effectiveness. Notably, some natural polysaccharides have been approved as adjuvants in human vaccines, owing to their intrinsic immunomodulation, low toxicity, and high safety. Natural polysaccharides are mainly derived from plants, bacteria, and yeast. Partly owing to the difficulty of obtaining them, synthetic polysaccharides emerged in clinical trials. The immune mechanisms of both natural and synthetic polysaccharides remain incompletely understood, hindering the rational development of polysaccharide adjuvants. This comprehensive review primarily focused on several promising polysaccharide adjuvants, discussing their recent applications in vaccines and highlighting their immune-modulatory effects. Furthermore, the future perspectives of polysaccharides offer insightful guidance to adjuvant development and application.

Structural analysis and adjuvant activity of a polysaccharide from Urtica macrorrhiza

Developing new vaccine adjuvants for clinical use remains a significant challenge. Herein, we reported a polysaccharide (UMRG) from Urtica macrorrhiza. It has a molecular weight of 743.35 kDa and is composed of rhamnose (Rha), glucuronic acid (GlcA), galacturonic acid (GalA), and galactose (Gal) in a molar ratio of 1.94: 1.00: 4.17: 1.79. Structural analysis revealed that UMRG contains a rhamnogalacturonan I backbone with short side chains of β-Galp-(1→4)-β-GlcAp-(1→4)-β-Glap-(1→ linked at the C-4 position of →2,4)-α-Rhap-(1→. In vivo, UMRG significantly increased the production of antigen-specific IgG, IgG1, and IgG2a by 1.91-, 2.09-, and 3.43-fold, respectively, on day 42 post-immunization. It also promoted the proliferation of splenic lymphocytes, increasing the proportion of CD3+ and CD3+CD4+ T lymphocytes from 32.63 ± 1.13 % to 38.13 ± 2.03 % and from 21.05 ± 0.93 % to 24.34 ± 1.21 %, respectively. Further investigation demonstrated that UMRG promoted the phagocytosis of antigens by dendritic cells, improved their maturation, and stimulated the secretion of the cytokines TNF-α, IL-12, and IL-6. Additionally, both in vitro and in vivo experiments demonstrated that UMRG displayed good biosafety. Our results suggested the Urtica macrorrhiza polysaccharide may exhibit the potential to be developed as a highly efficient and low-toxicity immune adjuvant.

A single-injection vaccine providing protection against two HPV types

Prophylactic human papillomavirus (HPV) vaccines against cervical cancer were successfully developed; however, challenges such as high cost and low compliance still remain to be overcome. In addition, because many HPV types can cause cervical cancer, antigens of multiple HPV types are needed to achieve broad protection. In this study, a bivalent single-injection HPV vaccine was designed in which virus-like particles (VLPs) of HPV 16 L1 and HPV 18 L1 were used as antigens. A recently developed drug carrier that uses tannic acid/polyethylene glycol films as the erodible layer was employed to accomplish multiple pulsatile releases of the antigens. Monovalent single-injection vaccines for HPV 16 and HPV 18 were first designed. A bivalent single-injection vaccine was then obtained by simply mixing the two monovalent vaccines. The bivalent vaccine provided protection against both HPV types. More importantly, it elicited both humoral and cellular immune responses as potent as those elicited by the corresponding multiple dose vaccine because of their similar release profile of antigens. Cross-reactivity was observed between HPV 16 and 18 in terms of cellular immune responses, while no cross-reactivity was found in terms of humoral immune responses. Note that other multivalent single-injection vaccines could be designed in the same way. These vaccines are expected to help prevent cervical cancer because of their broad protection, enhanced compliance and lowered vaccination cost.

The roles of rabies virus structural proteins in immune evasion and implications for vaccine development

Rabies is a zoonotic infectious disease that targets the nervous system of human and animals and has about 100% fatality rate without treatment. Rabies virus is a bullet-like viral particle composed of five structural proteins, including nucleoprotein (N), phosphorylated protein (P), matrix protein (M), glycoprotein (G), and large subunit (L) of RNA-dependent RNA polymerase. These multifunctional viral proteins also play critical roles in the immune escape by inhibiting specific immune responses in the host, resulting in massive replication of the virus in the nervous system and abnormal behaviors of patients such as brain dysfunction and hydrophobia, which ultimately lead to the death of patients. Herein, the role of five structural proteins of rabies virus in the viral replication and immune escape and its implication for the development of vaccines were systemically reviewed, so as to shed light on the understanding of pathogenic mechanism of rabies virus.

Demonstration of Tunable Control over a Delayed-Release Vaccine Using Atomic Layer Deposition

Many vaccines require multiple doses for full efficacy, posing a barrier for patient adherence and protection. One solution to achieve full vaccination may be attained with single-administration vaccines containing multiple controlled release doses. In this study, delayed-release vaccines were generated using atomic layer deposition (ALD) to coat antigen-containing powders with alumina. Using in vitro and in vivo methods, we show that increasing the coat thickness controls the kinetics of antigen release and antibody response, ranging from weeks to months. Our results establish an in vitro-in vivo correlation with a level of tunable control over the antigen release and antibody response times with the potential to impact future vaccine design.

Biological Activities of Secondary Metabolites from the Edible-Medicinal Macrofungi

Macrofungi are well-known as edible-medicinal mushrooms, which belong mostly to Basidiomycota, with a few from Ascomycota. In recent years, macrofungi have been recognized as a rich resource of structurally unique secondary metabolites, demonstrating a wide range of bioactivities, including anti-tumor, antioxidant, anti-inflammatory, antimicrobial, antimalarial, neuro-protective, hypoglycemic, and hypolipidemic activities. This review highlights over 270 natural products produced by 17 families of macrofungi covering 2017 to 2023, including their structures, bioactivities, and related molecular mechanisms.