Vaccine Carrier Research Articles

Extraction, Characterization and Immune Effect Analysis of Listeria Monocytogenes Membrane Vesicles

To establish a method for extracting Listeria monocytogenesmembrane vesicles (LM-MVs) and to analyze the characteristics of LM-MVs and their ability to induce innate immune effect in vitro so as to lay the foundation for research into using LM-MVs as vaccine carrier and drug delivery platform. The membrane vesicles secreted by Listeria monocytogenes were extracted through a continuous process, including culturing, centrifugation, filtration, ultrafiltration concentration and ultracentrifugation. The morphological characteristics of LM-MVs were observed with transmission electron microscope, and particle size distribution were measured by dynamic light scattering analysis. SDS-PAGE and Western blot were used to analyze the protein composition of LM-MVs. CCK-8 cell proliferation and toxicity determination experiments were done to analyze their effect on the proliferation of innate immune cells, and qPCR was used to analyze their ability to induce innate immune responses. A method for extracting LM-MVs was successfully established. Under the transmission electron microscope, LM-MVs presented a nearly circular film-like structure, and dynamic light scattering analysis showed that their sizes were between 65 and 190 nm. SDS-PAGE and Western blot showed that LM-MVs contained proteins, including listeriolysin O (LLO). CCK-8 cell proliferation and toxicity experiment showed that after intervention with 10, 20 and 50 μg/mL of LM-MVs for 24 hours, the proliferation rate of DC 2.4 mouse dendritic cell line was higher than that of non-interventional DC 2.4 cells ( P<0.05); after intervention with 0.1, 1, 10, 20 and 50 μg/mL of LM-MVs for 24 hours, the proliferation rate of RAW 264.7 cells was higher than that of non-interventional RAW 264.7 cells ( P<0.01). The results of qPCR showed that, after intervention with 50 μg/mL of LM-MVs, the expression levels of tumor necrosis factor (TNF)-α, interleukin (IL)-1β, IL-6 and IL-10 in RAW 264.7 cells were higher than those of non-intervention control cells ( P<0.05). The method established in the study can be used to extract LM-MVs. The extracted LM-MVs have a diameter of 65-190 nm and a nearly circular membrane-like structure. They can secrete a variety of protein components and stimulate innate immune responses.

Applying Chitosan-Modified Nanoemulsion in Nasal Vaccine Delivery

To prepare a chitosan-modified cationic nanoemulsion that could be used to prolong the residence time of nasal vaccines in the nasal cavity and improve the cellular uptake efficiency so as to enhance the immune efficacy of nasal vaccines. A nanoemulsion-based vaccine coated with chitosan was prepared, and the particle size, potential, antigen encapsulation efficiency, stability as well as cytotoxicity were examined. The uptake efficiency of vaccine on different cells and the residence time of vaccine in the nasal cavity were measured. Finally, nasal vaccine was administered on mice and the antibody levels in the serum and in the nasal lavage fluids of the immunized mice were examined. The nanoemulsion-based vaccine had an average particle size of (167.2±0.75) nm, a polydispersity index (PDI) of 0.21±0.01, and an average potential of (13.7±0.85) mV. The encapsulation efficiency of antigen was 92.7%. The nanoemulsion-based vaccine had good stability and did not show obvious cytotoxicity in Madin-Darby canine kidney (MDCK) epithelial cells. The vaccine demonstrated relatively high cellular uptake of antigens on DC2.4 and MDCK cells at (49.7±3.45)% and (59.7±2.19)%, respectively. Besides, the cationic nanoemulsion also significantly increased the residence time of the antigen, and a considerable amount of nanoemulsion-based vaccine was found remaining in the nasal cavity 60 minutes after administration. Compared with free antigen and the nanoemulsion without chitosan modification, the chitosan-modified nanoemulsion vaccine induced higher systemic and mucosal antibody levels in mice after nasal immunization ( P<0.01). The chitosan-modified nanoemulsion vaccine prepared in the study can enhance the immune efficacy of nasal vaccines, showing great potential to be used as a delivery carrier for nasal vaccines.

Should COVID-19 vaccination be made mandatory?

Should COVID-19 vaccination be made mandatory?

Vaccine Cold Chain Monitoring System Using IoT Vaccine Fridge for Developing Countries

콜드체인의 마지막 단계인 ë°±ì‹ ì „ë‹¬ ê³¼ì •ì—ì„œ 대부분 얼음을 넣은 ë‹¨ì—´ì»¨í Œì´ë„ˆë¡œ 온도를 ì¡°ì ˆí•˜ë©°, ë°±ì‹ ì˜ 온도 ì¡°ì ˆì´ ì ì ˆí•˜ì§€ 않아 낭비되는 ë°±ì‹ ì˜ 양이 상당하다. ì˜ˆë°©ì ‘ì¢ ì„ ê´€ë¦¬í•˜ê³ ìš´ì˜í•˜ëŠ”ë° 온도 데이터가 중요하며, 본 연구에서는 실시간 ë°±ì‹ ì „ë‹¬ 모니터링 ì‹œìŠ¤í œì„ 개발하였다. 휴대용 ë°±ì‹ ëƒ‰ìž¥ê³ ì˜ 온도, 위치 및 ì „ë ¥ 소비 데이터를 수집하기 위해 문자(Short Message Service) í†µì‹ ë°©ë²•ì„ ì‚¬ìš©í•˜ì˜€ê³ , 한국과 탄자니아(아루샤 및 킬리만자로 지역)에서 ì‹œìŠ¤í œì„ í ŒìŠ¤íŠ¸í•˜ì˜€ë‹¤. 개발된 ë°±ì‹ ëƒ‰ìž¥ê³ ëŠ” ë¬¸ìží†µì‹ ì„ 통해 데이터 손실없이 실시간으로 ë°±ì‹ ìƒíƒœë¥¼ 모니터링을 í• ìˆ˜ 있었다. ë°±ì‹ ì˜ 상태 및 데이터는 클라우드 서버를 통해 웹 기반 ìœ ì € 인터페이스에서 í™•ì¸í• ìˆ˜ 있었다. In the process of vaccine delivery and vaccination, temperature is mostly controlled by an insulated containers containing ice. Moreover, amount of wasted vaccine is significant because the temperature of the vaccine is not properly controlled. A core challenge of vaccination is temperature data monitoring, since it is critical for managing and operating strategical vaccination by health organizations. In this research, a real-time monitoring vaccine carrier system was developed. Temperature, location, and power consumption data of the vaccine carrier were monitored and working performances of the vaccine carrier were tested in both Korea and Tanzania (Arusha and Kilimanjaro regions). For both places, Short Message Service (SMS) communication method was used to send information of the carrier’s status. As a result, the monitoring system was able to transmit and receive real-time data of the vaccine carrier status while the vaccine carrier was tested. The vaccine status data can be accessed from any location through the cloud server and web-based user interface. Keywords: Real-time monitoring system, Rural village, SMS communication method, Vaccine fridge, Vaccination

An Emerging Era for Targeted Drug Delivery: Nanosponges

Many forms of Pharmaceutical product like nanosponge, nanoemulsion, nano-micelles, and nanosomes have been developed using nanotechnology. The size of Nanosponges is like that of a virus. They are very tiny in size and can permeate through the skin easily. Nanosponges can be distributed throughout the body until they reach their specific target area, where they adhere to the surface and the drug is released in a controlled manner, rather than circulating throughout the body. Nanosponge is a promising strategy to overcome problems associated with formulations such as poor bioavailability, drug toxicity, drug degradation, drug solubility and site specificity of drug. Both lipophillic and hydrophilic drug are incorporated in nanosponge. They can also act as biocatalysts and carrier for enzymes, antibodies, protein and vaccines. The use of a biodegradable polymer can help to maintain a constant drug level by allowing the drug to be released in a controlled way. Technologies employed in nanosponge formulations have been widely studied for drug delivery by topical, oral as well as parenteral administration. Improvement of solubility of poorly water soluble drug is another significant characteristic of Nanosponges. The primary goal of this review article is to provide a basic understanding of nanosponges, including their preparation process, advantages and disadvantages, as well as methods of evaluation and applications.

Activation and Conjugation of Soluble Polysaccharides using 1-Cyano-4-Dimethylaminopyridine Tetrafluoroborate (CDAP)

Conjugate vaccines are remarkable advances in vaccinology. For the preparation of polysaccharide conjugate vaccines, the polysaccharides can be conveniently functionalized and linked to vaccine carrier proteins using 1-cyano-4-dimethylaminopyridine tetrafluoroborate (CDAP), an easy-to-handle cyanylating reagent. CDAP activates polysaccharides by reacting with carbohydrate hydroxyl groups at pH 7-9. The stability and reactivity of CDAP are highly pH-dependent. The pH of the reaction also decreases during activation due to the hydrolysis of CDAP, which makes good pH control the key to reproducible activation. The original CDAP activation protocol was performed at room temperature in unbuffered pH 9 solutions. Due to the rapid reaction under this condition (<3 min) and the accompanying fast pH drop from the rapid CDAP hydrolysis, it was challenging to quickly adjust and maintain the target reaction pH in the short time frame. The improved protocol described here is performed at 0 °C, which slows CDAP hydrolysis and extends the activation time from 3 min to ~15 min. Dimethylaminopyridine (DMAP) was also used as a buffer to pre-adjust the polysaccharide solution to the target activation pH before adding the CDAP reagent. The longer reaction time, coupled with the slower CDAP hydrolysis and the use of DMAP buffer, makes it easier to maintain the activation pH for the entire duration of the activation process. The improved protocol makes the activation process less frenetic, more reproducible, and more amenable to scaling up.

Activation and Conjugation of Soluble Polysaccharides using 1-Cyano-4-Dimethylaminopyridine Tetrafluoroborate (CDAP).

Conjugate vaccines are remarkable advances in vaccinology. For the preparation of polysaccharide conjugate vaccines, the polysaccharides can be conveniently functionalized and linked to vaccine carrier proteins using 1-cyano-4-dimethylaminopyridine tetrafluoroborate (CDAP), an easy-to-handle cyanylating reagent. CDAP activates polysaccharides by reacting with carbohydrate hydroxyl groups at pH 7-9. The stability and reactivity of CDAP are highly pH-dependent. The pH of the reaction also decreases during activation due to the hydrolysis of CDAP, which makes good pH control the key to reproducible activation. The original CDAP activation protocol was performed at room temperature in unbuffered pH 9 solutions. Due to the rapid reaction under this condition (<3 min) and the accompanying fast pH drop from the rapid CDAP hydrolysis, it was challenging to quickly adjust and maintain the target reaction pH in the short time frame. The improved protocol described here is performed at 0 °C, which slows CDAP hydrolysis and extends the activation time from 3 min to ~15 min. Dimethylaminopyridine (DMAP) was also used as a buffer to pre-adjust the polysaccharide solution to the target activation pH before adding the CDAP reagent. The longer reaction time, coupled with the slower CDAP hydrolysis and the use of DMAP buffer, makes it easier to maintain the activation pH for the entire duration of the activation process. The improved protocol makes the activation process less frenetic, more reproducible, and more amenable to scaling up.

Nano and Microparticles as Potential Oral Vaccine Carriers and Adjuvants Against Infectious Diseases.

Mucosal surfaces are the first site of infection for most infectious diseases and oral vaccination can provide protection as the first line of defense. Unlike systemic administration, oral immunization can stimulate cellular and humoral immune responses at both systemic and mucosal levels to induce broad-spectrum and long-lasting immunity. Therefore, to design a successful vaccine, it is essential to stimulate the mucosal as well as systemic immune responses. Successful oral vaccines need to overcome the harsh gastrointestinal environment such as the extremely low pH, proteolytic enzymes, bile salts as well as low permeability and the low immunogenicity of vaccines. In recent years, several delivery systems and adjuvants have been developed for improving oral vaccine delivery and immunogenicity. Formulation of vaccines with nanoparticles and microparticles have been shown to improve antigen stability, availability and adjuvanticity as well as immunostimulatory capacity, target delivery and specific release. This review discusses how nanoparticles (NPs) and microparticles (MPs) as oral carriers with adjuvant characteristics can be beneficial in oral vaccine development.

Oral Salmonella msbB Mutant as a Carrier for a Salmonella-Based Vaccine for Prevention and Reversal of Type 1 Diabetes.

A therapy that includes an oral vaccine for type 1 diabetes (T1D) using live attenuated Salmonella MvP728 (ΔhtrA/ΔpurD), cytokines (IL10 and TGFβ) and preproinsulin (PPI) antigen in combination with a sub-therapeutic dose of anti-CD3 mAb was developed by our team. The vaccine combination therapy reduced insulitis and prevented and reversed diabetes in non-obese diabetic (NOD) mice. Here, we show the effectiveness of an alternative Salmonella mutant (ΔmsbB) as a carrier strain, which is anticipated to have lower risks of an inflammatory response and septicemia as a result of modification in the lipopolysaccharide (LPS) via detoxification of lipid A. This mutant strain proved to have highly reduced pathogenic side effects. Salmonella strain ΔmsbB expressed autoantigens and in combination with cytokines and anti-CD3 mAb, successfully prevented and reversed T1D to levels comparable to the previously used carrier strain ΔhtrA/ΔpurD. Additionally, the Salmonella msbB mutant resulted in higher rates of host cell infection. These results further demonstrate the potential of an oral Salmonella-based combined therapy in the treatment of early T1D.

Innate Immune Invisible Ultrasmall Gold Nanoparticles-Framework for Synthesis and Evaluation.

Nanomedicine is seen as a potential central player in the delivery of personalized medicine. Biocompatibility issues of nanoparticles have largely been resolved over the past decade. Despite their tremendous progress, less than 1% of applied nanosystems can hit their intended target location, such as a solid tumor, and this remains an obstacle to their full ability and potential with a high translational value. Therefore, achieving immune-tolerable, blood-compatible, and biofriendly nanoparticles remains an unmet need. The translational success of nanoformulations from bench to bedside involves a thorough assessment of their design, compatibility beyond cytotoxicity such as immune toxicity, blood compatibility, and immune-mediated destruction/rejection/clearance profile. Here, we report a one-pot process-engineered synthesis of ultrasmall gold nanoparticles (uGNPs) suitable for better body and renal clearance delivery of their payloads. We have obtained uGNP sizes of as low as 3 nm and have engineered the synthesis to allow them to be accurately sized (almost nanometer by nanometer). The synthesized uGNPs are biocompatible and can easily be functionalized to carry drugs, peptides, antibodies, and other therapeutic molecules. We have performed in vitro cell viability assays, immunotoxicity assays, inflammatory cytokine analysis, a complement activation study, and blood coagulation studies with the uGNPs to confirm their safety. These can help to set up a long-term safety-benefit framework of experimentation to reveal whether any designed nanoparticles are immune-tolerable and can be used as payload carriers for next-generation vaccines, chemotherapeutic drugs, and theranostic agents with better body clearance ability and deep tissue penetration.

Genipin‐crosslinked chitosan hydrogels: Preliminary evaluation of the in vitro biocompatibility and biodegradation

AbstractGenipin‐crosslinked chitosan hydrogels have gained attention as promising drug delivery vehicles. To bring them one step closer to clinical applications, this study evaluates the hydrogels' in vitro biocompatibility and biodegradation. Cytotoxicity test on 3T3 fibroblasts shows that the cells retain normal adhesive properties and high viability on gels with 3.1 and 4.4 mm genipin but not on gels with 1.7 mm genipin. The hydrogels with highest genipin content (4.4 mm) are studied further in the presence of RAW 264.7 macrophages and DC 2.4 dendritic cells. In both cases, cell viability is preserved and interferon‐β gene transcription is enhanced while over‐production of five inflammatory cytokines is not detected, suggesting the hydrogels' immune stimulating property and potential as vaccine carriers. The biodegradation is monitored efficiently using the hydrogels' intrinsic fluorescence upon crosslinking with genipin. Addition of poly (ethylene glycol) to form a semi‐interpenetrating hydrogel is found to enhance the cytocompatibility to 3T3 cells and delay the degradation. Collectively, our findings suggest that chitosan‐genipin hydrogels can be considered as biocompatible materials, with great potential for vaccine delivery applications.

Immunology of biodegradable nanoparticles: a brief overview on a wide growing field

Immunity is continuously evolving by evolutionary mechanisms shaped by pathogenic stimuli of different kinds. Man-made nanomaterials (NMs) have been developed in the last decades and represent a novel challenge for our immune system, especially when applied to medical science. Toxicological studies of such nanoparticles (NPs) revealed that size, shape, and surface chemistry are key parameters to understand their noxious effects on cellular mechanisms. Less is known on the immune reactions to NMs since prolonged exposure data are not so detailed as the results for acute administration. The importance of immunity to biocompatible NPs is underlined by their increasing use as drug or gene delivery carriers in common pharmaceutical preparations and vaccines. In the latter case, the immunomodulatory properties of NMs allow their use also as efficient adjuvants to enhance the innate immune response. In the current manuscript, the authors discuss the main concepts in this fast-growing field by restricting our view to NMs with consolidated application in biomedicine.

Apoferritin nanoparticle based dual-antigen influenza conjugate vaccine with potential cross-protective efficacy against heterosubtypic influenza virus

Ferritin nanoparticles with self-assembling properties have been widely explored as vaccine carrier by displaying foreign antigens through genetic fusion strategy. In the present work, an apoferritin (AFt) nanoparticle was tested as influenza vaccine carrier by chemically conjugating a matrix protein 2 ectodomain (M2e) antigen peptide or/and the full-length hemagglutinin (HA) antigen on the outer surface of the AFt, with heterobifunctional sSMCC or SM(PEG)24 containing PEG chain as linkers. To each AFt nanoparticle, about 30–32 M2e or 1.8 HA antigen could be coupled. The AFt-(PEG)24-M2e, in which the M2e was coupled through SM(PEG)24 containing PEG chain, conferred higher protective efficacy in immunized mice than AFt-M2e did, but was less effective than AFt-(PEG)24-HA. When both M2e and HA were coupled, the synthesized dual-antigen vaccine candidate AFt-(PEG)24-M2e/HA elicited high level of M2e and HA antigen-specific antibodies and conferred 100% protection against lethal infection of homologous PR8 H1N1 virus strain and 70% protection against a heterologous A/FM/1/47 (FM1, H1N1) strain, which was more effective than the M2e or HA single antigen vaccine candidates. The potential cross-protective effect of the dual-antigen vaccine was further demonstrated by significant specific hemagglutination inhibition (HAI) titers in serum of the immunized mice against three other heterologous viral strains including A/Singapore/GP1908/2015 (IVR-180) H1N1, A/Anhui/1/2005 H5N1, and A/Hong Kong H3N2.

PH-Controlled Release of Antigens Using Mesoporous Silica Nanoparticles Delivery System for Developing a Fish Oral Vaccine.

The development of effective vaccines and delivery systems in aquaculture is a long-term challenge for controlling emerging and reemerging infections. Cost-efficient and advanced nanoparticle vaccines are of tremendous applicability in prevention of infectious diseases of fish. In this study, dihydrolipoamide dehydrogenase (DLDH) antigens of Vibrio alginolyticus were loaded into mesoporous silica nanoparticles (MSN) to compose the vaccine delivery system. Hydroxypropyl methylcellulose phthalate (HP55) was coated to provide protection of immunogen. The morphology, loading capacity, acid-base triggered release were characterized and the toxicity of nanoparticle vaccine was determined in vitro. Further, the vaccine immune effects were evaluated in large yellow croaker via oral administration. In vitro studies confirmed that the antigen could be stable in enzymes-rich artificial gastric fluid and released under artificial intestinal fluid environment. In vitro cytotoxicity assessment demonstrated the vaccines within 120 μg/ml have good biocompatibility for large yellow croaker kidney cells. Our data confirmed that the nanoparticle vaccine in vivo could elicit innate and adaptive immune response, and provide good protection against Vibrio alginolyticus challenge. The MSN delivery system prepared may be a potential candidate carrier for fish vaccine via oral administration feeding. Further, we provide theoretical basis for developing convenient, high-performance, and cost-efficient vaccine against infectious diseases in aquaculture.

Multimode CaCO3/pneumolysin antigen delivery systems for inducing efficient cellular immunity for anti-tumor immunotherapy

Along with the clinical success of tumor immunotherapy, development of tumor vaccines has attracted more and more attention, the key of which is to induce efficient tumor antigen-specific cellular immunity. This usually relies on using intelligent antigen delivery systems to realize the cytoplasmic delivery and cross-presentation of exogenous tumor antigens to CD8+ T cells. In this study, multi-functional vaccine adjuvant pneumolysin (PLY) and carrier calcium carbonate (CaCO3) nanoparticles are combined by physical absorption of PLY onto CaCO3 nanoparticles to construct multimode antigen delivery systems CaCO3/PLY to induce cellular immunity for tumor vaccines. Here, both CaCO3 nanoparticles and PLY were adopted to induce the lysosomal escape, cytoplasmic delivery and cross-presentation of exogenous antigens to enhance cellular immunity. Based on this, minimalist tumor vaccines were prepared in a one-pot method through physical adsorption of model antigen ovalbumin (OVA) and PLY onto CaCO3 nanoparticles, termed as OVA/CaCO3/PLY. The in vitro results showed that OVA/CaCO3/PLY (5 μg) vaccine formulation promoted antigen cross-presentation by inducing effective lysosome escape and cytoplasmic delivery of the antigen protein OVA. The in vivo immunization results show that OVA/CaCO3/PLY (5 μg) vaccine formulation significantly enhanced cellular and humoral immunity. The anti-tumor assays demonstrate that OVA/CaCO3/PLY (5 μg) vaccine formulation displayed significantly effective preventive and therapeutic anti-tumor efficacy. Collectively, both CaCO3 nanoparticles and an appropriate dose of PLY contributed to strong anti-tumor cellular immunity. The multimode antigen delivery system CaCO3/PLY (5 μg) offers a promising platform for the construction of efficient tumor vaccines.

Shrimp disease management for sustainable aquaculture: innovations from nanotechnology and biotechnology

Infectious diseases in shrimp are one of the significant constraints in shrimp aquaculture across the globe. The alarming increase of antibiotic resistance in bacteria has rendered antibiotic therapy a controversial subject today. Therefore, the practice of antibiotic therapy in aquaculture needs to be dissuaded and appropriate alternatives have to be found out. For the past few decades, the field of nanotechnology and biotechnology has proposed novel and effective solutions involving the use of nanoparticles, biofilm-based vaccines, algal extracts, phytobiotics, probiotics, prebiotics, and synbiotics to combat infectious diseases. Algal extracts, phytobiotics, probiotics, prebiotics, and synbiotics are compounds of biological origin due to which they are safe to use in aquaculture settings. With the advent of green and bio-nanotechnology, nanomaterials are also becoming a safer alternative to antibiotic therapy. Vaccines developed from antigenic components of bacterial biofilms are more promising than regular vaccines synthesized from antigens of planktonic forms. Some of these methods have extended applications in shrimp aquaculture in the form of immunomodulants, diagnostic tools, drug and vaccine carriers. The hazards of chemotherapy in shrimp aquaculture can be overcome by replacing antibiotics and other chemical agents with these new approaches. Adopting these strategies makes aquaculture-based food more organic, consumer-friendly and helps in establishing sustainable aquaculture. This review reveals the ill effects of antibiotic therapy in shrimp aquaculture and casts light on the advantages and the research gaps in these strategies that need to be addressed.

On the use of adenovirus dodecahedron as a carrier for glycoconjugate vaccines.

Virus-Like Particles (VLPs) have been used as immunogenic molecules in numerous recombinant vaccines. VLPs can also serve as vaccine platform to exogenous antigens, usually peptides incorporated within the protein sequences which compose the VLPs or conjugated to them. We herein described the conjugation of a synthetic tetrasaccharide mimicking the Streptococcus pneumoniae serotype 14 capsular polysaccharide to recombinant adenoviral type 3 dodecahedron, formed by the self-assembling of twelve penton bases and investigated the induced immune response when administered subcutaneously (s.c.). Whether formulated in the form of a dodecahedron or disassembled, the glycoconjugate induced an anti-protein response after two and three immunizations equivalent to that observed when the native dodecahedron was administered. On the other hand, the glycoconjugate induced a weak anti-IgM response which diminishes after two doses but no IgM-to-IgG switch was observed in mice against the serotype 14 capsular polysaccharide. In definitive, the whole conjugation process preserved both particulate nature and immunogenicity of the adenoviral dodecahedron. Further studies are needed to fully exploit adenoviral dodecahedron potential in terms of plasticity towards sequence engineering and of its capacity to stimulate the immune system via the intranasal route of administration as well as to shift the response to the carbohydrate antigen by playing both with the carbohydrate to protein ratio and the length of the synthetic carbohydrate antigen.

Total Synthesis of the Repeating Unit of Bacteroides fragilis Zwitterionic Polysaccharide A1.

Zwitterionic polysaccharides isolated from commensal bacteria are endowed with unique immunological properties and are emerging as immunotherapeutic agents as well as vaccine carriers. Reported herein is a total synthesis of the repeating unit of Bacteroides fragilis zwitterionic polysaccharide A1 (PS A1). The structurally complex tetrasaccharide unit contains a rare sugar 2-acetamido-4-amino-2,4,6-trideoxy-d-galactose (AAT) and two consecutive 1,2-cis glycosidic linkages. The repeating unit was efficiently assembled by rapid synthesis of d-galactosamine and AAT building blocks from cheap and abundant d-mannose via a one-pot SN2 displacement of 2,4-bistriflates and installation of all of the glycosidic bonds in a highly stereoselective manner. The total synthesis involves a longest linear sequence of 17 steps with 3.47% overall yield.

Stability of Engineered Ferritin Nanovaccines Investigated by Combined Molecular Simulation and Experiments.

Human ferritin is regarded as an attractive and promising vaccine platform because of its uniform structure, good plasticity, and desirable thermal and chemical stabilities. Besides, it is biocompatible and presumed safe when used as a vaccine carrier. However, there is a lack of knowledge of how different antigen insertion sites on the ferritin nanocage impact the resulting protein stability and performance. To address this question, we selected Epstein-Barr nuclear antigen 1 as a model epitope and fused it at the DNA level with different insertion sites, namely, the N- and C-termini of ferritin, to engineer proteins E1F1 and F1E1, respectively. Protein properties including hydrophobicity and thermal, pH, and chemical stability were investigated both by molecular dynamics (MD) simulation and by experiments. Both methods demonstrate that the insertion site plays an important role in protein properties. The C-terminus insertion (F1E1) leads to a less hydrophobic surface and more tolerance to the external influence of high temperature, pH, and high concentration of chemical denaturants compared to N-terminus insertion (E1F1). Simulated protein hydrophobicity and thermal stability by MD were in high accordance with experimental results. Thus, MD simulation can be used as a valuable tool to engineer nanovaccine candidates, cutting down costs by reducing the experimental effort and accelerating vaccine design.

Advances in the development of Salmonella-based vaccine strategies for protection against Salmonellosis in humans.

Salmonella spp. are important human pathogens globally causing millions of cases of typhoid fever and non‐typhoidal salmonellosis annually. There are only a few vaccines licensed for use in humans which all target Salmonella enterica serovar Typhi. Vaccine development is hampered by antigenic diversity between the thousands of serovars capable of causing infection in humans. However, a number of attenuated candidate vaccine strains are currently being developed. As facultative intracellular pathogens with multiple systems for transporting effector proteins to host cells, attenuated Salmonella strains can also serve as ideal tools for the delivery of foreign antigens to create multivalent live carrier vaccines for simultaneous immunization against several unrelated pathogens. Further, the ease with which Salmonella can be genetically modified and the extensive knowledge of the virulence mechanisms of this pathogen means that this bacterium has often served as a model organism to test new approaches. In this review we focus on (1) recent advances in live attenuated Salmonella vaccine development, (2) improvements in expression of foreign antigens in carrier vaccines and (3) adaptation of attenuated strains as sources of purified antigens and vesicles that can be used for subunit and conjugate vaccines or together with attenuated vaccine strains in heterologous prime‐boosting immunization strategies. These advances have led to the development of new vaccines against Salmonella which have or will soon be tested in clinical trials.