Oral immunization of mice with a multivalent therapeutic subunit vaccine protects against Helicobacter pylori infection

Novel therapeutic regimens against Helicobacter pylori: an updated systematic review

Helicobacter pylori (H. pylori) is a strict microaerophilic bacterial species that exists in the stomach, and H. pylori infection is one of the most common chronic bacterial infections affecting humans. Eradicating H. pylori is the preferred method for the long-term prevention of complications such as chronic gastritis, peptic ulcers, gastric mucosa-associated lymphoid tissue lymphoma, and gastric cancer. However, first-line treatment with triple therapy and quadruple therapy has been unable to cope with increasing antibacterial resistance. To provide an updated review of H. pylori infections and antibacterial resistance, as well as related treatment options, we searched PubMed for articles published until March 2024. The key search terms were "H. pylori", "H. pylori infection", "H. pylori diseases", "H. pylori eradication", and "H. pylori antibacterial resistance." Despite the use of antimicrobial agents, the annual decline in the eradication rate of H. pylori continues. Emerging eradication therapies, such as the development of the new strong acid blocker vonoprazan, probiotic adjuvant therapy, and H. pylori vaccine therapy, are exciting. However, the effectiveness of these treatments needs to be further evaluated. It is worth mentioning that the idea of altering the oxygen environment in gastric juice for H. pylori to not be able to survive is a hot topic that should be considered in new eradication plans. Various strategies for eradicating H. pylori, including antibacterials, vaccines, probiotics, and biomaterials, are continuously evolving. A novel approach involving the alteration of the oxygen concentration within the growth environment of H. pylori has emerged as a promising eradication strategy.

Sodium sulfite-driven Helicobacter pylori eradication: Unraveling oxygen dynamics through multi-omics investigation

Due to the emergence and spread of multidrug resistance in Helicobacter pylori (H. pylori), its eradication has become difficult. Sodium sulfite (SS), a widely used food additive for ensuring food safety and storage, has been recognized as an effective nonbactericidal agent for H. pylori eradication. However, the mechanism by which H. pylori adapts and eventually succumbs under low- or no-oxygen conditions remains unknown. In this study, we aimed to evaluate the anti-H. pylori effect of SS and investigated the multiomics mechanism by which SS kills H. pylori. The results demonstrated that SS effectively eradicated H. pylori both in vitro and in vivo. H. pylori responds to the oxygen changes regulated by SS, downregulates the HcpE gene, which is responsible for redox homeostasis in bacteria, decreases the activities of enzymes related to oxidative stress, and disrupts the outer membrane structure, increasing susceptibility to oxidative stress. Furthermore, SS downregulates the content of cytochrome C in the microaerobic respiratory chain, leading to a sharp decrease in ATP synthesis. Consequently, the accumulation of triglycerides (TGs) in bacteria due to oxidative stress supports anaerobic respiration, meeting their energy requirements. The multifaceted death of H. pylori caused by SS does not result in drug resistance. Thus, screening of the redox homeostasis of HcpE as a new target for H. pylori infection treatment could lead to the development of a novel approach for H. pylori eradication therapy.

An intranasal influenza virus vector vaccine protects against Helicobacter pylori in mice

Helicobacter pylori is a human pathogen that infects almost half of the population. Antibiotic resistance in H. pylori threatens health and increases the demand for prophylactic and therapeutic vaccines. Traditional oral vaccine research faces considerable challenges because of the epithelial barrier, potential enterotoxicity of adjuvants, and the challenging conditions of the gastric environment. We developed an intranasal influenza A virus (IAV) vector vaccine based on two live attenuated influenza viruses with modified acidic polymerase protein (PA) genes encoding the A subunit of H. pylori neutrophil-activating protein (NapA), named IAV-NapA, including influenza virus A/WSN/33 (WSN)-NapA and A/Puerto Rico/8/34 (PR8)-NapA. These recombinant influenza viruses were highly attenuated and exhibited strong immunogenicity in mice. Vaccination with IAV-NapA induced antigen-specific humoral and mucosal immune responses while stimulating robust Th1 and Th17 cell immune responses in mice. Our findings suggest that prophylactic and therapeutic vaccination with influenza virus vector vaccines significantly reduces colonization of H. pylori and inflammation in the stomach of mice.IMPORTANCEHelicobacter pylori is the most common cause of chronic gastritis and leads to severe gastroduodenal pathology in some patients. Many studies have shown that Th1 and Th17 cellular and gastric mucosal immune responses are critical in reducing H. pylori load. IAV vector vaccines can stimulate these immune responses while overcoming potential adjuvant toxicity and antigen dosing issues. To date, no studies have demonstrated the role of live attenuated IAV vector vaccines in preventing and treating H. pylori infection. Our work indicates that vaccination with IAV-NapA induces antigen-specific humoral, cellular, and mucosal immunity, producing a protective and therapeutic effect against H. pylori infection in BALB/c mice. This undescribed H. pylori vaccination approach may provide valuable information for developing vaccines against H. pylori infection.

Recent advances in enterotoxin vaccine adjuvants

Enterotoxin adjuvants have been researched for their ability to promote immunity to co-delivered antigens. Outside of cholera vaccines, however, these proteins have yet to be included in any currently licensed vaccines. They include molecules derived from the bacterial toxins of Vibrio cholerae, cholera toxin, or Escherichia coli, heat-labile toxin, such as detoxified mutants or subunits. This class of adjuvants is distinguished by their delivery possibilities, which include parenteral injection, skin applications, or direct mucosal administration by oral, sublingual, or nasal routes. In addition, inclusion of an enterotoxin adjuvant is associated with development of multifaceted cellular and humoral immune responses to vaccination. Here, we review exciting progress in the past few years in clinical trials for safety and efficacy, preclinical vaccines studies, and new mechanistic insights for enterotoxin adjuvants. This includes recent reports of their use in vaccines targeting microbial infections (bacterial, viral, parasitic) or substance abuse drugs.

Identification of the immunogenic membrane proteins, catalase, PgbA, and PgbB, as potential antigens against Helicobacter pylori

AIMS

This study aims to investigate the specific membrane antigens that are targeted by antibodies raised against Helicobacter pylori.

METHODS AND RESULTS

Bovine milk antibodies were prepared using whole H. pylori, purified membrane proteins, or both. Enzyme-linked immunosorbent assay and sodium dodecyl sulfate-polyacrylamide gel electrophoresis experiments revealed that these immunogens triggered anti-H. pylori antibody production in milk. The highest antibody titer was induced by the mixture of whole bacteria and purified membrane proteins. The antibodies induced by mixed immunogens significantly inhibited H. pylori growth in vitro and were used to identify catalase, plasminogen-binding protein A (PgbA), and PgbB via western blotting, immunoprecipitation, and two-dimensional western blotting followed by liquid chromatography with tandem mass spectrophotometry. The immunogenicity of PgbA and PgbB was verified in mice vaccinated with their B-cell epitope vaccines. Following prophylactic vaccination of C57BL/6 mice, each of the three antigens alone and their combination reduced the weight loss in mice, increased antibody titers, and relieved the inflammatory status of the gastric mucosa following H. pylori infection.

CONCLUSIONS

Catalase, PgbA, and PgbB could serve as valuable membrane antigens for the development of anti-H. pylori immunotherapies.

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.

How Long Will It Take to Launch an Effective Helicobacter pylori Vaccine for Humans?

Helicobacter pylori infection often occurs in early childhood, and can last a lifetime if not treated with medication. H. pylori infection can also cause a variety of stomach diseases, which can only be treated with a combination of antibiotics. Combinations of antibiotics can cure H. pylori infection, but it is easy to relapse and develop drug resistance. Therefore, a vaccine is a promising strategy for prevention and therapy for the infection of H. pylori. After decades of research and development, there has been no appearance of any H. pylori vaccine reaching the market, unfortunately. This review summarizes the aspects of candidate antigens, immunoadjuvants, and delivery systems in the long journey of H. pylori vaccine research, and also introduces some clinical trials that have displayed encouraging or depressing results. Possible reasons for the inability of an H. pylori vaccine to be available over the counter are cautiously discussed and some propositions for the future of H. pylori vaccines are outlined.

Effect of probiotics as an immune modulator for the management of COVID-19

COVID-19, an acute respiratory viral infection conveyed by pneumonia caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has affected millions of individuals globally, and is a public health emergency of international concern. Till now, there are no highly effective therapies for this infection without vaccination. As they can evolve quickly and cross the strain level easily, these viruses are causing epidemics or pandemics that are allied with more severe clinical diseases. A new approach is needed to improve immunity to confirm the protection against emerging viral infections. Probiotics can modify gut microbial dysbiosis, improve the host immune system, and stimulate immune signaling, increasing systemic immunity. Several probiotic bacterial therapies have been proven to decrease the period of bacterial or viral infections. Superinduction of inflammation, termed cytokine storm, has been directly linked with pneumonia and severe complications of viral respiratory infections. In this case, probiotics as potential immunomodulatory agents can be an appropriate candidate to improve the host's response to respiratory viral infections. During this COVID-19 pandemic, any approach that can induce mucosal and systemic immunity could be helpful. Here, we summarize contexts regarding the effectiveness of various probiotics for preventing virus-induced respiratory infectious diseases, especially those that could be employed for COVID-19 patients. In addition, the effects of probiotics, their mechanisms on different aspects of immune responses against respiratory viral infection, and their antiviral properties in clinical findings have been described in detail.

A comprehensive evaluation of an animal model for Helicobacter pylori-associated stomach cancer: Fact and controversy

Even though Helicobacter pylori infection was the most causative factor of gastric cancer, numerous in vivo studies failed to induce gastric cancer using H. pylori infection only. The utilization of established animal studies in cancer research is crucial as they aim to investigate the coincidental association between suspected oncogenes and pathogenesis as well as generate models for the development and testing of potential treatments. The methods to establish gastric cancer using infected animal models remain limited, diverse in methods, and showed different results. This study investigates the differences in animal models, which highlight different pathological results in gaster by literature research. Electronic databases searched were performed in PubMed, Science Direct, and Cochrane, without a period filter. A total of 135 articles were used in this study after a full-text assessment was conducted. The most frequent animal models used for gastric cancer were Mice, while Mongolian gerbils and Transgenic mice were the most susceptible model for gastric cancer associated with H. pylori infection. Additionally, transgenic mice showed that the susceptibility to gastric cancer progression was due to genetic and epigenetic factors. These studies showed that in Mongolian gerbil models, H. pylori could function as a single agent to trigger stomach cancer. However, most gastric cancer susceptibilities were not solely relying on H. pylori infection, and numerous factors are involved in cancer progression. Further study using Mongolian gerbils and Transgenic mice is crucial to conduct and establish the best models for gastric cancer associated H. pylori.

Discussion on the common controversies of Helicobacter pylori infection

BACKGROUND

Helicobacter pylori ( H. pylori ) can persistently colonize on the gastric mucosa after infection and cause gastritis, atrophy, metaplasia, and even gastric cancer (GC).

METHODS

Therefore, the detection and eradication of H. pylori are the prerequisite.

RESULTS

Clinically, there are some controversial issues, such as why H. pylori infection is persistent, why it translocases along with the lesser curvature of the stomach, why there is oxyntic antralization, what the immunological characteristic of gastric chronic inflammation caused by H. pylori is, whether H. pylori infection is associated with extra-gastric diseases, whether chronic atrophic gastritis (CAG) is reversible, and what the potential problems are after H. pylori eradication. What are the possible answers?

CONCLUSION

In the review, we will discuss these issues from the attachment to eradication in detail.

The Role of Helicobacter pylori Neutrophil-Activating Protein in the Pathogenesis of H. pylori and Beyond: From a Virulence Factor to Therapeutic Targets and Therapeutic Agents

Helicobacter pylori neutrophil-activating protein (HP-NAP), a major virulence factor of H. pylori, plays a role in bacterial protection and host inflammation. HP-NAP activates a variety of innate immune cells, including neutrophils, monocytes, and mast cells, to induce their pro-oxidant and pro-inflammatory activities. This protein also induces T-helper type 1 (Th1) immune response and cytotoxic T lymphocyte (CTL) activity, supporting that HP-NAP is able to promote gastric inflammation by activation of adaptive immune responses. Thus, HP-NAP is a potential therapeutic target for the treatment of H. pylori-induced gastric inflammation. The inflammatory responses triggered by HP-NAP are mediated by a PTX-sensitive G protein-coupled receptor and Toll-like receptor 2. Drugs designed to block the interactions between HP-NAP and its receptors could alleviate the inflammation in gastric mucosa caused by H. pylori infection. In addition, HP-NAP acts as a promising therapeutic agent for vaccine development, allergy treatment, and cancer immunotherapy. The high antigenicity of HP-NAP makes this protein a component of vaccines against H. pylori infection. Due to its immunomodulatory activity to stimulate the Th1-inducing ability of dendritic cells, enhance Th1 immune response and CTL activity, and suppress Th2-mediated allergic responses, HP-NAP could also act as an adjuvant in vaccines, a drug candidate against allergic diseases, and an immunotherapeutic agent for cancer. This review highlights the role of HP-NAP in the pathogenesis of H. pylori and the potential for this protein to be a therapeutic target in the treatment of H. pylori infection and therapeutic agents against H. pylori-associated diseases, allergies, and cancer.

Gastrointestinal Involvement in SARS-CoV-2 Infection

SARS-CoV-2 has evolved into a virus that primarily results in mild or asymptomatic disease, making its transmission more challenging to control. In addition to the respiratory tract, SARS-CoV-2 also infects the digestive tract. Some gastrointestinal symptoms occur with or before respiratory symptoms in patients with COVID-19. Respiratory infections are known to cause intestinal immune impairment and gastrointestinal symptoms. When the intestine is inflamed, cytokines affect the lung immune response and inflammation through blood circulation. The gastrointestinal microbiome may be a modifiable factor in determining the risk of SARS-CoV-2 infection and disease severity. The development of oral SARS-CoV-2 vaccine candidates and the maintenance of gut microbiota profiles may contribute to the early control of COVID-19 outbreaks. To this end, this review summarizes information on the gastrointestinal complications caused by SARS-CoV-2, SARS-CoV-2 infection, the gastrointestinal–lung axis immune response, potential control strategies for oral vaccine candidates and maintaining intestinal microbiota homeostasis.

Resistance is futile? Mucosal immune mechanisms in the context of microbial ecology and evolution

In the beginning it was simple: we injected a protein antigen and studied the immune responses against the purified protein. This elegant toolbox uncovered thousands of mechanisms via which immune cells are activated. However, when we consider immune responses against real infectious threats, this elegant simplification misses half of the story: the infectious agents are typically evolving orders-of-magnitude faster than we are. Nowhere is this more pronounced than in the mammalian large intestine. A bacterium representing only 0.1% of the human gut microbiota will have a population size of 10⁹ clones, each actively replicating. Moreover, the evolutionary pressure from other microbes is at least as profound as direct effects of the immune system. Therefore, to really understand intestinal immune mechanisms, we need to understand both the host response and how rapid microbial evolution alters the apparent outcome of the response. In this review we use the examples of intestinal inflammation and secretory immunoglobulin A (SIgA) to highlight what is already known (Fig. 1). Further, we will explore how these interactions can inform immunotherapy and prophylaxis. This has major implications for how we design effective mucosal vaccines against increasingly drug-resistant bacterial pathogens Fig. 1 THE IMMUNE RESPONSE SHAPES THE FITNESS LANDSCAPE IN THE GASTRO-INTESTINAL TRACT.: The red arrows depict possible evolutionary paths of a novel colonizer along adaptive peaks in the intestinal fitness landscapes that change with the status of the host immune system. The flat surfaces represent the non-null fitness baselines (values x or y) at which a bacterium can establish at minimum carrying capacity. a In the healthy gut, metabolic competence, resistance to aggressions by competitors and predators, swift adaptation to rapid fluctuations as well as surviving acidic pH and the flow of the intestinal content, represent potent selective pressures and as many opportunities for bacteria to increase fitness by phenotypic or genetic variations. b When pathogens trigger acute inflammation, bacteria must adapt to iron starvation, killing by immune cells and antimicrobial peptides, and oxidative stress, while new metabolic opportunities emerge. c When high-affinity SIgA are produced against a bacterium, e.g., after oral vaccination, escape of SIgA by altering or losing surface epitopes becomes crucial for maximum fitness. However, escaping polyvalent SIgA responses after vaccination with "evolutionary trap" vaccines leads to evolutionary trade-offs: A fitness maximum is reached in the vaccinated host gut that represents a major disadvantage for transmission into naïve hosts (fitness diminished below x) (d).

Helicobacter pylori infection: from standard to alternative treatment strategies

Helicobacter pylori is the major component of the gastric microbiome of infected individuals and one of the aetiological factors of chronic gastritis, peptic ulcer disease and gastric cancer. The increasing resistance to antibiotics worldwide has made the treatment of H. pylori infection a challenge. As a way to overhaul the efficacy of currently used H. pylori antibiotic-based eradication therapies, alternative treatment strategies are being devised. These include probiotics and prebiotics as adjuvants in H. pylori treatment, antimicrobial peptides as alternatives to antibiotics, photodynamic therapy ingestible devices, microparticles and nanoparticles applied as drug delivery systems, vaccines, natural products, and phage therapy. This review provides an updated synopsis of these emerging H. pylori control strategies and discusses the advantages, hurdles, and challenges associated with their development and implementation. An effective human vaccine would be a major achievement although, until now, projects regarding vaccine development have failed or were discontinued. Numerous natural products have demonstrated anti-H. pylori activity, mostly in vitro, but further clinical studies are needed to fully disclose their role in H. pylori eradication. Finally, phage therapy has the potential to emerge as a valid alternative, but major challenges remain, namely the isolation of more H. pylori strictly virulent bacterio(phages).

Oral multivalent epitope vaccine, based on UreB, HpaA, CAT, and LTB, for prevention and treatment of Helicobacter pylori infection in C57BL / 6 mice

BACKGROUND

As the resistance of Helicobacter pylori to traditional triple therapy is gradually revealed, an increasing number of people are focusing on vaccine treatments for H. pylori infection. Epitope vaccines are a promising strategy for the treatment of H. pylori infection, and multivalent vaccines will be more effective than monovalent vaccines.

MATERIALS AND METHODS

In this study, we designed a multivalent vaccine named LHUC, which consists of the adjuvant LTB as well as three Th cell epitopes (HpaA_154-171 , UreB_237-251, and UreB_546-561 ) and five B-cell epitopes (UreB_349-363 , UreB_327-334 , CAT_394-405 , CAT_387-397, and HpaA_132-141 ) from UreB, HpaA, and catalase. In BALB/c mice, the specificity and immunogenicity of the fusion peptide LHUC and the neutralization of H. pylori urease and catalase by the specific IgG elicited by LHUC were evaluated. The preventive and therapeutic effects of LHUC were evaluated in C57BL/6 mice infected with H. pylori.

RESULTS

The results showed that compared with LTB and PBS, LHUC induced specific IgG and IgA antibody production in mice, and IgG antibodies significantly inhibited the H. pylori urease and catalase activities in vitro. Additionally, by detecting the levels of IFN-γ, IL-4, and IL-17 in lymphocyte supernatants, we proved that LHUC could activate Th1, Th2, and Th17 mixed T-cell immune responses in vivo. Finally, a C57BL/6 mouse model of gastric infection with H. pylori was established. The results showed that compared with the effects of LTB and PBS, the prevention and treatment effects of oral inoculation with LHUC significantly inhibited bacterial colonization.

CONCLUSIONS

In conclusion, LHUC, a multivalent vaccine based on multiple H. pylori antigens, is a promising and safe vaccine that can effectively reduce the colonization of H. pylori in the stomach.

Evaluation of the Immunogenic Response of a Novel Enterobactin Conjugate Vaccine in Chickens for the Production of Enterobactin-Specific Egg Yolk Antibodies

Passive immunization with specific egg yolk antibodies (immunoglobulin Y, IgY) is emerging as a promising alternative to antibiotics to control bacterial infections. Recently, we developed a novel conjugate vaccine that could trigger a strong immune response in rabbits directed against enterobactin (Ent), a highly conserved siderophore molecule utilized by different Gram-negative pathogens. However, induction of Ent-specific antibodies appeared to be affected by the choice of animal host and vaccination regimen. It is still unknown if the Ent conjugate vaccine can trigger a specific immune response in layers for the purpose of production of anti-Ent egg yolk IgY. In this study, three chicken vaccination trials with different regimens were performed to determine conditions for efficient production of anti-Ent egg yolk IgY. Purified Ent was conjugated to three carrier proteins, keyhole limpet hemocyanin (KLH), bovine serum albumin (BSA) and CmeC (a subunit vaccine candidate), respectively. Intramuscular immunization of Barred Rock layers with KLH-Ent conjugate four times induced strong immune response against whole conjugate vaccine but the titer of Ent-specific IgY did not change in yolk with only a 4 fold increase detected in serum. In the second trial, three different Ent conjugate vaccines were evaluated in Rhode Island Red pullets with four subcutaneous injections. The KLH-Ent or CmeC-Ent conjugate consistently induced high level of Ent-specific IgY in both serum (up to 2,048 fold) and yolk (up to 1,024 fold) in each individual chicken. However, the Ent-specific immune response was only temporarily and moderately induced using a BSA-Ent vaccination. In the third trial, ten White Leghorn layers were subcutaneously immunized three times with KLH-Ent, leading to consistent and strong immune response against both whole conjugate and the Ent molecule in each chicken; the mean titer of Ent-specific IgY increased approximately 32 and 256 fold in serum and yolk, respectively. Consistent with its potent binding to various Ent derivatives, the Ent-specific egg yolk IgY also inhibited in vitro growth of a representative Escherichia coli strain. Together, this study demonstrated that the novel Ent conjugate vaccine could induce strong, specific, and robust immune response in chickens. The Ent-specific hyperimmune egg yolk IgY has potential for passive immune intervention against Gram-negative infections.

Eradication of Helicobacter pylori and Gastric Cancer: A Controversial Relationship

Worldwide, gastric cancer (GC) represents the fifth cancer for incidence, and the third as cause of death in developed countries. Indeed, it resulted in more than 780,000 deaths in 2018. Helicobacter pylori appears to be responsible for the majority of these cancers. On the basis of recent studies, and either alone or combined with additional etiological factors, H. pylori is considered a "type I carcinogen." Over recent decades, new insights have been obtained into the strategies that have been adopted by H. pylori to survive the acidic conditions of the gastric environment, and to result in persistent infection, and dysregulation of host functions. The multistep processes involved in the development of GC are initiated by transition of the mucosa into chronic non-atrophic gastritis, which is primarily triggered by infection with H. pylori. This gastritis then progresses into atrophic gastritis and intestinal metaplasia, and then to dysplasia, and following Correa's cascade, to adenocarcinoma. The use of antibiotics for eradication of H. pylori can reduce the incidence of precancerous lesions only in the early stages of gastric carcinogenesis. Here, we first survey the etiology and risk factors of GC, and then we analyze the mechanisms underlying tumorigenesis induced by H. pylori, focusing attention on virulence factor CagA, inflammation, oxidative stress, and ErbB2 receptor tyrosine kinase. Moreover, we investigate the relationships between H. pylori eradication therapy and other diseases, considering not only cardia (upper stomach) cancers and Barrett's esophagus, but also asthma and allergies, through discussion of the "hygiene hypothesis. " This hypothesis suggests that improved hygiene and antibiotic use in early life reduces microbial exposure, such that the immune response does not become primed, and individuals are not protected against atopic disorders, asthma, and autoimmune diseases. Finally, we overview recent advances to uncover the complex interplay between H. pylori and the gut microbiota during gastric carcinogenesis, as characterized by reduced bacterial diversity and increased microbial dysbiosis. Indeed, it is of particular importance to identify the bacterial taxa of the stomach that might predict the outcome of gastric disease through the stages of Correa's cascade, to improve prevention and therapy of gastric carcinoma.

Immune evaluation of a Saccharomyces cerevisiae-based oral vaccine against Helicobacter pylori in mice

BACKGROUND

Helicobacter pylori (H. pylori) is a common human pathogenic bacterium that is associated with gastric diseases. The current leading clinical therapy is combination antibiotics, but this treatment has safety issues, especially the induction of drug resistance. Therefore, developing a safe and effective vaccine against H. pylori is one of the best alternatives.

OBJECTIVE

To develop Saccharomyces cerevisiae (S. cerevisiae)-based oral vaccines and then demonstrate the feasibility of this platform for preventing H. pylori infection in the absence of a mucosal adjuvant.

MATERIALS AND METHODS

Saccharomyces cerevisiae (S. cerevisiae)-based oral vaccines, including EBY100/pYD1-UreB and EBY100/pYD1-VacA, were generated and analyzed by Western blot, Immunofluorescence analysis, flow cytometric assay, and indirect enzyme-link immunosorbent assay (ELISA). Further, antibody responses induced by oral administration of EBY100/pYD1-UreB, EBY100/pYD1-VacA, or EBY100/pYD1-UreB + EBY100/pYD1-VacA were measured in a mouse model. Lastly, the vaccinated mice were infected with H. pylori SS1, and colonization in the stomach were evaluated.

RESULTS

Saccharomyces cerevisiae-based H. pylori oral vaccines were successfully constructed. Mice orally administered with EBY100/pYD1-UreB, EBY100/pYD1-VacA, or EBY100/pYD1-UreB + EBY100/pYD1-VacA exhibited a significant humoral immune response as well as a mucosal immune response. Importantly, S. cerevisiae-based oral vaccines could effectively reduce bacterial loads with statistical significance after H. pylori infection.

CONCLUSIONS

Our study shows that S. cerevisiae-based platforms can serve as an alternative approach for the future development of promising bacterial oral vaccine candidates.

The Role of Mucosal Immunity and Recombinant Probiotics in SARS-CoV2 Vaccine Development

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV2), causing the 2019 novel coronavirus disease (COVID-19), was introduced by WHO (World Health Organization) as "pandemic" in March 2020. According to WHO, thus far (23 November 2020) 58,425,681 infected cases including 1,385,218 deaths have been reported worldwide. In order to reduce transmission and spread of this lethal virus, attempts are globally being made to develop an appropriate vaccine. Intending to neutralize pathogens at their initial entrance site, protective mucosal immunity is inevitably required. In SARS-CoV2 infection and transmission, respiratory mucosa plays a key role; hence, apparently mucosal vaccination could be a superior approach to elicit mucosal and systemic immune responses simultaneously. In this review, the advantages of mucosal vaccination to control COVID-19 infection, limitations, and outcomes of mucosal vaccines have been highlighted. Considering the gut microbiota dysregulation in COVID-19, we further provide evidences on utilization of recombinant probiotics, particularly lactic acid bacteria (LAB) as vaccine carrier. Their intrinsic immunomodulatory features, natural adjuvanticity, and feasible expression of relevant antigen in the mucosal surface make them more appealing as live cell factory. Among all available platforms, bioengineered probiotics are considered as the most affordable, most practical, and safest vaccination approach to halt this emerging virus.

The emerging role of probiotics as a mitigation strategy against coronavirus disease 2019 (COVID-19)

COVID-19 is an acute respiratory infection accompanied by pneumonia caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which has affected millions of people globally. To date, there are no highly efficient therapies for this infection. Probiotic bacteria can interact with the gut microbiome to strengthen the immune system, enhance immune responses, and induce appropriate immune signaling pathways. Several probiotics have been confirmed to reduce the duration of bacterial or viral infections. Immune fitness may be one of the approaches by which protection against viral infections can be reinforced. In general, prevention is more efficient than therapy in fighting viral infections. Thus, probiotics have emerged as suitable candidates for controlling these infections. During the COVID-19 pandemic, any approach with the capacity to induce mucosal and systemic reactions could potentially be useful. Here, we summarize findings regarding the effectiveness of various probiotics for preventing virus-induced respiratory infectious diseases, especially those that could be employed for COVID-19 patients. However, the benefits of probiotics are strain-specific, and it is necessary to identify the bacterial strains that are scientifically established to be beneficial.

A recombinant Lactobacillus plantarum strain expressing the spike protein of SARS-CoV-2

Coronavirus disease 2019 (COVID-19), which is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has become a global pandemic in the past four months and causes respiratory disease in humans of almost all ages. Although several drugs have been announced to be partially effective treatments for this disease, no approved vaccine is available. Here, we described the construction of a recombinant Lactobacillus plantarum strain expressing the SARS-CoV-2 spike protein. The results showed that the spike gene with optimized codons could be efficiently expressed on the surface of recombinant L. plantarum and exhibited high antigenicity. The highest protein yield was obtained under the following conditions: cells were induced with 50 ng/mL SppIP at 37 °C for 6-10 h. The recombinant spike (S) protein was stable under normal conditions and at 50 °C, pH = 1.5, or a high salt concentration. Recombinant L. plantarum may provide a promising food-grade oral vaccine candidate against SARS-CoV-2 infection.

Review - Helicobacter, inflammation, immunology and vaccines

Understanding the mechanisms involved in induction and regulation of the immune and inflammatory response to Helicobacter pylori is extremely important in determining disease outcomes. H pylori expresses a plethora of factors that influence the host response. Vaccines against H pylori are desperately needed for the prevention of gastric carcinogenesis, especially with the increasing trends in antimicrobial resistance. This review summarizes some important findings, published between 1 April 2019 and 31 March 2020, in the areas of H pylori-mediated inflammation, immunity and vaccines.