Expression of Helicobacter pylori hspA Gene in Lactococcus lactis NICE System and Experimental Study on Its Immunoreactivity

Is Lactococcus lactis a Suitable Candidate for Use as a Vaccine Delivery System Against Helicobacter pylori?

Helicobacter pylori was described in 1979. This bacterium, which thrives in the harsh conditions of the stomach, is typically acquired during childhood and can remain colonized for life. Approximately, 90% of the global population is affected, and H. pylori is linked to various conditions, including gastritis, peptic ulcers, lymphoproliferative gastric lymphoma, and even gastric cancer. Currently, antibiotics are the primary treatment method, but the associated challenges of antibiotic use have led to the consideration of oral vaccination as a viable preventive measure against this infection. However, the stomach's harsh environment characterized by its acidic conditions and numerous proteolytic enzymes poses significant obstacles to the development and effectiveness of oral vaccines. To address these challenges, researchers have proposed and evaluated several delivery systems. One of the most promising options is the use of probiotics. Among the various probiotics, Lactococcus lactis stands out as a suitable candidate for oral vaccine delivery against H. pylori due to the advancements in genetic engineering that have been applied to it. This review article discusses the limitations of current treatment strategies and rationalizes the shift toward vaccination, particularly oral vaccination for this infection. It also explores the advantages and challenges of using probiotic bacteria, with a focus on L. lactis as a delivery system. Ultimately, despite the existing challenges, L. lactis continues to be recognized as a promising delivery system. Nonetheless, further research is essential to fully assess its effectiveness and address the challenges associated with this approach.

Perspectives from recent advances of Helicobacter pylori vaccines research

BACKGROUND

Helicobacter pylori (H. pylori) infection is the main factor leading to some gastric diseases. Currently, H. pylori infection is primarily treated with antibiotics. However, with the widespread application of antibiotics, H. pylori resistance to antibiotics has also gradually increased year by year. Vaccines may be an alternative solution to clear H. pylori.

AIMS

By reviewing the recent progress on H. pylori vaccines, we expected it to lead to more research efforts to accelerate breakthroughs in this field.

MATERIALS & METHODS

We searched the research on H. pylori vaccine in recent years through PubMed®, and then classified and summarized these studies.

RESULTS

The study of the pathogenic mechanism of H. pylori has led to the development of vaccines using some antigens, such as urease, catalase, and heat shock protein (Hsp). Based on these antigens, whole-cell, subunit, nucleic acid, vector, and H. pylori exosome vaccines have been tested.

DISCUSSION

At present, researchers have developed many types of vaccines, such as whole cell vaccines, subunit vaccines, vector vaccines, etc. However, although some of these vaccines induced protective immunity in mouse models, only a few were able to move into human trials. We propose that mRNA vaccine may play an important role in preventing or treating H. pylori infection. The current study shows that we have developed various types of vaccines based on the virulence factors of H. pylori. However, only a few vaccines have entered human clinical trials. In order to improve the efficacy of vaccines, it is necessary to enhance T-cell immunity.

CONCLUSION

We should fully understand the pathogenic mechanism of H. pylori and find its core antigen as a vaccine target.

Expression of Helicobacter pylori CagL gene in Lactococcus lactis MG1363 and evaluation of its immunogenicity as an oral vaccine in mice

Helicobacter pylori is a gram negative pathogen which commonly colonizes in the human gastric mucosa from early childhood and persists throughout life. CagL is a 27-kDa protein that is located at the tip of T4SS pili and highly conserved among pathogenic H. pylori strains. Lactic acid bacteria especially Lactococcus lactis (L. lactis) could serve as an antigen-delivering vehicle for the development of edible vaccine. In this study H. pylori CagL gene was cloned in pAMJ2008 vector and transferred to Lactococcus lactis MG1363 as the host for CagL antigen production. This recombinant bacterium was orally subjected to mice, and the immune response to CagL was evaluated by ELISA. Intracellular expression of CagL protein was confirmed by Western blot analysis. Mucosal immunization of mice with the recombinant L. lactis significantly stimulated CagL-Specific antibodies: IgA, IgG, cytokine IL-17 and IFN-γ. Moreover, the specific anti-CagL IgA response was detected in the feces of immunized mice. These results indicate that CagL of H. pylori was successfully expressed in L. lactis and the recombinant bacteria can be potentially used as an edible vaccine against H. pylori infection.

E. coli Enterotoxin LtB Enhances Vaccine-Induced Anti-H. pylori Protection by Promoting Leukocyte Migration into Gastric Mucus via Inflammatory Lesions

Current studies indicate that the anti-H. pylori protective efficacy of oral vaccines to a large extent depends on using mucosal adjuvants like E. coli heat-lable enterotoxin B unit (LtB). However, the mechanism by which Th17/Th1-driven cellular immunity kills H. pylori and the role of LtB remains unclear. Here, two L.lactis strains, expressing H. pylori NapA and LtB, respectively, were orally administrated to mice. As observed, the administration of LtB significantly enhanced the fecal SIgA level and decreased gastric H. pylori colonization, but also markedly aggravated gastric inflammatory injury. Both NapA group and NapA+LtB group had elevated splenocyte production of IL-8, IL-10, IL-12, IL-17, IL-23 and INF-γ. Notably, gastric leukocytes' migration or leakage into the mucus was observed more frequently in NapA+LtB group than in NapA group. This report is the first that discusses how LtB enhances vaccine-induced anti-H. pylori efficacy by aggravating gastric injury and leukocytes' movement into the mucus layer. Significantly, it brings up a novel explanation for the mechanism underlying mucosal cellular immunity destroying the non-invasive pathogens. More importantly, the findings suggest the necessity to further evaluate LtB's potential hazards to humans before extending its applications. Thus, this report can provide considerable impact on the fields of mucosal immunology and vaccinology.

Role of Nickel in Microbial Pathogenesis

Nickel is an essential cofactor for some pathogen virulence factors. Due to its low availability in hosts, pathogens must efficiently transport the metal and then balance its ready intracellular availability for enzyme maturation with metal toxicity concerns. The most notable virulence-associated components are the Ni-enzymes hydrogenase and urease. Both enzymes, along with their associated nickel transporters, storage reservoirs, and maturation enzymes have been best-studied in the gastric pathogen Helicobacter pylori, a bacterium which depends heavily on nickel. Molecular hydrogen utilization is associated with efficient host colonization by the Helicobacters, which include both gastric and liver pathogens. Translocation of a H. pylori carcinogenic toxin into host epithelial cells is powered by H2 use. The multiple [NiFe] hydrogenases of Salmonella enterica Typhimurium are important in host colonization, while ureases play important roles in both prokaryotic (Proteus mirabilis and Staphylococcus spp.) and eukaryotic (Cryptoccoccus genus) pathogens associated with urinary tract infections. Other Ni-requiring enzymes, such as Ni-acireductone dioxygenase (ARD), Ni-superoxide dismutase (SOD), and Ni-glyoxalase I (GloI) play important metabolic or detoxifying roles in other pathogens. Nickel-requiring enzymes are likely important for virulence of at least 40 prokaryotic and nine eukaryotic pathogenic species, as described herein. The potential for pathogenic roles of many new Ni-binding components exists, based on recent experimental data and on the key roles that Ni enzymes play in a diverse array of pathogens.

Construction of a Recombinant Lactococcus lactis Strain Expressing a Variant Porcine Epidemic Diarrhea Virus S1 Gene and Its Immunogenicity Analysis in Mice

Porcine epidemic diarrhea caused by porcine epidemic diarrhea virus (PEDV) is a highly contagious disease in newborn piglets. The spike (S) protein is the surface glycoprotein of PEDV, which can induce specific neutralization antibodies and is a candidate antigen for vaccination attempts. In our study, the S1 region of PEDV strain CH/JLDH/2016 spike gene was inserted into the Lactococcus lactis expression vector, pNZ8149, resulting in recombinant plasmid pNZ8149-S1, and the immunogenicity of recombinant L. lactis pNZ8149-S1/NZ3900 was evaluated in mice. After immunization, significantly higher levels of anti-PEDV serum IgG antibodies and mucosal sIgA antibodies were detected in mice orally administered with pNZ8149-S1/NZ3900, compared with control groups pNZ8149/NZ3900, NZ3900, and phosphate buffered saline (p < 0.01). Lymphocyte proliferation assay results showed that the recombinant L. lactis pNZ8149-S1/NZ3900 significantly stimulated the proliferation of splenic lymphocytes (p < 0.01). In addition, the recombinant L. lactis vaccine could induce high levels of IL-4 and IFN-γ in immunized mice (p < 0.01). The results of our study suggest that the recombinant L. lactis pNZ8149-S1/NZ3900 can provide a promising vaccine strategy against PEDV infection.

A novel food‐grade lactococcal expression system and its use for secretion and delivery of an oral vaccine antigen

BACKGROUND

Food‐grade bacterial expression systems are relatively rare, and increasing evidence indicates that subcellular location of antigens in bacterial vector vaccines may markedly affect the immune efficacy.

RESULTS

This study developed a novel food‐grade secretory expression system for heterologous protein production and oral vaccine delivery. Furthermore, by using the expression system, an engineered L. lactis strain secreting H. pylori UreB was constructed, and used to vaccinate SPF BALB/c mice. As results, the UreB expressed in L. lactis was detected in both cell lysates and culture supernatant of the engineered strain, constituting roughly 50% of the culture supernatant proteins, and recognized by mouse anti‐H. pylori sera. Oral vaccination with the engineered L. lactis produced a significantly elevated anti‐UreB serum antibody level in mice (P < 0.05).

CONCLUSION

These data show a novel food‐grade L. lactis secretory expression system, which may have distinct potential impact on edible and medicinal protein production and oral vaccine development. Moreover, this is the first report on secretory expression of a H. pylori antigen via using a food‐grade lactococcal expression system, and the engineered strain secreting UreB can be a hopeful H. pylori vaccine candidate. © 2017 Society of Chemical Industry

Production and delivery of Helicobacter pylori NapA in Lactococcus lactis and its protective efficacy and immune modulatory activity

Helicobacter pylori neutrophil-activating protein A subunit (NapA) has been identified as a virulence factor, a protective antigen and a potent immunomodulator. NapA shows unique application potentials for anti-H. pylori vaccines and treatment strategies of certain allergic diseases and carcinomas. However, appropriate production and utilization modes of NapA still remain uncertain to date. This work has established a novel efficient production and utilization mode of NapA by using L. lactis as an expression host and delivery vector, and demonstrated immune protective efficacy and immune modulatory activity of the engineered L. lactis by oral vaccination of mice. It was observed for the first time that H. pylori NapA promotes both polarized Th17 and Th1 responses, which may greatly affect the clinical application of NapA. This report offers a promising anti-H. pylori oral vaccine candidate and a potent mucosal immune modulatory agent. Meanwhile, it uncovers a way to produce and deliver the oral vaccine and immunomodulator by fermentation of food like milk, which might have striking effects on control of H. pylori infection, gastrointestinal cancers, and Th2 bias allergic diseases, including many food allergies.

The production of SPusp45-MSP-1₁₉ gene construct and its recombinant protein in <em>Lactococcus lactis</em> to be used as a malaria vaccine

Background: Merozoite surface protein 1 (MSP-1) is a major protein used by the Plasmodium during red blood cells invasion in malaria. MSP-119, one of MSP-1 is highly conserved, and  it is a potential malaria vaccine candidate because the monoclonal antibodies are capable blocking erythrocyte invasion in vitro. The aim of this study was to produce MSP-119 gene construct and the recombinant protein in Lactococcus lactis.Methods: Usp45-MSP-119, derived from codon optimization and the synthetic gene, was inserted into the pMAT cloning vector. A vector expressing MSP-119 included usp45 has been constructed by the manipulation of recombinant DNA using restriction enzymes. The MSP-119 protein was expressed to 45% ammonium sulfate precipitation and purified using Sephadex-G50 gel filtration chromatography. The expressed protein was characterized by SDS-PAGE and dot blot.Results: usp45-MSP-119 gene was amplified using specific primers and inserted into the multiple cloning sites in the expression vector pNZ8148 with size 3,538 bp as a recombinant vector. The protein of  MSP-119 was successfully expressed in L. lactis with molecular weight of 10.45 kDa. The dot blot was tested in 3 different comparisons between the host cells, non-induced cells, and induced cells with 10 ng/ml nisin. The results showed that 10 ng/ml nisin gave a positive reaction as detected by dot blot assay.Conclusion: This study confirmed that the usp45-MSP-119 gene was successfully inserted into the multiple cloning sites of the pNZ8148 expression vector and the MSP-119 protein expressed in the NICE system of the L. lactis host cell.

The study of H. pylori putative candidate factors for single- and multi-component vaccine development

Helicobacter pylori has grown to colonize inside the stomach of nearly half of the world's population, turning into the most prevalent infections in the universe. Medical care failures noticeably confirm the need for a vaccine to hinder or deal with H. pylori. This review is planned to discuss the most known factors as a vaccine candidate, including single (AhpC, BG, CagA, KatA, Fla, Hsp, HWC, Lpp, LPS, NAP, OMP, OMV, SOD, Tpx, Urease, VacA) and multi-component vaccines. Many promising results in the field of single and multivalent vaccine can be seen, but there is no satisfactory outcome and neither a prophylactic nor a therapeutic vaccine to treat or eradicate the infection in human has been acquired. Hence, selecting suitable antigen is an important factor as an appropriate adjuvant. Taken all together, the development of efficient anti-H. pylori vaccines relies on the fully understanding of the interactions between H. pylori and its host immune system. Therefore, more work should be done on epitope mapping, analysis of molecular structure, and determination of the antigen determinant region as well due to design a vaccine, preferably a multi-component vaccine to elicit specific CD4 T-cell responses that are required for H. pylori vaccine efficacy.

A review on Lactococcus lactis: from food to factory

Lactococcus lactis has progressed a long way since its discovery and initial use in dairy product fermentation, to its present biotechnological applications in genetic engineering for the production of various recombinant proteins and metabolites that transcends the heterologous species barrier. Key desirable features of this gram-positive lactic acid non-colonizing gut bacteria include its generally recognized as safe (GRAS) status, probiotic properties, the absence of inclusion bodies and endotoxins, surface display and extracellular secretion technology, and a diverse selection of cloning and inducible expression vectors. This have made L. lactis a desirable and promising host on par with other well established model bacterial or yeast systems such as Escherichia coli, Saccharomyces [corrected] cerevisiae and Bacillus subtilis. In this article, we review recent technological advancements, challenges, future prospects and current diversified examples on the use of L. lactis as a microbial cell factory. Additionally, we will also highlight latest medical-based applications involving whole-cell L. lactis as a live delivery vector for the administration of therapeutics against both communicable and non-communicable diseases.

An engineered food-grade Lactococcus lactis strain for production and delivery of heat-labile enterotoxin B subunit to mucosal sites

BACKGROUND

Recent researches have been focusing on mucosal immune adjuvants, which play the key roles in mucosal immunization and have become the limitation for non-injected vaccine development. Escherichia coli heat-labile enterotoxin B subunit (LTB) was regarded as a promising mucosal adjuvant for its nontoxicity and potent activity. LTB preparation issues have always been recurring, in part owing to that the recombinant LTB expressed by E. coli does not act as its native form.

RESULTS

We constructed an engineered Lactococcus lactis strain using a food-grade expression system. The LTB secreted by the engineered strain was detected in the culture supernatant, constituting 10.3% of the supernatant proteins, and recognized by mouse anti-LTB antibodies. The engineered strain, co-administered orally to SPF BALB/c mice with a H. pylori vaccine candidate expressing Lpp20 antigen, could significantly enhance the Lpp20-induced mucosal SIgA antibody responses against H. pylori.

CONCLUSIONS

This is the first report that LTB was efficiently produced and delivered via using a food-grade lactococcal expression system, which offers a novel production and utilization mode of this crucial mucosal adjuvant. The engineered L. lactis strain secreting LTB has considerable potential for oral vaccine formulation owing to its outstanding safety, adjuvant activity and high-level production.