An EGFP-marked recombinant lactobacillus oral tetravalent vaccine constitutively expressing α, ε, β1, and β2 toxoids for Clostridium perfringens elicits effective anti-toxins protective immunity

The Barrier Disruption and Pyroptosis of Intestinal Epithelial Cells Caused by Perfringolysin O (PFO) from Clostridium perfringens

Clostridium perfringens (C. perfringens), a Gram-positive bacterium, produces a variety of toxins and extracellular enzymes that can lead to disease in both humans and animals. Common symptoms include abdominal swelling, diarrhea, and intestinal inflammation. Severe cases can result in complications like intestinal hemorrhage, edema, and even death. The primary toxins contributing to morbidity in C. perfringens-infected intestines are CPA, CPB, CPB2, CPE, and PFO. Amongst these, CPB, CPB2, and CPE are implicated in apoptosis development, while CPA is associated with cell death, increased intracellular ROS levels, and the release of the inflammatory factor IL-18. However, the exact mechanism by which PFO toxins exert their effects in the infected gut is still unidentified. This study demonstrates that a C. perfringens PFO toxin infection disrupts the intestinal epithelial barrier function through in vitro and in vivo models. This study emphasizes the notable influence of PFO toxins on intestinal barrier integrity in the context of C. perfringens infections. It reveals that PFO toxins increase ROS production by causing mitochondrial damage, triggering pyroptosis in IPEC-J2 cells, and consequently resulting in compromised intestinal barrier function. These results offer a scientific foundation for developing preventive and therapeutic approaches against C. perfringens infections.

Display of porcine epidemic diarrhea virus spike protein B-cell linear epitope on Lactobacillus mucosae G01 S-layer surface induce a robust immunogenicity in mice

The Porcine epidemic diarrhea virus (PEDV) presents a substantial risk to the domestic pig industry, resulting in extensive and fatal viral diarrhea among piglets. Recognizing the mucosal stimulation triggered by PEDV and harnessing the regulatory impact of lactobacilli on intestinal function, we have developed a lactobacillus-based vaccine that is carefully designed to elicit a strong mucosal immune response. Through bioinformatics analysis, we examined PEDV S proteins to identify B-cell linear epitopes that meet the criteria of being non-toxic, soluble, antigenic, and capable of neutralizing the virus. In this study, a genetically modified strain of Lactobacillus mucosae G01 (L.mucosae G01) was created by utilizing the S layer protein (SLP) as a scaffold for surface presentation. Chimeric immunodominant epitopes with neutralizing activity were incorporated at various sites on SLP. The successful expression of SLP chimeric immunodominant epitope 1 on the surface of L.mucosae G01 was confirmed through indirect immunofluorescence and transmission electron microscopy, revealing the formation of a transparent membrane. The findings demonstrate that the oral administration of L.mucosae G01, which expresses the SLP chimeric immunodominant gene epitope1, induces the production of secreted IgA in the intestine and feces of mice. Additionally, there is an elevation in IgG levels in the serum. Moreover, the levels of cytokines IL-2, IL-4, IFN-γ, and IL-17 are significantly increased compared to the negative control group. These results suggest that L. mucosae G01 has the ability to deliver exogenous antigens and elicit a specific mucosal immune response against PEDV. This investigation presents new possibilities for immunoprophylaxis against PEDV-induced diarrhea.

Immunization effect of recombinant Lactobacillus casei displaying Aeromonas veronii Aha1 with an LTB adjuvant in carp

Aeromonas veronii is an important aquatic zoonotic, which elicits a range of diseases, such as haemorrhagic septicemia. To develop an effective oral vaccine against Aeromonas veronii infection in carp, the Aeromonas veronii adhesion (Aha1) gene was used as a target molecule to attach to intestinal epithelial cells. Two anchored recombinant. Lactic acid bacteria strains (LC-pPG-Aha1 1038 bp and LC-pPG-Aha1-LTB 1383 bp) were constructed by fusing them with the E. coli intolerant enterotoxin B subunit (LTB) gene and using Lactobacillus casei as antigen delivery vector to evaluate immune effects of these in carp. Western blotting and immunofluorescence were used to confirm that protein expression was successful. Additionally, levels of specific IgM in serum and the activities of ACP, AKP, SOD, LYS, C3, C4, and lectin enzymes-were assessed. Cytokines IL-10, IL-1β, TNF-α, IgZ1, and IgZ2 were measured in the liver, spleen, kidney, intestines, and gills tissue by qRT-PCR, which showed an increasing trend compared with the control group (P < 0.05). A colonization assay showed that the two L. casei recombinants colonized the middle and hind intestines of immunized fish. When immunized carp were experimentally challenged with Aeromonas veronii the relative percentage protection of LC-pPG-Aha1 was 53.57%, and LC-pPG-Aha1-LTB was 60.71%. In conclusion, these results demonstrate that Aha1 is a promising candidate antigen when it is displayed on lactic acid bacteria (Lc-pPG-Aha1 and Lc-pPG-Aha1-LTB) seems promising for a mucosal therapeutic approach. We plan to investigate the molecular mechanism of the L. casei recombinant in regulating the intestinal tissue of carp in future studies.

Oral or intranasal immunization with recombinant Lactobacillus plantarum displaying head domain of Swine Influenza A virus hemagglutinin protects mice from H1N1 virus

BACKGROUND

Swine influenza A virus (swIAV) is a major concern for the swine industry owing to its highly contagious nature and acute viral disease. Currently, most commercial swIAV vaccines are traditional inactivated virus vaccines. The Lactobacillus plantarum-based vaccine platform is a promising approach for mucosal vaccine development. Oral and intranasal immunisations have the potential to induce a mucosal immune response, which confers protective immunity. The aim of this study was to evaluate the probiotic potential and adhesion ability of three L. plantarum strains. Furthermore, a recombinant L. plantarum strain expressing the head domain of swIAV antigen HA1 was constructed and evaluated for its ability to prevent swIAV infection.

RESULTS

The three L. plantarum strains isolated from healthy pig faecal samples maintained the highest survival rate when incubated at pH 3 and at bile salt concentration of 0.3%. They also showed high adherence to intestinal cells. All three L. plantarum strains were monitored in live mice, and no major differences in transit time were observed. Recombinant L. plantarum expressed swIAV HA1 protein (pSIP401-HA1-ZN-3) and conferred effective mucosal, cellular and systemic immune responses in the intestine as well as in the upper respiratory airways of mice. In conclusion, the oral and intranasal administration of L. plantarum strain pSIP401-HA1-ZN-3 in mice induced mucosal immunity and most importantly, provided protection against lethal influenza virus challenge.

CONCLUSION

In summary, these findings suggest that the engineered L. plantarum strain pSIP401-HA1-ZN-3 can be considered as an alternative approach for developing a novel vaccine during an swine influenza A pandemic.

Use of genetically modified lactic acid bacteria and bifidobacteria as live delivery vectors for human and animal health

There is now strong evidence to support the interest in using lactic acid bacteria (LAB)in particular, strains of lactococci and lactobacilli, as well as bifidobacteria, for the development of new live vectors for human and animal health purposes. LAB are Gram-positive bacteria that have been used for millennia in the production of fermented foods. In addition, numerous studies have shown that genetically modified LAB and bifodobacteria can induce a systemic and mucosal immune response against certain antigens when administered mucosally. They are therefore good candidates for the development of new mucosal delivery strategies and are attractive alternatives to vaccines based on attenuated pathogenic bacteria whose use presents health risks. This article reviews the most recent research and advances in the use of LAB and bifidobacteria as live delivery vectors for human and animal health.

Oral Immunization of Chickens with Probiotic Lactobacillus crispatus Constitutively Expressing the α-β2-ε-β1 Toxoids to Induce Protective Immunity

Clostridium perfringens (C. perfringens) is a bacterium that commonly causes zoonotic disease. The pathogenicity of C. perfringens is a result of the combined action of α, β, and ε exotoxins. In this study, Lactobacillus crispatus (pPG-T7g10/L. crispatus) expressing the main toxoids of C. perfringens, α, ε, β1, and β2, with EGFP-labeling, was constructed, and the protective effect was estimated in chickens. The α-β2-ε-β1 toxoid was constitutively expressed for confirmation by laser confocal microscopy and western blotting, and its immunogenicity was analyzed by enzyme-linked immunosorbent assay (ELISA) and immunohistochemical assays. After booster immunization, the probiotic vaccine group showed significantly higher levels (p < 0.05) of specific secretory IgA (sIgA) and IgY antibodies in the serum and intestinal mucus. Furthermore, the levels of cytokines, including interferon (IFN)-γ, interleukin (lL)-2, IL-4, IL-10, IL-12, and IL-17, and the proliferation of spleen lymphocytes in chickens orally immunized with pPG-E-α-β2-ε-β1/L. crispatus increased significantly. Histopathological observations showed that the intestinal pathological changes in chickens immunized with pPG-E-α-β2ε-β1/L. crispatus were significantly alleviated. These data reveal that the probiotic vaccine could stimulate mucosal, cellular, and humoral immunity and provide an active defense against the toxins of C. perfringens, suggesting a promising candidate for oral vaccines against C. perfringens.

Next-generation probiotics: a promising approach towards designing personalized medicine

Second brain, forgotten organ, individual's identity card, and host's fingerprint are the few collective terms that are often used to describe the gut microbiome because of its variability, accountability, and its role in deciding the host's health. Also, the understanding of this host health-gut microbiota relationship can create an opportunity to control an individual's health by manipulating the gut microbiota composition. Several approaches like administration of probiotic, prebiotics, synbiotics, faecal microbiota transplantation have been tried to mitigate the dysbiosis originated ill effects. But the effects of these approaches are highly generic and non-specific. This creates the necessity to design personalized medicine that focuses on treatment of specific disease considering the individual specific gut microbiome. The health promoting commensals could be the new promising prophylactic and therapeutic agents for designing personalized medicine. These commensals are designated as next-generation probiotics (NGPs) and their unusual characteristics, unknown identity and special growth requirements have presented difficulties for researcher, industrial exploitation, and regulatory agencies. In this perspective, this review discusses the concept of NGPs, NGP candidates as tool for designing personalized medicine, designer probiotics as NGPs, required regulatory framework, and propose a road map to develop the NGP based product.

Surface display of spring viremia of carp virus glycoprotein on Lactococcus lactis and its protection efficacy in common carp (Cyprinus carpio L.)

Spring viremia of carp virus (SVCV) causes devastating disease in aquaculture, resulting in significant economic impact. To develop an effective means against SVCV infection, a Lactococcus lactis (L.lactis) based subunit vaccine (pNZ-UGA) was developed based on surface displaying of SVCV glycoprotein using anchoring motif of the cA (C terminus of the peptidoglyvsn-binding) domains of AcmA, a major autolysin from L.lactis. The surface expression of SVCV glycoprotein was verified by indirect immunofluorescence assay. The efficacy of the constructed vaccine was further evaluated in common carp. The results showed that the higher levels of specific IgM could be detected in fish vaccinated with pNZ-UGA, compared with that in PBS and L.lactis groups. Immune-related genes including TNF-α, IL-6b, IL-1β, Cxcr 1, Cxca, IFNg2b, I-IFN, and IgM expression in pNZ-UGA group were strongly up-regulated, revealing that robust innate immune response was induced. Notably, the lowest cumulative mortality (13.46%) was observed in fish vaccinated with pNZ-UGA vaccine after SVCV challenge, whereas the cumulative mortality were 100.00% and 92.31% in PBS and L.lactis groups, respectively. This study suggests the potential use of the recombinant L.lactis with surface displaying antigen proteins as effective vaccines against SVCV and other fish virus infection.

Protection Efficacy of Oral Bait Probiotic Vaccine Constitutively Expressing Tetravalent Toxoids against Clostridium perfringens Exotoxins in Livestock (Rabbits)

Clostridium perfringens is an opportunistic pathogen. Its main virulence factors are exotoxins, which are the etiological agents of enteritis necroticans and enterotoxemia caused in livestock (cattle, sheep, and rabbits). Here, we demonstrated effective immune protection for rabbits against α, β, and ε exotoxins of C. perfringens provided by an oral tetravalent bait probiotic vaccine delivering α, ε, β1, and β2 toxoids of C. perfringens. Results showed that the recombinant probiotic had good segregational stability and good colonization ability in the rabbit intestinal tract. Oral administration of the probiotic vaccine can effectively elicit significant levels of antigen-specific mucosa sIgA and sera IgG antibodies with exotoxin-neutralizing activity. Additionally, oral immunization with the probiotic vaccine effectively promoted lymphoproliferation and Th1/Th2-associated cytokine production. The protection rate of immunized rabbits with the probiotic vaccine was 80% after challenging rabbits with a combination of C. perfringens (toxinotypes A, C, and D) and exotoxin mixture, which was better than the 60% provided by a commercial inactivated C. perfringens A, C, and D trivalent vaccine. Moreover, obvious histopathological changes were observed in the intestinal tissues of rabbits in the commercial vaccine and PBS groups. The bait probiotic vaccine can provide effective protection against C. perfringens exotoxins, suggesting a promising C. perfringens vaccination strategy.