Mucosal immunization with lactiplantibacillus plantarum-displaying recombinant SARS-CoV-2 epitopes on the surface induces humoral and mucosal immune responses in mice

Mucosal immunotherapy targeting APC in lung disease

Several studies have demonstrated that the pulmonary immune response is primarily facilitated by antigen-presenting cells (APCs), and that both professional and non-professional APCs contribute to overall pulmonary immunity. APCs play unique roles and mechanisms in pathogen elimination and immunomodulation. Mucosal immunity exhibits potential advantages over traditional parenteral immunity in that it stimulates immune defenses in mucosal and systemic tissues, which is important for reducing the burden of lung disease. However, obtaining a comprehensive understanding of the crosstalk between mucosal immunity and APC in the context of various lung diseases remains challenging. This mini-review aimed to elucidate the mechanisms of novel mucosal immunity, targeting APC action during lung infections, allergies, and malignant tumorigenesis. This minreview provides important insights into more effective therapeutic approaches for various lung diseases.

Effect of microencapsulated Fiber2-displaying probiotics loaded with inulin nanoparticles on immunity against fowl adenovirus serotype 4 in chickens

In this study, phthalate inulin nanoparticles (PINs) were chemically modified and characterized. The internalization of PINs into the probiotic E. faecalis, which delivering Fiber2 protein of fowl adenovirus serotype 4 (FAdV-4), was investigated. The expression of the Fiber2 protein in E. faecalis was detected using western blot analysis. To protect recombinant E. faecalis from degradation of in the gastric acid environment, sodium alginate was used to encapsulate the bacteria. The survival ratio and release of E. faecalis in simulated gastrointestinal fluid was assessed. Oral administration of microencapsulated E. faecalis loaded with PINs (Micro-E/Fiber2-PINs) or inulin (Micro-E/Fiber2-inulin) was conducted, followed by an experimental challenge with FAdV-4 in chickens to evaluate immune responses and protection. The results showed the internalization of PINs into the bacteria promoted bacteria growth, and significantly improved the expression level of Fiber2. After incubation in simulated gastric fluid, the number of viable bacteria from the Micro-E/Fiber2-PINs group was significantly higher than that from the E. faecalis/Fiber2 group. The release of bacteria from the microcapsules was completed within 30 min. Animal experiments demonstrated that oral immunization with Micro-E/Fiber2-PINs significantly enhanced humoral and cellular immune responses, relieved inflammatory injury in FAdV-targeted organs, and improved survival rate of challenged chickens. This study presents promising potential for developing oral vaccines against pathogen infection.

Oral Immunisation With Non-GMO Surface Displayed SARS-CoV-2 Spike Epitopes on Bacteria-Like Particles Provokes Robust Humoral and Cellular Immune Responses, and Modulated the Gut Microbiome in Mice

The coronavirus disease 2019 (COVID-19) is a fatal disease caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). To date, several vaccines have been developed to combat the spread of this virus. Mucosal vaccines using food-grade bacteria, such as Lactobacillus spp., are promising strategies for developing safe and effective vaccines against SARS-CoV-2. In this study, we designed a non-GMO surface-displayed SARS-CoV-2 spike S1 epitope on Limosilactobacillus fermentum-derived bacteria-like particles (BLPs). After that, we evaluated its efficacy to induce immune responses in immunocompetent mice. Moreover, we examined the influence of oral immunisation on the gut microbiome and microbiota metabolites. Twenty-eight 6-week-old male C57BL/6 mice were orally immunised with the following: PBS (control), Lm. fermentum-derived BLPs only, BLPs displaying SARS-CoV-2 spike S1-2, or BLPs displaying SARS-CoV-2 spike S1-3 epitopes. Our results showed that mucosal immunisation of mice with surface-displayed SARS-CoV-2 spike epitopes provoked high-level secretory IgA and systemic IgG production. Moreover, the immunisation exhibited a Th1-like immune response, characterised by an elevated IgG2a-to-IgG1 ratio and high antiviral IFN-γ production. In addition, we observed gut microbiome modulation and increased butyrate production in immunised mice. Overall, the use of Lm. fermentum-derived BLPs and the anchor CshA to display SARS-CoV-2 spike S1epitopes is a promising novel strategy in developing a cost-effective, non-GMO mucosal vaccine alternative against SARS-CoV-2.

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.

Recombinant L. lactis vaccine LL-plSAM-WAE targeting four virulence factors provides mucosal immunity against H. pylori infection

BACKGROUND

Helicobacter pylori (H. pylori) causes chronic gastric disease. An efficient oral vaccine would be mucosa-targeted and offer defense against colonization of invasive infection in the digestive system. Proteolytic enzymes and acidic environment in the gastrointestinal tract (GT) can, however, reduce the effectiveness of oral vaccinations. For the creation of an edible vaccine, L. lactis has been proposed as a means of delivering vaccine antigens.

RESULTS

We developed a plSAM (pNZ8148-SAM) that expresses a multiepitope vaccine antigen SAM-WAE containing Urease, HpaA, HSP60, and NAP extracellularly (named LL-plSAM-WAE) to increase the efficacy of oral vaccinations. We then investigated the immunogenicity of LL-plSAM-WAE in Balb/c mice. Mice that received LL-plSAM-WAE or SAM-WAE with adjuvant showed increased levels of antibodies against H. pylori, including IgG and sIgA, and resulted in significant reductions in H. pylori colonization. Furthermore, we show that SAM-WAE and LL-plSAM-WAE improved the capacity to target the vaccine to M cells.

CONCLUSIONS

These findings suggest that recombinant L. lactis could be a promising oral mucosa vaccination for preventing H. pylori infection.

Oral administration of a recombinant modified RBD antigen of SARS-CoV-2 as a possible immunostimulant for the care of COVID-19

BACKGROUND

Developing effective vaccines against SARS-CoV-2 that consider manufacturing limitations, equitable access, and acceptance is necessary for developing platforms to produce antigens that can be efficiently presented for generating neutralizing antibodies and as a model for new vaccines.

RESULTS

This work presents the development of an applicable technology through the oral administration of the SARS-CoV-2 RBD antigen fused with a peptide to improve its antigenic presentation. We focused on the development and production of the recombinant receptor binding domain (RBD) produced in E. coli modified with the addition of amino acids extension designed to improve antigen presentation. The production was carried out in shake flask and bioreactor cultures, obtaining around 200 mg/L of the antigen. The peptide-fused RBD and peptide-free RBD proteins were characterized and compared using SDS-PAGE gel, high-performance chromatography, and circular dichroism. The peptide-fused RBD was formulated in an oil-in-water emulsion for oral mice immunization. The peptide-fused RBD, compared to RBD, induced robust IgG production in mice, capable of recognizing the recombinant RBD in Enzyme-linked immunosorbent assays. In addition, the peptide-fused RBD generated neutralizing antibodies in the sera of the dosed mice. The formulation showed no reactive episodes and no changes in temperature or vomiting.

CONCLUSIONS

Our study demonstrated the effectiveness of the designed peptide added to the RBD to improve antigen immunostimulation by oral administration.

Stable expression of HIV-1 MPER extended epitope on the surface of the recombinant probiotic bacteria Escherichia Coli Nissle 1917 using CRISPR/Cas9

BACKGROUND

Mucosal vaccines have the potential to induce protective immune responses at the sites of infection. Applying CRISPR/Cas9 editing, we aimed to develop a probiotic-based vaccine candidate expressing the HIV-1 envelope membrane-proximal external region (MPER) on the surface of E. coli Nissle 1917.

RESULTS

The HIV-1 MPER epitope was successfully introduced in the porin OmpF of the E. coli Nissle 1917 (EcN-MPER) and the modification was stable over 30 passages of the recombinant bacteria on the DNA and protein level. Furthermore, the introduced epitope was recognized by a human anti-HIV-1 gp41 (2F5) antibody using both live and heat-killed EcN-MPER, and this antigenicity was also retained over 30 passages. Whole-cell dot blot suggested a stronger binding of anti-HIV-1 gp41 (2F5) to heat-killed EcN-MPER than their live counterpart. An outer membrane vesicle (OMV) - rich extract from EcN-MPER culture supernatant was equally antigenic to anti-HIV-1 gp41 antibody which suggests that the MPER antigen could be harboured in EcN-MPER OMVs. Using quantitative ELISA, we determined the amount of MPER produced by the modified EcN to be 14.3 µg/108 cfu.

CONCLUSIONS

The CRISPR/Cas9 technology was an effective method for establishment of recombinant EcN-MPER bacteria that was stable over many passages. The developed EcN-MPER clone was devoid of extraneous plasmids and antibiotic resistance genes which eliminates the risk of plasmid transfer to animal hosts, should this clone be used as a vaccine. Also, the EcN-MPER clone was recognised by anti-HIV-1 gp41 (2F5) both as live and heat-killed bacteria making it suitable for pre-clinical evaluation. Expression of OmpF on bacterial surfaces and released OMVs identifies it as a compelling candidate for recombinant epitope modification, enabling surface epitope presentation on both bacteria and OMVs. By applying the methods described in this study, we present a potential platform for cost-effective and rational vaccine antigen expression and administration, offering promising prospects for further research in the field of vaccine development.

Alterations in the gut microbiome and its metabolites are associated with the immune response to mucosal immunization with Lactiplantibacillus plantarum-displaying recombinant SARS-CoV-2 spike epitopes in mice

Lactic acid bacteria (LAB) expressing foreign antigens have great potential as mucosal vaccines. Our previous study reported that recombinant Lactiplantibacillus plantarum SK156 displaying SARS-CoV-2 spike S1 epitopes elicited humoral and cell-mediated immune responses in mice. Here, we further examined the effect of the LAB-based mucosal vaccine on gut microbiome composition and function, and gut microbiota-derived metabolites. Forty-nine (49) female BALB/c mice were orally administered L. plantarum SK156-displaying SARS-CoV-2 spike S1 epitopes thrice (at 14-day intervals). Mucosal immunization considerably altered the gut microbiome of mice by enriching the abundance of beneficial gut bacteria, such as Muribaculaceae, Mucispirillum, Ruminococcaceae, Alistipes, Roseburia, and Clostridia vadinBB60. Moreover, the predicted function of the gut microbiome showed increased metabolic pathways for amino acids, energy, carbohydrates, cofactors, and vitamins. The fecal concentration of short-chain fatty acids, especially butyrate, was also altered by mucosal immunization. Notably, alterations in gut microbiome composition, function, and butyrate levels were positively associated with the immune response to the vaccine. Our results suggest that the gut microbiome and its metabolites may have influenced the immunogenicity of the LAB-based SARS-CoV-2 vaccine.