A Lactococcus lactis-vectored oral vaccine induces protective immunity of mice against enterotoxigenic Escherichia coli lethal challenge

Chloroplast display of subunit vaccines and their efficacy via oral administration

As a safe and natural "capsule," plants have several advantages over mammals and microorganisms for the production of oral vaccines. In this study, we innovatively utilized the transmembrane region of the pea Translocase of chloroplast 34 (TOC34) protein to display two subunit vaccines, capsid protein VP2 of Porcine parvovirus (PPV) and the heat-labile enterotoxin B (LTB) of Escherichia coli, on the surface of chloroplasts. Unlike microbial display techniques, chloroplast display circumvents antigen degradation in the stomach while retaining the size characteristic of microorganisms. Additionally, a co-expressed peptide adjuvant, antimicrobial peptide protegin-1 (PG1), was used to enhance the strength of oral immunization. Immunohistochemistry and trypsin digestion of chloroplast surface proteins confirmed the successful localization of both antigens on the chloroplast surface. In stable transgenic tobacco plants, the expression level of VP2-TOC34 ranged from 0.21 to 6.83 μg/g FW, while LTB-TOC34 ranged from 2.42 to 10.04 μg/g FW. By contrasting the digestive characteristics of plant materials with different particle sizes, it was observed that plant materials with diameters around 1 mm exhibited more prominent advantages in terms of chloroplast release and antigen exposure compared to both larger and smaller particles. Oral immunization resulted in significantly increased levels of specific IgG and secretory IgA in the mice compared to the control, with similar effects observed between the groups receiving oral immunization alone and those receiving a combination of initial injection and subsequent oral immunization. Challenge experiments further demonstrated the effective protection against infection in mice using this approach. These findings highlight the potential of chloroplast display technology for the development of effective oral vaccines.

Design of an oral vaccine using Lactococcus lactis against brucellosis: an in vitro and in vivo study

Brucellosis is regarded as one of the world's most severe zoonotic diseases. This study aimed to investigate the possibility of using recombinant Lactococcus lactis (L. lactis) as a live vector to produce recombinant Brucella abortus (B. abortus) Omp10. The gene sequences were obtained from GenBank. The proteins' immunogenicity was assessed using Vaxijen. After confirming the cloning of the Omp10 gene in the pNZ8148 vector by enzymatic digestion and PCR, transformation into L. lactis was done. SDS-PAGE and western blot methods evaluated omp10 protein expression. Mice received oral recombinant L. lactis vaccines. IgG antibodies against Omp10 were tested using ELISA. Real-time PCR and ELISA were used to analyze cytokine responses. Survival rate and histopathological changes were evaluated after the challenge. Omp10 was chosen for its 1.5524 antigenicity score. Enzymatic digestion and PCR identified a 381-bp gene fragment. A 10 kDa band indicated the success of L. lactis transformation. Mice administered the L. lactis-pNZ8148-Omp10-Usp45 vaccination 14 days after priming showed significantly higher Omp10-specific total IgG and IgG1 (P < 0.001) than the PBS control group. The mice who received the L. lactis-pNZ8148-Omp10-Usp45 and IRBA vaccines had significantly elevated levels of IFN-γ, TNFα, IL-4, and IL-10 in samples collected on days 14 and 28 (P < 0.001). Inflammatory response, morphological damage, alveolar edema, and lymphocyte infiltration were reduced in the target group. A recombinant L. lactis expressing the Omp10 protein was constructed as an oral Lactococcus-based vaccine and compared to live attenuated vaccines for future brucellosis investigations.

Immunization of BALB/c mice with BAB1-0278: An initial investigation of a novel potential vaccine for brucellosis based on Lactococcus Lactis vector

The gram-negative intracellular bacterium Brucella abortus causes bovine brucellosis, a zoonotic disease that costs a lot of money. This work developed a vector vaccine against brucellosis utilizing recombinant L. lactis expressing Brucella outer membrane protein BAB1-0278. Gene sequences were obtained from GenBank. The proteins' immunogenicity was tested with Vaxijen. The target vector was converted into L. lactis after enzymatic digestion and PCR validated the BAB1-0278 gene cloning in the pNZ8148 vector. The target protein was extracted using a Ni-NTA column and confirmed using SDS-PAGE and western blot. After vaccination with the target vaccine, the expression of IgG subclasses was evaluated by the ELISA method. Cytokine production was also measured by the qPCR method in the small intestine and spleen. Lymphocyte proliferation and innate immune response (NLR, CRP, and PLR) were also assessed. Finally, after the challenge test, the spleen tissue was examined by H&E staining. BAB1-0278 was chosen because of its antigenicity score of 0.5614. A 237-bp gene fragment was discovered using enzymatic digestion and PCR. The presence of a 13 kDa protein band was confirmed by SDS-PAGE and western blot. In comparison to the PBS group, mice given the L. lactis-pNZ8148-BAB1-0278-Usp45 vaccine 14 days after priming had substantially greater levels of total IgG, IgG1, and IgG2a (P < 0.001). Also, the production of cytokines (IFN-γ, TNFα, IL-4, and IL-10) indicating cellular immunity increased compared to the control group (P < 0.001). The target group had a lower inflammatory response, morphological impairment, alveolar edema, and lymphocyte infiltration. An efficient probiotic-based oral brucellosis vaccination was created. These studies have proven that the recommended immunization gives the best protection, which supports its promotion.

Lactococcus lactis, a bacterium with probiotic functions and pathogenicity

Lactococcus lactis (L. lactis) is the primary organism for lactic acid bacteria (LAB) and is a globally recognized safe microorganism for the regulation of the intestinal micro-ecological balance of animals and improving the immune performance of the host. L. lactis is known to play a commercially important role in feed fortification, milk fermentation, and vaccine production, but pathogenic L. lactis has been isolated from many clinical cases in recent years, such as the brain of silver carp with Lactococcosis, the liver and spleen of diseased waterfowl, milk samples and padding materials with cow mastitis, and blood and urine from human patients with endocarditis. In dairy farming, where L. lactis has been used as a probiotic in the past, however, some studies have found that L. lactis can cause mastitis in cows, but the lack of understanding of the pathogenesis of mastitis in cows caused by L. lactis has become a new problem. The main objective of this review is to analyze the increasingly serious clinical mastitis caused by L. lactis and combined with the wide application of L. lactis as probiotics, to comprehensively discuss the characteristics and diversity of L. lactis.

Immunomodulatory action of Lactococcuslactis

Fermented foods are gaining popularity due to health-promoting properties with high levels of nutrients, phytochemicals, bioactive compounds, and probiotic microorganisms. Due to its unique fermentation process, Lactococcus lactis plays a key role in the food business, notably in the manufacturing of dairy products. The superior biological activities of L. lactis in these functional foods include anti-inflammatory and immunomodulatory capabilities. L. lactis boosted growth performance, controlled amino acid profiles, intestinal immunology, and microbiota. Besides that, the administration of L. lactis increased the rate of infection clearance. Innate and acquired immune responses would be upregulated in both local and systemic compartments, resulting in these consequences. L. lactis is often employed in the food sector and is currently being exploited as a delivery vehicle for biological research. These bacteria are being eyed as potential candidates for biotechnological applications. With this in mind, we reviewed the immunomodulatory effects of different L. lactis strains.

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 With a M Cell-Targeting Recombinant L. Lactis Vaccine LL-plSAM-FVpE Stimulate Protective Immunity Against H. Pylori in Mice

There are many virulence factors of H. pylori that contribute in diverse ways to gastric disease. Therefore, designing multivalent epitope vaccines against many key virulence factors virulence factors of H. pylori is a promising strategy to control H. pylori infection. In previous studies, we constructed a multivalent epitope vaccine FVpE against four key virulence factors of H. pylori (Urease, CagA, VacA, and NAP), and oral immunization with the FVpE vaccine plus a polysaccharide adjuvant (PA) containing lycium barbarum polysaccharide and chitosan could provide protection against H. pylori infection in the Mongolian gerbil model. Oral vaccines have many advantages over injected vaccines, such as improved safety and compliance, and easier manufacturing and administration. However, the harsh gastrointestinal (GI) environment, such as gastric acid and proteolytic enzymes, limits the development of oral vaccines to some extent. Oral vaccines need a gastrointestinal delivery system with high safety, low price and promoting vaccine antigen to stimulate immune response in the gastrointestinal mucosa. Lactic acid bacteria are gastrointestinal probiotics that have unique advantages as a delivery system for oral vaccines. In this study, a M cell-targeting surface display system for L. lactis named plSAM was designed to help vaccine antigens to stimulate effective immune responses in the gastrointestinal tract, and a M cell-targeting recombinant L. lactis vaccine LL-plSAM-FVpE was constructed by using the surface display system plSAM. recombinant L. lactis vaccine LL-plSAM-FVpE could secretively express the SAM-FVpE protein and display it on the bacterial surface. Moreover, experimental results confirmed that LL-plSAM-FVpE had an enhanced M cell-targeting property. In addition, LL-plSAM-FVpE had excellent M cell-targeting property to promote the phagocytosis and transport of the antigen SAM-FVpE by gastrointestinal M cells. More importantly, oral immunization of LL-plSAM-FVpE or SAM-FVpE plus PA can stimulate IgG and sIgA antibodies and CD4⁺ T cell immune responses against four virulence factors of H. pylori (Urease, CagA, VacA, and NAP), thus providing protective immunity against H. pylori infection in mice. The M cell-targeting recombinant L. lactis vaccine against various key H. pylori virulence factors could be a promising vaccine candidate for controlling H. pylori infection.

Recombinant lactic acid bacteria as promising vectors for mucosal vaccination

Lactic acid bacteria (LAB), a diverse family of gram-positive bacteria, has been proven effective in delivering varieties of therapeutic and prophylactic molecules such as antigens and cytokines. Featuring the properties of acid-resistant, high uptake into Peyer's patches, and superior capacity for inducing secretory IgA antibodies, LAB have good potential to be used as vaccine vectors for mucosal vaccination. Mucosal immunization enables both mucosal and systemic immune responses, which are critical for resisting pathogens that invade the host through the mucosal surfaces. With the development of genetic engineering, LAB strains, primarily Lactococcus and Lactobacillus have been exploited to express a range of heterologous antigens. Numerous studies have demonstrated that LAB mucosal vaccines can stimulate all arms of the immune system to provide adequate protection against pathogen infections. Additionally, several LAB-based human papillomavirus vaccines have entered the clinical trial studies, which suggest the great promise of LAB vaccines for new interventions in mucosal transport diseases. Herein, we will discuss the factors that influence the immunogenicity of LAB vaccines, including LAB strains, the location of antigens, and administration routes, and focus on the current strategies that have been reported for optimizing LAB vaccines.

Plasmid Replicons for the Production of Pharmaceutical-Grade pDNA, Proteins and Antigens by Lactococcus lactis Cell Factories

The Lactococcus lactis bacterium found in different natural environments is traditionally associated with the fermented food industry. But recently, its applications have been spreading to the pharmaceutical industry, which has exploited its probiotic characteristics and is moving towards its use as cell factories for the production of added-value recombinant proteins and plasmid DNA (pDNA) for DNA vaccination, as a safer and industrially profitable alternative to the traditional Escherichia coli host. Additionally, due to its food-grade and generally recognized safe status, there have been an increasing number of studies about its use in live mucosal vaccination. In this review, we critically systematize the plasmid replicons available for the production of pharmaceutical-grade pDNA and recombinant proteins by L. lactis. A plasmid vector is an easily customized component when the goal is to engineer bacteria in order to produce a heterologous compound in industrially significant amounts, as an alternative to genomic DNA modifications. The additional burden to the cell depends on plasmid copy number and on the expression level, targeting location and type of protein expressed. For live mucosal vaccination applications, besides the presence of the necessary regulatory sequences, it is imperative that cells produce the antigen of interest in sufficient yields. The cell wall anchored antigens had shown more promising results in live mucosal vaccination studies, when compared with intracellular or secreted antigens. On the other side, engineering L. lactis to express membrane proteins, especially if they have a eukaryotic background, increases the overall cellular burden. The different alternative replicons for live mucosal vaccination, using L. lactis as the DNA vaccine carrier or the antigen producer, are critically reviewed, as a starting platform to choose or engineer the best vector for each application.

Salmonella Vaccine Vector System for Foot-and-Mouth Disease Virus and Evaluation of Its Efficacy with Virus-Like Particles

Foot-and-mouth disease virus (FMDV) causes a highly contagious and devastating disease in livestock animals and has a great potential to cause severe economic loss worldwide. The major antigen of FMDV capsid protein, VP1, contains the major B-cell epitope responsible for effectively eliciting protective humoral immunity. In this study, irradiated Salmonella Typhimurium (KST0666) were used as transgenic vectors containing stress-inducible plasmid pRECN-VP1 to deliver the VP1 protein from FMDV-type A/WH/CHA/09. Mice were orally inoculated with ATOMASal-L3 harboring pRECN-VP1, and FMDV virus-like particles, where (VLP_FMDV)-specific humoral, mucosal, and cellular immune responses were evaluated. Mice vaccinated with attenuated Salmonella (KST0666) expressing VP1 (named KST0669) showed high levels of VLP-specific IgA in feces and IgG in serum, with high FMDV neutralization titer. Moreover, KST0669-vaccinated mice showed increased population of IFN-γ (type 1 T helper cells; Th1 cells)-, IL-5 (Th2 cells)-, and IL-17A (Th17 cells)-expressing CD4⁺ as well as activated CD8⁺ T cells (IFN-γ⁺CD8⁺ cells), detected by stimulating VLP_FMDV. All data indicate that our Salmonella vector system successfully delivered FMDV VP1 to immune cells and that the humoral and cellular efficacy of the vaccine can be easily evaluated using VLP_FMDV in a Biosafety Level I (BSL1) laboratory.