Assessment of Lactobacillus gasseri as a candidate oral vaccine vector

Lactobacillus gasseri ATCC33323 affects the intestinal mucosal barrier to ameliorate DSS-induced colitis through the NR1I3-mediated regulation of E-cadherin

Inflammatory bowel disease (IBD) is an immune system disorder primarily characterized by colitis, the exact etiology of which remains unclear. Traditional treatment approaches currently yield limited efficacy and are associated with significant side effects. Extensive research has indicated the potent therapeutic effects of probiotics, particularly Lactobacillus strains, in managing colitis. However, the mechanisms through which Lactobacillus strains ameliorate colitis require further exploration. In our study, we selected Lactobacillus gasseri ATCC33323 from the intestinal microbiota to elucidate the specific mechanisms involved in modulation of colitis. Experimental findings in a DSS-induced colitis mouse model revealed that L. gasseri ATCC33323 significantly improved physiological damage in colitic mice, reduced the severity of colonic inflammation, decreased the production of inflammatory factors, and preserved the integrity of the intestinal epithelial structure and function. It also maintained the expression and localization of adhesive proteins while improving intestinal barrier permeability and restoring dysbiosis in the gut microbiota. E-cadherin, a critical adhesive protein, plays a pivotal role in this protective mechanism. Knocking down E-cadherin expression within the mouse intestinal tract significantly attenuated the ability of L. gasseri ATCC33323 to regulate colitis, thus confirming its protective role through E-cadherin. Finally, transcriptional analysis and in vitro experiments revealed that L. gasseri ATCC33323 regulates CDH1 transcription by affecting NR1I3, thereby promoting E-cadherin expression. These findings contribute to a better understanding of the specific mechanisms by which Lactobacillus strains alleviate colitis, offering new insights for the potential use of L. gasseri as an alternative therapy for IBD, particularly in dietary supplementation.

Display of FliC131 on the Surface of Lactococcus lactis as a Strategy to Increase its Adjuvanticity for Mucosal Immunization

Research on innovative mucosal adjuvants is essential to develop new vaccines for safe mucosal application. In this work, we propose the development of a Lactococcus lactis that expresses a variant of flagellin on its surface (FliC131*), to increase the adjuvanticity of the living cell and cell wall-derived particles (CWDP). We optimized the expression of FliC131*, and confirmed its identity and localization by Western blot and flow cytometry. We also generated CWDP containing FliC131* (CDWP-FliC131*) and evaluated their storage stability. Lastly, we measured the human TLR5 stimulating activity in vitro and assessed the adjuvanticity in vivo using ovalbumin (OVA) as a model antigen. As a result, we generated L. lactis/pCWA-FliC131*, that expresses and displays FliC131* on its surface, obtained the corresponding CWDP-FliC131*, and showed that both activated hTLR5 in vitro in a dose-dependent manner. Furthermore, CWDP-FliC131* retained this biological activity after being lyophilized and stored for a year. Finally, intranasal immunization of mice with OVA plus live L. lactis/pCWA-FliC131* or CWDP-FliC131* induced OVA-specific IgG and IgA in serum, intestinal lavages, and bronchoalveolar lavages. Our work demonstrates the potential of this recombinant L. lactis with an enhanced adjuvant effect, prompting its further evaluation for the design of novel mucosal vaccines.

Host Functional Response to a Prototypic Orally Delivered Self-Replicating Vaccine Platform

The development of mucosal vaccines has been limited and could be aided by a systems vaccinology approach to identify platforms and adjuvant strategies that induce protective immune responses. The induction of local immune responses by mucosal-delivered vaccines has been difficult to evaluate from peripheral samples, as systemic responses often do not correlate with the mucosal response. Here, we utilized transcriptomics in combination with Gene Set Enrichment Analysis (GSEA) to assess innate immune activation by an oral probiotic Lactobacillus acidophilus-based vaccine platform in mice. The goal was to explore the earliest immune responses elicited after oral immunization at the Peyer's patch. Twenty-four hours after oral delivery of the L. acidophilus vaccine platform, we found an abundance of L. acidophilus at Peyer's patches and detected expression of the vaccine viral proteins and adjuvants, confirming in vivo vaccine delivery. Compared to mice orally dosed with buffer or wild-type L. acidophilus, we identified enhanced responses in immune pathways related to cytokine and gene signaling, T and B cell activation, phagocytosis, and humoral responses. While more work is needed to correlate these pathways with protection from infection and/or disease, they indicate this method's potential to evaluate and aid in the iterative development of next-generation mucosal vaccines.

Lactobacillus acidophilus Expressing Murine Rotavirus VP8 and Mucosal Adjuvants Induce Virus-Specific Immune Responses

Rotavirus diarrhea-associated illness remains a major cause of global death in children under five, attributable in part to discrepancies in vaccine performance between high- and low-middle-income countries. Next-generation probiotic vaccines could help bridge this efficacy gap. We developed a novel recombinant Lactobacillus acidophilus (rLA) vaccine expressing rotavirus antigens of the VP8* domain from the rotavirus EDIM VP4 capsid protein along with the adjuvants FimH and FliC. The upp-based counterselective gene-replacement system was used to chromosomally integrate FimH, VP8Pep (10 amino acid epitope), and VP8-1 (206 amino acid protein) into the L. acidophilus genome, with FliC expressed from a plasmid. VP8 antigen and adjuvant expression were confirmed by flow cytometry and Western blot. Rotavirus naïve adult BALB/cJ mice were orally immunized followed by murine rotavirus strain ECWT viral challenge. Antirotavirus serum IgG and antigen-specific antibody-secreting cell responses were detected in rLA-vaccinated mice. A day after the oral rotavirus challenge, fecal antigen shedding was significantly decreased in the rLA group. These results indicate that novel rLA constructs expressing VP8 can be successfully constructed and used to generate modest homotypic protection from rotavirus challenge in an adult murine model, indicating the potential for a probiotic next-generation vaccine construct against human rotavirus.

The Impacts of Acidophilic Lactic Acid Bacteria on Food and Human Health: A Review of the Current Knowledge

The need to improve the safety/quality of food and the health of the hosts has resulted in increasing worldwide interest in acidophilic lactic acid bacteria (LAB) for the food, livestock as well as health industries. In addition to the use of acidophilic LAB with probiotic potential for food fermentation and preservation, their application in the natural disposal of acidic wastes polluting the environment is also being investigated. Considering this new benefit that has been assigned to probiotic microorganisms in recent years, the acceleration in efforts to identify new, efficient, promising probiotic acidophilic LAB is not surprising. One of these effots is to determine both the beneficial and harmful compounds synthesized by acidophilic LAB. Moreover, microorganisms are of concern due to their possible hemolytic, DNase, gelatinase and mucinolytic activities, and the presence of virulence/antibiotic genes. Hence, it is argued that acidophilic LAB should be evaluated for these parameters before their use in the health/food/livestock industry. However, this issue has not yet been fully discussed in the literature. Thus, this review pays attention to the less-known aspects of acidophilic LAB and the compounds they release, clarifying critical unanswered questions, and discussing their health benefits and safety.

Expression of E. coli FimH Enhances Trafficking of an Orally Delivered Lactobacillus acidophilus Vaccine to Immune Inductive Sites via Antigen-Presenting Cells

The development of lactic acid bacteria as mucosal vaccine vectors requires the identification of robust mucosal adjuvants to increase vaccine effectiveness. The E. coli type I fimbriae adhesion protein FimH is of interest as a mucosal adjuvant as it targets microfold (M) cells enhancing vaccine uptake into Peyer's patches and can activate the innate immune system via Toll-like receptor (TLR) 4 binding. Here, we displayed the N-terminal domain of FimH on the surface of a Lactobacillus acidophilus vaccine vector and evaluated its ability to increase uptake of L. acidophilus into Peyer's patches and activate innate immune responses. FimH was robustly displayed on the L. acidophilus surface but did not increase uptake into the Peyer's patches. FimH did increase trafficking of L. acidophilus to mesenteric lymph nodes by antigen-presenting cells including macrophages and dendritic cells. It also increased transcription of retinaldehyde dehydrogenase and decreased transcription of IL-21 in the Peyer's patches and mesenteric lymph nodes. The N-terminal domain of FimH did not activate TLR4 in vitro, indicating that FimH may stimulate innate immune responses through a not-yet-identified mechanism. These results indicate that E. coli FimH alters the innate immune response to L. acidophilus and should be further studied as an adjuvant for lactic acid bacterial vaccine platforms.

Probiotic characteristics of Lactobacillus gasseri TF08-1: A cholesterol-lowering bacterium, isolated from human gut

Lactobacillus contribute to maintain the human healthy and use for nutritional additives as probiotics. In this study, a cholesterol-lowering bacterium, Lactobacillus gasseri TF08-1, was isolated from the feces of a healthy adolescent, and its probiotic potentials were evaluated through genomic mining and in vitro test. The assembled draft genome comprised of 1,974,590 bp and was predicted total of 1,940 CDSs. The annotation of the genome revealed that L. gasseri TF08-1 harbored abundant categories of functional genes in metabolic and information processing. Moreover, strain TF08-1 has capacity to utilize D-Glucose, Sucrose, D-Maltose, Salicin, D-Xylose, D-Cellobiose, D-Mannose, and D-Trehalose, as the carbon source. The safety assessment showed strain TF08-1 contained few antibiotic resistance genes and virulence factors and was only resistant to 2 antibiotics detected by antimicrobial susceptibility test. A high bile salt hydrolase activity was found and a cholesterol-reducing effect was determined in vitro, which the result showed a remarkable cholesterol removal capability of L. gasseri TF08-1 with an efficiency of 84.40 %. This study demonstrated that the strain showed great capability of exopolysaccharide production, and tolerance to acid and bile salt. Therefore, these results indicate that L. gasseri TF08-1 can be considered as a safe candidate for probiotic, especially its potential in biotherapeutic for metabolic diseases.

Enhancement of live vaccines by co-delivery of immune modulating proteins

Vaccines are very effective in providing protection against many infectious diseases. However, it has proven difficult to develop highly efficacious vaccines against some pathogens and so there is a continuing need to improve vaccine technologies. The first successful and widely used vaccines were based on attenuated pathogens (e.g., laboratory passaged Pasteurella multocida to vaccinate against fowl cholera) or closely related non-pathogenic organisms (e.g., cowpox to vaccinate against smallpox). Subsequently, live vaccines, either attenuated pathogens or non-pathogenic microorganisms modified to deliver heterologous antigens, have been successfully used to induce protective immune responses against many pathogens. Unlike conventional killed and subunit vaccines, live vaccines can deliver antigens to mucosal surfaces in a similar manner and context as the natural infection and hence can often produce a more appropriate and protective immune response. Despite these advantages, there is still a need to improve the immunogenicity of some live vaccines. The efficacy of injectable killed and subunit vaccines is usually enhanced using adjuvants such mineral salts, oils, and saponin, but such adjuvants cannot be used with live vaccines. Instead, live vaccines can be engineered to produce immunomodulatory molecules that can stimulate the immune system to induce more robust and long-lasting adaptive immune responses. This review focuses on research that has been undertaken to engineer live vaccines to produce immunomodulatory molecules that act as adjuvants to increase immunogenicity. Adjuvant strategies with varying mechanisms of action (inflammatory, antibody-mediated, cell-mediated) and delivery modes (oral, intramuscular, intranasal) have been investigated, with varying degrees of success. The goal of such research is to define adjuvant strategies that can be adapted to enhance live vaccine efficacy by triggering strong innate and adaptive immune responses and produce vaccines against a wider range of pathogens.

Dietary soya saponin improves the lipid metabolism and intestinal health of laying hens

Soya saponin (SS) is a natural active substance of leguminous plant, which could improve lipid metabolism and regulate immune function. Intestinal flora might play a key role in the biological functions of SS. The objective of this study was to measure the effects of dietary SS on immune function, lipid metabolism, and intestinal flora of laying hens with or without antibiotic treated. The experiment was designed as a factorial arrangement of 3 dietary SS treatments × 2 antibiotic treatments. Birds were fed a basal diet (CON) or a low-SS diet (50 SS) containing 50 mg/kg SS, or a high-SS diet (500 SS) containing 500 mg/kg SS. Birds were cofed with or without antibiotics. The growth experiment lasted for 10 wk. Results showed that birds fed the 50 mg/kg SS diet tended to have lower abdominal fat rate. The gene expression of liver X receptor-α (LxR-α) in liver and serum total cholesterol (TC) were dropped, and the gene expression of acyl-CoA thioesterase 8 (ACOT8) in liver were upregulated. Compared with CON group, the levels of lysozyme, IL-10, and transforming growth factor (TGF-β) in the serum were elevated as along with gene expression of IL-10, TGF-β, and LYZ in ileum of both 50 and 500 SS group. However, the level of secretory immunoglobulin A (sIgA) and Mucin-2 in the ileum were downregulated in the 500 SS group. Additionally, Lactobacillus and Lactobacillus gasseri were the dominant bacteria in the 50 SS group, whereas the relative abundance of Lactobacillus was dropped in the 500 SS group. With combined antibiotics treatment, the α-diversity of bacteria was reduced, and the biological effects of SS were eliminated. In conclusion, the lipid metabolism, immune function, and intestinal flora of the laying hens were improved with the dietary supplementation of 50 mg/kg SS. But dietary 500 mg/kg SS had negative effects on laying hens.

Identification of Bile Salt Hydrolase and Bile Salt Resistance in a Probiotic Bacterium Lactobacillus gasseri JCM1131T

Lactobacillus gasseri is one of the most likely probiotic candidates among many Lactobacillus species. Although bile salt resistance has been defined as an important criterion for selection of probiotic candidates since it allows probiotic bacteria to survive in the gut, both its capability and its related enzyme, bile salt hydrolase (BSH), in L. gasseri is still largely unknown. Here, we report that the well-known probiotic bacterium L. gasseri JCM1131^T possesses BSH activity and bile salt resistance capability. Indeed, this strain apparently showed BSH activity on the plate assay and highly tolerated the primary bile salts and even taurine-conjugated secondary bile salt. We further isolated a putative BSH enzyme (LagBSH) from strain JCM1131^T and characterized the enzymatic function. The purified LagBSH protein exhibited quite high deconjugation activity for taurocholic acid and taurochenodeoxycholic acid. The lagBSH gene was constitutively expressed in strain JCM1131^T, suggesting that LagBSH likely contributes to bile salt resistance of the strain and may be associated with survival capability of strain JCM1131^T within the human intestine by bile detoxification. Thus, this study first demonstrated the bile salt resistance and its responsible enzyme (BSH) activity in strain JCM1131^T, which further supports the importance of the typical lactic acid bacterium as probiotics.

Can Probiotics and Diet Promote Beneficial Immune Modulation and Purine Control in Coronavirus Infection?

Infection caused by the SARS-CoV-2 coronavirus worldwide has led the World Health Organization to declare a COVID-19 pandemic. Because there is no cure or treatment for this virus, it is emergingly urgent to find effective and validated methods to prevent and treat COVID-19 infection. In this context, alternatives related to nutritional therapy might help to control the infection. This narrative review proposes the importance and role of probiotics and diet as adjunct alternatives among the therapies available for the treatment of this new coronavirus. This review discusses the relationship between intestinal purine metabolism and the use of Lactobacillus gasseri and low-purine diets, particularly in individuals with hyperuricemia, as adjuvant nutritional therapies to improve the immune system and weaken viral replication, assisting in the treatment of COVID-19. These might be promising alternatives, in addition to many others that involve adequate intake of vitamins, minerals and bioactive compounds from food.

Impact of oral probiotic Lactobacillus acidophilus vaccine strains on the immune response and gut microbiome of mice

The potential role of probiotic bacteria as adjuvants in vaccine trials led to their use as nonparenteral live mucosal vaccine vectors. Yet, interactions between these vectors, the host and the microbiome are poorly understood. This study evaluates impact of three probiotic, Lactobacillus acidophilus, vector strains, and their interactions with the host's immune response, on the gut microbiome. One strain expressed the membrane proximal external region from HIV-1 (MPER). The other two expressed MPER and either secreted interleukin-1ß (IL-1ß) or expressed the surface flagellin subunit C (FliC) as adjuvants. We also used MPER with rice bran as prebiotic supplement. We observed a strain dependent, differential effect suggesting that MPER and IL-1β induced a shift of the microbiome while FliC had minimal impact. Joint probiotic and prebiotic use resulted in a compound effect, highlighting a potential synbiotic approach to impact efficacy of vaccination. Careful consideration of constitutive adjuvants and use of prebiotics is needed depending on whether or not to target microbiome modulation to improve vaccine efficacy. No clear associations were observed between total or MPER-specific IgA and the microbiome suggesting a role for other immune mechanisms or a need to focus on IgA-bound, resident microbiota, most affected by an immune response.

Formulation technologies for oral vaccines

Many options now exist for constructing oral vaccines which, in experimental systems, have shown themselves to be able to generate highly effective immunity against infectious diseases. Their suitability for implementation in clinical practice, however, for prevention of outbreaks, particularly in low- and middle-income countries (LMIC), is not always guaranteed, because of factors such as cost, logistics and cultural and environmental conditions. This brief overview provides a summary of the various approaches which can be adopted, and evaluates them from a pharmaceutical point, taking into account potential regulatory issues, expense, manufacturing complexity, etc., all of which can determine whether a vaccine approach will be successful in the late stages of development. Attention is also drawn to problems arising from inadequate diet, which impacts upon success in stimulating effective immunity, and identifies the use of lipid-based carriers as a way to counteract the problem of nutritional deficiencies in vaccination campaigns.

Adjuvant Strategies for Lactic Acid Bacterial Mucosal Vaccines

Lactic acid bacteria (LAB) are Gram-positive, acid-tolerant bacteria that have long been used in food fermentation and are generally recognized as safe (GRAS). LAB are a part of a normal microbiome and act as probiotics, improving the gastrointestinal microbiome and health when consumed. An increasing body of research has shown the importance of the microbiome on both mucosal immune heath and immune response to pathogens and oral vaccines. Currently, there are few approved mucosal vaccines, and most are attenuated viruses or bacteria, which necessitates cold chain, carries the risk of reversion to virulence, and can have limited efficacy in individuals with poor mucosal health. On account of these limitations, new types of mucosal vaccine vectors are necessary. There has been increasing interest and success in developing recombinant LAB as next generation mucosal vaccine vectors due to their natural acid and bile resistance, stability at room temperature, endogenous activation of innate and adaptive immune responses, and the development of molecular techniques that allow for manipulation of their genomes. To enhance the immunogenicity of these LAB vaccines, numerous adjuvant strategies have been successfully employed. Here, we review these adjuvant strategies and their mechanisms of action which include: Toll-like receptor ligands, secretion of bacterial toxins, secretion of cytokines, direct delivery to antigen presenting cells, and enterocyte targeting. The ability to increase the immune response to LAB vaccines gives them the potential to be powerful mucosal vaccine vectors against mucosal pathogens.

Vaccines against Trichinella spiralis: Progress, challenges and future prospects

Trichinella spiralis, the causative agent of trichinellosis, is able to infect a wide range of carnivores and omnivores including human beings. In the past 30 years, a mass of vaccination efforts has been performed to control T. spiralis infection with the purpose of reduction in worm fecundity or decrease in muscle larval and adult burdens. Here, we summarize the development of veterinary vaccines against T. spiralis infection. During recent years, increasing numbers of new vaccine candidates have been developed on the protective immunity against T. spiralis infection in murine model. The vaccine candidates were not only selected from excretory-secretory (ES) antigens, but also from the recombinant functional proteins, such as proteases and some other antigens participated in T. spiralis intracellular processes. However, immunization with a single antigen generally revealed lower protective effects against T. spiralis infection in mice compared to that with the inactivated whole worms or crude extraction and ES productions. Future study of T. spiralis vaccines should focus on evaluation of the protective efficacy of antigens and/or ligands delivered by nanoparticles that could elicit Th2-type immune response on experimental pigs.

Nod2 is required for antigen-specific humoral responses against antigens orally delivered using a recombinant Lactobacillus vaccine platform

Safe and efficacious orally-delivered mucosal vaccine platforms are desperately needed to combat the plethora of mucosally transmitted pathogens. Lactobacillus spp. have emerged as attractive candidates to meet this need and are known to activate the host innate immune response in a species- and strain-specific manner. For selected bacterial isolates and mutants, we investigated the role of key innate immune pathways required for induction of innate and subsequent adaptive immune responses. Co-culture of murine macrophages with L. gasseri (strain NCK1785), L. acidophilus (strain NCFM), or NCFM-derived mutants—NCK2025 and NCK2031—elicited an M2b-like phenotype associated with TH2 skewing and immune regulatory function. For NCFM, this M2b phenotype was dependent on expression of lipoteichoic acid and S layer proteins. Through the use of macrophage genetic knockouts, we identified Toll-like receptor 2 (TLR2), the cytosolic nucleotide-binding oligomerization domain containing 2 (NOD2) receptor, and the inflammasome-associated caspase-1 as contributors to macrophage activation, with NOD2 cooperating with caspase-1 to induce inflammasome derived interleukin (IL)-1β in a pyroptosis-independent fashion. Finally, utilizing an NCFM-based mucosal vaccine platform with surface expression of human immunodeficiency virus type 1 (HIV-1) Gag or membrane proximal external region (MPER), we demonstrated that NOD2 signaling is required for antigen-specific mucosal and systemic humoral responses. We show that lactobacilli differentially utilize innate immune pathways and highlight NOD2 as a key mediator of macrophage function and antigen-specific humoral responses to a Lactobacillus acidophilus mucosal vaccine platform.

Enhancement of IFNγ Production by Distinct Commensals Ameliorates Salmonella-Induced Disease

The microbiota contributes to colonization resistance against invading pathogens by competing for metabolites, producing inhibitory substances, and priming protective immune responses. However, the specific commensal bacteria that promote host resistance and immune-mediated protection remain largely elusive. Using isogenic mouse lines with distinct microbiota profiles, we demonstrate that severity of disease induced by enteric Salmonella Typhimurium infection is strongly modulated by microbiota composition in individual lines. Transferring a restricted community of cultivable intestinal commensals from protected into susceptible mice decreases S. Typhimurium tissue colonization and consequently disease severity. This reduced tissue colonization, along with ameliorated weight loss and prolonged survival, depends on microbiota-enhanced IFNγ production, as IFNγ-deficient mice do not exhibit protective effects. Innate cells and CD4⁺ T cells increase in number and show high levels of IFNγ after transfer of the commensal community. Thus, distinct microbiota members prevent intestinal Salmonella infection by enhancing antibacterial IFNγ responses.

Adjuvant Probiotics and the Intestinal Microbiome: Enhancing Vaccines and Immunotherapy Outcomes

Immune defence against pathogenic agents comprises the basic premise for the administration of vaccines. Vaccinations have hence prevented millions of infectious illnesses, hospitalizations and mortality. Acquired immunity comprises antibody and cell mediated responses and is characterized by its specificity and memory. Along a similar congruent yet diverse mode of disease prevention, the human host has negotiated from in utero and at birth with the intestinal commensal bacterial cohort to maintain local homeostasis in order to achieve immunological tolerance in the new born. The advent of the Human Microbiome Project has redefined an appreciation of the interactions between the host and bacteria in the intestines from one of a collection of toxic waste to one of a symbiotic existence. Probiotics comprise bacterial genera thought to provide a health benefit to the host. The intestinal microbiota has profound effects on local and extra-intestinal end organ physiology. As such, we further posit that the adjuvant administration of dedicated probiotic formulations can encourage the intestinal commensal cohort to beneficially participate in the intestinal microbiome-intestinal epithelia-innate-cell mediated immunity axes and cell mediated cellular immunity with vaccines aimed at preventing infectious diseases whilst conserving immunological tolerance. The strength of evidence for the positive effect of probiotic administration on acquired immune responses has come from various studies with viral and bacterial vaccines. We posit that the introduction early of probiotics may provide significant beneficial immune outcomes in neonates prior to commencing a vaccination schedule or in elderly adults prior to the administration of vaccinations against influenza viruses.

Live Faecalibacterium prausnitzii induces greater TLR2 and TLR2/6 activation than the dead bacterium in an apical anaerobic co-culture system

Inappropriate activation of intestinal innate immune receptors, such as toll-like receptors (TLRs), by pathogenic bacteria is linked to chronic inflammation. In contrast, a "tonic" level of TLR activation by commensal bacteria is required for intestinal homeostasis. A technical challenge when studying this activation in vitro is the co-culturing of oxygen-requiring mammalian cells with obligate anaerobic commensal bacteria. To overcome this, we used a novel apical anaerobic co-culture system to successfully adapt a TLR activation assay to be conducted in conditions optimised for both cell types. Live Faecalibacterium prausnitzii, an abundant obligate anaerobe of the colonic microbiota, induced higher TLR2 and TLR2/6 activation than the dead bacterium. This enhanced TLR induction by live F. prausnitzii, which until now has not previously been described, may contribute to maintenance of gastrointestinal homeostasis. This highlights the importance of using physiologically relevant co-culture systems to decipher the mechanisms of action of live obligate anaerobes.

Effects of deoxynivalenol- and zearalenone-contaminated feed on the gene expression profiles in the kidneys of piglets

Objective

Fusarium mycotoxins deoxynivalenol (DON) and zearalenone (ZEN), common contaminants in the feed of farm animals, cause immune function impairment and organ inflammation. Consequently, the main objective of this study was to elucidate DON and ZEN effects on the mRNA expression of pro-inflammatory cytokines and other immune related genes in the kidneys of piglets.

Methods

Fifteen 6-week-old piglets were randomly assigned to three dietary treatments for 4 weeks: control diet, and diets contaminated with either 8 mg DON/kg feed or 0.8 mg ZEN/kg feed. Kidney samples were collected after treatment, and RNA-seq was used to investigate the effects on immune-related genes and gene networks.

Results

A total of 186 differentially expressed genes (DEGs) were screened (120 upregulated and 66 downregulated). Gene ontology analysis revealed that the immune response, and cellular and metabolic processes were significantly controlled by these DEGs. The inflammatory stimulation might be an effect of the following enriched Kyoto encyclopedia of genes and genomes pathway analysis found related to immune and disease responses: cytokine-cytokine receptor interaction, chemokine signaling pathway, toll-like receptor signaling pathway, systemic lupus erythematosus (SLE), tuberculosis, Epstein-Barr virus infection, and chemical carcinogenesis. The effects of DON and ZEN on genome-wide expression were assessed, and it was found that the DEGs associated with inflammatory cytokines (interleukin 10 receptor, beta, chemokine [C-X-C motif] ligand 9, CXCL10, chemokine [C-C motif] ligand 4), proliferation (insulin like growth factor binding protein 4, IgG heavy chain, receptor-type tyrosine-protein phosphatase C, cytochrome P450 1A1, ATP-binding cassette sub-family 8), and other immune response networks (lysozyme, complement component 4 binding protein alpha, oligoadenylate synthetase 2, signaling lymphocytic activation molecule-9, α-aminoadipic semialdehyde dehydrogenase, Ig lambda chain c region, pyruvate dehydrogenase kinase, isozyme 4, carboxylesterase 1), were suppressed by DON and ZEN.

Conclusion

In summary, our results indicate that high concentrations of DON and ZEN suppress the inflammatory response in kidneys, leading to potential effects on immune homeostasis.

Deoxynivalenol- and zearalenone-contaminated feeds alter gene expression profiles in the livers of piglets

Objective

The Fusarium mycotoxins of deoxynivalenol (DON) and zerolenone (ZEN) cause health hazards for both humans and farm animals. Therefore, the main intention of this study was to reveal DON and ZEN effects on the mRNA expression of pro-inflammatory cytokines and other immune related genes in the liver of piglets.

Methods

In the present study, 15 six-week-old piglets were randomly assigned to the following three different dietary treatments for 4 weeks: control diet, diet containing 8 mg DON/kg feed, and diet containing 0.8 mg ZEN/kg feed. After 4 weeks, liver samples were collected and sequenced using RNA-Seq to investigate the effects of the mycotoxins on genes and gene networks associated with the immune systems of the piglets.

Results

Our analysis identified a total of 249 differentially expressed genes (DEGs), which included 99 upregulated and 150 downregulated genes in both the DON and ZEN dietary treatment groups. After biological pathway analysis, the DEGs were determined to be significantly enriched in gene ontology terms associated with many biological pathways, including immune response and cellular and metabolic processes. Consistent with inflammatory stimulation due to the mycotoxin-contaminated diet, the following Kyoto encyclopedia of genes and genomes pathways, which were related to disease and immune responses, were found to be enriched in the DEGs: allograft rejection pathway, cell adhesion molecules, graft-versus-host disease, autoimmune thyroid disease (AITD), type I diabetes mellitus, human T-cell leukemia lymphoma virus infection, and viral carcinogenesis. Genome-wide expression analysis revealed that DON and ZEN treatments downregulated the expression of the majority of the DEGs that were associated with inflammatory cytokines (interleukin 10 receptor, beta, chemokine [C-X-C motif] ligand 9), proliferation (insulin-like growth factor 1, major facilitator superfamily domain containing 2A, insulin-like growth factor binding protein 2, lipase G, and salt inducible kinase 1), and other immune response networks (paired immunoglobulin-like type 2 receptor beta, Src-like-adaptor-1 [SLA1], SLA3, SLA5, SLA7, claudin 4, nicotinamide N-methyltransferase, thyrotropin-releasing hormone degrading enzyme, ubiquitin D, histone H₂B type 1, and serum amyloid A).

Conclusion

In summary, our results demonstrated that high concentrations DON and ZEN disrupt immune-related processes in the liver.

Impact of Exopolysaccharides (EPSs) of Lactobacillus gasseri strains isolated from human vagina on cervical tumor cells (HeLa)

Lactobacilli, commonly used as probiotics, have been shown to maintain vaginal health and contribute to host microbiota interaction. Exopolysaccharides (EPSs) produced by lactobacillus have been found to have an important role in probiotic activity; however, there is limited knowledge concerning their impact on cervical cancer and urogenital health. The objective of this study is to investigate and compare EPSs of L. gasseri strains (G10 and H15), isolated from a healthy human vagina, for their capability to inhibit cervical cancer cell (HeLa) growth and modulate immune response. HeLa cells were treated with live culture at ∼10⁸ CFU/ml or increasing concentration of lyophilized EPS (L-EPS) (100, 200, or 400 μg/ml) of L. gasseri strains and their ability to adhere to host cells, inhibit proliferation, and modulate immune response were evaluated. Additionally, monosaccharide composition of the L-EPSs produced by L. gasseri strains was determined by HPLC. The sugar component was the same; however, relative proportions of the individual monosaccharides except mannose were different. Although they both produce similar amount of EPS, the most adhesive strain was G10. Both live and L-EPS of L. gasseri strains were capable of inhibiting the cell proliferation of HeLa cells with the impact of L-EPS being strain specific. L-EPSs of L. gasseri strains induced apoptosis in HeLa cells in a strain dependent manner. The ability to induce apoptosis by G10 associated with an upregulation of Bax and Caspase 3. L. gasseri strains showed an anti-inflammatory impact on HeLa cells by decreasing the production of TNF-α and increasing the IL-10 production. In conclusion, diversity in sugar composition of EPS might contribute to adhesion and proliferation properties. Although our results suggest a relationship between the ability of a strain to induce apoptosis and its sugar composition of EPS, further research is required to determine the probiotic mechanisms of action by which L. gasseri strains result in strain specific anti-proliferative activity.

Oral administration of recombinant Mycobacterium smegmatis expressing a tripeptide construct derived from endogenous and microbial antigens prevents atherosclerosis in ApoE(-/-) mice

INTRODUCTION

Immunotherapy by inducing oral tolerance to atherogenic self-antigens is gaining importance as an alternative treatment modality for atherosclerosis. The use of live bacterial vectors to express the recombinant antigen in vivo will obviate the need for large-scale purification of recombinant protein and may also augment the efficacy of oral tolerance induction.

AIM

The objective of the study was to explore the use of recombinant Mycobacterium smegmatis as a live vector for oral delivery of antigens to induce immune tolerance.

METHOD AND RESULTS

We developed a M. smegmatis vector to secrete a recombinant tripeptide construct (AHC; peptides from Apolipoprotein B, Heat-shock protein 60 and Chlamydia pneumoniae outer membrane protein) expressed in a dendroaspin protein scaffold in pJH154 background. Immune response and oral tolerance to the cloned peptides were studied in C57/BL6 mice. The efficacy of this live vaccine to control atherosclerosis was studied in ApoE(-/-) knockout mice in C57/BL6 background. Oral administration of M. smegmatis secreting the cloned AHC antigen was found to induce tolerance to cloned protein and reduce the development of atherosclerosis by 24.0% compared to control. Protection against atherosclerosis was associated with increase in expression of regulatory T cell-associated markers including CTLA4 (1.8-fold), Foxp3 (2.6-fold), TGF-β (2.8-fold), IL10 (2.9-fold), and reduction in lipids, macrophage infiltration, and expression of inflammatory mediators in aorta.

CONCLUSIONS

Our results suggest that M. smegmatis can be developed as an oral carrier of recombinant proteins to treat inflammatory autoimmune diseases.

Recombinant lactic acid bacteria as delivery vectors of heterologous antigens: the future of vaccination?

Lactic acid bacteria (LABs) are good candidates for the development of new oral vaccines and are attractive alternatives to attenuated pathogens. This review focuses on the use of wild-type and recombinant lactococci and lactobacilli with emphasis on their molecular design, immunomodulation and treatment of bacterial infections. The majority of studies related to recombinant LABs have focused on Lactococcus lactis, however, molecular tools have been successfully used for Lactobacillus spp.

RESEARCH

Recombinant lactobacilli and lactococci have several health benefits, such as immunomodulation, restoration of the microbiota, synthesis of antimicrobial substances and inhibition of virulence factors. In addition, protective immune responses that are well tolerated are induced by the expression of heterologous antigens from recombinant probiotics.

Construction and characterization of three protein-targeting expression system in Lactobacillus casei

We previously reported that the β-1,4-Mannanase (manB) gene from Bacillus pumilus functions as a good reporter gene in Lactobacillus casei. Two vectors were constructed. One carries the signal peptide of secretion protein Usp45 (SPUsp45) from Lactococcus lactis (pELSH), and the other carries the full-length S-layer protein, SlpA, from L. acidophilus (pELWH). In this work, another vector, pELSPH, was constructed to include the signal peptide of protein SlpA (SPSlpA), and the capacity of all three vectors to drive expression of the manB gene in L. casei was evaluated. The results showed that SPUsp45 is functionally recognized and processed by the L. casei secretion machinery. The SPUsp45-mediated secretion efficiency was ∼87%, and SPSlpA drove the export of secreted ManB with ∼80% efficiency. SPSlpA secretion was highly efficient, and expressed SlpA was anchored to the cell wall by an unknown secretion mechanism. Full-length SlpA drove the cell wall-anchored expression of an SlpA-ManB fusion protein but at a much lower level than that of protein SlpA.

Heterologous Expression of Mannanase and Developing a New Reporter Gene System in Lactobacillus casei and Escherichia coli

Reporter gene systems are useful for studying bacterial molecular biology, including the regulation of gene expression and the histochemical analysis of protein products. Here, two genes, β-1,4-mannanase (manB) from Bacillus pumilus and β-glucuronidase (gusA) from Escherichia coli K12, were cloned into the expression vector pELX1. The expression patterns of these reporter genes in Lactobacillus casei were investigated by measuring their enzymatic activities and estimating their recombinant protein yields using western blot analysis. Whereas mannanase activity was positively correlated with the accumulation of ManB during growth, GusA activity was not; western blot analysis indicated that while the amount of GusA protein increased during later growth stages, GusA activity gradually decreased, indicating that the enzyme was inactive during cell growth. A similar trend was observed in E. coli JM109. We chose to use the more stable mannanase gene as the reporter to test secretion expression in L. casei. Two pELX1-based secretion vectors were constructed: one carried the signal peptide of the unknown secretion protein Usp45 from Lactococcus lactis (pELSH), and the other contained the full-length SlpA protein from the S-layer of L. acidophilus (pELWH). The secretion of ManB was detected in the supernatant of the pELSH-ManB transformants and in the S-layer of the cell surface of the pELWH-ManB transformants. This is the first report demonstrating that the B. pumilus manB gene is a useful reporter gene in L. casei and E.coli.

Mucosal Immunogenicity of Genetically Modified Lactobacillus acidophilus Expressing an HIV-1 Epitope within the Surface Layer Protein

Surface layer proteins of probiotic lactobacilli are theoretically efficient epitope-displaying scaffolds for oral vaccine delivery due to their high expression levels and surface localization. In this study, we constructed genetically modified Lactobacillus acidophilus strains expressing the membrane proximal external region (MPER) from human immunodeficiency virus type 1 (HIV-1) within the context of the major S-layer protein, SlpA. Intragastric immunization of mice with the recombinants induced MPER-specific and S-layer protein-specific antibodies in serum and mucosal secretions. Moreover, analysis of systemic SlpA-specific cytokines revealed that the responses appeared to be Th1 and Th17 dominant. These findings demonstrated the potential use of the Lactobacillus S-layer protein for development of oral vaccines targeting specific peptides.

Mucosally administered Lactobacillus surface-displayed influenza antigens (sM2 and HA2) with cholera toxin subunit A1 (CTA1) Induce broadly protective immune responses against divergent influenza subtypes

The development of a universal influenza vaccine that provides broad cross protection against existing and unforeseen influenza viruses is a critical challenge. In this study, we constructed and expressed conserved sM2 and HA2 influenza antigens with cholera toxin subunit A1 (CTA1) on the surface of Lactobacillus casei (pgsA-CTA1sM2HA2/L. casei). Oral and nasal administrations of recombinant L. casei into mice resulted in high levels of serum immunoglobulin G (IgG) and their isotypes (IgG1 & IgG2a) as well as mucosal IgA. The mucosal administration of pgsA-CTA1sM2HA2/L. casei may also significantly increase the levels of sM2- or HA2-specific cell-mediated immunity because increased release of both IFN-γ and IL-4 was observed. The recombinant pgsA-CTA1sM2HA2/L. casei provided better protection of BALB/c mice against 10 times the 50% mouse lethal doses (MLD50) of homologous A/EM/Korea/W149/06(H5N1) or A/Aquatic bird/Korea/W81/2005 (H5N2) and heterologous A/Puerto Rico/8/34(H1N1), or A/Chicken/Korea/116/2004(H9N2) or A/Philippines/2/08(H3N2) viruses, compared with L. casei harboring sM2HA2 and also the protection was maintained up to seven months after administration. These results indicate that recombinant L. casei expressing the highly conserved sM2, HA2 of influenza and CTA1 as a mucosal adjuvant could be a potential mucosal vaccine candidate or tool to protect against divergent influenza viruses for human and animal.

Zearalenone mycotoxin affects immune mediators, MAPK signalling molecules, nuclear receptors and genome-wide gene expression in pig spleen

The toxicity of zearalenone (ZEA) was evaluated in swine spleen, a key organ for the innate and adaptative immune response. Weaned pigs were fed for 18 days with a control or a ZEA contaminated diet. The effect of ZEA was assessed on wide genome expression, pro- (TNF-α, IL-8, IL-6, IL-1β, IFN-γ) and anti-inflammatory (IL-10, IL-4) cytokines, other molecules involved in inflammatory processes (MMPs/TIMPs), as well as signaling molecules, (p38/JNK1/JNK2-MAPKs) and nuclear receptors (PPARγ/NFkB/AP-1/STAT3/c-JUN). Microarray analysis showed that 46% of total number of differentially expressed genes was involved in cellular signaling pathway, 13% in cytokine network and 10% in the inflammatory response. ZEA increased expression and synthesis of pro- inflammatory (TNF-α, IL-8, IL-6, IL-1β) and had no effect on IFN-γ, IL-4 and IL-10 cytokines in spleen. The inflammatory stimulation might be a consequence of JNK pathway activation rather than of p-38MAPK and NF-kB involvement whose gene and protein expression were suppressed by ZEA action. In summary, our findings indicated the role of ZEA as an immune disruptor at spleen level.

Lactic acid bacteria--20 years exploring their potential as live vectors for mucosal vaccination

Lactic acid bacteria (LAB) are a diverse group of Gram-positive, nonsporulating, low G + C content bacteria. Many of them have been given generally regarded as safe status. Over the past two decades, intensive genetic and molecular research carried out on LAB, mainly Lactococcus lactis and some species of the Lactobacillus genus, has revealed new, potential biomedical LAB applications, including the use of LAB as adjuvants, immunostimulators, or therapeutic drug delivery systems, or as factories to produce therapeutic molecules. LAB enable immunization via the mucosal route, which increases effectiveness against pathogens that use the mucosa as the major route of entry into the human body. In this review, we concentrate on the encouraging application of Lactococcus and Lactobacillus genera for the development of live mucosal vaccines. First, we present the progress that has recently been made in the field of developing tools for LAB genetic manipulations, which has resulted in the successful expression of many bacterial, parasitic, and viral antigens in LAB strains. Next, we discuss the factors influencing the efficacy of the constructed vaccine prototypes that have been tested in various animal models. Apart from the research focused on an application of live LABs as carriers of foreign antigens, a lot of work has been recently done on the potential usage of nonliving, nonrecombinant L. lactis designated as Gram-positive enhancer matrix (GEM), as a delivery system for mucosal vaccination. The advantages and disadvantages of both strategies are also presented.

Induction of pro-inflammatory gene expression by Escherichia coli and mycotoxin zearalenone contamination and protection by a Lactobacillus mixture in porcine IPEC-1 cells

This work investigated the effect of Escherichia coli K88 and zearalenone contamination on pro-inflammatory gene expression (Toll like receptors, cytokines) and signalling molecules and the protective activity of a mixture of Lactobacilli sp. (Lactobacillus plantarum, Lactobacillus acidofilus and Lactobacillus paracasei) in porcine intestinal epithelial cells as part of the local immune system. IPEC-1 cell monolayer was exposed for 1 h to the individual or combined action of E. coli, zearalenone and lactobacilli mixture. Our results showed that TLRs (1-10) and cytokine (IL-1,-6,-8,-10, TNF-α, IFN-γ) genes expressed early (after 1 h of culture) in IPEC-1 cells. E. coli alone increased the TLRs mRNA expression, especially TLR4 and the inflammatory cytokines while ZEA alone showed either no effect or a marginally effect on TLRs, cytokines, and signalling genes when compared to untreated cells. The combined actions of the two contaminants lead to a synergistically up-regulation of key cytokines (IFN-γ, IL-10 and TNF-α) and TLRs (-2,-3,-4,-6, and -10). The live lactobacilli mixture was able to attenuate the pathogen and mycotoxin-induced response by downregulated the majority of inflammatory related genes suggesting that this mixture has an immunomodulatory potential and may be used to lower the inflammatory response.

Purified cell wall from the probiotic bacterium Lactobacillus gasseri activates systemic inflammation and, at higher doses, produces lethality in a rat model

Introduction

One proposed benefit of probiotic therapy is that probiotic bacterial cell-wall binding to intestinal cell pathogen-recognition receptors activates protective innate immunity. However, in critically ill patients, intestinal epithelium disruption by shock or other insults may compromise this compartmentalized response and cause systemic bacteria and cell-wall translocation. The effects of intravascular introduction of probiotic bacterial cell wall are unclear.

Methods

We investigated 24-hour infusions of purified cell wall from Lactobacillus gasseri ATC33323 (L. gasseri), a probiotic bacterium, in Sprague–Dawley rats (n = 49).

Results

Increasing cell-wall doses (0 (control), 10, 20, 40, 80, or 160 mg/kg over 24 hours) produced dose-ordered decreases in survival measured after 168 hours (11 survivors/11 total (100%), seven of seven (100%), seven of seven (100%), six of eight (75%), five of eight (63%), and one of nine (11%), respectively, P < 0.0001). The L. gasseri cell wall was equally or more lethal than Staphylococcus aureus cell wall, which was previously studied (100% to 88% survival with the same increasing doses). During challenge, compared with controls, L. gasseri cell wall produced increases in blood IL-1β, IL-10, tumor necrosis factor-α, migratory inhibitory protein-1α, monocyte chemotactic protein-1, and nitric oxide, and decreases in neutrophils, lymphocytes, and platelets that were greater with higher versus lower doses (P ≤ 0.05). Medium-dose cell wall (40 and 80 mg/kg combined) progressively decreased blood pressure and increased heart rate, and all doses increased lactate, hepatic transaminases, and creatinine phosphokinase (P ≤ 0.05).

Conclusion

Although L. gasseri, like other probiotic bacteria, is considered safe, its cell wall can stimulate the maladaptive inflammatory response associated with pathogenic bacteria. Such effects deserve study, especially regarding critically ill patients.

Impact of genomics on the field of probiotic research: historical perspectives to modern paradigms

For thousands of years, humans have safely consumed microorganisms through fermented foods. Many of these bacteria are considered probiotics, which act through diverse mechanisms to confer a health benefit to the host. However, it was not until the availability of whole-genome sequencing and the era of genomics that mechanisms of probiotic efficacy could be discovered. In this review, we explore the history of the probiotic concept and the current standard of integrated genomic techniques to discern the complex, beneficial relationships between probiotic microbes and their hosts.

Development of an integration mutagenesis system in Lactobacillus gasseri

Lactobacillus gasseri ATCC 33323 is a member of the acidophilus-complex group, microbes of human origin with significant potential for impacting human health based on niche-specific traits. In order to facilitate functional analysis of this important species, a upp-based counterselective chromosomal integration system was established and employed for targeting the lipoteichoic acid (LTA) synthesis gene, ltaS, in L. gasseri ATCC 33323. The ltaS gene encodes a phosphoglycerol transferase responsible for building the glycerol chain of LTA. No isogenic mutant bearing the deletion genotype was recovered, but an integration knockout mutant was generated with insertion inactivation at the ltaS locus. The ltaS deficient derivative exhibited an altered cellular morphology and significantly reduced ability to adhere to Caco-2 intestinal cell monolayers, relative to the wild-type parent strain.

Characterization of pMC11, a plasmid with dual origins of replication isolated from Lactobacillus casei MCJ and construction of shuttle vectors with each replicon

Many lactic acid bacteria carry different plasmids, particularly those that replicate via a theta mechanism. Here we describe Lactobacillus casei MCJ(CCTCC AB20130356), a new isolate that contains pMC11, carrying two distinct theta-type replicons. Each replicon contained an iteron in the origin of replication (oriV1 or oriV2) and a gene coding for the replicase (RepA_1 or RepB_1), both of which are essential for plasmid replication. Escherichia coli/Lactobacillus shuttle vectors were constructed with each replicon, yielding pEL5.7 and pEL5.6 that are based on oriV2 and oriV1 replicons, respectively. These plasmids showed distinct properties: pEL5.7 was capable of replicating in L. casei MCJΔ1 and Lactobacillus delbrueckii subsp. lactic LBCH-1 but failed to do so in two other tested lactobacilli strains whereas pEL5.6 replicated in three different strains, including L. casei MCJΔ1, L. casei NJ, Lactobacillus paracasei LPC-37 and L. delbrueckii subsp. lactic LBCH-1. Plasmid stability was studied: pEL5.6 and pEL5.7 were very stably maintained in L. casei, as the loss rate was lower than 1 % per generation. pEL5.7 was also stable in L. delbrueckii subsp. lactic LBCH-1 with the loss rate estimated to be 3 %. These vectors were employed to express a green fluorescent protein (GFP) using the promoter of S-layer protein SlpA from Lactobacillus acidophilus. And a growth-phase regulated expression of GFP was observed in different strains. In conclusion, these shuttle vectors provide efficient genetic tools for DNA cloning and heterologous gene expression in lactobacilli.

Heterologous protein secretion in Lactobacilli with modified pSIP vectors

We describe new variants of the modular pSIP-vectors for inducible gene expression and protein secretion in lactobacilli. The basic functionality of the pSIP system was tested in Lactobacillus strains representing 14 species using pSIP411, which harbors the broad-host-range Lactococcus lactis SH71rep replicon and a β-glucuronidase encoding reporter gene. In 10 species, the inducible gene expression system was functional. Based on these results, three pSIP vectors with different signal peptides were modified by replacing their narrow-host-range L. plantarum 256rep replicon with SH71rep and transformed into strains of five different species of Lactobacillus. All recombinant strains secreted the target protein NucA, albeit with varying production levels and secretion efficiencies. The Lp_3050 derived signal peptide generally resulted in the highest levels of secreted NucA. These modified pSIP vectors are useful tools for engineering a wide variety of Lactobacillus species.

Differential modulation of innate immunity in vitro by probiotic strains of Lactobacillus gasseri

Background

Probiotics species appear to differentially regulate the intestinal immune response. Moreover, we have shown that different immune-modulatory abilities can be found among probiotic strains belonging to the same species. In this study, we further addressed this issue while studying L. gasseri, a species that induces relevant immune activities in human patients.

Results

We determined the ability of two strains of L. gasseri, OLL2809 and L13-Ia, to alter cell surface antigen expression, cytokine production and nuclear erythroid 2-related factor 2 (Nrf2)-mediated cytoprotection in murine bone marrow-derived dendritic cells (DCs) and MODE-K cells, which represent an enterocyte model. Differential effects of L. gasseri strains were observed on the expression of surface markers in mature DCs; nevertheless, both strains dramatically induced production of IL-12, TNF-α and IL-10. Distinctive responses to OLL2809 and L13-Ia were also shown in MODE-K cells by analyzing the expression of MHC II molecules and the secretion of IL-6; however, both L. gasseri strains raised intracellular glutathione. Treatment of immature DCs with culture medium from MODE-K monolayers improved cytoprotection and modified the process of DC maturation by down-regulating the expression of co-stimulatory markers and by altering the cytokine profile. Notably, bacteria-conditioned MODE-K cell medium suppressed the expression of the examined cytokines, whereas cytoprotective defenses were significantly enhanced only in DCs exposed to OLL2809-conditioned medium. These effects were essentially mediated by secreted bacterial metabolites.

Conclusions

We have demonstrated that L. gasseri strains possess distinctive abilities to modulate in vitro DCs and enterocytes. In particular, our results highlight the potential of metabolites secreted by L. gasseri to influence enterocyte-DC crosstalk. Regulation of cellular mechanisms of innate immunity by selected probiotic strains may contribute to the beneficial effects of these bacteria in gut homeostasis.

Identification of extracellular surface-layer associated proteins in Lactobacillus acidophilus NCFM

Bacterial surface (S-) layers are crystalline arrays of self-assembling, proteinaceous subunits called S-layer proteins (Slps), with molecular masses ranging from 40 to 200 kDa. The S-layer-forming bacterium Lactobacillus acidophilus NCFM expresses three major Slps: SlpA (46 kDa), SlpB (47 kDa) and SlpX (51 kDa). SlpA has a demonstrated role in adhesion to Caco-2 intestinal epithelial cells in vitro, and has been shown to modulate dendritic cell (DC) and T-cell functionalities with murine DCs. In this study, a modification of a standard lithium chloride S-layer extraction revealed 37 proteins were solubilized from the S-layer wash fraction. Of these, 30 have predicted cleavage sites for secretion, 24 are predicted to be extracellular, six are lipid-anchored, three have N-terminal hydrophobic membrane spanning regions and four are intracellular, potentially moonlighting proteins. Some of these proteins, designated S-layer associated proteins (SLAPs), may be loosely associated with or embedded within the bacterial S-layer complex. Lba-1029, a putative SLAP gene, was deleted from the chromosome of L. acidophilus. Phenotypic characterization of the deletion mutant demonstrated that the SLAP LBA1029 contributes to a pro-inflammatory TNF-α response from murine DCs. This study identified extracellular proteins and putative SLAPs of L. acidophilus NCFM using LC-MS/MS. SLAPs appear to impart important surface display features and immunological properties to microbes that are coated by S-layers.

Modulation of vaccine response by concomitant probiotic administration

Evidence suggests that probiotic bacteria modulate both innate and adaptive immunity in the host, and in some situations can result in reduced severity of common illnesses, such as acute rotavirus infection and respiratory infections. Responses to vaccination are increasingly being used to provide high quality information on the immunomodulatory effects of dietary components in humans. The present review focuses on the effect of probiotic administration upon vaccination response. The majority of studies investigating the impact of probiotics on responses to vaccination have been conducted in healthy adults, and at best they show modest effects of probiotics on serum or salivary IgA titres. Studies in infants and in elderly subjects are very limited, and it is too early to draw any firm conclusions regarding the potential for probiotics to act as adjuvants in vaccination. Although some studies are comparable in terms of duration of the intervention, age and characteristics of the subjects, most differ in terms of the probiotic selected. Further well designed, randomized, placebo-controlled studies are needed to understand fully the immunomodulatory properties of probiotics, whether the effects exerted are strain-dependent and age-dependent and their clinical relevance in enhancing immune protection following vaccination.

Genomic and phenotypic evidence for probiotic influences of Lactobacillus gasseri on human health

Certain lactic acid bacteria (LAB) have the capacity to occupy mucosal niches of humans, including the oral cavity, gastrointestinal tract, and vagina. Among commensal, LAB are species of the acidophilus complex, which have proven to be a substantial reservoir for microorganisms with probiotic attributes. Specifically, Lactobacillus gasseri is an autochthonous microorganism which has been evaluated for probiotic activity based on the availability of genome sequence and species-specific adaptation to the human mucosa. Niche-related characteristics of L. gasseri contributing to indigenous colonization include tolerance of low pH environments, resistance to bile salts, and adhesion to the host epithelium. In humans, L. gasseri elicits various health benefits through its antimicrobial activity, bacteriocin production, and immunomodulation of the innate and adaptive systems. The genomic and empirical evidence supporting use of L. gasseri in probiotic applications is substantiated by clinical trial data displaying maintenance of vaginal homeostasis, mitigation of Helicobacter pylori infection, and amelioration of diarrhea.

Mucosal Lactobacillus vectored vaccines

Traditional non-gastrointestinal vaccines can prevent effectively the invasion of pathogens; however, these vaccines are less effective against mucosal infections because there is not a sufficient immune response at the mucosa. Most pathogens invade via a mucosal pathway (oral, intranasal, or vaginal). It is widely accepted that Lactobacillus species play a critical role as commensals in the gastrointestinal (GI) tract. Their ability to survive in the digestive tract, their close association with the intestinal epithelium, their immunomodulatory properties and their safety even when consumed in large amounts make lactobacilli attractive candidates for live vehicles for the delivery of immunogens to the intestinal mucosa. The oral or intranasal administration of Lactobacillus-based vaccines is a promising method to control mucosal infection because these vaccines could induce strong humoral and cellular immune responses both in the blood and at mucosal sites.

Recombinant influenza vaccines

This review covers the problems encountered in the construction and production of new recombinant influenza vaccines. New approaches to the development of influenza vaccines are investigated; they include reverse genetics methods, production of virus-like particles, and DNA- and viral vector-based vaccines. Such approaches as the delivery of foreign genes by DNA- and viral vector-based vaccines can preserve the native structure of antigens. Adenoviral vectors are a promising gene-delivery platform for a variety of genetic vaccines. Adenoviruses can efficiently penetrate the human organism through mucosal epithelium, thus providing long-term antigen persistence and induction of the innate immune response. This review provides an overview of the practicability of the production of new recombinant influenza cross-protective vaccines on the basis of adenoviral vectors expressing hemagglutinin genes of different influenza strains.

Construction and immunological evaluation of dual cell surface display of HIV-1 gag and Salmonella enterica serovar Typhimurium FliC in Lactobacillus acidophilus for vaccine delivery

Oral vaccines that elicit a mucosal immune response may be effective against human immunodeficiency virus type 1 (HIV-1) because its transmission occurs mainly at the mucosa. The aim of this study was to construct recombinant Lactobacillus for oral delivery of oral vaccines against HIV-1 and to evaluate their immunogenicity. A recombinant Lactobacillus acidophilus strain expressing the HIV-1 Gag on the bacterial cell surface was established by fusion with the signal peptide and anchor motif of a mucus binding protein (Mub) from L. acidophilus with or without coexpression of Salmonella enterica serovar Typhimurium flagellin (FliC) fused to a different Mub signal peptide and anchor. Using HEK293 cells engineered to express Toll-like receptor 5 (TLR5), the biological activity of FliC on the bacterial cell surfaces was determined. The surface-exposed flagellin retained its TLR5-stimulating activity, suggesting that the recombinant strain with Gag and FliC dual display might provide a different immunopotency than the strain expressing only Gag. The immunological properties of the recombinant strains were assessed by coculture with human myeloid dendritic cells (DCs). The heterologous antigens on the cell surface affected maturation and cytokine responses of DCs. Acquired immune responses were also investigated by intragastric immunization of mice. The enzyme-linked immunosorbent spot assay showed induction of gamma interferon-producing cells at local mucosa after immunization of mice with the Gag-producing strain. Meanwhile, the immunization with L. acidophilus displaying both Gag and FliC resulted in an increase of Gag-specific IgA-secreting cells. These results suggested that the Gag-displaying L. acidophilus elicited specific immune responses and the coexistence of FliC conferred an adjuvant effect on local IgA production.