Probiotics and probiotic-based vaccines: A novel approach for improving vaccine efficacy

Intestinal Microbiota and Its Effect on Vaccine-Induced Immune Amplification and Tolerance

This review provides the potential of intestinal microbiota in vaccine design and application, exploring the current insights into the interplay between the intestinal microbiota and the immune system, with a focus on its intermediary function in vaccine efficacy. It summarizes families and genera of bacteria that are part of the intestinal microbiota that may enhance or diminish vaccine efficacy and discusses the foundational principles of vaccine sequence design and the application of gut microbial characteristics in vaccine development. Future research should further investigate the use of multi-omics technologies to elucidate the interactive mechanisms between intestinal microbiota and vaccine-induced immune responses, aiming to optimize and improve vaccine design.

Pediococcus pentosaceus MIANGUAN Enhances the Immune Response to Vaccination in Mice

Increasing evidence shows that some probiotics can improve vaccine responses as adjuvants. This study aimed to evaluate the effect of Pediococcus pentosaceus MIANGUAN (PPM) on SARS-CoV-2 vaccine-elicited immune response in mice. Six-week-old female ICR mice were primed and boosted with SARS-CoV-2 vaccine intramuscularly at weeks 0 and 4, respectively. Mice were gavaged with PPM (5 × 109 CFU/mouse) or PBS (control) for 3 days immediately after boosting vaccination. Compared to the control, oral PPM administration resulted in significantly higher levels of RBD-specific IgG binding antibodies (> 2.3-fold) and RBD-specific IgG1 binding antibodies (> 4-fold) in the serum. Additionally, PPM-treated mice had higher titers of RBD-specific IgG binding antibodies (> 2.29-fold) and neutralization antibodies (> 1.6-fold) in the lung compared to the control mice. The transcriptional analyses showed that the B cell receptor (BCR) signaling pathway was upregulated in both splenocytes and BAL cells in the PPM group vs. the control group. In addition, the number of IFN-γ-producing splenocytes (mainly in CD4 + T cells as determined by flow cytometry) in response to restimulation of RBD peptides was significantly increased in the PPM group. RNA sequencing showed that the genes associated with T cell activation and maturation and MHC class II pathway (CD4, H2-DMa, H2-DMb1, H2-Oa, Ctss) were upregulated, suggesting that oral administration of PPM may enhance CD4 + T cell responses through MHC class II pathway. Furthermore, PPM administration could downregulate the expression level of proinflammatory genes. To conclude, oral administration of PPM could boost SARS-CoV-2 vaccine efficacy through enhancing the specific humoral and cellular immunity response and decrease the expression of inflammation pathways.

Immune protection of grass carp by oral vaccination with recombinant Bacillus methylotrophicus expressing the heterologous tolC gene

In the field of aquaculture, the enhancement of animal health and disease prevention is progressively being tackled using alternatives to antibiotics, including vaccines and probiotics. This study was designed to evaluate the potential of a recombinant Bacillus methylotrophicus, engineered to express the outer membrane channel protein TolC of Aeromonas hydrophila AH3 and the green fluorescent protein GFP, as an oral vaccine. Initially, the genes encoding tolC and GFP were cloned into a prokaryotic expression system, and anti-TolC mouse antiserum was generated. Subsequently, the tolC gene was subcloned into a modified pMDGFP plasmid, which was transformed into B. methylotrophicus WM-1 for protein expression. The recombinant B. methylotrophicus BmT was then administered to grass carp via co-feeding, and its efficacy as an oral vaccine was assessed. Our findings demonstrated successful expression of the 55 kDa TolC and 28 kDa GFP proteins, and the preparation of polyclonal antibodies with high specificity. The BmT exhibited stable expression of the GFP-TolC fusion protein and excellent genetic stability. Following oral immunization, significant elevations were observed in serum-specific IgM levels and the activities of acid phosphatase (ACP), alkaline phosphatase (AKP), superoxide dismutase (SOD), and lysozyme (LZM) in grass carp. Concurrently, significant upregulation of immune-related genes, including IFN-I, IL-10, IL-1β, TNF-α, and IgT, was noted in the intestines, head kidney, and spleen of the grass carp. Colonization tests further revealed that the BmT persisted in the gut of immunized fish even after a fasting period of 7 days. Notably, oral administration of BmT enhanced the survival rate of grass carp following A. hydrophila infection. These results suggest that the oral BmT vaccine developed in this study holds promise for future applications in aquaculture.

Deciphering the Potential of Probiotics in Vaccines

The demand for vaccines, particularly those prepared from non-conventional sources, is rising due to the emergence of drug resistance around the globe. Probiotic-based vaccines are a wise example of such vaccines which represent new horizons in the field of vaccinology in providing an enhanced and diversified immune response. The justification for incorporating probiotics into vaccines lies in the fact that that they hold the capacity to regulate immune function directly or indirectly by influencing the gastrointestinal microbiota and related pathways. Several animal-model-based studies have also highlighted the efficacy of these vaccines. The aim of this review is to collect and summarize the trends in the recent scientific literature regarding the role of probiotics in vaccines and vaccinology, along with their impact on target populations.

Probiotic bacteria can modulate immune responses to paratuberculosis vaccination

Mycobacterium avium subsp. paratuberculosis (Map) is the etiological agent of paratuberculosis (PTB), a chronic intestinal inflammatory disease that causes high economical losses in dairy livestock worldwide. Due to the absence of widely available preventive or therapeutical treatments, new alternative therapies are needed. In this study, the effect of a probiotic alone or in combination with a commercial vaccine has been evaluated in a rabbit model. Vaccination enhanced the humoral response, exerted a training effect of peripheral polymorphonuclear neutrophils (PMNs) against homologous and heterologous stimuli, stimulated the release of pro-inflammatory cytokines by gut-associated lymphoid tissue (GALT) macrophages, and reduced the bacterial burden in GALT as well. However, the administration of the probiotic after vaccination did not affect the PMN activity, increased metabolic demand, and supressed pro-inflammatory cytokines, although humoral response and bacterial burden decrease in GALT was maintained similar to vaccination alone. The administration of the probiotic alone did not enhance the humoral response or PMN activity, and the bacterial burden in GALT was further increased compared to the only challenged group. In conclusion, the probiotic was able to modulate the immune response hampering the clearance of the infection and was also able to affect the response of innate immune cells after vaccination. This study shows that the administration of a probiotic can modulate the immune response pathways triggered by vaccination and/or infection and even exacerbate the outcome of the disease, bringing forward the importance of verifying treatment combinations in the context of each particular infectious agent.

Microbiome Dynamics: A Paradigm Shift in Combatting Infectious Diseases

Infectious diseases have long posed a significant threat to global health and require constant innovation in treatment approaches. However, recent groundbreaking research has shed light on a previously overlooked player in the pathogenesis of disease-the human microbiome. This review article addresses the intricate relationship between the microbiome and infectious diseases and unravels its role as a crucial mediator of host-pathogen interactions. We explore the remarkable potential of harnessing this dynamic ecosystem to develop innovative treatment strategies that could revolutionize the management of infectious diseases. By exploring the latest advances and emerging trends, this review aims to provide a new perspective on combating infectious diseases by targeting the microbiome.

Nuxcell Neo® improves vaccine efficacy in antibody response

Current vaccination protocols raise concerns about the efficacy of immunization. There is evidence that changes in the gut microbiota can impact immune response. The formation of the gut microbiota in newborns plays a crucial role in immunity. Probiotic bacteria and prebiotics present important health-promoting and immunomodulatory properties. Thus, we hypothesize that pro and prebiotic supplementation can improve the efficacy of vaccination in newborns. In this protocol, newborn mice were used and treated with a single-dose rabies vaccine combined with Nuxcell Neo® (2 g/animal/week) for 3 weeks. Samples were collected on days 7, 14, and 21 after vaccination for analysis of cytokines and concentration of circulating antibodies. Our results show an increased concentration of antibodies in animals vaccinated against rabies and simultaneously treated with Nuxcell Neo® on days 14 and 21 when compared to the group receiving only the vaccine. In the cytokine levels analysis, it was possible to observe that there weren't relevant and significant changes between the groups, which demonstrates that the health of the animal remains stable. The results of our study confirm the promising impact of the use of Nuxcell Neo® on the immune response after vaccination.

Current Views about the Inflammatory Damage Triggered by Bacterial Superantigens and Experimental Attempts to Neutralize Superantigen-Mediated Toxic Effects with Natural and Biological Products

Superantigens, i.e., staphylococcal enterotoxins and toxic shock syndrome toxin-1, interact with T cells in a different manner in comparison to conventional antigens. In fact, they activate a larger contingent of T lymphocytes, binding outside the peptide-binding groove of the major histocompatibility complex class II. Involvement of many T cells by superantigens leads to a massive release of pro-inflammatory cytokines, such as interleukin (IL)-1, IL-2, IL-6, tumor necrosis factor-alpha and interferon-gamma. Such a storm of mediators has been shown to account for tissue damage, multiorgan failure and shock. Besides conventional drugs and biotherapeutics, experiments with natural and biological products have been undertaken to attenuate the toxic effects exerted by superantigens. In this review, emphasis will be placed on polyphenols, probiotics, beta-glucans and antimicrobial peptides. In fact, these substances share a common functional denominator, since they skew the immune response toward an anti-inflammatory profile, thus mitigating the cytokine wave evoked by superantigens. However, clinical applications of these products are still scarce, and more trials are needed to validate their usefulness in humans.

The effect of Bacteroides fragilis and its postbiotics on the expression of genes involved in the endocannabinoid system and intestinal epithelial integrity in Caco-2 cells

Purpose

Gut microbiota and its derivatives by constantly interacting with the host, regulate the host function. Intestinal epithelium integrity is under the control of various factors including the endocannabinoid system (ECS). Accordingly, we aimed at investigating the effect of Bacteroides fragilis and its postbiotics (i.e., heat-inactivated, cell-free supernatants (CFS) and outer membrane vesicles (OMVs)) on the expression of genes involved in ECS (cnr1, faah, pparg) and the epithelial barrier permeability (ocln, tjp1) in a Caco-2 cell line.

Methods

Caco-2 cell line was treated with live or heat-inactivated B. fragilis at MOIs of 50 and 100, or stimulated with 7% V/V CFS and B. fragilis OMVs at a dose of 50 and 100 µg/ml overnight. RT-qPCR was applied for expression analysis.

Results

Heat-inactivated B. fragilis induced cnr1, pparg, tjp1, and suppressed faah expression, while live B. fragilis had the opposite effect. OMVs increased pparg, and tjp1 expression by reducing the activity of ECS through an increase in faah and a reduction in cnr1 expression. Finally, an increase in the expression of pparg and ocln, and a reduction in the expression of cnr1 was detected in Caco-2 cells treated with CFS.

Conclusion

The live and heat-inactivated B. fragilis inversely affected cnr1, faah, pparg, and tjp1 expression in Caco-2 cells. Increased tjp1 mRNA levels by affecting the expression of ECS related genes is taken as an indication of the potential beneficial effects of B. fragilis postbiotics and making them potential candidates for improving permeability in the leaky gut syndrome.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40200-023-01264-8.

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.

The oral antigen-adjuvant fusion vaccine P-MCP-FlaC provides effective protective effect against largemouth bass ranavirus infection

Largemouth bass ranavirus (LMBV) is highly contagious and lethal to largemouth bass, causing significant economic losses to the aquaculture industry. Oral vaccination is generally considered the most ideal strategy for protecting fish from viral infection. In this study, the fusion protein MCP-FlaC, consisting of the main capsid protein (MCP) as the antigen and flagellin C (FlaC) as the adjuvant, was intracellularly expressed in Pichia pastoris. Subsequently, the recombinant P. pastoris was freeze-dried to prepare the oral vaccine P-MCP-FlaC. Transmission electron microscopy and scanning electron microscopy analysis showed that the morphology and structure of the freeze-dried recombinant P. pastoris vaccine remained intact. The experiment fish (n = 100) was divided into five groups (P-MCP-FlaC, P-MCP, P-FlaC, P-pPIC3.5K, control) to evaluate the protective efficacy of the recombinant vaccine. Oral P-MCP-FlaC vaccine effectively up-regulated the serum enzymes activity (total superoxide dismutase, lysozyme, total antioxidant capacity, and complement component 3). The survival rate of P-MCP-FlaC group was significantly higher than that of the other groups. The mRNA expression of crucial immune genes (IL-1β, TNF-α, MHC-II, IFN-γ, Mx, IgM, IgT) was also signally elevated in P-MCP-FlaC group. Vaccine P-MCP-FlaC markedly inhibited the replication of LMBV in the spleen, head kidney, and intestine, while reducing the degree of lesion in the spleen. These results suggest that the oral P-MCP-FlaC vaccine could effectively control LMBV infection, proving an effective strategy for viral diseases prevention in aquaculture.

Lactobacillus plantarum surface-displayed FomA (Fusobacterium nucleatum) protein generally stimulates protective immune responses in mice

A significant correlation is observed between Fusobacterium nucleatum (F. nucleatum) and the evolution of inflammatory bowel disease (IBD). Particularly, FomA, a critical pathogenic element of F. nucleatum, inflicts substantial detriment to human intestinal health. Our research focused on the development of recombinant Lactobacillus plantarum that expresses FomA protein, demonstrating its potential in protecting mice from severe IBD induced by F. nucleatum. To commence, two recombinant strains, namely L. plantarum NC8-pSIP409-pgsA'-FomA and NC8-pSIP409-FnBPA-pgsA'-FomA, were successfully developed. Validation of the results was achieved through flow cytometry, ELISA, and MTT assays. It was observed that recombinant L. plantarum instigated mouse-specific humoral immunity and elicited mucosal and T cell-mediated immune responses. Significantly, it amplified the immune reaction of B cells and CD4+T cells, facilitated the secretion of cytokines such as IgA, IL4, and IL10, and induced lymphocyte proliferation in response to FomA protein stimulation. Finally, we discovered that administering recombinant L. plantarum could protect mice from severe IBD triggered by F. nucleatum, subsequently reducing pathological alterations and inflammatory responses. These empirical findings further the study of an innovative oral recombinant Lactobacillus vaccine.

Immune-adjuvant effect of vitamin A and probiotics supplementation on humoral response to cell culture rabies vaccine in rabbits

This study was carried out to evaluate the effects of vitamin A (Vit A) and probiotic co-supplementation with rabies vaccine on humoral immune response in New Zealand white (NZW) rabbits. For this experiment, 54 rabbits were randomized into six experimental and three control groups. Mixed cultures of commercial probiotics supplements and a dose of Vit A were administered to each animal. Results were compared with the control group fed with only basal diet. Animals in different treatment groups showed significantly higher sero-conversions against rabies vaccine. There was a significant increase (p < 0.001) in the titers of rabies antibodies in all treatment groups on 14th and 35th days than control C3 group. Both commercial probiotics irrespective of brand increase the humoral immune response of rabbits against rabies vaccine. The mean titer values of all groups G1-G6 and sub-controls (C1, C2) were generally above 3.6 EU/ml on day 14th and between 3.7 and 3.9 EU/ml, showing highest sero-conversion on 35th day than mean titer of C3 control = 3.091 and 3.505 EU/ml respectively on both days. The maximum titer values were obtained with the addition of organic carrots to the daily diet. These results suggest that simple dietary interventions using probiotics and Vit A in natural form may enhance the efficacy of rabies vaccine in the host. These cost-effective strategies can be applied for getting higher yields of polyclonal antibody production in animal models, thus providing promising means of improving the final product yield and can be adopted easily by the manufacturers.

Oral Immunization with Escherichia coli Nissle 1917 Expressing SARS-CoV-2 Spike Protein Induces Mucosal and Systemic Antibody Responses in Mice

As of October 2022, the COVID-19 pandemic continues to pose a major public health conundrum, with increased rates of symptomatic infections in vaccinated individuals. An ideal vaccine candidate for the prevention of outbreaks should be rapidly scalable, easy to administer, and able to elicit a potent mucosal immunity. Towards this aim, we proposed an engineered Escherichia coli (E. coli) Nissle 1917 (EcN) strain with SARS-CoV-2 spike protein (SP)-coding plasmid, which was able to expose SP on its cellular surface by a hybridization with the adhesin involved in diffuse adherence 1 (AIDA1). In this study, we presented the effectiveness of a 16-week intragastrically administered, engineered EcN in producing specific systemic and mucosal immunoglobulins against SARS-CoV-2 SP in mice. We observed a time-dependent increase in anti-SARS-CoV-2 SP IgG antibodies in the sera at week 4, with a titre that more than doubled by week 12 and a stable circulating titre by week 16 (+309% and +325% vs. control; both p < 0.001). A parallel rise in mucosal IgA antibody titre in stools, measured via intestinal and bronchoalveolar lavage fluids of the treated mice, reached a plateau by week 12 and until the end of the immunization protocol (+300, +47, and +150%, at week 16; all p < 0.001 vs. controls). If confirmed in animal models of infection, our data indicated that the engineered EcN may be a potential candidate as an oral vaccine against COVID-19. It is safe, inexpensive, and, most importantly, able to stimulate the production of both systemic and mucosal anti-SARS-CoV-2 spike-protein antibodies.

Probiotic of Lactiplantibacillus plantarum NWAFU-BIO-BS29 Isolated from Chinese Traditional Fermented Milk and Its Potential Therapeutic Applications Based on Gut Microbiota Regulation

Lactic acid bacteria are one of the bioresources that can promote the host's health and have potential therapeutic applications. This study aimed to evaluate the probiotic properties of novel Lactiplantibacillus plantarum NWAFU-BISO-BS29 isolated in vitro from traditional Chinese fermented milk, assess its safety, and study its interaction with the gut microbiota using a BALB/c mouse model. The findings reveal that this strain had a high tolerance to gastric acidity (64.4%) and bile salts (19.83-87.92%) with remarkable auto-aggregation and co-aggregation abilities (33.01-83.96%), respectively. Furthermore, it lowered the cholesterol levels in dead cells (44.02%) and live cells (34.95%) and produced short-chain fatty acids (SCFAs). Likewise, it showed good antioxidant properties and strong antipathogen activity against Escherichia coli and Staphylococcus aureus with inhibition zones at 21 and 25 mm, respectively. The safety assessment results indicate that all of the virulence factor genes were not detected in the whole DNA; additionally, no hemolysis or resistance to antibiotics commonly used in food and feed was observed. Interestingly, the 16S rRNA gene sequencing of the mouse gut microbiota showed a marked alteration in the microbial composition of the administrated group, with a noticeable increase in Firmicutes, Patescibacteria, Campylobacterota, Deferribacterota, Proteobacteria, and Cyanobacteria at the phylum level. The modulation of gut microbial diversity significantly improved the production of SCFCs due to the abundance of lactobacillus genera, which was consistent with the functional gene predictive analysis and is believed to have health-promoting properties. Based on these results, our novel strain is considered a safe and good probiotic and could hold high potential to be used as a starter culture or to safely supplement functional foods as a probiotic and may provide new insights into therapeutic interventions.