Probiotics as Adjuvants in Vaccine Strategy: Is There More Room for Improvement?

Probiotics and other adjuvants in allergen-specific immunotherapy for food allergy: a comprehensive review

This review delves into the potential of manipulating the microbiome to enhance oral tolerance in food allergy, focusing on food allergen-specific immunotherapy (FA-AIT) and the use of adjuvants, with a significant emphasis on probiotics. FA-AIT, including oral (OIT), sublingual (SLIT), and epicutaneous (EPIT) immunotherapy, has shown efficacy in desensitizing patients and achieving sustained unresponsiveness (SU). However, the long-term effectiveness and safety of FA-AIT are still under investigation. Probiotics, particularly strains of Lactobacillus, play a crucial role in enhancing immune tolerance by promoting regulatory T cells (Tregs) and modulating cytokine profiles. These probiotics can induce semi-mature dendritic cells, enhance CD40 expression, inhibit IL-4 and IL-5, and promote IL-10 and TGF-β, thus contributing to mucosal defense and immunological tolerance. Clinical trials combining probiotics with FA-AIT have demonstrated improved desensitization rates and immune tolerance in food-allergic patients. For example, the combination of Lactobacillus rhamnosus with peanut OIT resulted in a significantly higher rate of SU compared to the placebo group, along with notable immune changes such as reduced peanut-specific IgE and increased IgG4 levels. The review also explores other adjuvants in FA-AIT, such as biologic drugs, which target specific immune pathways to improve treatment outcomes. Additionally, nanoparticles and herbal therapies like food allergy herbal formula 2 (FAHF-2) are discussed for their potential to enhance allergen delivery and immunogenicity, reduce adverse events, and improve desensitization. In conclusion, integrating probiotics and other adjuvants into FA-AIT protocols could significantly enhance the safety and efficacy of FA-AIT, leading to better patient outcomes and quality of life.

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.

An updated review on oral protein-based antigen vaccines efficiency and delivery approaches: a special attention to infectious diseases

Various infectious agents affect human health via the oral entrance. The majority of pathogens lack approved vaccines. Oral vaccination is a convenient, safe and cost-effective approach with the potential of provoking mucosal and systemic immunity and maintaining individual satisfaction. However, vaccines should overcome the intricate environment of the gastrointestinal tract (GIT). Oral protein-based antigen vaccines (OPAVs) are easier to administer than injectable vaccines and do not require trained healthcare professionals. Additionally, the risk of needle-related injuries, pain, and discomfort is eliminated. However, OPAVs stability at environmental and GIT conditions should be considered to enhance their stability and facilitate their transport and storage. These vaccines elicit the local immunity, protecting GIT, genital tract and respiratory epithelial surfaces, where numerous pathogens penetrate the body. OPAVs can also be manipulated (such as using specific incorporated ligand and receptors) to elicit targeted immune response. However, low bioavailability of OPAVs necessitates development of proper protein carriers and formulations to enhance their stability and efficacy. There are several strategies to improve their efficacy or protective effects, such as incorporation of adjuvants, enzyme inhibitors, mucoadhesive or penetrating devices and permeation enhancers. Hence, efficient delivery of OPAVs into GIT require proper delivery systems mainly including smart target systems, probiotics, muco-adhesive carriers, lipid- and plant-based delivery systems and nano- and microparticles.

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.

Dietary intervention with functional foods modulating gut microbiota for improving the efficacy of COVID-19 vaccines

Dysbiosis of the gut microbiota with aging contributes to a reduction in important cross-feeding bacterial reactions in the gut and immunosenescence, which could contribute to a decrease in vaccine efficacy. Fever, cough, and fatigue are the main signs of coronavirus disease 2019 (COVID-19); however, some patients with COVID-19 present with gastrointestinal symptoms. COVID-19 vaccination against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is one of the best measures to reduce SARS-CoV-2 infection rates and the severity of COVID-19. The immunogenicity of COVID-19 vaccines is influenced by the composition of the gut microbiota, and the immune response to COVID-19 vaccines decreases with age. In this review, we discuss gut microbiota dysbiosis and immunosenescence in the older adults, the role of gut microbiota in improving the efficacy of COVID-19 vaccines, and dietary interventions to improve the efficacy of COVID-19 vaccines in the older adults.

Influence of Microbiota on Vaccine Effectiveness: "Is the Microbiota the Key to Vaccine-induced Responses?"

Vaccines are one of the most powerful tools for preventing infectious diseases. To effectively fight pathogens, vaccines should induce potent and long-lasting immune responses that are specific to the pathogens. However, not all vaccines can induce effective immune responses, and the responses vary greatly among individuals and populations. Although several factors, such as age, host genetics, nutritional status, and region, affect the effectiveness of vaccines, increasing data have suggested that the gut microbiota is critically associated with vaccine-induced immune responses. In this review, I discuss how gut microbiota affects vaccine effectiveness based on the clinical and preclinical data, and summarize possible underlying mechanisms related to the adjuvant effects of microbiota. A better understanding of the link between vaccine-induced immune responses and the gut microbiota using high-throughput technology and sophisticated system vaccinology approaches could provide crucial insights for designing effective personalized preventive and therapeutic vaccination strategies.

Emerging in ovo technologies in poultry production and the re-discovered chicken model in preclinical research

Prenatal programming is a concept based on assumptions that the events occurring in critical points of embryonic development may pose epigenetic changes resulting from chemical rearrangements on the DNA structure. Epigenetic changes may pose life lasting phenotypic effects in the animal, or can be heritable, like gene silencing associated with methylation in gene promoters regions. The technical advancements in biotechnology, bioinformatics, molecular techniques and robotization have brought to new technological applications in poultry production. Intentional stimulation of embryonic development and determination of the future health of the hatched organism is possible by in ovo application of natural antioxidants and prebiotics, gut stabilizers like probiotics and other immunological enhancements, including vaccines. In parallel, the fine-tuned and generally accessible techniques of chicken embryo incubation along with the novel tissue engineering tools have led to focus the attention of scientists on chicken embryo as the alternative animal model for some pre-clinical approaches, in the context of reducing and replacing the experiments on animals. In this chapter, some key highlights are provided on current achievements in poultry embryonic applications, with the attention put to the emerging in ovo technologies (in ovo feeding, immunological stimulation and in ovo oncological tools), that address the societal challenges in food production and health management.

Nano selenium-enriched probiotic Lactobacillus enhances alum adjuvanticity and promotes antigen-specific systemic and mucosal immunity

Nano selenium-enriched probiotics have been identified to improve immune responses, such as alleviating inflammation, antioxidant function, treatment of tumors, anticancer activity, and regulating intestinal flora. However, so far, there is little information on improving the immune effect of the vaccine. Here, we prepared nano selenium-enriched Levilactobacillus brevis 23017 (SeL) and heat-inactivated nano selenium-enriched L. brevis 23017 (HiSeL) and evaluated their immune enhancing functions on the alum-adjuvanted, inactivated Clostridium perfringens type A vaccine in mouse and rabbit models, respectively. We found that SeL enhanced immune responses of the vaccine by inducing a more rapid antibody production, eliciting higher immunoglobulin G (IgG) antibody titers, improving secretory immunoglobulin A (SIgA) antibody level and cellular immune response, and regulating Th1/Th2 immune response, thus helping to induce better protective efficacy after challenge. Moreover, we confirmed that the immunoenhancement effects are related to regulating oxidative stress, cytokine secretion, and selenoprotein expression. Meanwhile, similar effects were observed in HiSeL. In addition, they show enhanced humoral immune response at 1/2 and 1/4 standard vaccine doses, which confirms their prominent immune enhancement effect. Finally, the effect of improving vaccine immune responses was further confirmed in rabbits, which shows that SeL stimulates the production of IgG antibodies, generates α toxin-neutralizing antibodies rapidly, and reduces the pathological damage to intestine tissue. Our study demonstrates that nano selenium-enriched probiotics improve the immune effect of the alum adjuvants vaccine and highlight its potential usage in remedying the disadvantages of alum adjuvants.

Probiotics Mechanism of Action on Immune Cells and Beneficial Effects on Human Health

Immune cells and commensal microbes in the human intestine constantly communicate with and react to each other in a stable environment in order to maintain healthy immune activities. Immune system-microbiota cross-talk relies on a complex network of pathways that sustain the balance between immune tolerance and immunogenicity. Probiotic bacteria can interact and stimulate intestinal immune cells and commensal microflora to modulate specific immune functions and immune homeostasis. Growing evidence shows that probiotic bacteria present important health-promoting and immunomodulatory properties. Thus, the use of probiotics might represent a promising approach for improving immune system activities. So far, few studies have been reported on the beneficial immune modulatory effect of probiotics. However, many others, which are mainly focused on their metabolic/nutritional properties, have been published. Therefore, the mechanisms behind the interaction between host immune cells and probiotics have only been partially described. The present review aims to collect and summarize the most recent scientific results and the resulting implications of how probiotic bacteria and immune cells interact to improve immune functions. Hence, a description of the currently known immunomodulatory mechanisms of probiotic bacteria in improving the host immune system is provided.

The Gut Microbiome of Children during the COVID-19 Pandemic

The gut microbiome has been shown to play a critical role in maintaining a healthy state. Dysbiosis of the gut microbiome is involved in modulating disease severity and potentially contributes to long-term outcomes in adults with COVID-19. Due to children having a significantly lower risk of severe illness and limited sample availability, much less is known about the role of the gut microbiome in children with COVID-19. It is well recognized that the developing gut microbiome of children differs from that of adults, but it is unclear if this difference contributes to the different clinical presentations and complications. In this review, we discuss the current knowledge of the gut microbiome in children with COVID-19, with gut microbiome dysbiosis being found in pediatric COVID-19 but specific taxa change often differing from those described in adults. Additionally, we discuss possible mechanisms of how the gut microbiome may mediate the presentation and complications of COVID-19 in children and the potential role for microbial therapeutics.

The Efficacy of Probiotics as Antiviral Agents for the Treatment of Rotavirus Gastrointestinal Infections in Children: An Updated Overview of Literature

Enteric viruses, including the rotavirus, norovirus, and adenoviruses, are the most common cause of acute gastroenteritis. The rotavirus disease is especially prevalent among children, and studies over the past decade have revealed complex interactions between rotaviruses and the gut microbiota. One way to treat and prevent dysbiosis is the use of probiotics as an antiviral agent. This review focuses on the latest scientific evidence on the antiviral properties of probiotics against rotavirus gastroenteric infections in children. A total of 19 studies exhibited a statistically significant antiviral effect of probiotics. The main probiotics that were effective were Saccharomyces cerevisiae var. boulardii, Lacticaseibacillus rhamnosus GG, and various multi-strain probiotics. The underlying mechanism of the probiotics against rotavirus gastroenteric infections in children included immune enhancement and modulation of intestinal microbiota leading to shortening of diarrhoea. However, several clinical studies also found no significant difference in the probiotic group compared to the placebo group even though well-known strains were used, thus showing the importance of correct dosage, duration of treatment, quality of probiotics and the possible influence of other factors, such as the production process of probiotics and the influence of immunisation on the effect of probiotics. Therefore, more robust, well-designed clinical studies addressing all factors are warranted.

Irradiated Non-replicative Lactic Acid Bacteria Preserve Metabolic Activity While Exhibiting Diverse Immune Modulation

In the recent years, safety concerns regarding the administration of probiotics led to an increased interest in developing inactivated probiotics, also called “paraprobiotics”. Gamma irradiation represents a promising tool that can be used to produce safe paraprobiotics by inhibiting replication while preserving the structure, the metabolic activity, and the immunogenicity of bacteria. In this study, we evaluated the ability of four strains of lactic acid bacteria (LAB: Lacticaseibacillus casei, Lactobacillus acidophilus, Lactiplantibacillus plantarum, and Lacticaseibacillus paracasei) in preserving the metabolic activity and the immune modulation of swine porcine peripheral blood mononuclear cells, after gamma irradiation or heat inactivation. Our results show that all four strains retained the metabolic activity following gamma irradiation but not after heat inactivation. In terms of immune-modulatory capacity, irradiated L. acidophilus and Lc. paracasei were able to maintain an overall gene expression pattern similar to their live state, as heat inactivation did with Lc. casei. Moreover, we show that the two inactivation methods applied to the same strain can induce an opposed expression of key genes involved in pro-inflammatory response (e.g., IFNα and interleukin-6 for Lc. casei), whereas gamma irradiation of L. acidophilus and Lc. paracasei was able to induce a downregulation of the anti-inflammatory TGFβ. Taken together, our data show that immune modulation can be impacted not only by different inactivation methods but also by the strain of LAB selected. This study highlights that gamma irradiation harbors the potential to produce safe non-replicative metabolically active LAB and identifies immunomodulatory capacities that may be applied as vaccine adjuvants.

Fighting the SARS-CoV-2 pandemic requires a global approach to understanding the heterogeneity of vaccine responses

Host genetic and environmental factors including age, biological sex, diet, geographical location, microbiome composition and metabolites converge to influence innate and adaptive immune responses to vaccines. Failure to understand and account for these factors when investigating severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccine efficacy may impair the development of the next generation of vaccines. Most studies aimed at identifying mechanisms of vaccine-mediated immune protection have focused on adaptive immune responses. It is well established, however, that mobilization of the innate immune response is essential to the development of effective cellular and humoral immunity. A comprehensive understanding of the innate immune response and environmental factors that contribute to the development of broad and durable cellular and humoral immune responses to SARS-CoV-2 and other vaccines requires a holistic and unbiased approach. Along with optimization of the immunogen and vectors, the development of adjuvants based on our evolving understanding of how the innate immune system shapes vaccine responses will be essential. Defining the innate immune mechanisms underlying the establishment of long-lived plasma cells and memory T cells could lead to a universal vaccine for coronaviruses, a key biomedical priority.

Effects of Loigolactobacillus coryniformis K8 CECT 5711 on the Immune Response of Elderly Subjects to COVID-19 Vaccination: A Randomized Controlled Trial

Elderly people are particularly vulnerable to COVID-19, with a high risk of developing severe disease and a reduced immune response to the COVID-19 vaccine. A randomized, placebo-controlled, double-blind trial to assess the effect of the consumption of the probiotic Loigolactobacillus coryniformis K8 CECT 5711 on the immune response generated by the COVID-19 vaccine in an elderly population was performed. Two hundred nursing home residents >60 yrs that had not COVID-19 were randomized to receive L. coryniformis K8 or a placebo daily for 3 months. All volunteers received a complete vaccination schedule of a mRNA vaccine, starting the intervention ten days after the first dose. Specific IgG and IgA antibody levels were analyzed 56 days after the end of the immunization process. No differences between the groups were observed in the antibody levels. During the intervention, 19 subjects had COVID-19 (11 receiving K8 vs. 8 receiving placebo, p = 0.457). Subgroup analysis in these patients showed that levels of IgG were significantly higher in those receiving K8 compared to placebo (p = 0.038). Among subjects >85 yrs that did not get COVID-19, administration of K8 tended to increase the IgA levels (p = 0.082). The administration of K8 may enhance the specific immune response against COVID-19 and may improve the COVID-19 vaccine-specific responses in elderly populations.