Lactobacillus GG as an immune adjuvant for live-attenuated influenza vaccine in healthy adults: a randomized double-blind placebo-controlled trial

Nanoplatform Based Intranasal Vaccines: Current Progress and Clinical Challenges

Multiple vaccine platforms have been employed to develop the nasal SARS-CoV-2 vaccines in preclinical studies, and the dominating pipelines are viral vectored as protein-based vaccines. Among them, several viral vectored-based vaccines have entered clinical development. Nevertheless, some unsatisfactory results were reported in these clinical studies. In the face of such urgent situations, it is imperative to rapidly develop the next-generation intranasal COVID-19 vaccine utilizing other technologies. Nanobased intranasal vaccines have emerged as an approach against respiratory infectious diseases. Harnessing the power of nanotechnology, these vaccines offer a noninvasive yet potent defense against pathogens, including the threat of COVID-19. The improvements made in vaccine mucosal delivery technologies based on nanoparticles, such as lipid nanoparticles, polymeric nanoparticles, inorganic nanoparticles etc., not only provide stability and controlled release but also enhance mucosal adhesion, effectively overcoming the limitations of conventional vaccines. Hence, in this review, we overview the evaluation of intranasal vaccine and highlight the current barriers. Next, the modern delivery systems based on nanoplatforms are summarized. The challenges in clinical application of nanoplatform based intranasal vaccine are finally discussed.

Molecular Mechanisms of Lacticaseibacillus rhamnosus, LGG® Probiotic Function

To advance probiotic research, a comprehensive understanding of bacterial interactions with human physiology at the molecular and cellular levels is fundamental. Lacticaseibacillus rhamnosus LGG® is a bacterial strain that has long been recognized for its beneficial effects on human health. Probiotic effector molecules derived from LGG®, including secreted proteins, surface-anchored proteins, polysaccharides, and lipoteichoic acids, which interact with host physiological processes have been identified. In vitro and animal studies have revealed that specific LGG® effector molecules stimulate epithelial cell survival, preserve intestinal barrier integrity, reduce oxidative stress, mitigate excessive mucosal inflammation, enhance IgA secretion, and provide long-term protection through epigenetic imprinting. Pili on the cell surface of LGG® promote adhesion to the intestinal mucosa and ensure close contact to host cells. Extracellular vesicles produced by LGG® recapitulate many of these effects through their cargo of effector molecules. Collectively, the effector molecules of LGG® exert a significant influence on both the gut mucosa and immune system, which promotes intestinal homeostasis and immune tolerance.

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

BACKGROUND

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

RESULTS

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

CONCLUSIONS

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

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.

Harnessing Innate Immunity to Treat Mycobacterium tuberculosis Infections: Heat-Killed Caulobacter crescentus as a Novel Biotherapeutic

Tuberculosis, caused by Mycobacterium tuberculosis (Mtb), is a serious and devastating infectious disease worldwide. Approximately a quarter of the world population harbors latent Mtb infection without pathological consequences. Exposure of immunocompetent healthy individuals with Mtb does not result in active disease in more than 90% individuals, suggesting a defining role of host immunity to prevent and/or clear early infection. However, innate immune stimulation strategies have been relatively underexplored for the treatment of tuberculosis. In this study, we used cell culture and mouse models to examine the role of a heat-killed form of a non-pathogenic microbe, Caulobacter crescentus (HKCC), in inducing innate immunity and limiting Mtb infection. We also examined the added benefits of a distinct chemo-immunotherapeutic strategy that incorporates concurrent treatments with low doses of a first-line drug isoniazid and HKCC. This therapeutic approach resulted in highly significant reductions in disseminated Mtb in the lungs, liver, and spleen of mice compared to either agent alone. Our studies demonstrate the potential of a novel innate immunotherapeutic strategy with or without antimycobacterial drugs in controlling Mtb infection in mice and open new avenues for the treatment of tuberculosis in humans.

Influence of biotic interventions on the immune response to vaccines in young and older adults

Vaccination is the most effective way to confer potent and long-term protection from infectious diseases. However, poorer responses to immunization are common in young adults with sub-optimal immune health and the elderly because of immunosenescence and increased comorbidities. Recent mechanistic studies have highlighted that the microbiota and its compounds modulate many molecular pathways that can influence the host immune system. Consequently, altering the microbiota composition or activity with immunonutrition, specifically with biotic interventions (probiotics, prebiotics, synbiotics, or postbiotics), may enhance the immune response and vaccine efficacy. This review aims to examine the available data for these biotic strategies to provide clinicians, researchers, and vaccine developers with a mechanistically driven synthesis of how biotic interventions could modulate the immune responses to vaccination. The article describes some postulated mechanistic pathways involved in immunological responses to vaccines and immunomodulation with biotic interventions. Randomized clinical trials were also reviewed to evaluate the impact of specific biotic interventions on vaccination outcomes in different age groups. Few strains and formulations significantly increased antigen-specific antibody titers in individual of all ages. However, studies have also pointed to a substantial heterogeneity that can be attributed to the difference in biotic intervention, strain, dose, viability, type of vaccine antigen, study location, as well as duration, and timing of administration. Future investigations should focus on establishing optimal strains, doses, and timing of administration with respect to vaccination, especially in the elderly and children, where vaccine effectiveness and duration of immunization matter.

Consumption of yogurt fermented with Lactobacillus delbrueckii ssp. bulgaricus OLL1073R-1 augments serum antibody titers against seasonal influenza vaccine in healthy adults

Seasonal influenza is a major upper respiratory tract infection occurring in winter. Vaccination is the best method for preventing this infection. We conducted two randomized, double-blind, placebo-controlled trials to examine whether consumption of yogurt fermented with Lactobacillus delbrueckii ssp. bulgaricus OLL1073R-1, which has been reported to reduce the risk of catching the common cold, augments serum antibody titers against seasonal influenza vaccines. In the first trial, which included university students, serum antibody titers against influenza A (H3N2) and B viruses were significantly higher in the yogurt group than in the placebo group. According to the guidelines established by the European Medicines Agency (EMA) for the assessment of vaccines, the seroconversion rate and mean geometric increase of influenza A (H3N2) and seroprotection of influenza B met the criteria only in the yogurt group. In the second trial, which included healthy adults, serum antibody titers against influenza A (H1N1) and B viruses were significantly higher in the yogurt group than in the placebo group. The seroconversion rate and mean geometric increase of influenza B met the EMA criteria only in the yogurt group. Furthermore, the cumulative days of ill health, such as throat complaints, upper respiratory inflammation, and cold, were significantly lower in the yogurt group than in the placebo group. Therefore, daily intake of yogurt fermented with L. bulgaricus OLL1073R-1 could reduce the duration of symptoms caused by respiratory infections and act as a mucosal adjuvant enhancing acquired immune responses against vaccines, leading to the improvement of public health.

Impact of oral administration of single strain Lactococcus lactis spp. cremoris on immune responses to keyhole limpet hemocyanin immunization and gut microbiota: A randomized placebo-controlled trial in healthy volunteers

Introduction

Lactococcus lactis spp. cremoris has been associated with promising immunomodulatory results in preclinical trials. The aim of this study was to investigate the pharmacodynamic (PD) effects of three monoclonal microbial formulations of L. lactis spp. cremoris (EDP1066) on the immune response to keyhole limpet hemocyanin (KLH). Potential effects on the gut microbiota were also investigated.

Methods

The trial was registered on Netherlands Trial Register (trial ID NL7519, https://trialsearch.who.int). Eighty-one healthy subjects (median 28, range 18-59 years) were randomized to 28 days of enteric-coated capsules at five doses (n = 13) (1.5 * 1012 total cells daily), freeze-dried powder at one dose (n = 12) (3.0 * 1011 total cells daily) or five doses (n = 12), minitablets at one dose (n = 12) or five doses (n = 12), or placebo (n = 20) prior to KLH immunization. Antibody responses and circulating regulatory T cells (Tregs) were measured after KLH immunization, and skin responses were evaluated after a KLH rechallenge by laser speckle contrast imaging and multispectral imaging. Ex vivo lymphocyte (phytohemagglutinin) and monocyte (lipopolysaccharide (LPS)) cytokine release assays were explored in the minitablet-treated groups only. The prevalence of L. lactis spp. cremoris in the gastrointestinal tract and the impact on the fecal microbiota were assessed by qPCR and 16S rRNA sequencing, respectively.

Results

Repeated-measures analysis of covariances revealed no significant treatment effects on the antibody responses to KLH, number of Tregs, or KLH skin rechallenge outcomes. Ex vivo LPS-driven cytokine responses in whole blood were lower in the low dose minitablet group compared to placebo: tumor necrosis factor (estimated difference (ED) from placebo: -44.2%, 95% confidence interval (CI) -65.3% to -10.3%), interleukin (IL)-1β (ED -41.4%, 95% CI -63.5% to -5.8%), and IL-6 (ED -39.2%, 95% CI -56.8% to -14.5%). The fecal presence of L. lactis spp. cremoris increased during treatment by all EDP1066 formulations and normalized 5 days after the last dose. Microbiome α-diversity did not change by the treatments compared to placebo.

Discussion

The EDP1066 formulations did not affect the immune response to KLH immunization in healthy individuals. However, exposure to L. lactis spp. cremoris in minitablet formulation impacted ex vivo whole blood LPS cytokine response. The clinical impact of these effects awaits further investigations.

Netherlands Trial Register

trialsearch.who.int, trial ID NL7519.

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

Vaccination is defined as the stimulation and development of the adaptive immune system by administering specific antigens. Vaccines' efficacy, in inducing immunity, varies in different societies due to economic, social, and biological conditions. One of the influential biological factors is gut microbiota. Cross-talks between gut bacteria and the host immune system are initiated at birth during microbial colonization and directly control the immune responses and protection against pathogen colonization. Imbalances in the gut microbiota composition, termed dysbiosis, can trigger several immune disorders through the activity of the adaptive immune system and impair the adequate response to the vaccination. The bacteria used in probiotics are often members of the gut microbiota, which have health benefits for the host. Probiotics are generally consumed as a component of fermented foods, affect both innate and acquired immune systems, and decrease infections. This review aimed to discuss the gut microbiota's role in regulating immune responses to vaccination and how probiotics can help induce immune responses against pathogens. Finally, probiotic-based oral vaccines and their efficacy have been discussed.

Pharmacological Efficacy of Probiotics in Respiratory Viral Infections: A Comprehensive Review

Mortality and morbidity from influenza and other respiratory viruses are significant causes of concern worldwide. Infections in the respiratory tract are often underappreciated because they tend to be mild and incapacitated. On the other hand, these infections are regarded as a common concern in clinical practice. Antibiotics are used to treat bacterial infections, albeit this is becoming more challenging since many of the more prevalent infection causes have acquired a wide range of antimicrobial resistance. Resistance to frontline treatment medications is constantly rising, necessitating the development of new antiviral agents. Probiotics are one of several medications explored to treat respiratory viral infection (RVI). As a result, certain probiotics effectively prevent gastrointestinal dysbiosis and decrease the likelihood of secondary infections. Various probiotic bacterias and their metabolites have shown immunomodulating and antiviral properties. Unfortunately, the mechanisms by which probiotics are effective in the fight against viral infections are sometimes unclear. This comprehensive review has addressed probiotic strains, dosage regimens, production procedures, delivery systems, and pre-clinical and clinical research. In particular, novel probiotics' fight against RVIs is the impetus for this study. Finally, this review may explore the potential of probiotic bacterias and their metabolites to treat RVIs. It is expected that probiotic-based antiviral research would be benefitted from this review's findings.

Association between Recent Usage of Antibiotics and Immunogenicity within Six Months after COVID-19 Vaccination

Background: Gut microbiota can be associated with COVID-19 vaccine immunogenicity. We investigated whether recent antibiotic use influences BNT162b2 vaccine immunogenicity. Methods: BNT162b2 recipients from three centers were prospectively recruited. Outcomes of interest were seroconversion of neutralising antibody (NAb) at day 21, 56 and 180 after first dose. We calculated the adjusted odds ratio (aOR) of seroconversion with antibiotic usage (defined as ever use of any antibiotics within six months before first dose of vaccine) by adjusting for covariates including age, sex, smoking, alcohol, and comorbidities. Results: Of 316 BNT162b2 recipients (100 [31.6%] male; median age: 50.1 [IQR: 40.0–57.0] years) recruited, 29 (9.2%) were antibiotic users. There was a trend of lower seroconversion rates in antibiotic users than non-users at day 21 (82.8% vs. 91.3%; p = 0.14) and day 56 (96.6% vs. 99.3%; p = 0.15), but not at day 180 (93.3% vs. 94.1%). A multivariate analysis showed that recent antibiotic usage was associated with a lower seroconversion rate at day 21 (aOR 0.26;95% CI: 0.08–0.96). Other factors associated with a lower seroconversion rate after first dose of the BNT162b2 vaccine included age ≥ 60 years (aOR: 0.34;95% CI: 0.13–0.95) and male sex (aOR: 0.14, 95% CI: 0.05–0.34). There were no significant factors associated with seroconversion after two doses of BNT16b2, including antibiotic use (aOR: 0.03;95% CI: 0.001–1.15). Conclusions: Recent antibiotic use may be associated with a lower seroconversion rate at day 21 (but not day 56 or 180) among BNT162b2 recipients. Further long-term follow-up data with a larger sample size is needed to reach a definite conclusion on how antibiotics influence immunogenicity and the durability of the vaccine response.

Factors Limiting the Translatability of Rodent Model-Based Intranasal Vaccine Research to Humans

The intranasal route of vaccination presents an attractive alternative to parenteral routes and offers numerous advantages, such as the induction of both mucosal and systemic immunity, needle-free delivery, and increased patient compliance. Despite demonstrating promising results in preclinical studies, however, few intranasal vaccine candidates progress beyond early clinical trials. This discrepancy likely stems in part from the limited predictive value of rodent models, which are used frequently in intranasal vaccine research. In this review, we explored the factors that limit the translatability of rodent-based intranasal vaccine research to humans, focusing on the differences in anatomy, immunology, and disease pathology between rodents and humans. We also discussed approaches that minimize these differences and examined alternative animal models that would produce more clinically relevant research.

Rationale, design, and methods: A randomized placebo-controlled trial of an immunomodulatory probiotic intervention for Veterans with PTSD

Background

United States military Veterans from recent conflicts are experiencing symptoms related to posttraumatic stress disorder (PTSD). Many Veterans are resistant to conventional health and mental health interventions (e.g., medication, psychotherapy). Alternative treatment approaches are needed. An underlying feature of PTSD is exaggerated inflammation, both peripherally and in the central nervous system. This inflammation is thought to play an important role in the vulnerability to, aggravation of, and persistence of PTSD symptoms. Therefore, an innovative intervention strategy would be the use of immunoregulatory/anti-inflammatory probiotics to reduce inflammation. Here we describe the rationale, design, and methods of a randomized placebo-controlled trial (RCT) of Lactobacillus rhamnosus GG (LGG; ATCC 53103) for posttraumatic stress disorder (PTSD).

Methods

This is a Phase IIa trial of LGG for United States military Veterans with PTSD, using a longitudinal, double-blind, randomized placebo-controlled design. The primary outcome measure is plasma concentration of high-sensitivity C-reactive protein.

Conclusion

Despite the fact that symptoms associated with PTSD can be disabling, individuals living with this trauma-related disorder have limited options in terms of evidence-based interventions. Recent research efforts aimed at highlighting the biological mechanisms of PTSD suggest that increased inflammation and altered autonomic nervous system activity may be treatment targets, and that immunoregulatory probiotics, such as LGG, have the potential to decrease trauma-induced inflammatory responses, as well as associated symptoms. This manuscript describes the best powered human subjects Phase IIa trial, to date, of a probiotic intervention for those living with PTSD.

Bioactive metabolites in functional and fermented foods and their role as immunity booster and anti-viral innate mechanisms

Live microorganisms in the fermented foods termed probiotics and their secondary metabolites with bioactive potential were considered as potential anti-viral capabilities through various mechanisms. Given the importance of functional and fermented foods in disease prevention, there is a need to discuss the contextualization and deep understanding of the mechanism of action of these foods, particularly considering the appearance of coronavirus (COVID-19) pandemic, which is causing health concerns and increased social services globally. The mechanism of probiotic strains or their bioactive metabolites is due to stimulation of immune response through boosting T-lymphocytes, cytokines, and cell toxicity of natural killer cells. Proper consumption of these functional and fermented foods may provide additional antiviral approaches for public benefit by modulating the immune functions in the hosts.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13197-022-05528-8.

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.

Role of Lipoteichoic Acid from the Genus Apilactobacillus in Inducing a Strong IgA Response

Lactic acid bacterium-containing fermentates provide beneficial health effects by regulating the immune response. A naturally fermented vegetable beverage, a traditional Japanese food, reportedly provides health benefits; however, the beneficial function of its bacteria has not been clarified. Apilactobacillus kosoi is the predominant lactic acid bacterium in the beverage. Using murine Peyer's patch cells, we compared the immunoglobulin A (IgA)-inducing activity of A. kosoi 10H^T to those of 29 other species of lactic acid bacteria and found that species belonging to the genus Apilactobacillus (A. kosoi 10H^T, A. apinorum JCM30765^T, and A. kunkeei JCM16173^T) possessed significantly higher activity than the others. Thereafter, lipoteichoic acids (LTAs), important immunostimulatory molecules of Gram-positive bacteria, were purified from the three Apilactobacillus species, and their IgA-inducing activity was compared to those of LTAs from Lactiplantibacillus plantarum JCM1149^T and a probiotic strain, Lacticaseibacillus rhamnosus GG. The results revealed that LTAs from Apilactobacillus species had significantly higher activity than others. We also compared the LTA structure of A. kosoi 10H^T with that of L. plantarum JCM1149^T and L. rhamnosus GG. Although d-alanine or both d-alanine and carbohydrate residues were substituents of free hydroxyl groups in the polyglycerol phosphate structure in LTAs from strains JCM1149^T and GG, d-alanine residues were not found in LTA from strain 10H^T by ¹H nuclear magnetic resonance (NMR) analysis. Matrix-assisted laser desorption ionization-time-of-flight mass spectrometry (MALDI-TOF MS) analysis of the glycolipid structure of LTA revealed that LTA from strain 10H^T contained dihexosyl glycerol, whereas trihexosyl glycerol was detected in LTAs from other strains. These structural differences may be related to differences in IgA-inducing activity. IMPORTANCE The components of lactic acid bacteria that exert immunostimulatory effects are of increasing interest for therapeutic and prophylactic options, such as alternatives to antibiotics, cognitive enhancements, and vaccine adjuvants. LTAs act as immunostimulatory molecules in the host innate immune system by interacting with pattern recognition receptors. However, as LTA structures differ among species, detailed knowledge of the structure-function relationship for immunostimulatory effects is required. Comparisons of the IgA-inducing activity of LTAs have demonstrated that LTAs from the genus Apilactobacillus possess distinctive activities to stimulate mucosal immunity. The first analysis of the LTA structure from the genus Apilactobacillus suggests that it differs from structures of LTAs of related species of lactic acid bacteria. This knowledge is expected to aid in the development of functional foods containing lactic acid bacteria and pharmaceutical applications of immunostimulatory molecules from lactic acid bacteria.

Vaccines, Microbiota and Immunonutrition: Food for Thought

Vaccines are among the most effective health measures and have contributed to eradicating some diseases. Despite being very effective, response rates are low in some individuals. Different factors have been proposed to explain why some people are not as responsive as others, but what appears to be of critical importance is the presence of a healthy functioning immune system. In this respect, a key factor in modulating the immune system, both in its adaptive and innate components, is the microbiota. While microbiota can be modulated in different ways (i.e., antibiotics, probiotics, prebiotics), an effective and somewhat obvious mechanism is via nutrition. The science of nutrients and their therapeutic application is called immunonutrition, and it is increasingly being considered in several conditions. Our review will focus on the importance of nutrition and microbiota modulation in promoting a healthy immune system while also discussing the overall impact on vaccination response.

The Lactobacillus as a Probiotic: Focusing on Liver Diseases

Over the past decade, scientific evidence for the properties, functions, and beneficial effects of probiotics for humans has continued to accumulate. Interest in the use of probiotics for humans has increased tremendously. Among various microorganisms, probiotics using bacteria have been widely studied and commercialized, and, among them, Lactobacillus is representative. This genus contains about 300 species of bacteria (recently differentiated into 23 genera) and countless strains have been reported. They improved a wide range of diseases including liver disease, gastrointestinal diseases, respiratory diseases, and autoimmune diseases. Here, we intend to discuss in depth the genus Lactobacillus as a representative probiotic for chronic liver diseases.

Probiotic Lacticaseibacillus rhamnosus GG Increased Longevity and Resistance Against Foodborne Pathogens in Caenorhabditis elegans by Regulating MicroRNA miR-34

In this study, we investigated the relation of probiotic activity of Lacticaseibacillus rhamnosus strain GG (LGG) and expression of microRNA to immune response and longevity in Caenorhabditis elegans host model. First, we evaluated the survival rate of C. elegans due to LGG exposure and bacterial colonization in the intestine. Next, the expression of mRNA and miRNA was analyzed in C. elegans exposure to LGG for 24 h using microarray. After exposure to LGG to C. elegans, colonized LGG was observed in the intestines of C. elegans and induced to extend lifespan. Moreover, persistent LGG in the intestine significantly enhanced the resistance of C. elegans exposed to both pathogenic bacteria and prolonged the lifespan of C. elegans. Transcriptome analysis indicated that LGG affected the expression levels of genes related to the innate immune response and upregulated the abundance of genes in multiple pathways of C. elegans, including Wnt signaling, TGF-beta signaling and mitogen-activated protein kinase (MAPK) pathways. In addition, qRT-PCR analysis confirmed that the expression of antibacterial genes was increased by LGG. Moreover, as the expression of microRNA miR-34 and immune-related pathways increased by exposure to LGG, the lifespan of C. elegans increased. However, in the miR-34 mutant C. elegans, the lifespan by LGG did not increase, so it was determined that miR-34 indirectly affects immune-related pathways. There was no significant difference in the expression of PMK-1 for LGG exposure in miR-34 mutants, suggesting that miR-34 may regulate PMK-1. In conclusion, we suggest that exposure of LGG to C. elegans enhances lifespan and resistance to food-borne pathogen infection by stimulating miR-34 and indirectly promoting PMK-1 activity.

Emerging cellular senescence-centric understanding of immunological aging and its potential modulation through dietary bioactive components

Immunological aging is strongly associated with the observable deleterious effects of human aging. Our understanding of the causes, effects, and therapeutics of aging immune cells has long been considered within the sole purview of immunosenescence. However, it is being progressively realized that immunosenescence may not be the only determinant of immunological aging. The cellular senescence-centric theory of aging proposes a more fundamental and specific role of immune cells in regulating senescent cell (SC) burden in aging tissues that has augmented the notion of senescence immunotherapy. Now, in addition, several emerging studies are suggesting that cellular senescence itself may be prevalent in aging immune cells, and that senescent immune cells exhibiting characteristic markers of cellular senescence, similar to non-leucocyte cells, could be among the key drivers of various facets of physiological aging. The present review integrates the current knowledge related to immunosenescence and cellular senescence in immune cells per se, and aims at providing a cohesive overview of these two phenomena and their significance in immunity and aging. We present evidence and rationalize that understanding the extent and impact of cellular senescence in immune cells vis-à-vis immunosenescence is necessary for truly comprehending the notion of an 'aged immune cell'. In addition, we also discuss the emerging significance of dietary factors such as phytochemicals, probiotic bacteria, fatty acids, and micronutrients as possible modulators of immunosenescence and cellular senescence. Evidence and opportunities related to nutritional bioactive components and immunological aging have been deliberated to augment potential nutrition-oriented immunotherapy during aging.

Selection of Probiotics in the Prevention of Respiratory Tract Infections and Their Impact on Occupational Health: Scoping Review

The occupational health impact of respiratory infectious diseases is costly to the economy and the health care system. Probiotics are non-pathogenic live microorganisms that, when ingested in adequate amounts, can colonize the intestinal tract, and enhance the immune system. In recent years, numerous studies have described the possible usefulness of certain probiotic strains in the treatment and prevention of respiratory tract infections, with disparate results. In order to assess the possible efficacy and safety of these microorganisms to prevent or ameliorate respiratory tract infections, we systematically searched the bibliographic databases MEDLINE (via Pubmed), EMBASE, The Cochrane library, Scopus, and Web of science, using the descriptors “Respiratory Tract Infections”, “Probiotics”, “Occupational Health”, “Humans”, and “Clinical Trials”. After applying our inclusion and exclusion criteria, 18 studies were accepted for review and critical analysis. Our analysis suggests that a combination of different probiotics, most of them in the genus Bifidobacterium sp. and Lactobacillus sp., could be a good mix to strengthen the immune system and reduce the symptoms of URTIs in the healthy working population.

Genomic Stability and Phenotypic Characteristics of Industrially Produced Lacticaseibacillus rhamnosus GG in a Yogurt Matrix

Lacticaseibacillus rhamnosus GG is a widely marketed probiotic with well-documented probiotic properties. Previously, deletion of the mucus-adhesive spaCBA-srtC1 genes in dairy isolates was reported. In this study, we examined the genome preservation of industrially produced L. rhamnosus GG (DSM 33156) cofermented in yogurts. In total, DNA of 66 samples, including 60 isolates, was sequenced. Population samples and 59 isolates exhibited an intact genome. One isolate exhibited loss of spaCBA-srtC1. In addition, we examined phenotypes related to the probiotic properties of L. rhamnosus GG either from frozen pellets or cofermented in yogurt. L. rhamnosus GG from frozen pellets induced a response in intestinal barrier function in vitro, in contrast to frozen pellets of the starter culture. Yogurt matrix, containing only the starter culture, induced a response, but cofermentation with L. rhamnosus GG induced a higher response. Conversely, only the starter culture stimulated cytokine secretion in dendritic cells, and it was observed that the addition of L. rhamnosus GG to the starter culture reduced the response. We conclude that the L. rhamnosus GG genome is preserved in yogurt and that common in vitro probiotic effects of L. rhamnosus GG are observed when examined in the yogurt matrix. IMPORTANCE Lacticaseibacillus rhamnosus GG is a well-documented probiotic strain recognized for its high acid and bile tolerance and properties of adhesion to enterocytes and mucus. The strain exhibits SpaCBA pili, which have been demonstrated to play an important role in adhesion and therefore are relevant for persistence in the gastrointestinal tract. Recently we demonstrated that the genome and phenotypes of L. rhamnosus GG are preserved throughout an industrial production pipeline. However, as gene deletions in L. rhamnosus GG were previously reported for isolates from dairy products, a key question on the genomic stability of L. rhamnosus GG in a yogurt matrix remained. The aim of this study was to analyze genome stability and phenotypic characteristics of L. rhamnosus GG in yogurt. We found that the genome of L. rhamnosus GG is well conserved when the organism is cofermented in yogurt. Some phenotypic characteristics are consistent in all product matrixes, while other characteristics are modulated.

Probiotics against Viral Infections: Current Clinical Trials and Future Perspectives

Viral infections represent a major health problem worldwide. Due to the wide variety of etiological agents and their increasing resistance to anti-virals and antibiotics treatments, new strategies for effective therapies need to be developed. Scientific evidence suggests that probiotics may have prophylactic and therapeutic effects in viral diseases. Indeed, these microorganisms interact harmoniously with the intestinal microbiota and protect the integrity of the intestinal barrier as well as modulate the host immune system. Currently, clinical trials with probiotics have been documented in respiratory tract infections, infections caused by human immunodeficiency viruses, herpes, human papillomavirus and hepatic encephalopathy. However, the benefits documented so far are difficult to extrapolate, due to the strain-dependent effect. In addition, the dose of the microorganism used as well as host characteristics are other parameters that should be consider when advocating the use of probiotics to treat viral infections. This review addresses the scientific evidence of the efficacy of probiotics in clinical strains perspective in viral infectious diseases in the last 10 years.

Effect of processed aloe vera gel on immunogenicity in inactivated quadrivalent influenza vaccine and upper respiratory tract infection in healthy adults: A randomized double-blind placebo-controlled trial

BACKGROUND

Aloe vera is a functional food with various pharmacological functions, including an immune-modulating effect. Until now, A. vera has never been studied as an adjuvant in influenza vaccine, and its effects on upper respiratory tract infection (URI) are unknown.

PURPOSE

The objective of our study was to investigate the effect of processed A. vera gel (PAG) on immunogenicity of quadrivalent inactivated influenza vaccine and URI in healthy adults.

STUDY DESIGN

A randomized, double-blind, placebo-controlled clinical trial was performed.

METHODS

This study was conducted in 100 healthy adults at a single center from September 2017 to May 2018. Subjects were randomly divided into a PAG group (n = 50) and a placebo group (n = 50). The enrolled subjects were instructed to ingest the study drug for 8 weeks. The participants received a single dose of quadrivalent inactivated influenza vaccine after taking the study drug for the first 4 weeks of the study. The primary endpoint was seroprotection rate against at least one viral strain at 4 weeks post-vaccination. Other outcomes were seroprotection rate at 24 weeks post-vaccination, seroconversion rate, geometric mean fold increase (GMFI) at 4 and 24 weeks post-vaccination, seroprotection rate ratio and geometric mean titer ratio (GMTR) at 4 weeks post-vaccination between PAG and placebo groups, and incidence, severity, and duration of URI.

RESULTS

The European Committee for proprietary medicinal products (CPMP) evaluation criteria were met at least one in the PAG and placebo groups for all strains. However, there was no significant difference in the seroprotection rate at 4 weeks post-vaccination against all strains in both PAG and placebo groups. Among secondary endpoints, the GMFI at 4 weeks post-vaccination for the A/H3N2 was significantly higher in the PAG than in placebo group. The GMTR as adjuvant effect was 1.382 (95% CI, 1.014-1.1883). Kaplan-Meier curve analysis showed a reduction in incidence of URI (p = 0.035), and a generalized estimating equation model identified a decrease in repeated URI events (odds ratio 0.57; 95% CI, 0.39-0.83; p = 0.003) in the PAG group.

CONCLUSIONS

Oral intake of PAG did not show a significant increase in seroprotection rate from an immunogenicity perspective. However, it reduced the number of URI episodes. A well-designed further study is needed on the effect of PAG's antibody response against A/H3N2 in the future.

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

BACKGROUND

It has been recognized that microbiota plays a key role in shaping immune system maturation and activity. Since probiotic administration influences the microbiota composition and acts as a biological response modifier, the efficacy of an adjuvant for boosting vaccine-specific immunity is investigated.

METHODS

A review of the literature was performed, starting from the mechanisms to laboratory and clinical evidence.

RESULTS

The mechanisms, and in vitro and animal models provide biological plausibility for microbiota use. Probiotics have been investigated as adjuvants in farm conditions and as models to understand their potential in human vaccinations with promising results. In human studies, although probiotics were effective in ameliorating seroconversion to vaccines for influenza, rotavirus and other micro-organisms, the results for clinical use are still controversial, especially in particular settings, such as during the last trimester of pregnancy.

CONCLUSION

Although this topic remains controversial, the use of probiotics as adjuvant factors in vaccination represents a strategic key for different applications. The available data are deeply influenced by heterogeneity among studies in terms of strains, timing and duration of administration, and patients. Although these do not allow us to draw definitive conclusions, probiotics as adjuvants in vaccination should be considered in future studies, especially in the elderly and in children, where vaccine effectiveness and duration of immunization really matter.

Lactobacillus rhamnosus GG Orchestrates an Antitumor Immune Response

BACKGROUND & AIMS

In colorectal cancer, approximately 95% of patients are refractory to immunotherapy because of low antitumor immune responses. Therefore, there is an exigent need to develop treatments that increase antitumor immune responses and decrease tumor burden to enhance immunotherapy.

METHODS

The gut microbiome has been described as a master modulator of immune responses. We administered the human commensal, Lactobacillus rhamnosus GG (LGG), to mice and characterized the changes in the gut immune landscape. Because the presence of lactobacilli in the gut microbiome has been linked with decreased tumor burden and antitumor immune responses, we also supplemented a genetic and a chemical model of murine intestinal cancer with LGG. For clinical relevance, we therapeutically administered LGG after tumors had formed. We also tested for the requirement of CD8 T cells in LGG-mediated modulation of gut tumor burden.

RESULTS

We detected increased colonic CD8 T-cell responses specifically in LGG-supplemented mice. The CD8 T-cell induction was dependent on dendritic cell activation mediated via Toll-like receptor-2, thereby describing a novel mechanism in which a member of the human microbiome induces an intestinal CD8 T-cell response. We also show that LGG decreased tumor burden in the murine gut cancer models by a CD8 T-cell-dependent manner.

CONCLUSIONS

These data support the potential use of LGG to augment antitumor immune responses in colorectal cancer patients and ultimately for increasing the breadth and efficacy of immunotherapy.

Probiotic-Based Vaccines May Provide Effective Protection against COVID-19 Acute Respiratory Disease

Severe acute respiratory syndrome coronavirus 2 virus (SARS-CoV-2) infection, the causative agent of COVID-19, now represents the sixth Public Health Emergency of International Concern (PHEIC)—as declared by the World Health Organization (WHO) since 2009. Considering that SARS-CoV-2 is mainly transmitted via the mucosal route, a therapy administered by this same route may represent a desirable approach to fight SARS-CoV-2 infection. It is now widely accepted that genetically modified microorganisms, including probiotics, represent attractive vehicles for oral or nasal mucosal delivery of therapeutic molecules. Previous studies have shown that the mucosal administration of therapeutic molecules is able to induce an immune response mediated by specific serum IgG and mucosal IgA antibodies along with mucosal cell-mediated immune responses, which effectively concur to neutralize and eradicate infections. Therefore, advances in the modulation of mucosal immune responses, and in particular the use of probiotics as live delivery vectors, may encourage prospective studies to assess the effectiveness of genetically modified probiotics for SARS-CoV-2 infection. Emerging trends in the ever-progressing field of vaccine development re-emphasize the contribution of adjuvants, along with optimization of codon usage (when designing a synthetic gene), expression level, and inoculation dose to elicit specific and potent protective immune responses. In this review, we will highlight the existing pre-clinical and clinical information on the use of genetically modified microorganisms in control strategies against respiratory and non-respiratory viruses. In addition, we will discuss some controversial aspects of the use of genetically modified probiotics in modulating the cross-talk between mucosal delivery of therapeutics and immune system modulation.

From the Role of Microbiota in Gut-Lung Axis to SARS-CoV-2 Pathogenesis

Severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2) is responsible for the outbreak of a new viral respiratory infection. It has been demonstrated that the microbiota has a crucial role in establishing immune responses against respiratory infections, which are controlled by a bidirectional cross-talk, known as the “gut-lung axis.” The effects of microbiota on antiviral immune responses, including dendritic cell (DC) function and lymphocyte homing in the gut-lung axis, have been reported in the recent literature. Additionally, the gut microbiota composition affects (and is affected by) the expression of angiotensin-converting enzyme-2 (ACE2), which is the main receptor for SARS-CoV-2 and contributes to regulate inflammation. Several studies demonstrated an altered microbiota composition in patients infected with SARS-CoV-2, compared to healthy individuals. Furthermore, it has been shown that vaccine efficacy against viral respiratory infection is influenced by probiotics pretreatment. Therefore, the importance of the gut microbiota composition in the lung immune system and ACE2 expression could be valuable to provide optimal therapeutic approaches for SARS-CoV-2 and to preserve the symbiotic relationship of the microbiota with the host.

The effect of probiotics on respiratory tract infection with special emphasis on COVID-19: Systemic review 2010-20

To evaluate the effects of probiotics on respiratory tract infection (RTI) a systematic review of randomized controlled trials (RCTs) from January 2010 to January 2020 was conducted. The PubMed, Google Scholar, Embase, Scopus, Clinicaltrials.gov, and International Clinical Trials Registry Platform databases were systematically searched for the following keywords: respiratory tract infection, probiotics, viral infection, COVID-19, and clinical trial. A total of 27 clinical trials conducted on 9433 patients with RTI plus 10 ongoing clinical studies of probiotics intervention in Coronavirus disease 2019 (COVID-19) were reviewed. The review looked at the potency of probiotics for the hindrance and/or treatment of RTI diseases, this may also apply to COVID-19. The review found that probiotics could significantly increase the plasma levels of cytokines, the effect of influenza vaccine and quality of life, as well as reducing the titer of viruses and the incidence and duration of respiratory infections. These antiviral and immune-modulating activities and their ability to stimulate interferon production recommend the use of probiotics as an adjunctive therapy to prevent COVID-19. Based on this extensive review of RCTs we suggest that probiotics are a rational complementary treatment for RTI diseases and a viable option to support faster recovery.

In the Age of Viral Pandemic, Can Ingredients Inspired by Human Milk and Infant Nutrition Be Repurposed to Support the Immune System?

In 2020, with the advent of a pandemic touching all aspects of global life, there is a renewed interest in nutrition solutions to support the immune system. Infants are vulnerable to infection and breastfeeding has been demonstrated to provide protection. As such, human milk is a great model for sources of functional nutrition ingredients, which may play direct roles in protection against viral diseases. This review aims to summarize the literature around human milk (lactoferrin, milk fat globule membrane, osteopontin, glycerol monolaurate and human milk oligosaccharides) and infant nutrition (polyunsaturated fatty acids, probiotics and postbiotics) inspired ingredients for support against viral infections and the immune system more broadly. We believe that the application of these ingredients can span across all life stages and thus apply to both pediatric and adult nutrition. We highlight the opportunities for further research in this field to help provide tangible nutrition solutions to support one's immune system and fight against infections.

Effects of therapeutic probiotics on modulation of microRNAs

Probiotics are beneficial bacteria that exist within the human gut, and which are also present in different food products and supplements. They have been investigated for some decades, due to their potential beneficial impact on human health. Probiotics compete with pathogenic microorganisms for adhesion sites within the gut, to antagonize them or to regulate the host immune response resulting in preventive and therapeutic effects. Therefore, dysbiosis, defined as an impairment in the gut microbiota, could play a role in various pathological conditions, such as lactose intolerance, gastrointestinal and urogenital infections, various cancers, cystic fibrosis, allergies, inflammatory bowel disease, and can also be caused by antibiotic side effects. MicroRNAs (miRNAs) are short non-coding RNAs that can regulate gene expression in a post-transcriptional manner. miRNAs are biochemical biomarkers that play an important role in almost all cellular signaling pathways in many healthy and disease states. For the first time, the present review summarizes current evidence suggesting that the beneficial properties of probiotics could be explained based on the pivotal role of miRNAs. Video Abstract.

Probiotic Effects against Virus Infections: New Weapons for an Old War

This review aimed to gather the available literature investigating the effects of probiotics against the most common viral infections using in vitro trials in cell lines and in vivo clinical trials in both experimental animals and humans. Probiotics were employed to prevent and reduce symptoms of infections caused by common viruses, especially respiratory tract viruses, but also for viral digestive infections (such as rotavirus, coronavirus, or norovirus) and other viral infections (such as viruses that cause hepatitis, human papillomavirus, human immunodeficiency virus, and herpes simplex virus). Different probiotics have been studied to see their possible effect against the abovementioned viruses, among which different Lactobacillus species, Bifidobacterium, Clostridium, Enterococcus, and Streptococcus can be highlighted. In many cases, mixtures of various probiotic strains were used. Although the results obtained did not show similar results, in most cases, probiotic supplementation improved both barrier and biochemical immune responses, decreased susceptibility to viral infections, and enhanced the effects of concomitant vaccines. Works collected in this review show a beneficial effect of probiotics in the prevention and treatment of different viral infections. We found interesting results related to the prevention of viral infections, reduction of the duration of diseases, and decrease of symptoms.

Aging, Frailty, and the Microbiome-How Dysbiosis Influences Human Aging and Disease

The human gut microbiome is a collection of bacteria, protozoa, fungi, and viruses that coexist in our bodies and are essential in protective, metabolic, and physiologic functions of human health. Gut dysbiosis has traditionally been linked to increased risk of infection, but imbalances within the intestinal microbial community structure that correlate with untoward inflammatory responses are increasingly recognized as being involved in disease processes that affect many organ systems in the body. Furthermore, it is becoming more apparent that the connection between gut dysbiosis and age-related diseases may lie in how the gut microbiome communicates with both the intestinal mucosa and the systemic immune system, given that these networks have a common interconnection to frailty. We therefore discuss recent advances in our understanding of the important role the microbiome plays in aging and how this knowledge opens the door for potential novel therapeutics aimed at shaping a less dysbiotic microbiome to prevent or treat age-related diseases.

Probiotic Lactobacilli Enhance Immunogenicity of an Inactivated H9N2 Influenza Virus Vaccine in Chickens

Avian influenza viruses (AIVs) infect a wide range of hosts, including humans and many avian species. Efforts have been made to control this pathogen in chickens using vaccination programs, but that has been met with varying degrees of success. Therefore, identification of more efficacious vaccination strategies is warranted. This study was undertaken to investigate the potential effects of probiotics on the immunogenicity of a beta-propiolactone-whole inactivated virus (WIV) vaccine of H9N2 subtype adjuvanted with the Toll-like receptor-21 ligand, CpG oligodeoxynucleotides 2007 (CpG). Eighty-four 1-day-old White Leghorn layers were allocated into six groups. Two out of six groups received a mixture of probiotic Lactobacillus spp. (PROB) biweekly from days 1 35 of age. Chickens were intramuscularly vaccinated with WIV either alone or adjuvanted with AddaVax™ (WIV+Add) or CpG (WIV+CpG), and one group received saline (phosphate-buffered saline). Primary and secondary vaccinations occurred at days 14 and 28 of age, respectively. The results revealed that the group that received probiotics and was vaccinated with CpG-adjuvanted WIV H9N2 vaccine had higher hemagglutination inhibition titers than the other treatment groups at days 14 and 21 postprimary vaccination. Probiotics did not induce higher IgM or IgY titers in chickens receiving the WIV vaccine only. Concerning their effect on cell-mediated immune responses, probiotics enhanced interferon-gamma (IFN-γ) gene expression and significantly increased secretion of IFN-γ protein by splenocytes in chickens vaccinated with CpG-adjuvanted WIV H9N2. Together, these findings suggest the use of probiotics to enhance the immunogenicity of CpG-adjuvanted WIV H9N2 vaccines. Additional studies are required to better understand the specific interactions between probiotics and the gut microbiota and different types of cells of the gastrointestinal tract to decipher the underlying mechanisms of how probiotics modulate immune responses to vaccines.

Effects of non-pharmacological interventions as vaccine adjuvants in humans: a systematic review and network meta-analysis

INTRODUCTION

Psychological and behavioural may enhance vaccine effectiveness. We conducted a systematic review and network meta-analysis (NMA) to examine the effects of non-pharmacological adjuvants on vaccine effectiveness, as measured by antibody responses to vaccination.

AREAS COVERED

Electronic databases (EMBASE, Medline, PsychINFO, CINAHL) were searched from inception to 6th February 2018. This yielded 100 eligible papers, reporting 106 trials: 79 interventions associated with diet and/or nutrition; 12 physical activity interventions and 9 psychological interventions.Over half (58/106) of trials reported evidence of an enhanced antibody response to vaccination across one or more outcomes. The NMA considered the comparative effects between all intervention types, control and placebo for antibody titres (48 studies), seroconversion (25 studies) and seroprotection (23 studies) separately. The NMA provided weak evidence in support of nutritional formulae and probiotics in increasing antibody titres.

EXPERT OPINION

This review offers a comprehensive summary of the literature on non-pharmacological interventions as vaccine adjuvants. The evidence is characterised by considerable heterogeneity but provides early evidence in support of nutritional formulae and probiotic interventions. Psychological and exercise-based interventions were characterised by limited and unreliable evidence. Large, well-designed studies including consistent core outcomes and measures of intervention adherence and fidelity are required.

Personalized B cell response to the Lactobacillus rhamnosus GG probiotic in healthy human subjects: a randomized trial

The specific effects of administering live probiotics in the human gut are not well characterized. To this end, we investigated the immediate effect of Lactobacillus rhamnosus GG (LGG) in the jejunum of 27 healthy volunteers 2 h after ingestion using a combination of global RNA sequencing of human biopsies and bacterial DNA sequencing in a multi-visit, randomized, cross-over design (ClinicalTrials.gov number NCT03140878). While LGG was detectable in jejunum after 2 h in treated subjects, the gene expression response vs. placebo was subtle if assessed across all subjects. However, clustering analysis revealed that one-third of subjects exhibited a strong and consistent LGG response involving hundreds of genes, where genes related to B cell activation were upregulated, consistent with prior results in mice. Immunohistochemistry and single cell-based deconvolution analyses showed that this B cell signature likely is due to activation and proliferation of existing B cells rather than B cell immigration to the tissue. Our results indicate that the LGG strain has an immediate effect in the human gut in a subpopulation of individuals. In extension, our data strongly suggest that studies on in vivo probiotic effects in humans require large cohorts and must take individual variation into account.

Immune enhancing effects of Lactobacillus acidophilus on Newcastle disease vaccination in chickens

INTRODUCTION AND PURPOSE

Despite the various vaccination programs for protection against New Castle disease, it remains an important threat to the poultry industry. The ability of the probiotic bacteria to improve the immune system in both animals and humans supports their use as immune adjuvants for vaccination. The aim of the present study was to examine the effects of Lactobacillus acidophilus in ND vaccination.

MATERIALS AND METHODS

A total of 170 one day old chicks were divided in 5 groups. In groups A, B and C chicks were received L. acidophilus (5 × 10⁹, 3 × 10⁹ and 2 × 10⁹) and also vaccinated with inactivated and attenuated ND vaccines. In group D, chicks only vaccinated without bacterial inoculation and group E was negative control with neither vaccine nor bacteria. Then IgG and HI NDV antibody titers were measured in all tested groups.

RESULTS

IgG and HI NDV antibody levels were significantly higher in Lactobacillus treated groups especially in group A with 5 × 10⁹ bacteria, than only vaccinated and negative control groups. Also antibody levels against NDV increased during the vaccination period especially in probiotic treated groups.

CONCLUSION

In conclusion, L. acidophilus can use for improving immunogenicity of NDV vaccination programs.

The Promising Role of Probiotics in Managing the Altered Gut in Autism Spectrum Disorders

Gastrointestinal symptoms (GIS) have been reported repeatedly in people with autism spectrum disorder (ASD) and studies have reported interesting correlations between severity of behavioral and gastrointestinal symptoms. Growing evidence indicates that the gut microbiota in ASD is altered with various shifts described at different taxonomic levels, pointing to the importance of considering the gut-brain axis in treatment of these disorders. Probiotics are live beneficial bacteria that are ingested as food or customized pills. These beneficial bacteria, when added in sufficient amounts, can correct the dysbiosis. Because probiotics have shown success in treating irritable bowel syndrome (IBS), it is plausible to investigate whether they can induce alleviation of behavioral symptoms as well. Probiotics show, in some clinical studies, their potential benefits (1) in improving gastrointestinal dysfunction, (2) in correcting dysbiosis, (3) in consequently reducing the severity of ASD symptoms. This review compiles data from selected studies that investigate these benefits and the mechanisms that mediate these effects, which include the production of metabolites, hormones, and neurotransmitters and the regulation of pro-inflammatory and regulatory cytokines. Future research based on more randomized, controlled studies with a larger population size and standardized use of strains, concentration of probiotics, duration of treatments, and methods of DNA extraction is still needed in this area, which may lead to more robust results.

Immune modulatory capacity of probiotic lactic acid bacteria and applications in vaccine development

Vaccination is one of the most important prevention tools providing protection against infectious diseases especially in children below the age of five. According to estimates, more than 5 million lives are saved annually by the implementation of six standard vaccines, including diphtheria, hepatitis B, Haemophilus influenza type b, polio, tetanus and yellow fever. Despite these efforts, we are faced with challenges in developing countries where increasing population and increasing disease burden and difficulties in vaccine coverage and delivery cause significant morbidity and mortality. Additionally, the high cost of these vaccines is also one of the causes for inappropriate and inadequate vaccinations in these regions. Thus, developing cost-effective vaccine strategies that could provide a stronger immune response with reduced vaccination schedules and maximum coverage is of critical importance. In last decade, different approaches have been investigated; among which live bacterial vaccines have been the focus of attention. In this regard, probiotic lactic acid bacteria have been extensively studied as safe and effective vaccine candidates. These microorganisms represent the largest group of probiotic bacteria in the intestine and are generally recognised as safe (GRAS) bacteria. They have also attracted attention due to their immunomodulatory actions and their effective role as novel vaccine adjuvants. A significant property of these bacteria is their ability to mimic natural infections, while intrinsically possessing mucosal adjuvant properties. Additionally, as live bacterial vaccines are administered orally or nasally, they have higher acceptance and better safety, but also avoid the risk of contamination due to needles and syringes. In this review, we emphasise the role of probiotic Lactobacillus strains as putative oral vaccine carriers and novel vaccine adjuvants.

Host Factors Impact Vaccine Efficacy: Implications for Seasonal and Universal Influenza Vaccine Programs

Influenza is a global public health problem. Current seasonal influenza vaccines have highly variable efficacy, and thus attempts to develop broadly protective universal influenza vaccines with durable protection are under way. While much attention is given to the virus-related factors contributing to inconsistent vaccine responses, host-associated factors are often neglected. Growing evidences suggest that host factors including age, biological sex, pregnancy, and immune history play important roles as modifiers of influenza virus vaccine efficacy. We hypothesize that host genetics, the hormonal milieu, and gut microbiota contribute to host-related differences in influenza virus vaccine efficacy. This review highlights the current insights and future perspectives into host-specific factors that impact influenza vaccine-induced immunity and protection. Consideration of the host factors that affect influenza vaccine-induced immunity might improve influenza vaccines by providing empirical evidence for optimizing or even personalizing vaccine type, dose, and use of adjuvants for current seasonal and future universal influenza vaccines.

Host Factors Impact Vaccine Efficacy: Implications for Seasonal and Universal Influenza Vaccine Programs

Influenza is a global public health problem. Current seasonal influenza vaccines have highly variable efficacy, and thus attempts to develop broadly protective universal influenza vaccines with durable protection are under way. While much attention is given to the virus-related factors contributing to inconsistent vaccine responses, host-associated factors are often neglected. Growing evidences suggest that host factors including age, biological sex, pregnancy, and immune history play important roles as modifiers of influenza virus vaccine efficacy. We hypothesize that host genetics, the hormonal milieu, and gut microbiota contribute to host-related differences in influenza virus vaccine efficacy. This review highlights the current insights and future perspectives into host-specific factors that impact influenza vaccine-induced immunity and protection. Consideration of the host factors that affect influenza vaccine-induced immunity might improve influenza vaccines by providing empirical evidence for optimizing or even personalizing vaccine type, dose, and use of adjuvants for current seasonal and future universal influenza vaccines.

Translating Recent Microbiome Insights in Otitis Media into Probiotic Strategies

The microbiota of the upper respiratory tract (URT) protects the host from bacterial pathogenic colonization by competing for adherence to epithelial cells and by immune response regulation that includes the activation of antimicrobial and (anti-)inflammatory components. However, environmental or host factors can modify the microbiota to an unstable community that predisposes the host to infection or inflammation. One of the URT diseases most often encountered in children is otitis media (OM). The role of pathogenic bacteria like Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis in the pathogenesis of OM is well documented. Results from next-generation-sequencing (NGS) studies reveal other bacterial taxa involved in OM, such as Turicella and Alloiococcus Such studies can also identify bacterial taxa that are potentially protective against URT infections, whose beneficial action needs to be substantiated in relevant experimental models and clinical trials. Of note, lactic acid bacteria (LAB) are members of the URT microbiota and associated with a URT ecosystem that is deemed healthy, based on NGS and some experimental and clinical studies. These observations have formed the basis of this review, in which we describe the current knowledge of the molecular and clinical potential of LAB in the URT, which is currently underexplored in microbiome and probiotic research.

Commensal gut microbiota can modulate adaptive immune responses in chickens vaccinated with whole inactivated avian influenza virus subtype H9N2

Variations in the composition of commensal gut microbiota have been reported to be major contributors to differences in responses to vaccination among individuals. In chickens, there is limited information on the role of gut microbiota in responses to vaccination. The current study studied the role of gut microbiota in cell- and antibody-mediated immune responses to vaccination with a whole inactivated avian influenza virus, subtype H9N2. A total of 166 one-day-old specific pathogen free layer chickens (SPF) were randomly assigned to treatments, where a combination of antibiotic depletion, and probiotics (a combination of five Lactobacillus species) or fecal microbial transplant (FMT) reconstitution were used to study the dynamics of cell- and antibody-mediated immune responses to primary and secondary vaccinations at days 15 and 29 of age, respectively. Overall, at days 7 and 14 post primary vaccination (p.p.v.), administration of probiotics to non-depleted chickens resulted in significantly higher mean hemagglutination (HI) titre compared to antibiotic treated chickens. Furthermore, at day 21 p.p.v., chickens treated with probiotics or FMT post-antibiotic treatment showed a significantly higher mean HI titre compared to non-depleted chickens treated with probiotics. At day 7 p.p.v., a significantly higher virus specific IgM and IgG titres were observed in non-depleted chickens administered with probiotics compared to antibiotic depleted chickens, and a significantly higher IgG titre was observed in chickens treated with FMT following antibiotic treatment compared to only antibiotic treatment. Analysis of interferon gamma expression in splenocytes to assess cell-mediated immune responses showed a significantly lower expression in antibiotic-treated chickens compared to non-depleted chickens and FMT reconstituted chickens. Taken together, the current study suggests that shifts in the composition of gut microbiota of chickens may result in changes in cell- and antibody-mediated immune responses to vaccination against influenza viruses. Further studies will be needed to highlight the mechanisms involved in this modulation.

Effects of probiotic administration on immune responses of children and adolescents with type 1 diabetes to a quadrivalent inactivated influenza vaccine

This study was planned to evaluate whether a 3-month treatment with Lactobacillus rhamnosus GG (LGG) can modify immune system functions in children and adolescents with type 1 diabetes (T1D), leading to an increased immune response to an injectable quadrivalent inactivated influenza vaccine (QIV). A total of 87 pediatric patients with T1D were screened, although 34 patients in the Probiotic group and 30 in the Control group accepted to be vaccinated with QIV and completed the study. Vaccine immunogenicity and safety and the inflammatory cytokine response were studied. Results showed that QIV was immunogenic and safe in T1D pediatric patients and pre-administration of LGG for three months did not substantially modify the QIV humoral immunity. The combination of QIV and LGG reduced inflammatory responses (i.e., IFN-γ, IL17A, IL-17F, IL-6, and TNF-α) from activated PBMCs of pediatric patients with T1D, without dampening the production of seroprotective antibodies. In conclusion, QIV is associated with an adequate immunogenicity in children and adolescents with T1D in presence of a good safety profile. Although a systematic administration of LGG did not result in an improvement of humoral responses to an influenza vaccine, the probiotic did induce important anti-inflammatory effects.

Protocol for a double-blind placebo-controlled trial to evaluate the efficacy of probiotics in reducing antibiotics for infection in care home residents: the Probiotics to Reduce Infections iN CarE home reSidentS (PRINCESS) trial

INTRODUCTION

Care home residents are at increased risk of infections and antibiotic prescription. Reduced antibiotic use from fewer infections would improve quality of life. The Probiotics to Reduce Infections iN CarE home reSidentS (PRINCESS) trial aims to determine the efficacy and investigate mechanisms of daily probiotics on antibiotic use and incidence of infections in care home residents.

METHODS AND ANALYSIS

PRINCESS is a double-blind, individually randomised, placebo-controlled trial that will assess the effect of a daily oral probiotic combination of Lactobacillus rhamnosus, GG (LGG) and Bifidobacterium animalis subsp. lactis, BB-12 (BB-12) on cumulative antibiotic administration days (CAADs) (primary outcome) for infection in up to 330 care home residents aged ≥65 years over up to 12 months. Secondary outcomes include: Infection: Total number of days of antibiotic administration for each infection type (respiratory tract infection, urinary tract infection, gastrointestinal infection, unexplained fever and other); number, site, duration of infection; estimation of incidence and duration of diarrhoea and antibiotic-associated diarrhoea; Stool microbiology: Clostridium difficile infection; Gram-negative Enterobacteriaceae and vancomycin-resistant enterococci; LGG and BB-12. Oral microbiology: Candida spp. Health and well-being: Self and/or proxy health-related quality of life EQ5D (5 L); self-and/or proxy-reported ICEpop CAPability measure for older people. Hospitalisations: number and duration of all-cause hospital stays. Mortality: deaths. Mechanistic immunology outcomes: influenza vaccine efficacy (haemagglutination inhibition assay and antibody titres); full blood count and immune cell phenotypes, plasma cytokines and chemokines; cytokine and chemokine response in whole blood stimulated ex vivo by toll-like receptor 2 and 4 agonists; monocyte and neutrophil phagocytosis of Escherichia coli; serum vitamin D.

ETHICS AND DISSEMINATION

Ethics approval is from the Wales Research Ethics Committee 3. Findings will be disseminated through peer-reviewed journals and conferences; results will be of interest to patient and policy stakeholders.

TRIAL REGISTRATION NUMBER

ISRCTN16392920; Pre-results.

Factors That Influence the Immune Response to Vaccination

There is substantial variation between individuals in the immune response to vaccination. In this review, we provide an overview of the plethora of studies that have investigated factors that influence humoral and cellular vaccine responses in humans. These include intrinsic host factors (such as age, sex, genetics, and comorbidities), perinatal factors (such as gestational age, birth weight, feeding method, and maternal factors), and extrinsic factors (such as preexisting immunity, microbiota, infections, and antibiotics). Further, environmental factors (such as geographic location, season, family size, and toxins), behavioral factors (such as smoking, alcohol consumption, exercise, and sleep), and nutritional factors (such as body mass index, micronutrients, and enteropathy) also influence how individuals respond to vaccines. Moreover, vaccine factors (such as vaccine type, product, adjuvant, and dose) and administration factors (schedule, site, route, time of vaccination, and coadministered vaccines and other drugs) are also important. An understanding of all these factors and their impacts in the design of vaccine studies and decisions on vaccination schedules offers ways to improve vaccine immunogenicity and efficacy.

Nutritional Modulation of Immune Function: Analysis of Evidence, Mechanisms, and Clinical Relevance

It is well-established that the nutritional deficiency or inadequacy can impair immune functions. Growing evidence suggests that for certain nutrients increased intake above currently recommended levels may help optimize immune functions including improving defense function and thus resistance to infection, while maintaining tolerance. This review will examine the data representing the research on prominent intervention agents n-3 polyunsaturated fatty acids (PUFA), micronutrients (zinc, vitamins D and E), and functional foods including probiotics and tea components for their immunological effects, working mechanisms, and clinical relevance. Many of these nutritive and non-nutritive food components are related in their functions to maintain or improve immune function including inhibition of pro-inflammatory mediators, promotion of anti-inflammatory functions, modulation of cell-mediated immunity, alteration of antigen-presenting cell functions, and communication between the innate and adaptive immune systems. Both animal and human studies present promising findings suggesting a clinical benefit of vitamin D, n-3 PUFA, and green tea catechin EGCG in autoimmune and inflammatory disorders, and vitamin D, vitamin E, zinc, and probiotics in reduction of infection. However, many studies report divergent and discrepant results/conclusions due to various factors. Chief among them, and thus call for attention, includes more standardized trial designs, better characterized populations, greater consideration for the intervention doses used, and more meaningful outcome measurements chosen.