Probiotics and the immune response to vaccines

INVITED REVIEW: Advances in Yogurt Development: Microbiological Safety, Quality, Functionality, Sensory Evaluation, and Consumer Perceptions across Different Dairy and Plant-based Alternative Sources

Yogurt, as a globally prevalent fermented dairy product, is renowned for its substantial nutritional value and a myriad of health benefits, particularly pertaining to the digestive system. This narrative review elucidates the latest advancements in yogurt development from 2019 to 2024, addressing aspects of microbiological safety, quality, functionality, sensory evaluation, and consumer perceptions across diverse protein sources. The intrinsic quality of yogurt is significantly influenced by its primary ingredient, milk, traditionally derived from animals such as cows, goats, and sheep. In recent years, plant-based yogurts (PBYs) have emerged as a popular alternative to traditional dairy yogurts, that are made from plant sources and offer similar textures and flavors, catering to those seeking non-dairy options. This discussion encompasses the advantages and limitations of various sources and explores methodologies to enhance yogurt quality using these diverse sources. Ensuring the microbiological safety of yogurt is thus paramount to its quality, as it involves both preventing the presence of harmful pathogens and managing spoilage to maintain freshness. This article encapsulates the potential hazards and corresponding antibacterial strategies that safeguard yogurt consumption. These strategies include the use of natural preservatives, advancements in packaging technologies, and the implementation of stringent hygiene practices throughout the production process. Morever, the quality of yogurt is not only dependent on the source but also on the fermentation process and additional ingredients used. By addressing both the prevention of pathogen contamination and the control of spoilage organisms, this article explores not only explores comprehensive approaches but also examines the use of high-quality starter cultures, the role of prebiotics in enhancing probiotic efficacy, and genetic advancements, as well as improvements in the overall nutritional profile and shelf life of yogurt. Techniques to improve texture, flavor, and nutrient content are also discussed, providing a comprehensive overview of current quality enhancement methods.This analysis delves into the intricate mechanisms underpinning probiotic development, including the roles of prebiotics, supplementary starter cultures, and genetic factors that facilitate probiotic proliferation. These benefits include improved digestive health, enhanced immune function, and potential reductions in the risk of certain chronic diseases. Beyond quality and functionality, the sensory evaluation of yogurt remains crucial for consumer acceptance. In recent years, the incorporation of diverse additional ingredients into yogurt has been observed, aimed at augmenting its sensory attributes. This examination reveals these ingredients and their respective functions, such as natural flavorings, sweeteners, and texturizing agents, with the ultimate goal of enhancing overall consumer satisfaction. Consumer preferences exert a profound influence on yogurt production, rendering the understanding of customer opinions essential for devising competitive industry strategies. This article consolidates consumer feedback and preferences, striving to elevate yogurt quality and promote dietary diversity. The analysis includes trends such as the growing demand for organic and non-dairy yogurts, the importance of sustainable practices, and the impact of marketing and packaging on consumer choices. This comprehensive overview serves as a valuable reference for the dairy industry and researchers dedicated to the advancement of yogurt development.

Immunomodulatory effect of Lacticaseibacillus casei CB054 supplementation in calves vaccinated against infectious bovine rhinotracheitis

Probiotics are live microorganisms that, confer health benefits to the host when supplemented in adequate amounts. They can promote immunomodulation by inducing phagocyte activity, leukocyte proliferation, antibody production, and cytokine expression. Lactic acid bacteria (BAL) are important probiotic specimens with properties that can improves ruminant nutrition, productivity and immunity. The aim of the present study was to evaluate the immunomodulatory effect of the supplementation with Lacticaseibacillus casei CB054 in calve vaccinated against bovine infectious rhinotracheitis (IBR). Calve were vaccinated with a commercial IBR vaccine, on day 0 and received a booster dose on day 21. L. casei CB054 was orally administered (4 ×109 UFC) for 35 days, while a non-supplemented control group received Phosphate Buffer Saline (PBS). Stimulation of bovine splenocytes with L. casei CB054 markedly enhanced mRNA transcription levels of cytokines IL2, IL4, IL10 and IL17 genes. Calves supplemented with L. casei CB054 showed significantly higher (p < 0.05) specific anti-BoHV-1 IgG levels, higher serum neutralization, as well as higher mRNA transcription for IL2, IL4, IL10 and IL17 genes in Peripheral Blood Mononuclear Cells (PBMCs) comparing with control calves. Supplemented calve had an average weight gain of ∼14 kg more than non-supplemented during the experimental period. These results suggest that L. casei CB054 supplementation increase immunogenicity of a commercial IBR vaccine in cattle and improve weight gain.

Role of Acacia catechu and Scutellaria baicalensis in Enhancing Immune Function Following Influenza Vaccination of Healthy Adults: A Randomized, Triple-Blind, Placebo-Controlled Clinical Trial

OBJECTIVE

The study aimed to examine the role of an Acacia catechu and Scutellaria baicalensis formulation, UP446, on supporting immune function in response to influenza vaccination.

METHODS

A randomized, triple-blind, placebo-controlled, parallel study consisted of a 56-day intervention period with a 28-day pre-vaccination period, an influenza vaccination on Day 28 and 28-day post-vaccination period. Fifty healthy adults 40-80 years of age who had not received their flu vaccine were randomized to either UP446 or Placebo. At baseline, Days 28 and 56, immune and oxidative stress markers were measured in blood and a quality of life questionnaire was administered. Participants completed the Wisconsin Upper Respiratory Symptom Survey (WURSS)-24 daily.

RESULTS

In the post-vaccination period, total IgA and IgG levels increased in participants supplemented with UP446 vs. those on Placebo (p ≤ 0.026). As well, influenza B-specific IgG increased 19.4% from Day 28 to 56 and 11.6% from baseline at Day 56 (p ≤ 0.0075). Serum glutathione peroxidase (GSH-Px) was increased in the pre-vaccination period and from baseline at Day 56 with UP446 supplementation (p ≤ 0.0270).

CONCLUSION

These results suggest a 56-day supplementation with UP446 was beneficial in mounting a robust humoral response following vaccination. Increasing GSH-Px in the pre-vaccination period may help improve antioxidant functions and potentially mitigate the oxidative stress induced following vaccination.

Effects of yogurt containing probiotics on respiratory virus infections: Influenza H1N1 and SARS-CoV-2

Respiratory virus infections are an escalating issue and have become common worldwide. Influenza and COVID-19 are typical infectious respiratory diseases, and they sometimes lead to various complications. In a situation in which no established drug or treatment exists, consumption of proper food might be beneficial in maintaining health against external infections. We studied the potential effects of mixtures of probiotic strains on various viral infections. The purpose of this study was to assess the ability of yogurt containing probiotics to reduce the risk of respiratory viruses such as influenza H1N1 and SARS-CoV-2 infection. First, we performed in vitro tests using infected Madin-Darby canine kidney (MDCK) and Vero E6 cells, to evaluate the potential effects of yogurt containing high-dose probiotics against influenza H1N1 and SARS-CoV-2 infection. The yogurt significantly reduced plaque formation in the virus-infected cells. We also performed in vivo tests using influenza H1N1-infected C57BL/6 mice and SARS-CoV-2-infected Syrian golden hamsters, to evaluate the potential effects of yogurt. Yogurt was administered orally once daily during the experimental period. Yogurt was also administered orally as pretreatment once daily for 3 wk before viral infection. Regarding influenza H1N1, it was found that yogurt caused an increase in the survival rate, body weight, and IFN-γ, IgG1, and IL-10 levels against viral infection and a decrease in the inflammatory cytokines TNF-α and IL-6. Although the SARS-CoV-2 copy number was not significantly reduced in the lungs of yogurt-treated SARS-CoV-2-infected hamsters, the body weights and histopathological findings of the lungs were improved in the yogurt-treated group. In conclusion, we suggest that consumption of yogurt containing probiotics can lead to beneficial effects to prevent respiratory viral infections.

Microbiota and Lifestyle: A Special Focus on Diet

It is widely known that a good balance and healthy function for bacteria groups in the colon are necessary to maintain homeostasis and preserve health. However, the lack of consensus on what defines a healthy gut microbiota and the multitude of factors that influence human gut microbiota composition complicate the development of appropriate dietary recommendations for our gut microbiota. Furthermore, the varied response to the intake of probiotics and prebiotics observed in healthy adults suggests the existence of potential inter- and intra-individual factors, which might account for gut microbiota changes to a greater extent than diet. The changing dietary habits worldwide involving consumption of processed foods containing artificial ingredients, such as sweeteners; the coincident rise in emotional disorders; and the worsening of other lifestyle habits, such as smoking habits, drug consumption, and sleep, can together contribute to gut dysbiosis and health impairment, as well as the development of chronic diseases. This review summarizes the current literature on the effects of specific dietary ingredients (probiotics, prebiotics, alcohol, refined sugars and sweeteners, fats) in the gut microbiota of healthy adults and the potential inter- and intra-individual factors involved, as well as the influence of other potential lifestyle factors that are dramatically increasing nowadays.

Bacillus toyonensis improves immune response in the mice vaccinated with recombinant antigen of bovine herpesvirus type 5

Probiotics modulate the immune response and can increase the effectiveness of vaccines. Bacillus toyonensis is widely used as a probiotic in animal feed. The aim of this study was to assess the effects of B. toyonensis administration on the immune response to an experimental recombinant vaccine against bovine herpesvirus type 5 (BoHV-5) in mice. Mice were vaccinated with BoHV-5 recombinant glycoprotein D and supplemented with the probiotic B. toyonensis in two regimes: one group received the probiotic only during seven days prior to the initial vaccination while the second group was given the probiotic throughout the experimental period of seven weeks. Animals supplemented with probiotic B. toyonensis in two regimes showed an increase in total immunoglobulin (Ig)G, IgG1 and IgG2a levels in serum, in addition to higher titres of antibodies capable of neutralising the BoHV-5 virus than non-supplemented animals (P<0.05). Splenocytes from the supplemented mice had higher mRNA transcription levels of cytokines interleukin (IL)-4 and IL-12. These results show that the use of this probiotic may significantly contribute to the response elicited by recombinant vaccines, especially those that rely on increasing antibody and cell-mediated immune responses for efficacy. Further, the data support an immunomodulatory effect for probiotic B. toyonensis and imply that enhance effect on the immune response against a BoHV-5 recombinant vaccine in mice.

Can probiotics enhance vaccine-specific immunity in children and adults?

The growing use of probiotics by the general public has heightened the interest in understanding the role of probiotics in promoting health and preventing disease. General practitioners and specialists often receive inquiries from their patients regarding probiotic products and their use to ward off systemic infection or intestinal maladies. Enhanced immune function is among the touted health benefits conferred by probiotics but has not yet been fully established. Results from recent clinical trials in adults suggest a potential role for probiotics in enhancing vaccine-specific immunity. Although almost all vaccinations are given during infancy and childhood, the numbers of and results from studies using probiotics in pediatric subjects are limited. This review evaluates recent clinical trials of probiotics used to enhance vaccine-specific immune responses in adults and infants. We highlight meaningful results and the implications of these findings for designing translational and clinical studies that will evaluate the potential clinical role for probiotics. We conclude that the touted health claims of probiotics for use in children to augment immunity warrant further investigation. In order to achieve this goal, a consensus should be reached on common study designs that apply similar treatment timelines, compare well-characterised probiotic strains and monitor effective responses against different classes of vaccines.

Evaluation of Lactobacillus coryniformis CECT5711 strain as a coadjuvant in a vaccination process: a randomised clinical trial in healthy adults

BACKGROUND

Although the effects of probiotics on the immune system have been extensively evaluated under disease states, their role in healthy situations remains unclear, since changes are hardly expected under immunological homeostasis. EFSA indicates that vaccination protocols could be used to evaluate the potential role of probiotics to improve the immune response against antigen challenges. The aim of the study was to evaluate the effect of Lactobacillus coryniformis CECT5711 (Lc) on the specific immunity of healthy volunteers undergoing vaccination with Hepatitis A virus (HAV).

METHODS

One hundred twenty-three healthy adults were randomised into three groups to follow a 6-week (wk) intervention and all received an intramuscular HAV vaccine 2 weeks after starting the intervention: 1) PRO1 received Lc for 2weeks (1 capsule/day; 3 × 10⁹ CFU/capsule) and placebo capsules after vaccination; 2) PRO2 received a daily capsule of Lc (3 × 10⁹ cfu/day) before and after the challenge; 3) Control group (C) received a daily placebo capsule before and after the vaccine. Blood samples were collected at the beginning (visit 1; V1) and after 2 (V2) and 6 weeks (V3) of the intervention. At each visit, lymphocyte subset counts and cytokine levels were analysed. Specific HAV antibodies were analysed at V1 and V3. To evaluate differences between groups, one-way ANOVA with Bonferroni post-hoc test were used regarding lymphocyte subset counts and specific HAV antibodies production, and Friedman test of related samples and Kendall concordance coefficient for cytokines production. Chi square test was used to analyse seroconversion rates.

RESULTS

Specific HAV antibodies were significantly higher in PRO1 (50.54 ± 29.57) compared to C (36.23 ± 16.45) (P = 0.017) and showed an intermediate value in PRO2 (41.61 ± 15.74). Seroconversion rates were similar in the three groups (97.3, 92.3 and 97.4% in C, PRO1 and PRO2 respectively). Memory T-helper lymphocytes increased in V3 vs. V1 (P = 0.032) in PRO2. No differences were found in cytokine concentrations.

CONCLUSION

Mixed results have been found regarding the usefulness of Lc supplementation to increase the antigen-specific antibody response to an immune challenge. Clinical trial registration number: EudraCT Number 2016-000183-42. Registered 19 January 2016. Retrospectively registered.

Ageing alters the impact of nutrition on immune function

Immunosenescence during ageing is a major challenge which weakens the ability of older individuals to respond to infection or vaccination. There has been much interest in dietary strategies to improve immunity in older people, but there is an assumption that modulation of the immune response in older people will be based on the same principles as for younger adults. Recent evidence suggests that ageing fundamentally alters the impact of nutrition on immune function. As a result, interpretation of data from studies investigating the impact of diet on immune function is highly dependent on subject age. Study design is critically important when investigating the efficacy of dietary components, and most studies involving older people include rigorous inclusion/exclusion criteria based on medical history, laboratory tests, general health status and often nutritional status. However, immunological status is rarely accounted for, but can vary significantly, even amongst healthy older people. There are several clear examples of age-related changes in immune cell composition, phenotype and/or function, which can directly alter the outcome of an intervention. This review uses two case studies to illustrate how the effects of n-3 PUFA and probiotics differ markedly in young v. older subjects. Evidence from both suggests that baseline differences in immunosenescence influence the outcome of an intervention, highlighting the need for detailed immunological characterisation of subjects prior to interventions. Finally, future work elucidating alterations in metabolic regulation within cells of the immune system as a result of ageing may be important in understanding the impact of diet on immune function in older people.

Taxa of the Nasal Microbiome Are Associated with Influenza-Specific IgA Response to Live Attenuated Influenza Vaccine

Live attenuated influenza vaccine (LAIV) has demonstrated varying levels of efficacy against seasonal influenza; however, LAIV may be used as a tool to measure interactions between the human microbiome and a live, replicating virus. To increase our knowledge of this interaction, we measured changes to the nasal microbiome in subjects who received LAIV to determine if associations between influenza-specific IgA production and the nasal microbiome exist after immunization with a live virus vaccine. The anterior nares of 47 healthy subjects were swabbed pre- (Day 0) and post- (Days 7 and 28) LAIV administration, and nasal washes were conducted on Days 0 and 28. We performed next-generation sequencing on amplified 16s rRNA genes and measured mucosal influenza-specific IgA titers via enzyme-linked immunosorbent assay (ELISA). A significant increase in alpha diversity was identified (Observed, CHAO, and ACE) between Days 7 vs 0 (p-values = 0.017, 0.005, 0.005, respectively) and between Days 28 vs 0 (p-values = 0.054, 0.030, 0.050, respectively). Several significant associations between the presence of different microbial species, including Lactobacillus helveticus, Prevotella melaninogenica, Streptococcus infantis, Veillonella dispar, and Bacteroides ovatus, and influenza-specific H1 and H3 IgA antibody response were demonstrated. These data suggest that LAIV alters the nasal microbiome, allowing several less-abundant OTUs to establish a community niche. Additionally, specific alterations in the nasal microbiome are significantly associated with variations in influenza-specific IgA antibody production and could be clinically relevant.

Effects of Bifidobacterium supplementation on intestinal microbiota composition and the immune response in healthy infants

BACKGROUND

Intestinal microbiotas are thought to be the most important source of maturational stimuli to the development of the immune system. However, few studies have focused on the development of T helper (Th) 1 immune response and antibody response to vaccinations in healthy infants, especially in a large cohort. Through this randomized, double-blind control trial, we investigated the effects of Bifidobacterium longum BB536 (BB536) supplementation on intestinal microbiota composition and the immune response in term infants.

METHODS

In total, 300 healthy newborns were recruited, randomized and fed formula either supplemented with BB536 or with no supplementation. Stool samples were analyzed at months 2, 4 and 11. The representative cytokine for Th1 [interferon-γ (IFN-γ)] and Th2 [interleukin-4 (IL-4)] secretion cells were measured using enzyme-linked immunospot assay at 4 and 7 months of age. The antibody response to vaccines was measured at months 7 and 11.

RESULTS

A total of 264 infants completed the study. The amount of bifidobacteria and the bifidobacteria/ Enterobacteriaceae ratio (B/E) were significantly higher in the BB536 supplementation group at months 2 and 4. The number of IFN-γ secretion cells and the ratio of IFN-γ/IL-4 secretion cells were increased in the BB536 supplementation group at 7 months. Moreover, the higher value of B/E in the early stages seems to be related to the increased Th1 response. No difference was observed between groups in the antibody response after vaccination.

CONCLUSION

BB536 has positive effects on establishing a healthy intestinal microbiota early in life, and it also plays an important role in improving the Th1 immune response.

Effect of a synbiotic on the response to seasonal influenza vaccination is strongly influenced by degree of immunosenescence

Background

Ageing increases risk of respiratory infections and impairs the response to influenza vaccination. Pre- and probiotics offer an opportunity to modulate anti-viral defenses and the response to vaccination via alteration of the gut microbiota. This study investigated the effect of a novel probiotic, Bifidobacterium longum bv. infantis CCUG 52,486, combined with a prebiotic, gluco-oligosaccharide (B. longum + Gl-OS), on the response to seasonal influenza vaccination in young and older subjects in a double-blind, randomized controlled trial, taking into account the influence of immunosenescence markers at baseline.

Results

Vaccination resulted in a significant increase in total antibody titres, vaccine-specific IgA, IgM and IgG and seroprotection to all three subunits of the vaccine in both young and older subjects, and in general, the increases in young subjects were greater. There was little effect of the synbiotic, although it tended to reduce seroconversion to the Brisbane subunit of the vaccine and the vaccine-specific IgG response in older subjects. Immunological characterization revealed that older subjects randomized to the synbiotic had a significantly higher number of senescent (CD28⁻CD57⁺) helper T cells at baseline compared with those randomized to the placebo, and they also had significantly higher plasma levels of anti-CMV IgG and a greater tendency for CMV seropositivity. Moreover, higher numbers of CD28⁻CD57⁺ helper T cells were associated with failure to seroconvert to Brisbane, strongly suggesting that the subjects randomized to the synbiotic were already at a significant disadvantage in terms of likely ability to respond to the vaccine compared with those randomized to the placebo.

Conclusions

Ageing was associated with marked impairment of the antibody response to influenza vaccination in older subjects and the synbiotic failed to reverse this impairment. However, the older subjects randomized to the synbiotic were at a significant disadvantage due to a greater degree of immunosenscence at baseline compared with those randomized to the placebo. Thus, baseline differences in immunosenescence between the randomized groups are likely to have influenced the outcome of the intervention, highlighting the need for detailed immunological characterization of subjects prior to interventions.

Trial registration

Clinicaltrials.gov NCT01066377.

Electronic supplementary material

The online version of this article (doi:10.1186/s12979-016-0061-4) contains supplementary material, which is available to authorized users.

Food-producing animals and their health in relation to human health

The fields of immunology, microbiology, and nutrition converge in an astonishing way. Dietary ingredients have a profound effect on the composition of the gut microflora, which in turn regulates the physiology of metazoans. As such, nutritional components of the diet are of critical importance not only for meeting the nutrient requirements of the host, but also for the microbiome. During their coevolution, bacterial microbiota has established multiple mechanisms to influence the eukaryotic host, generally in a beneficial fashion. The microbiome encrypts a variety of metabolic functions that complements the physiology of their hosts. Over a century ago Eli Metchnikoff proposed the revolutionary idea to consume viable bacteria to promote health by modulating the intestinal microflora. The idea is more applicable now than ever, since bacterial antimicrobial resistance has become a serious worldwide problem both in medical and agricultural fields. The impending ban of antibiotics in animal feed due to the current concern over the spread of antibiotic resistance genes makes a compelling case for the development of alternative prophylactics. Nutritional approaches to counteract the debilitating effects of stress and infection may provide producers with useful alternatives to antibiotics. Improving the disease resistance of animals grown without antibiotics will benefit the animals’ health, welfare, and production efficiency, and is also a key strategy in the effort to improve the microbiological safe status of animal-derived food products (e.g. by poultry, rabbits, ruminants, or pigs). This review presents some of the alternatives currently used in food-producing animals to influence their health in relation to human health.

Influence of the microbiota on vaccine effectiveness

Studies of the relationship between the microbiome and the development and function of the immune system are demonstrating novel concepts that could significantly alter the way we treat disease and promote wellness. Several diseases, including inflammatory bowel disease, allergy/asthma, and diabetes, are associated with changes in composition of the microbiome. Recent findings suggest novel complex mechanisms by which the microbiome impacts immune cell development and differentiation. A major implication of these findings is that the composition of microbiome may ultimately affect vaccine efficacy. We explore here the potential role of the microbiome in vaccine responses in the context of our growing understanding of the relationship between the gastrointestinal microbiota, resident immune cell populations, and systemic immunity.

Dietary Enterococcus faecium NCIMB 10415 and zinc oxide stimulate immune reactions to trivalent influenza vaccination in pigs but do not affect virological response upon challenge infection

Swine influenza viruses (SIV) regularly cause significant disease in pigs worldwide. Since there is no causative treatment of SIV, we tested if probiotic Enterococcus (E.) faecium NCIMB 10415 or zinc (Zn) oxide as feed supplements provide beneficial effects upon SIV infection in piglets. Seventy-two weaned piglets were fed three different diets containing either E. faecium or different levels of Zn (2500 ppm, Zn^high; 50 ppm, Zn^low). Half of the piglets were vaccinated intramuscularly (VAC) twice with an inactivated trivalent SIV vaccine, while all piglets were then infected intranasally with H3N2 SIV. Significantly higher weekly weight gains were observed in the E. faecium group before virus infection, and piglets in Zn^high and E. faecium groups gained weight after infection while those in the control group (Zn^low) lost weight. Using ELISA, we found significantly higher H3N2-specific antibody levels in the E. faecium+VAC group 2 days before and at the day of challenge infection as well as at 4 and 6 days after challenge infection. Higher hemagglutination inhibition (HI) titers were also observed in the Zn^high+VAC and E. faecium+VAC groups at 0, 1 and 4 days after infection. However, there were no significant differences in virus shedding and lung lesions between the dietary groups. Using flow cytometry analysis significantly higher activated T helper cells and cytotoxic T lymphocyte percentages in the PBMCs were detected in the Zn^high and E. faecium groups at single time points after infection compared to the Zn^low control group, but no prolonged effect was found. In the BAL cells no influence of dietary supplementation on immune cell percentages could be detected. Our results suggest that feeding high doses of zinc oxide and particularly E. faecium could beneficially influence humoral immune responses after vaccination and recovery from SIV infection, but not affect virus shedding and lung pathology.

Ageing, immunity and influenza: a role for probiotics?

Influenza is a major cause of death in the over 65s. Increased susceptibility to infection and reduced response to vaccination are due to immunosenscence in combination with medical history and lifestyle factors. Age-related alterations in the composition of the gut microbiota have a direct impact on the immune system and it is proposed that modulation of the gut microbiota using pre- and probiotics could offer an opportunity to improve immune responses to infections and vaccination in older people. There is growing evidence that probiotics have immunomodulatory properties, which to some extent are strain-dependent, and are strongly influenced by ageing. Randomised controlled trials suggest that probiotics may reduce the incidence and/or severity of respiratory infections, although there is limited data on older people. A small number of studies have examined the potential adjuvant effects of selected probiotics for vaccination against influenza; however, the data is inconsistent, particularly in older people. This review describes the impact of age-related changes in the gut on the immune response to respiratory infections and evaluates whether restoration of gut microbial homoeostasis by probiotics offers an opportunity to modulate the outcome of respiratory infections and vaccination against influenza in older people. Although there is promising evidence for effects of probiotics on human health, there is a lack of consistent data, perhaps partly due to strain-specific differences and an influence of the age of the host. Further research is critical in evaluating the potential use of probiotics in respiratory infections and vaccination in the ageing population.

Enhancement of the immune response against Salmonella infection of mice by heat-killed multispecies combinations of lactic acid bacteria

Heat-killed lactic acid bacteria (LAB) has advantages over live LAB in that it has a long shelf‐life and is therefore easy to store and transport. From four LAB strains selected by immunomodulatory activity and adherent properties, we prepared the heat-killed multispecies combination of LAB (MLAB) and the cell walls from MLAB under two conditions (100 °C for 30 min and 121 °C for 15 min). Different effects on the adherent properties of these four LAB strains were observed, depending on the heating conditions. With mouse macrophage cells, the two heat-killed MLABs (HMLABs) showed significantly higher induction activities on the production of interleukin 12 (IL-12) than their individual strains did. Heat-killed MLABs and cell‐wall preparations were able to reduce the Salmonella invasion of Caco-2 and mouse macrophage cells. Feeding mice with HMLAB could inhibit the Salmonella invasion of mice significantly. For these mice, the expression level of pro-inflammatory cytokines, such as TNF-α and IL-6, in mouse serum was reduced while that of the anti-inflammatory cytokine, i.e. IL-10, was enhanced. The HMLABs developed in this study showed higher protective effect against Salmonella invasion either of Caco-2 cells or of mice, relative to the heat-killed lactobacilli, which consisted of Lactobacillus acidophilus strains selected at random. In conclusion, the HMLABs were potentially useful for the protection of mice against Salmonella infection and the induced inflammation.

Modulation of vaccine response by concomitant probiotic administration

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

Anti-influenza virus effects of both live and non-live Lactobacillus acidophilus L-92 accompanied by the activation of innate immunity

The antiviral effects of both a live and non-live Lactobacillus acidophilus strain L-92 (L-92) were investigated by oral administration (10 mg/mouse per d) daily for 21 d in a mouse model infected intranasally with influenza virus (H1N1). Virus titres in the lung of mice administered either live or non-live L-92 cells daily for 15 d were repressed 6 d after virus infection compared with the control group. Natural killer (NK) activity in the orally administered non-live L-92 group was higher compared with that of the control group before virus infection and on day 6. In contrast, NK activity in the live L-92 group compared with the control group was not significantly changed on both days, but was significantly higher on day 1. In contrast, live L-92 showed a greater repression of virus proliferation compared with non-live L-92, 6 d after the infection. Live L-92 decreased the number of neutrophils in the lung and suppressed lung weight, leading to the consequent deterioration of consolidation scores of the lung. These results indicated that pretreatment of live or non-live L-92 cells had protective effects against influenza virus infection. Among the measured cytokines and chemokines, eotaxin, macrophage colony-stimulating factor, IL-1b, RANTES (regulated on activation, normal T cell expressed and secreted) and interferon-a were significantly increased in the lung: IL-17 was significantly increased in Peyer’s patch of the live L-92 group compared with the control group. A mechanistic study suggested that the enhancement of NK activity in the lung caused by stimulating various antiviral cytokines and chemokines after the oral administration of L-92 cells might be important in protecting against virus infection.

Are vaccination models suitable to determine whether probiotics have beneficial health effects in the general population?

The European Food Safety Authority (EFSA) has indicated that stimulation of protective antibody titers from vaccination could be used to substantiate a supplement or food health claim on the function of the immune system related to defense against pathogens in healthy individuals. Vaccination allows exposure of the immune system to controlled quantities of antigen and also for assessment of median antibody responses and percentage of responders/non-responders, which provides indication of an integrated immune response to challenge. Probiotic vaccination studies have shown enhanced antibody titers, lower percentages of non-seroconverters and greater percentages reaching minimum cut-off titer values in healthy adults, elderly and children. These results indicate that probiotics are a good candidate to stimulate responses to vaccines and thus, according to EFSA, enhance the function of the immune system related to defense against infection. However, animal research has recently indicated that Foxp3+ T-regulatory cells, recognized suppressors of immune activity, were paradoxically associated with reduced respiratory viral morbidity without compromising viral clearance. These effects conflict with vaccine research findings, which suggest a depletion of Foxp3+ T-regs enhances the immune response. Many probiotics exert anti-inflammatory influence on the immune system and induce T-regs. Given this, caution regarding the applicability of the vaccination model as indicated by EFSA must be exercised. Induction of T-cell immune modulatory pathways may also explain the reduced duration of respiratory illness observed in probiotic clinical studies.

Oral treatment of chickens with lactobacilli influences elicitation of immune responses

Commensal microbes in the intestine are in constant interaction with host cells and play a role in shaping the immune system. Lactobacillus acidophilus, Lactobacillus reuteri, and Lactobacillus salivarius are members of the chicken intestinal microbiota and have been shown to induce different cytokine profiles in mononuclear cells in vitro. The objective of the present study was to examine the effects of these bacteria individually or in combination on the induction of antibody- and cell-mediated immune responses in vivo. The birds received lactobacilli weekly via oral gavage starting on day of hatch and subsequently, at 14 and 21 days, were immunized with sheep red blood cells (SRBC), keyhole limpet hemocyanin (KLH), Newcastle disease virus vaccine, and infectious bursal disease virus vaccine. Antibody responses in serum were measured weekly for 4 weeks beginning on the day of primary immunization. The cell-mediated immune response was evaluated at 21 days postimmunization by measurement of gamma interferon (IFN-γ) production in splenocytes stimulated with inactivated vaccine antigens. L. salivarius-treated birds had significantly more serum antibody to SRBC and KLH than birds that were not treated with probiotics. L. salivarius-treated birds also had decreased cell-mediated immune responses to recall antigen stimulation. L. reuteri treatment did not significantly affect the systemic immune response, while L. acidophilus treatment increased the antibody response to KLH. These results indicate that systemic antibody- and cell-mediated immune responses can be modulated by oral treatment with lactobacilli but that these bacteria may vary in their ability to modulate the immune response.

Fractal immunology and immune patterning: potential tools for immune protection and optimization

Fractals are self-similar geometric patterns that are inherently embedded throughout nature. Their discovery and application have produced significant benefits across a wide variety of biomedical applications. Recently, complex physiological systems (e.g., neurological, respiratory, cardiovascular) have been shown to exhibit fractal dimensions that are capable of distinguishing among physiologic function versus dysfunction and, in turn, health versus disease. Additionally, fractal data suggest that the immune system operates under similar patterned relationships, and this is in keeping with the recent findings that immune-based diseases are organized according to specific patterns. This review considers the potential benefits of using fractal analysis along with considerations of nonlinearity, scaling, and chaos as calibration tools to obtain holistic information on immune-environment interactions. The potential uses of both synthetic and artificial immune systems for improved protection of the biological immune system are also discussed. The addition of holistic measures of immune status to currently collected biomarkers of immunotoxicity has the potential to increase the effectiveness of health risk assessment. The objective of extending fractal physiology analyses to the immune system would be to promote immune optimization as a public health benefit, which would include improved: (1) immunotoxicity testing and effective health risk reduction and (2) measures of effective immune management for children, adults, and aged individuals.

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

Background/Objectives

Live attenuated influenza vaccine (LAIV) protects against influenza by mucosal activation of the immune system. Studies in animals and adults have demonstrated that probiotics improve the immune response to mucosally delivered vaccines. We hypothesized that Lactobacillus GG (LGG) would act as an immune adjuvant to increase rates of seroconversion after LAIV administration.

Subjects/Methods

We conducted a randomized double-blind placebo-controlled pilot study to determine if LGG improved rates of seroconversion after administration of LAIV. We studied 42 healthy adults during the 2007–8 influenza season. All subjects received LAIV and then were randomized to LGG or placebo twice daily for 28 days. HAI titers were assessed at baseline, day 28, and day 56 to determine rates of seroconversion. Subjects were assessed for adverse events throughout the study period.

Results

39 subjects completed the per protocol analysis. Both LGG and LAIV were well tolerated. Protection rates against the vaccine H1N1 and B strains was similar suboptimal in subjects receiving LGG and placebo. For the H3N2 strain, 84% receiving LGG vs. 55% receiving placebo had a protective titer 28 days after vaccination (odds of having a protective titer was 1.84 95% CI 1.04–3.22, P=0.048).

Conclusion

Lactobacillus GG is potential as an important adjuvant to improve influenza vaccine immunogenicity. Future studies of probiotics as immune adjuvants may need to consider specifically examining vaccine naïve or seronegative subjects, target mucosal immune responses, or focus on groups known to have poor response to influenza vaccines.

Heat-killed Lactobacillus acidophilus La205 enhances NK cell cytotoxicity through increased granule exocytosis

Heat-killed lactic acid bacteria (LAB) are known to be important immunomodulators that stimulate tumor necrosis factor-α (TNF-α) and nitric oxide (NO) production as well as increase phagocytic activity in macrophages. NK cells play a critical role in innate immune response and induce spontaneous killing of tumor cells and virus-infected cells. However, the effect of heat-killed LAB on NK cells is still unclear. In this study, we investigated the effect of heat-killed Lactobacillus acidophilus La205 (La205) on NK cytolytic activity. We found that heat-killed La205 directly stimulated NK cytolytic activity in dose- and time-dependent manners. To determine the mechanism underlying heat-killed La205-enhanced NK cytotoxicity, the expression of NK activating receptors was tested. Heat-killed La205 did not affect the expression of NK activating receptors. To investigate whether NK degranulation is related to heat-killed La205-enhanced NK cytotoxicity, NK degranulation inhibitor concanamycin A (CMA) was used. CMA effectively blocked heat-killed La205-induced NK cytotoxicity, and an assay for detection of a degranulation marker, CD107a, showed that heat-killed La205 increased granule exocytosis approximately 2-fold in comparison to non-treated NK cells. In addition, heat-killed La205 dramatically elevated mRNA expression of granulysin, a component of the cytolytic granule contents, in NK cells. However, other granule contents, including perforin and granzymes, were not changed by heat-killed La205. From these data, we concluded that heat-killed La205 stimulated NK cytolytic activity through enhancement of granule exocytosis, and granulysin may be a critical mediator in heat-killed La205-induced granule exocytosis.

Progress in the field of probiotics: year 2011

PURPOSE OF REVIEW

The interest and scope for research in the field of probiotics has significantly widened in recent years. This brief review covers the significant advances in the field of probiotics.

RECENT FINDINGS

These include conclusive evidence for the benefits of probiotics in preventing all cause mortality and necrotizing enterocolitis (NEC) in preterm very low birth weight (VLBW) neonates, understanding the role of probiotics as vaccine adjuvants, and in modulating inflammatory bowel diseases, bowel cancer, type 1 diabetes mellitus, obesity, high cholesterol levels, and bacterial resistance. Other areas of progress include understanding the role of probiotics in oral health and ageing.

SUMMARY

Current evidence will lead to routine probiotic supplementation to prevent all cause mortality and NEC in preterm VLBW neonates. Probiotics may also become novel agents as vaccine adjuvants, and in dealing with major public health issues such as obesity, type I diabetes mellitus, and poor oral health. Research in applications of probiotics in food products will rationalize product development, and health claims. As new frontiers continue to be explored the challenges to the basis of the hygiene hypothesis will influence further developments in the field of probiotics.