Alterations in regulatory T cells induced by specific oligosaccharides improve vaccine responsiveness in mice

Analysis of the Cellular Immune Responses to Vaccines

Flow cytometry, enzyme-linked immunospot (ELISpot), and cellular cytotoxicity assays are powerful tools for studying the cellular immune response toward intracellular pathogens and vaccines in livestock species. Lymphocytes from immunized animals can be purified using Ficoll-Paque density gradient centrifugation and evaluated for their antigen specificity or reactivity toward a vaccine. Here, we describe staining of bovine lymphocytes with peptide (p)-MHC class I tetramers and antibodies specific toward cellular activation markers for evaluation by multiparametric flow cytometry, as well as interferon (IFN)-γ ELISpot and cytotoxicity using chromium (⁵¹Cr) release assays. A small component on the use of immunoinformatics for fine-tuning the identification of a minimal CTL epitope is included, and a newly developed and simple assay to measure TCR avidity.

Exposure to Deoxynivalenol During Pregnancy and Lactation Enhances Food Allergy and Reduces Vaccine Responsiveness in the Offspring in a Mouse Model

Deoxynivalenol (DON), a highly prevalent contaminant of grain-based products, is known to induce reproductive- and immunotoxicities. Considering the importance of immune development in early life, the present study investigated the effects of perinatal DON exposure on allergy development and vaccine responsiveness in the offspring. Pregnant mice received control or DON-contaminated diets (12.5 mg/kg diet) during pregnancy and lactation. After weaning, female offspring were sensitized to ovalbumin (OVA) by oral administration of OVA with cholera toxin (CT). Male offspring were injected with Influvac vaccine. OVA-specific acute allergic skin response (ASR) in females and vaccine-specific delayed-type hypersensitivity (DTH) in males were measured upon intradermal antigen challenge. Immune cell populations in spleen and antigen-specific plasma immunoglobulins were analyzed. In female CT+OVA-sensitized offspring of DON-exposed mothers ASR and OVA-specific plasma immunoglobulins were significantly higher, compared to the female offspring of control mothers. In vaccinated male offspring of DON-exposed mothers DTH and vaccine-specific antibody levels were significantly lower, compared to the male offspring of control mothers. In both models a significant reduction in regulatory T cells, Tbet+ Th1 cells and Th1-related cytokine production of the offspring of DON-exposed mothers was observed. In conclusion, early life dietary exposure to DON can adversely influence immune development in the offspring. Consequently, the immune system of the offspring may be skewed towards an imbalanced state, resulting in an increased allergic immune response to food allergens and a decreased immune response to vaccination against influenza virus in these models.

Human Milk Oligosaccharide 3'-GL Improves Influenza-Specific Vaccination Responsiveness and Immunity after Deoxynivalenol Exposure in Preclinical Models

Deoxynivalenol (DON), a highly prevalent mycotoxin food contaminant, is known to have immunotoxic effects. In the current study, the potential of dietary interventions with specific mixtures of trans-galactosyl-oligosaccharides (TOS) to alleviate these effects were assessed in a murine influenza vaccination model. Vaccine-specific immune responses were measured in C57Bl/6JOlaHsd mice fed diets containing DON, TOS or a combination, starting 2 weeks before the first vaccination. The direct effects of TOS and its main oligosaccharide, 3'-galactosyl-lactose (3'-GL), on DON-induced damage were studied in Caco-2 cells, as an in vitro model of the intestinal epithelial barrier. Exposure to DON significantly reduced vaccine-specific immune responses and the percentages of Tbet+ Th1 cells and B cells in the spleen. DON significantly altered epithelial structure and integrity in the ileum and reduced the SCFA levels in the cecum. Adding TOS into DON-containing diets significantly improved vaccine-specific immune responses, restored the immune cell balance in the spleen and increased SCFA concentrations in the cecum. Incubating Caco-2 cells with TOS and 3'-GL in vitro further confirmed their protective effects against DON-induced barrier disruption, supporting immune modulation. Overall, dietary intervention with TOS can attenuate the adverse effects of DON on Th1-mediated immune responses and gut homeostasis. These beneficial properties might be linked to the high levels of 3'-GL in TOS.

A Fermented Milk Matrix Containing Postbiotics Supports Th1- and Th17-Type Immunity In Vitro and Modulates the Influenza-Specific Vaccination Response In Vivo in Association with Altered Serum Galectin Ratios

During a specific milk fermentation process with Bifidobacterium breve C50 and Streptococcus thermophilus 065 (Lactofidus^TM), postbiotics with possible immunomodulatory properties are produced. We investigated the effects of this fermentation product (FP) in vitro using a model that allows crosstalk between intestinal epithelial (IEC) and immune cells. IECs were exposed to FP and αCD3/CD28-activated peripheral blood mononuclear cells after which the mediator secretion was measured. Additionally, using a murine influenza vaccination model, immune development was assessed. Mice were fed an AIN93G diet containing FP or lactose as control. Vaccine-specific immunity was measured as delayed-type hypersensitivity (DTH) and correlated to intestinal and systemic immunomodulation levels. In vitro, exposure to FP enhanced IFNγ, TNFα and IL-17A concentrations. Moreover, IEC-derived galectin-3/galectin-9 and galectin-4/galectin-9 ratios were increased. In vivo, dietary intervention with FP increased vaccine-specific DTH responses as compared to the lactose-receiving group. Although no effects on humoral immunity and vaccine-specific T-cell responses were detected, an enhanced systemic serum galectin-3/galectin-9 and galectin-4/galectin-9 ratio correlated with a shift in RORγ (Th17) mRNA expression over regulatory TGFβ1 in the ileum. This was also positively correlated with the increased DTH response. These results indicate that FP can enhance epithelial galectin-3 and -4 over galectin-9 release, and boost adaptive immunity by promoting Th1- and Th17-type cytokines under inflammatory conditions in vitro. Similar variations in galectin and immune balance were observed in the vaccination model, where FP improved the influenza-specific DTH response.

Human Milk Oligosaccharide 2'-Fucosyllactose Improves Innate and Adaptive Immunity in an Influenza-Specific Murine Vaccination Model

Background

Human milk is uniquely suited to provide optimal nutrition and immune protection to infants. Human milk oligosaccharides are structural complex and diverse consisting of short chain and long chain oligosaccharides typically present in a 9:1 ratio. 2′-Fucosyllactose (2′FL) is one of the most prominent short chain oligosaccharides and is associated with anti-infective capacity of human milk.

Aim

To determine the effect of 2′FL on vaccination responsiveness (both innate and adaptive) in a murine influenza vaccination model and elucidate mechanisms involved.

Methods

A dose range of 0.25–5% (w/w) dietary 2′FL was provided to 6-week-old female C57Bl/6JOlaHsd mice 2 weeks prior primary and booster vaccination until the end of the experiment. Intradermal (i.d.) challenge was performed to measure the vaccine-specific delayed-type hypersensitivity (DTH). Antigen-specific antibody levels in serum as well as immune cell populations within several organs were evaluated using ELISA and flow cytometry, respectively. In an ex vivo restimulation assay, spleen cells were cocultured with influenza-loaded bone marrow-derived dendritic cells (BMDCs) to study the effects of 2′FL on vaccine-specific CD4+ and CD8+ T-cell proliferation and cytokine secretions. Furthermore, the direct immune regulatory effects of 2′FL were confirmed using in vitro BMDCs T-cell cocultures.

Results

Dietary 2′FL significantly (p < 0.05) enhanced vaccine specific DTH responses accompanied by increased serum levels of vaccine-specific immunoglobulin (Ig) G1 and IgG2a in a dose-dependent manner. Consistently, increased activation marker (CD27) expression on splenic B-cells was detected in mice receiving 2′FL as compared to control mice. Moreover, proliferation of vaccine-specific CD4+ and CD8+ T-cells, as well as interferon-γ production after ex vivo restimulation were significantly increased in spleen cells of mice receiving 2′FL as compared to control mice, which were in line with changes detected within dendritic cell populations. Finally, we confirmed a direct effect of 2′FL on the maturation status and antigen presenting capacity of BMDCs.

Conclusion

Dietary intervention with 2′FL improves both humoral and cellular immune responses to vaccination in mice, which might be attributed in part to the direct effects of 2′FL on immune cell differentiation.

Health Effects and Sources of Prebiotic Dietary Fiber

Prebiotic dietary fibers act as carbon sources for primary and secondary fermentation pathways in the colon, and support digestive health in many ways. Fructooligosaccharides, inulin, and galactooligosaccharides are universally agreed-upon prebiotics. The objective of this paper is to summarize the 8 most prominent health benefits of prebiotic dietary fibers that are due to their fermentability by colonic microbiota, as well as summarize the 8 categories of prebiotic dietary fibers that support these health benefits. Although not all categories exhibit similar effects in human studies, all of these categories promote digestive health due to their fermentability. Scientific and regulatory definitions of prebiotics differ greatly, although health benefits of these compounds are uniformly agreed upon to be due to their fermentability by gut microbiota. Scientific evidence suggests that 8 categories of compounds all exhibit health benefits related to their metabolism by colonic taxa.

Diversity of Human Milk Oligosaccharides and Effects on Early Life Immune Development

One of the well-known features of human milk, is the capacity to protect against the risk and impact of neonatal infections, as well as to influence the onset of allergic and metabolic disease manifestations. The major objective of this review is to provide a detailed overview regarding the role of human milk, more specifically the diversity in human milk oligosaccharides (HMOS), on early life immune development. Novel insights in immune modulatory effects of HMOS obtained by in vitro as well as in vivo studies, adds to the understanding on how early life nutrition may impact immune development. Extensive description and analysis of single HMOS contributing to the diversity within the composition provided during breastfeeding will be discussed with specific emphasis on immune development and the susceptibility to neonatal and childhood infections.

Immunological Effects of Human Milk Oligosaccharides

Human milk oligosaccharides (HMOs) comprise a group of structurally complex, unconjugated glycans that are highly abundant in human milk. HMOs are minimally digested in the gastrointestinal tract and reach the colon intact, where they shape the microbiota. A small fraction of HMOs is absorbed, reaches the systemic circulation, and is excreted in urine. HMOs can bind to cell surface receptors expressed on epithelial cells and cells of the immune system and thus modulate neonatal immunity in the infant gut, and possibly also sites throughout the body. In addition, they have been shown to act as soluble decoy receptors to block the attachment of various microbial pathogens to cells. This review summarizes the current knowledge of the effects HMOs can have on infections, allergies, auto-immune diseases and inflammation, and will focus on the role of HMOs in altering immune responses through binding to immune-related receptors.

Analysis of the Cellular Immune Responses to Vaccines

Flow cytometry, enzyme-linked immunospot (ELISpot) and cellular cytotoxicity assays are powerful tools for studying the cellular immune response towards intracellular pathogens and vaccines in livestock species. Lymphocytes from immunized animals can be purified using Ficoll-Paque density gradient centrifugation and evaluated for their antigen specificity or reactivity towards a vaccine. Here, we describe staining of bovine lymphocytes with peptide (p)-MHC class I tetramers and antibodies specific towards cellular activation markers for evaluation by multiparametric flow cytometry, as well as interferon (IFN)-γ ELISpot and cytotoxicity using chromium ((51)Cr) release assays. A small component on the use of immunoinformatics for fine-tuning the identification of a minimal CTL epitope is included.

In vitro proliferation and production of cytokine and IgG by human PBMCs stimulated with polysaccharide extract from plants endemic to Gabon

Polysaccharides were extracted from seven plants endemic to Gabon to study their potential immunological activities. Peripheral blood mononuclear cell (PBMC) (5 × 10⁵ cells/mL) proliferation, cytokine and immunoglobulin G (IgG) assays were performed after stimulation with different concentrations of polysaccharide fractions compared with lipopolysaccharides (LPS) and concanavalin A (ConA) from healthy volunteers. The culture supernatants were used for cytokine and IgG detection by enzyme-linked immunosorbent assay (ELISA). The results show that pectin and hemicellulose extracts from Uvaria klainei, Petersianthus macrocarpus, Trichoscypha addonii, Aphanocalyx microphyllus, Librevillea klaineana, Neochevalierodendron stephanii and Scorodophloeus zenkeri induced production levels that were variable from one individual to another for IL-12 (3–40 pg/mL), IL-10 (6–443 pg/mL), IL-6 (7–370 pg/mL), GM-CSF (3–170 pg/mL) and IFN-γ (5–80 pg/mL). Only hemicelluloses from Aphanocalyx microphyllus produce a small amount of IgG (OD = 0.034), while the proliferation of cells stimulated with these polysaccharides increased up to 318% above the proliferation of unstimulated cells. However, this proliferation of PBMCs was abolished when the pectin of some of these plants was treated with endopolygalacturonase (p < 0.05), but the trend of cytokine synthesis remained the same, both before and after enzymatic treatment or saponification. This study suggests that these polysaccharides stimulate cells in a structure-dependent manner. The rhamnogalacturonan-I (RGI) fragment alone was not able to induce the proliferation of PBMC.

Gut microbiota and allergic disease: new findings

PURPOSE OF REVIEW

Disturbed gut colonization patterns are proposed to be associated with the development of allergic disease.

RECENT FINDINGS

Studies using new systems biology methods confirm previous findings that early environmental exposures, for example cesarean delivery, are associated with disturbed gut colonization patterns and reduced microbial diversity. Low microbial diversity in infancy is also observed to precede onset of allergic disease. In a large population-based cohort study, probiotic consumption in pregnancy was associated with reduced risk of eczema and rhinoconjunctivitis in the child, but not asthma. The association between probiotics and rhinoconjunctivitis appeared stronger if both mother and child (from 6 months) consumed probiotics. Follow-up data from primary prevention studies with probiotics do not support a role for probiotics in asthma prevention. In meta-analyses, both prebiotics (high-risk infants only) and probiotics modestly reduce the eczema risk, but no other allergic manifestations. Their use is not generally recommended for prevention, or treatment, of allergic disease.

SUMMARY

Gut microbial patterns are associated with susceptibility to allergic disease, but the incomplete understanding of what constitutes a healthy gut microbiota that promotes tolerance, remains a challenge. Further understanding of gut microbial functions may pave the way for more effective allergy prevention and treatment strategies.