The Role Of The Probiotic Bifidobacterium Animalis Subsp. Lactis On Systemic Immune Function In Healthy Adults
Open Access
- Author:
- Meng, Huicui
- Graduate Program:
- Nutritional Sciences
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- June 08, 2015
- Committee Members:
- Connie Jo Rogers, Dissertation Advisor/Co-Advisor
Connie Jo Rogers, Committee Chair/Co-Chair
A Catharine Ross, Committee Member
Shannon Leanne Kelleher, Committee Member
Margherita Teresa Anna Cantorna, Committee Member
Mary Jane De Souza, Committee Member - Keywords:
- probiotics
clinical trial
upper respiratory tract infection
Tumor necrosis factor alpha
delivery matrix - Abstract:
- Probiotic bacteria are functional ingredients that provide significant health benefits, including modulation of host immune function and attenuating the risk and severity of infections. Numerous studies have examined the influence of probiotic bacteria, either alone or combined, on innate and adaptive immune function in an effort to link probiotic use with changes in inflammatory mediators or risk of infection. However, observed results vary by genus, species and strain of organism studied. Furthermore, the use of mixtures of probiotic bacteria makes it difficult to determine the immunomodulatory properties of BB-12 or other probiotic species. Thus, careful analysis of the immune outcomes affected by each of the commonly used probiotic strains is necessary. Bifidobacterium animalis subsp. lactis BB-12 is a widely used strain in the genera Bifidobacterium. Evidence suggests that consumption of BB-12 combined with other probiotic species can modulate both innate and adaptive immune responses in human subjects. A limited number of studies have investigated the role of BB-12 alone on immunity and disparate effects of BB-12 on immune outcomes are reported. Therefore, the primary aim of this project was to evaluate the effect of oral consumption of one strain of probiotic bacteria, BB-12, at a dose of log 10 ± 0.5 CFUs/day, on innate and adaptive immune responses in healthy adults in a randomized, partially blinded, 4-period cross-over free-living study. There is evidence that the matrix used to deliver probiotic bacteria may influence the performance and efficacy of probiotic interventions in vivo. BB-12 can be consumed either in dairy products, especially yogurt, or in capsule form. Furthermore, BB-12 can be added into yogurt either prior to or following the yogurt fermentation process, which varies among manufacturers. Thus, a secondary goal of this study was to determine if the delivery matrix (yogurt smoothies vs capsule), and timing of the addition of BB-12 to the yogurt smoothies (pre- or post-fermentation) impacted the immunological responses to BB-12 in humans. Healthy adults (n=30) aged 18-40 years old were recruited, and received 4 treatments for 4 weeks in a random order: A) yogurt smoothies alone; smoothies with BB-12 added B) before or C) after yogurt fermentation, or D) BB-12 given in capsule form. At baseline and after each 4-week treatment, peripheral blood mononuclear cells (PBMCs) were isolated, and functional immune outcomes and phenotypic marker expression on immune cells was assessed. Dietary intake of total calories and various nutrients were assessed via self-reported 3-day dietary recall. Physical activity status was evaluated via self-reported IPAQ questionnaire. Incidence and severity of cold or flu infection in the past month was assessed using established self-reported URTI questionnaire. The goal of study 1 was to determine at baseline which endogenous and exogenous host factors contribute to the heterogeneity in innate and adaptive immune responses and cold or flu status among healthy subjects; and if these host factors also confound the relationship between phenotypic marker expression, immune function, and cold or flu status. We analyzed baseline immune function of participants. This included anti-CD3 induced T cell proliferation and secretion of IL-2 and IFN-γ, and LPS stimulated TNF-α and IL-6 secretion from PBMCs. We also examined dietary intake, physical activity level, and the incidence and severity of cold or flu symptoms in our participants. We demonstrated that host-related factors (including age, BMI, physical activity, and daily intake of total calorie and various dietary components) contributed significantly to heterogeneity in T cell effector function and cold or flu status, and confounded the association between activation marker expression on T cells and T cell effector function. These factors also impacted the association between innate and adaptive immune response and incidence and severity of cold or flu infection. We also found that individual lifestyle and dietary variables contribute a small amount to T cell effector function and cold or flu status. However, combinations of these variables significantly improved the predictive relationship between activation marker expression and T cell proliferation and IL-2 secretion, and also strengthened the associations between IL-6 and IFN-γ secretion and the incidence and severity of cold or flu symptoms, respectively. In conclusion, these results suggest that lifestyle and dietary factors are important variables that contribute to immune responses and should be included in human clinical trials that assess immune endpoints. The analysis with baseline immune data has enabled us to understand the variability in human immune outcomes and has been insightful about how to analyze the treatment effects of BB-12 consumption on immune outcomes in our clinical trial. The goal of study 2 was to evaluate the effect of BB-12 consumption on innate immune responses; and to determine if the innate immune response to BB-12 differed depending on the delivery matrix (yogurt smoothies vs capsule) of BB-12 and timing of addition of BB-12 to yogurt fermentation process (pre- or post-fermentation). We found that consumption of BB-12 delivered in yogurt smoothies post-fermentation significantly reduced pro-inflammatory cytokine (TNF-α) secretion from peripheral myeloid cells stimulated with heat-inactivated BB-12 (p=0.0490) or LPS (p=0.0387) compared to baseline in young healthy adults, suggesting an anti-inflammatory effect of BB-12. We also found that BB-12 interacted with peripheral myeloid cells via Toll-like receptor 2 (TLR-2), and consumption of yogurt smoothies with BB-12 added post-fermentation for 4 weeks significantly decreased TLR-2 expression on peripheral blood derived monocytes, which may contribute to the reduction in TNF-α secretion in participants. These findings are not only the first to demonstrate anti-inflammatory properties of BB-12, but also indicate that the matrix of BB-12, and the timing of its addition to yogurt fermentation process influenced the immunological effects of BB-12. The goal of study 3 was to evaluate the effect of BB-12 consumption on T cell and NK cell function and concurrently self-reported cold or flu incidence and severity. A sub-aim was to determine if delivery matrix (yogurt smoothies vs capsule) of BB-12 and timing of addition of BB-12 to yogurt fermentation process (pre- or post-fermentation) influenced immune responses and related cold or flu status. We found that participants who consumed yogurt smoothies alone, yogurt smoothies with BB-12 added pre-fermentation or BB-12 in capsule form increased T cell proliferation and cytokine (TNF-α and IL-2) secretion, and NK cell cytotoxicity, and concurrently reduced number of days with cold or flu by 2-3 days. However, consumption of yogurt smoothies with BB-12 added post-fermentation did not change T cell and NK cell function; and did not alter severity of cold or flu. These findings demonstrate that the timing of addition of BB-12 to yogurt smoothies influenced the immunomodulatory properties of BB-12. Combined, the results from our clinical trial demonstrate that diet and physical activity variables should be assessed in clinical trials to control for variability in immune outcomes. Furthermore, consumption of 109-1010 cfu/d of BB-12 for 4 weeks was effective in modulating responses of both innate (cytokine secretion from myeloid cells and NK cell cytotoxicity) and adaptive cells (T cell proliferation and cytokine secretion) in young adults. We also found that the delivery matrix of BB-12 (e.g. yogurt smoothies vs. capsule) and timing of BB-12 addition to yogurt influences the effect of BB-12 on immune responses, and inflammatory and infection-related outcomes. Specifically, the consumption of yogurt smoothies with BB-12 added post-fermentation results in blunted innate and adaptive immune responses, suggesting that this processing technique influences the probiotic activity of BB-12, and warrants further study. Lastly, we found strong correlation between changes in T cell and NK cell function and URTI severity suggesting that immune modulation may be one mechanism underlying the link between probiotic consumption and infection-related outcomes. Results from the current studies will contribute to our understanding that BB-12 alone modulates systemic immunity in humans and sheds light on potential mechanisms by which BB-12 is exerting its effects on immunity and infection risk.