Supplementation with a single and double strain probiotic on the innate immune system for respiratory illness

Background and aimsThe immune mechanisms by which probiotics reduce susceptibility to upper respiratory tract illness is uncertain. The aim of this study was to examine purported cell-mediated immune mechanisms that might explain the reduction in respiratory illness observed following daily supplementation with Bifidobacterium animalis subsp. lactis Bl-04 (Bl-04) and a combined Lactobacillus acidophilus NCFM & B. animalis subsp. lactis BI-07 (NCFM & Bi-07).MethodsA cohort of 144 healthy physically active individuals were allocated to daily supplementation consumed as a beverage with Bl-04 (n = 46) supplemented at a dosage of 2.0 × 109 colony forming units (cfu) per day, NCFM & Bi-07 (n = 47) at a dosage of 5.0 × 109 CFU per day each, or a placebo (n = 51) over 150 d. Markers included plasma cytokines, metalloproteinases and neurotrophins, peripheral blood leucocyte numbers, antibody-dependent and antibody-independent NK cell activity (NKCA), and peripheral blood mononuclear cell (PBMC) phagocytosis.ResultsA total of 125 subjects were included in the final analysis. No significant effects were observed on cytokines, on white cell differentials, NKCA or PBMC phagocytosis from pre- to post-supplementation. The biomarkers that increased significantly from pre- to post-supplementation were the concentration of plasma macrophage inflammatory protein (MIP)-1δ which was higher in the Bl-04 than placebo group (Bl-04 25% ± 11%, placebo −3.3% ± 9.4%; mean ± SD, P = 0.003) while the concentration of plasma matrix metallo-proteinase (MMP)-1 decreased by 11% ± 16% in the NCFM & Bi-07 group and increased by 21% ± 17% in the placebo group, which was a significant 26% difference (8–41%; P = 0.02).ConclusionProbiotic supplementation had little effect on parameters of the innate immune system. Mechanisms explaining the beneficial effect of Bl-04 or NCFM & Bi-07 supplementation on respiratory illness remain unclear.