Study on the regulatory effect of Bifidobacterium animalis subsp. lactis BLa80 on immune function of healthy mice and pathogenicity in animals.

Abstract

Bifidobacteria are known for their health-promoting effects, particularly in the context of gut microbiota modulation and immune system support. Bifidobacterium animalis subsp. lactis BLa80 is a novel probiotic strain isolated from human breast milk. This article evaluates the immunomodulatory effects of BLa80 on healthy mice through indicators such as cellular immunity, humoral immunity, monocyte-macrophage phagocytic function, natural killer cell activity, and immunoglobulins in serum. Concurrently, animal pathogenicity tests were conducted to complement earlier safety studies of BLa80. The mice were treated with low, middle and high doses (12.5, 25, 75 mg/kg BW; 0.25 × 106, 0.5 × 106, 1.5 × 106 cfu/d) of BLa80 solution for 30 days. Body weight, organ-to-body weight ratio, cellular immune function (delayed-type hypersensitivity and lymphocyte transformation), humoral immune function (antibody-forming cell and serum haemolysin), monocyte-macrophage phagocytic function (monocyte-macrophage carbon clearance, Peritoneal macrophage phagocytosis of chicken red blood cells) and natural killer cell activity were observed and recorded. Additionally, the contents of IgG, IgM and IgA in serum of mice, as well as the concentrations of cAMP and cGMP in the spleen and serum, were detected. Healthy mice were administered a certain dose of BLa80 solution through both intraperitoneal injection (BLa80 Group: 1 × 107 cfu/d) and oral gavage (BLa80 Group: 1 × 108 cfu/d, 5 × Concentrated BLa80: 5 × 108 cfu/d). After the mice consumed the BLa80 solution, their general health condition, body weight, and mortality were observed and recorded daily. Compared with the blank control group, the haemolysis values of the middle and high dose groups were significantly different ( P < 0.05), and the monocyte-macrophage carbon clearance values of each dose group were significantly different ( P < 0.05). The carbon clearance phagocytic index in all three dosage groups was better than that in the blank control group. Additionally, the IgM levels in all three dosage groups were higher than those in the blank control group, with the high-dose group showing a significant difference compared to the blank control group ( P < 0.05). During the 21-day observation period, the test substance had no adverse effects on the general health of the mice, and there was no statistically significant difference in weight and other indicators compared to the control group ( P < 0.05), with no deaths observed among the mice. Based on the 'Testing and Evaluation Methods for Health Food Functions (2023 Version)', it is determined that Bifidobacterium animalis subsp. lactis BLa80 can enhance the immune function of healthy mice. Concurrently, according to the 'Guidelines on Safety Assessment and Evaluation of Microbial Strains Used as Health Food Raw Materials (2020 Edition, Appendix A)', BLa80 is determined to be non-pathogenic to animals.