Modulation of the peripheral innate immune system towards increased phagocytic capabilities following probiotic supplementation with B. subtilis CU1
Objective
Bacillus subtilis CU1 (BSCU1) has been shown to be effective in stimulating immune responses in the elderly. An exploratory clinical study was conducted to gain insight into the potential mechanism of action by which BSCU1 may modulate the immune system and contribute to protection against infection.
Method
To evaluate the effects of a four-week probiotic supplement on immune function in different age groups, a series of complementary immunoassays were selected, including immune phenotyping, gene expression, cytokine levels in LPS-stimulated whole blood and phagocytosis assay.
Results
BSCU1 supplementation promoted pro-inflammatory cytokines (IL-1beta, IL-6, IFN-gamma, IL-12, TNF-alpha, MIP-1alpha, IL-8) secretion upon LPS stimulation. Percentages of myeloid cells were increased in peripheral blood after treatment. In addition, the activation marker CD69 was found to be overexpressed on peripheral blood monocytes after probiotic intervention. BSCU1 supplementation resulted in significant enrichment of clusters of genes involved in phagocytosis pathway. Consistently, phagocytosis assays showed increased capacity of monocytes to engulf bacteria and higher phagosome maturation. Consequently, BSCU1 supplementation promoted the phagocytic capacity of myeloid cells, especially monocytes.
Conclusions
This clinical study shows that BSCU1 primes the peripheral innate immune system. Immune profiling combined with transcriptomic analysis and ex vivo functional assays provided consistent evidence of increased phagocytic capacity following BSCU1 supplementation.