To Investigate the Effects of Bifidobacterium Animalis Subsp. Lactis XLTG11 on Growth and Development, Incidence of Allergy and Immune Function in Infants

Early childhood represents a critical developmental window during which the gut microbiome, immune system, and mucosal defense pathways undergo coordinated maturation. Dysregulation during this period contributes substantially to allergic sensitization, respiratory morbidity, and gastrointestinal disorders, which collectively represent major pediatric health burdens worldwide. Infants and young children frequently experience high symptom burden across these domains, reflecting vulnerability to microbial instability and disrupted mucosal homeostasis. The underlying causes are multifactorial, involving dietary transitions, environmental exposures, infections, and immune programming. Growing evidence suggests that disruptions in gut microbial stability, rather than merely compositional changes, may influence susceptibility to multi-system symptoms through interconnected immune and metabolic pathways.

The gastrointestinal tract and respiratory tract are interconnected components of the common mucosal immune system. Immune responses generated in the gut-associated lymphoid tissue can influence distant mucosal sites, including the respiratory epithelium and skin-associated lymphoid tissues. Probiotics can stimulate gut-associated lymphoid tissue, leading to enhanced production of antimicrobial peptides (β-defensin 2, LL-37), immunoglobulins, cytokines, and short-chain fatty acids. These immune mediators circulate systemically and contribute to strengthened epithelial barrier function and immune surveillance at multiple sites. In addition, maintaining functional stability of the gut microbial ecosystem, rather than simply increasing diversity, may be essential for safeguarding against stress-driven metabolic reprogramming and pathobiont expansion during early life.

Children affected by allergic, respiratory, and gastrointestinal symptoms often exhibit instability in microbial community architecture, including bloom of opportunistic taxa (Escherichia coli, Klebsiella, Enterococcus faecalis, Ruminococcus gnavus, Ruminococcus torques) and depletion of short-chain fatty acid-producing fermenters (Eubacterium rectale, Anaerostipes hadrus, Coprococcus species). Dysbiosis and functional instability weaken both local and systemic immunity, particularly through reduced production of antimicrobial peptides and impaired epithelial barrier function. Probiotic supplementation with Bifidobacterium animalis subsp. lactis XLTG11 may help restore microbial functional homeostasis, suppress pathobiont-associated trajectories, and enhance the host's innate mucosal defense profile.

Based on current scientific understanding, this 180-day randomized controlled trial enrolled healthy infants and young children under 3 years of age with elevated allergy risk. Participants received daily Bifidobacterium animalis subsp. lactis XLTG11 (1 × 10¹⁰ CFU) or placebo to evaluate clinical benefits across allergic, respiratory, and gastrointestinal domains, as well as safety outcomes including growth parameters and bowel habits. Additionally, shotgun metagenomic sequencing was performed on fecal samples collected at baseline and 180 days to assess changes in gut microbiota composition, taxonomic remodeling, KEGG pathways, KEGG enrichment patterns, COG functional profiles, and Gene Ontology terms. Mucosal innate immune markers (β-defensin 2, LL-37, calprotectin, secretory IgA) were quantified to assess host immune modulation.

Through these integrated clinical, immunological, and multi-omic metagenomic measures, the study aims to clarify whether B. animalis subsp. lactis XLTG11 reduces symptom burden by buffering against microbiome functional instability, preserving genomic and metabolic homeostasis, reinforcing epithelial innate defense, and suppressing pathobiont emergence-rather than by driving compositional expansion alone. This functional buffering mechanism represents a novel paradigm for probiotic action during the critical early-life window of immune and microbiome development.

• Microbiota profiles of fecal samples in young children upon administration of probiotic or placebo as assessed via 16s rRNA and metagenomics gene sequencing [Срок оценки: Day-0, day-180]
• Gut immune biomarkers of fecal samples in young children upon administration of probiotic or placebo as assessed via Enzyme-Linked Immunosorbent Assay (ELISA) [Срок оценки: Day-0, Day-180]
• Defecation frequency in children upon administration of probiotic or placebo as assessed via daily stool diary [Срок оценки: Day-0, day-180]
• Stool consistency (Bristol Stool Scale characteristics) in children upon administration of probiotic or placebo as assessed via standardized stool form classification [Срок оценки: Day-0, Day-180]
• Growth index (age- and sex-standardized Z-score) in children upon administration of probiotic or placebo as assessed via anthropometric measurements. [Срок оценки: Day-0, Day-180]