Gut commensal Lactobacillus strain induces a balanced trained immunity phenotype to enhance vaccine efficacy through JAK-STAT-SOCS pathway.

The gut microbiota plays a complex role in immune system maturation and function. The induction of memory in innate immune cells appears to be part of a co-adaptation between the host and microbiome. As important gut commensals, certain Lactobacillus have been shown to induce innate immune memory. However, the universality, phenotypic characteristics, mechanisms of Lactobacillus-induced innate immune memory, and its potential applications in vaccine immunology remain poorly understood. Here, we discovered that specific strains of the gut commensal Lactobacillus can induce innate immune memory, resulting in a more balanced trained immunity phenotype through SOCS activation. Upon secondary stimulation, macrophages exhibited increased expression of IL-6, IL-1β, IL-10, IL-12, IFN-β, and TGF-β. Peptidoglycan and components in the secretome sensitive to pancreatic enzymes were identified as key elements in inducing trained immunity. Furthermore, mice that underwent training demonstrated rapid resistance to S. aureus infection. Additionally, Lactobacillus-induced trained immunity significantly enhanced the protective efficacy of vaccines against MRSA. Our findings demonstrate that certain Lactobacillus strains can activate non-classical trained immunity, offering potential for enhancing vaccine efficacy. Our study provides new insights into the role of some gut commensals in immune modulation and suggests a novel approach to vaccine enhancement through trained immunity induced by specific gut commensals.