Introduction: Vaccination is an essential means for prevention of tuberculosis infection, but the effects of various vaccines on the intestinal flora of mice and their response to Mycobacterium tuberculosis (Mtb) infection remain poorly understood. Methodology: In this study, two different vaccinations − ESAT6 and ESAT6 + TLR8 agonists - were administered to mice transgenic for human TLR8 to investigate gut microbiota characteristics following vaccination. Gut microbiota was investigated by next generation sequencing in the MiSeq Sequencing System. Adonis analysis was used to evaluate the effect of variables on gut bacterial community stucture. Chao1, Shannon index, and phylogenetic diversity index were used to explore the gut bacterial diversity. Results: The results showed that different vaccines have significant influence on mice intestinal bacteria (adonis analysis, p < 0.01), with gut bacterial diversity within the ESAT6 + TLR8 agonists group being significantly decreased compared to the ESAT6 treatment group (p < 0.01). Following infection with Mtb via tail vein injection, the bacterial community structure within the control versus vaccinated groups altered significantly (adonis analysis, p < 0.01), and the altered changed genera were markedly different between the groups. Following infection, Bifidobacteria differed between the groups, indicated that they play a vital role in the response to infection. Conclusions: Our results indicated that different vaccines might have distinct influences on intestinal flora, and their role should not be ignored.

PM_2.5, recognized as a potential pathogenic factor for nervous system diseases, remains an area with many unknowns, particularly regarding its effects on human health. After five-month real-ambient PM_2.5 exposure, we observed no significant pathological damage to the lung, liver, spleen, or kidney tissues. However, PM_2.5 exposure led to neuronal degeneration in the hippocampal CA1 region of Brown Norway (BN) rats. The level of IL-6, IL-13, IL-1β, IL-12, IL-4, GRO/KC, MIP-1α, CM-CSF significantly increased in lung lavage fluid (P < 0.05 for all). Notably, we detected a slight impairment in spatial learning ability, as evidenced by the Barnes maze training outcomes. There were no significant changes in the bacterial community in lung lavage fluid (P = 0.621), but the bacterial community in the gut significantly changed (P < 0.001), with more species identified (P < 0.05). The metabolomic analysis revealed 147 and 149 significantly changed metabolites in the pulmonary system and serum, respectively (P < 0.05). PM_2.5 exposure caused a decrease in Nervonic acid (NA) in both the lung and serum, which likely contributed to spatial learning impairment (P < 0.01). The correlation between lung metabolites, gut bacterial species, and serum metabolites indicated that PM_2.5 exposure likely impaired spatial learning through the lung-gut-brain axis pathway. Lung and serum metabolic disorders and intestinal microbial imbalance occurred in BN rats post-five-month real-ambient PM_2.5 exposure. There were two potential ways that PM_2.5 exposure caused the decline of spatial learning ability in wild-type BN rats: (1) PM_2.5 exposure led to a significant decrease of neuroprotective Nervonic acid in lung and serum metabolites. (2) PM_2.5 exposure likely led to reduced spatial learning ability through the lung-gut-brain axis.