Immunomodulatory effect and mechanism of the combination of live Bifidobacterium, Lactobacillus, Enterococcus and Bacillus on immunocompromised rats

Immune deficiency is very common in subhealth status and in the occurrence of some diseases. Probiotics have become an important means for immune regulation. This work aimed to investigate the immunomodulatory effect and mechanism of the combination of live Bifidobacterium, Lactobacillus, Enterococcus and Bacillus (CBLEB), which is a drug used by approximately 10 million patients every year, on cyclophosphamide-immunosuppressed rats. Cyclophosphamide (40 mg/kg) was intraperitoneally injected to induce immunosuppressed rat model on the 1st, 2nd, 3rd and 10th days. Starting on the 4th day, the rats were continuously gavaged with the CBLEB solution for 15 days. Samples were collected to determine the routine blood test, the liver and kidney function, serum cytokine levels, the gut microbiota, the fecal and serum metabolome, transcriptome, and histopathological features. Our results showed that CBLEB treatment not only reduced cyclophosphamide-induced death, weight loss and organ damage but also eliminated the cyclophosphamide-induced increase in the mean hemoglobin content, GGT, M-CSF and MIP-3a levels and decrease in the red blood cell distribution width, total protein and creatinine. Additionally, CBLEB treatment eliminated the cyclophosphamide-induced enrichment of Clostridium sensu stricto 1, Dubosiella, Faecalibaculum, Morganella, and Eggerthellaceae unclassified and depletion of Prevotella, Roseburia, and Lachnospiraceae FCS020 group. Furthermore, CBLEB treatment alleviated the cyclophosphamide-induced alterations in the fecal metabolome profile, including the enrichment of 1-heptadecanol, succinic acid, hexadecane-1,2-diol, nonadecanoic acid and pentadecanoic acid, and the depletion of benzenepropanoic acid and hexane. CBLEB treatment also alleviated the cyclophosphamide-induced enrichment of serum D-lyxose and depletion of serum succinic acid, D-galactose, L-5-oxoproline, L-alanine and malic acid. CBLEB partially recovers the cyclophosphamide-induced alterations in metabolism and signal transduction pathways in the spleen and colon. The mechanism is related to the ability of CBLEB to induce recovery of the cyclophosphamide-altered carbohydrate metabolism and signal transduction. This study provides an experimental basis and good enlightenment with respect to the application of CBLEB for the prevention and treatment of immunodeficiency.