Thymosin alpha-1 (Tα1) has been used as an immune potentiator for treatment of immune deficiency diseases by injection administration. However, injection is inconvenient and may cause many side effects. In order to improve the administration convenience of Tα1, a human Tα1 gene transformed Bifidobacterium longum (BL-Tα1) was prepared and its effects on mice immunity by oral administration were investigated. The Balb/c mice were treated with BL-Tα1, which was pre-induced with 0.2% l-arabinose, every other day for 2 weeks. The B. longum transformed with empty vector (BL-0) was used as the negative control, and normal saline (NS, 0.9% saline) was used as the blank control. The results shown that (1) the CD3(+)CD4(+) and CD3(+)CD8(+) T-cells in blood, spleen and thymus, and the CD4(+)CD8(+) cells in thymus and spleen of BL-Tα1 group were all significantly increased than that of negative control BL-0 group respectively; (2) the interferon-γ (IFN-γ) and interleukin-12 (IL-12) in serum of BL-Tα1 group were significantly increased. No significant differences were found in the levels of tumor necrosis factor-α (TNF-α) and interleukin-4 (IL-4) between BL-Tα1 group and BL-0 group; (3) thymic hyperplasia and lymphadenectasis were observed in BL-Tα1 group after three-month treatment. In conclusion, the Tα1-transformed B. longum promotes thymus and lymph nodes growth, stimulates T cell proliferation and maturation, and enhances cellular immunity through Th1 pathway by oral administration.
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