ObjectiveTo prepare Mycobacterium tuberculosis ESAT6-Fc fusion protein and evaluate its efficacy and safety on ovalbumin(OVA)-induced allergic rhinitis(AR) in mice, so as to provide experimental basis for the development of novel AR immunothera-peutic agents.MethodsThe recombinant plasmid pcDNA3.1(+)-Rv3875-Fc was transfected into CHO-K1 cells to obtain ESAT6-Fc fusion protein, which was purified by Protein G affinity chromatography. The female C57 BL/6J mice of AR model sensitized by OVA were randomly divided into five groups: normal control, OVA, CpG, ESAT6-Fc + CpG and dexamethasone(DEX) group, six mice each group, which were challenged with atomized OVA after the corresponding preparation was given to the nasal cavity for intervention. HE staining method was used to evaluate the inflammatory infiltration of mouse nasal mucosa, and ELISA method was used to detect the content of histidine(HIS), leukotriene B4(LTB4), IgE, IL-4,IL-13 and IL-17A in the nasal lavage fluid. The structural changes of heart, liver, spleen and kidney tissues were observed by HE staining, and the levels of glutamic oxaloacetic transaminase(AST) and lactate dehydrogenase(LDH) in mouse heart,liver, spleen and kidney were measured by ELISA.ResultsESAT6-Fc fusion protein with high purity(> 95%) was successfully obtained. Compared with the normal control group, the inflammatory cell infiltration in nasal mucosa of the OVA group was significantly aggravated(t = 11. 180, P < 0. 001), and the levels of HIS, LTB4, IgE, IL-4, IL-13 and IL-17A in the nasal lavage fluid significantly increased(t = 3. 843, 4. 237, 5. 996, 3. 561, 4. 544, 5. 773, respectively, each P < 0. 05). Compared with the OVA group, the infiltration of inflammatory cells in nasal mucosa of mice in the ESAT6-Fc + CpG and DEX groups was significantly reduced(t = 4. 472 and 5. 582, respectively, each P < 0. 001), and the levels of HIS, IgE, LTB4, IL-4, IL-13 and IL-17A in the nasal lavage fluid significantly decreased(t = 0. 000-1. 061, each P < 0. 05). There was no significant difference in the levels of HIS, IgE, LTB4, IL-4, IL-13 and IL-17A between the ESAT6-Fc + CpG and DEX groups(t = 0. 048, 0. 000,0. 968, 1. 061, 0. 375 and 0. 638, respectively, each P > 0. 05). Intranasal immunization with ESAT6-Fc did not cause pathological damage to the heart, liver, spleen, and kidney of mice, and the levels of AST and LDH in the above organs showed no significant difference from those in the normal control group(t = 0. 001-1. 036, each P > 0. 05).ConclusionThe prepared ESAT6-Fc fusion protein has high purity, and intranasal immunization with the fusion protein can safely and effectively alleviate OVA-induced AR symptoms in mice, and inhibit the expression of related inflammatory factors, without obvious organ toxicity observed, indicating that ESAT6-Fc fusion protein is expected to become a new type of immunotherapeutic agent for AR.