Abstract: Objective  To study the immunogenicity of Mycobacterial tuberculosis Ag85A DNA vaccine with pilot scale production in mice.  Methods  Twenty BALB/c mice were randomly divided into 2 groups, and then immunized intramuscularly for 3 times with Mtb Ag85A DNA or PBS respectively. The mice were killed and the whole blood samples were collected at 3 weeks after the last immunization. The specific antibody and cytokines (IL-4) in sera were detected. The Mtb Ag85A specific interferon-γ (IFN-γ) level and the percentages of CD4⁺ or CD8⁺ T cell in mouse spleen cells were also detected.  Results  The data obtained by statistical analyses demonstrated that: (1) The absorbance values of Ag85A-specific antibody in the sera of each group mice before and after immunization were all less than 0.2. (2) The IL-4 level in sera from Ag85A DNA group［(146.2±34.3) pg/ml］was significantly lower than that from PBS group ［(177.7±28.1) pg/ml］(t=2.244，P=0.038). The IFN-γ level in sera from Ag85A DNA group ［(129.6±159.0) pg/ml］was higher than that from PBS group ［(76.5±21.5) pg/ml］, but there was no significant difference (t=－1.047，P=0.309). (3) The data from the ELISPOT assay for IFN-γ showed that the number of spot-forming spleen cells in Ag85A DNA group(103.60±112.14) was significantly higher than that in PBS group(5.78±5.83) (t=36.538，P=0.018). (4) The percentage (21.57%) of CD4⁺ T cells in Ag85A DNA group was higher than that (12.17%) in PBS group (t=3.043，P=0.038); however, there was no significant difference on the percentage of CD8⁺ T cells between the two groups (13.70% vs. 10.57%, t=0.847，P=0.445).  Conclusion  The Th1 cellular immunity was mainly stimulated in the mice immunized by Mtb Ag85A DNA vaccine. But Th2 cellular immune response was not significantly induced in these mice.

Key words: Vaccines, , DNA, Acyltransferases, Antigens, bacterial, Immunocompetence