Therapeutic effects and immunogenicity of Ag85A DNA vaccines from Mycobacterium tuberculosis

Objective To evaluate the therapeutic effects and immunogenicity of Ag85A DNA vaccines in mouse models of M.tuberculosis infection to develop new immunotherapeutic agents for treatment of tuberculosis.Methods Fourty female BALB/c mice were immunized intramuscularly with saline,plasmid vector pVAX1,M.vaccae vaccine and Ag85A DNA for three times at two-week intervals to evaluate immunogenicity of Ag85A DNA vaccines.Fourty female BALB/c mice were infected intravenously via the tail vein with M.tuberculosis H37RV,then randomly divided into 4 groups based and treated as follow at the third day after infection:saline,plasmid vector,rifampin,Ag 85A plasmid DNA vaccines.DNA vaccines were injected intramuscularly 3 times at two-week intervals.Mice were sacrificed two weeks after the final immunization.The lungs and spleens from the mice were taken and their pathological changes,weight and number of mycobacterial colony were examined.ELISPOT assay for IFN-γ was performed with ELISPOT assay kit as instructed by the manufacture.Results Ag85A DNA vaccines had a significantly increased amount of T cells that secreted IFN-γ in response to Ag85A protein than mice treated with control groups(S=11.832,P=0.0080).The histopathological changes in lung showed that the lung lesions were severe and extensive in saline and plasmid vector pVAX1 group,the lung lesions were slight and limited,there were relatively clear and normal structure of alveoli in Ag85A DNA vaccine group,there were no lung lesions in RFP group.Compared with saline group,Ag85A DNA vaccine group and RFP group reduced the pulmonary bacterial loads by 0.73 log and 2.11 log,liver bacterial loads by 0.88 log and 2.11 log(P0.01),respectively.Conclusions The immunotherapeutic effects of Ag85A DNA are significant in the mouse model of tuberculosis.