Abstract: Objective   To investigate the immunogenicity of recombinant plasmid pcDNA3.1-amastin with Leishmania donovani amastin gene.  Methods   Eighteen female BALB/c mice were randomly divided into experimental group and control group. Mice in experimental group and control group were intramuscularly injected with 50 μg recombinant plasmid pcDNA3.1-amastin and blank plasmid vector pcDNA3.1（+）， respectively, and then received equivalent dose of plamid after 2 weeks. On days 7, 14, and 21 after the second immunization， serum samples were collected from 3 mice each group. The mice were then sacrificed, spleens were removed and splenocytes were collected. Serum antibody level was determined by indirect ELISA. Splenocyte proliferation responses and cytotoxicity of spleen-derived lymphocytes were analyzed by MTT colorimetry after stimulation with ConA. Level of IFN-γ， IL-2 and IL-4 in the splenocyte culture supernatants was determined by double antibody sandwich ELISA.   Results   On days 7, 14, and 21 after the second immunization， specific IgG antibody （more than 1 ∶ 640） was found in experimental group, but not in the control（P＜0.01）； stimulation index （SI） of spleen cells in experimental group （4.28±0.51, 5.01±0.60, and 4.39±0.50） was higher than that of control group （P＜0.01）; the level of IFN-γ［（42.06±4.26）, （66.02±6.02）, and （58.29±3.75） pg/ml］ and IL-2 ［（38.21±5.11）, （64.79±8.67）, and （52.69±7.15） pg/ml］ in splenocyte culture supernatants of experimental group was higher than that of control group （P＜0.01）; IL-4 was not found in the two groups; cytotoxicity of spleen-derived lymphocytes in experimental group ［（42.20±5.96）%, （63.66±5.44）%, and （52.24±4.56）%］was stronger than that of control （P＜0.01）.   Conclusion   The recombinant plasmid pcDNA3.1-amastin can induce specific humoral and Th1 type cellular immune responses in mice.

Key words: Leishmania donovani, Amastin, DNA vaccine, Immunogenicity