Abstract:

Objective To study the effect of a recombinant plasmid encoding mouse interleukin 2 （mIL-2） on the immunogenicity of DNA vaccine against Chlamydia trachomatis （Ct） serovar E. Methods BALB/c mice were divided into 4 groups to be intramuscularly inoculated with blank plasmid （negative control group）, DNA vaccine against Ct serovar E （DNA vaccine group）, DNA vaccine against Ct serovar E and a recombinant plasmid containing mIL-2 （combination group）, and inactivated Ct serovar E elementary bodies （positive control group）, respectively. The immunological effects were evaluated by posterior foot pad thickness, proliferation level of spleen lymphocytes, serum level of IL-4 and interferon （IFN）-γ in mice, and the capability to clear Ct genital tract infection. Results The proliferation index of spleen lymphocytes in the combination group and positive control group was similar （3.64 ± 0.41 vs. 3.77 ± 0.34）, but was significantly different from that in the blank control group and DNA vaccine group （1.37 ± 0.21 and 2.52 ± 0.30）. The serum level of IL-4 was （38.49 ± 12.24） pg/ml in the positive control group, significantly higher than in the negative control group, DNA vaccine group and combination group （（25.37 ± 18.93）, （24.75 ± 8.49）, （21.74 ± 6.43） pg/ml，respectively）. With respect to the serum level of IFN-γ, the combination group and positive control group were similar （（1923.3 ± 518.1） pg/ml vs. （2712.5 ± 887.2） pg/ml）, but were significantly different from the negative control group and vaccine group （（310.8 ± 160.7） pg/ml and （601.3 ± 357.9） pg/ml）. Six days after Ct challenge, the exfoliated cells from genital tract were positive for Ct culture in the negative control group, but negative in the other 3 groups. Conclusion IL-2 genetic adjuvant can enhance the immune response, especially Th1 type response, induced by the DNA vaccine against Ct serovar E.

Key words: interleukin 2, gene adjuvant, trachomatis,Chlamydia, DNA vaccine, Immunological effects