Expression and purification of the recombinant outermembrane protein Tp0453 of Treponema pallidum and its characterization of immuno-competence

ELISA test has been shown to have some advan tages in relation to the tests used for the diagnosisof syphilis because of its easy and quick perfor mance and result readings. With recent develop ment of the gene engineering technology and eluci dation of the whole genome of Nichols strain ofTreponema pallidum, new protein coding openreading frames (ORFs) are available for testing,and the study on the serological tests based on therecombinant protein have been become the focus ofinter…

Expression and purification of the recombinant outer membrane protein Tp0453 of Treponema pallidum and its characterization of immuno-competence

To clone and express the recombinant outer membrane protein Tp0453 of Treponema pallidum and to analyze the immuno-reactivity and immunogenicity of the expressed protein, the immuno-dominant epitope of the Tp0453 was amplified from the complete genome of T. pallidum by PCR, subcloned into expression vector pQE32 to generate the recombinant plasmid pQE32/Tp0453, then expressed in E. coli M15 and analyzed by SDS/PAGE and Western blotting. The fusion protein expressed was purified with Ni-NTA affinity chromatography. Its immuno-reactivity was assayed by indirect ELISA, and the immunogenicity was determined by immunization with this fusion protein in New Zealand rabbits. In the presentstudy, a fusion protein of molecular weight about 32 kDa was obtained. As demonstrated by Western blotting, the recombinant protein could react specifically with positive IgG sera of patients with syphilis, and the antibodies against T. pallidum in human sera were successfully detected by indirect ELISA. Both the sensitivity and specificity of ELISA based on the Tp0453 fusion protein as were 100% (30/30) when detected with control sera. In comparison with the results of IgG ELISA with those of TPPA. It was found that the sensitivity of ELISA was 96.8% and the specificity was 100%. The difference of ELISA and TPPA was not significant, and the concordance of results between ELISA and TPPA was 98.2 %. In addition, specific humoral responses could be elicited by immunization with the recombinant fusion protein in New Zealand rabbits with a specific antibody titer of 1:1280 after 3 successive doses of immunization.These results demonstrate that the expressed recombinant fusion protein shows excellent immuno-competence and provide foundation to develop a quick diagnostic kid applied to detect the presence of T. pallidum infections.