A new technology for obtaining a recombinant version of a new dedicated protein T. pallidum Tp0319 for the serological diagnostics of syphilis was gene engineered. As a result, a homogeneous (according to denaturating polyacrylamide gel electrophoresis) recombinant version of T. pallidum Tp0319 protein was obtained. The molecular mass of recombinant T. pallidum Tp0319 protein according to electrophoretic mobility is about 37 kDa, which corresponds to the molecular mass of a fragment of Tp0319 protein without a signal peptide calculated based on the amino-acid sequence (37.3 kDa). According to the developed technology, purified recombinant T. pallidum Tp0319 and Tp0453 proteins were obtained. The proteins were used as antigens as a part of a solid-phase immunoadsorbent for detecting specific IgG to the study protein in the serum of patients suffering from different types of acquired syphilis. The use of the resulting recombinant protein enabled the authors to reveal T. pallidum antibodies in the blood serum in patients suffering from syphilis (primary, secondary, latent early and late stage syphilis). The examination of blood serum samples taken from healthy donors revealed no antibodies. Based on the study results, it is possible to make a conclusion about the possibility to use the resulting recombinant protein (Тр0319) as an extra antigen for diagnostics of syphilis. The introduction of the new antigen in the immunoadsorbent for test systems used for diagnosing syphilis (in the form of immune-enzyme assay, immunoblotting or immune chips) expands the potential of serological diagnostics of this disease due to the expansion of the range of T. pallidum antibodies to be revealed.

Goal. Production of a recombinant T. pallidum antigen Tp0453 and the evaluation of the efficacy of its clinical use for syphilis diagnosis. Materials and methods. To produce the target recombinant T. pallidum antigen, a Tp0453 protein coding fragment of the DNA of the causative agent of syphilis, was cloned into the pET28а vector. Heterological expression of the recombinant T. pallidum antigen was performed in the E. coli BL21 (DE3) strain. The recombinant Tp0453 six-histidine-tagged protein was purified by the metal-chelate affinity chromatography. The resulting homogenous recombinant T. pallidum Tp0453 protein was used to reveal specific IgG antibodies in the serum of syphilis patients using a microarray technology. Results and conclusion. The use of the resulting recombinant protein enabled authors to reveal anti- T. pallidum antibodies in the blood serum of patients suffering from syphilis (primary, secondary, early and late latent syphilis). None of the uninfected controls had a significant reactivity to the recombinant Tp0453. These data allow to propose, that the recombinant protein Tp0453 show promise for laboratory diagnosis of syphilis. The introduction of Tp0453 antigen into the test systems for diagnosis of syphilis (ELISA, immunoblotting or microarray) increases the potential of serodiagnosis of this disease due to the broader range of the revealed antitreponemal antibodies.