[Bioinformatics analysis and purification of Treponema pallidum OmpH protein and preparation of polyclonal antibody].

Abstract

Objective: To analyze and predict the biological properties and function of Treponema pallidum OmpH protein by bioinformatics methods, purify the target protein, and prepare polyclonal antibodies. Methods: From January 2024 to February 2025, the research team from the Department of Clinical Laboratory at The First Affiliated Hospital of Hunan Traditional Chinese Medical College (Hunan Province Directly Affiliated Traditional Chinese Medical Hospital) conducted a study employing integrative approaches combining bioinformatics analysis with animal experimentation. During this investigation, the coding sequence of the T. pallidum outer membrane protein H (TpOmpH) was systematically retrieved from the National Center for Biotechnology Information (NCBI) database. And the bioinformatics tools, such as Protparam, Protscale,SignalP 6.0,NetNGlyc-1.0,TMHMM2.0,NetPhos-3.1,SOPMA,AlphaFold3,IEDB,STRING,C-immsim were used to analyze and predict the biological and immunological characteristics of TpOmpH protein. The full length of TpOmpH gene was synthesized and was cloned into the pET28a to construct the recombinant plasmid pET28a-TpOmpH. The the expression of target protein was induced by IPTG and was purified using affinity chromatography. The TpOmpH protein was used to immunize mice and the anti-serum was harvested, then the titer of antibody was detected. Results: TpOmpH is a hydrophobic outer membrane protein with a molecular weight of 19.7 kDa and strong stability. The TpOmpH protein is located outside the cell membrane and contains 11 serine, 4 threonine, and 1 tyrosine phosphorylation site, but no glycosylation sites. The 77.91% of the amino acids in TpOmpH protein are alpha helix, 8.72% are extended strand, 10.47% are random coils, and 2.91% are beta turns. The tertiary structure predicted by AlphaFold3 is in its optimal state. The TpOmpH protein has 4 CTL epitopes, 4 linear epitopes, and 5 spatial epitopes. The TpOmpH protein can interact with Tp92,MutS,SurA,TPANIC_0600 and other proteins which may be involved in Tp invasion. TpOmpH protein can induce an increase in B cell count, antibody content, Th cell count, NK cell count, as well as the expression of various cytokines. High purity TpOmpH protein was obtained through Ni²⁺ affinity chromatography, which is consistent with the theoretical molecular weight. TpOmpH protein can induce mice to secrete polyclonal antibodies with antibody titers higher than 1∶10 000. Conclusion: TpOmpH protein is a hydrophobic protein located on the outer membrane of Tp, can induce mice to secrete high titer antibodies, which providing experimental basis for the pathogenesis of Tp and vaccine development.