Characterization of immunologic and adhesive abilities of Mycoplasma pneumoniae P1 protein segment

Abstract

Objective To determine the immunogenic and adhesive abilities of a segment (P1C protein) that located at the carboxy terminal region of P1 protein (1125 to 1395 amino acids).Methods A recombinant prokaryotic vector (pGEX6p-2/p1c) was constructed for P1C protein expression in E.coli BL21DE3.The expressed target recombinant protein (rP1C) was identified using SDS-PAGE and Western blot assay,and then extracted by GST-based affinity chromatography.The purified rP1C was used to immunize BALB/c mice to obtain rP1C-antiserum and titer of the antiserum was determined by ELISA.Immunoreactivity of the rP1C to the sera form M.pneumoniae-infected patients was detected using Western blot assay,while activity of the rP1C adhering to HeLa cells as well as adhesion blockage of the rP1C antiserum were detected using indirect immunofluorescence assays.Results The constructed prokaryotic expression system could efficiently express soluble rP1C with a relative molecular weight of 66×103.The antiserum from rP1Cimmunized mice showed an ELISA titer as high as 1:64 000.Both the M.pneumoniae-infected patients' sera and the mouse antiserum against rP1C could recognize as well as combine with the rP1C.rP1C could adhere to HeLa cells and the adhesion could be blocked by the mouse antiserum with an antiserum concentration-dependent manner.Conclusion P1C,a segment of M.pneumoniae P1 protein,possesses powerful immunogenicity and immunoreactivity and cell-adhered activity,indicating the protein segment can be used as an antigen candidate for developing vaccines and serological diagnostic methods of M.pneumoniae-induced diseases. Key words: Mycoplasma pneumoniae; P1 protein segment; Immunologic activity; Adhesion