Genotypic Analysis, Construction of the Expression System and Immunological Identification of the Recombinant Proteins of the LipL32 Gene in the Dominant Serogroups of Leptospira interrogans in China

【Abstract】 To investigate the existence of the major outer membrane protein (MOMP) gene LipL32 in 15 dominant Chinese strains of 15 serogroups of Leptospira interrogans and 2 international strains of 2 serogroups of Leptospira biflexa, and to clone and construct the expression system as well as to identify the recombinant proteins, genomic DNAs from strains of leptospira were prepared by routine phenol-chloroform method, and the fragments of the LipL32 gene with the whole length from the strains were amplified with high fidelity PCR. The target amplification products were sequenced after T-A cloning, and the expression system for the genes were thereby constructed. Expression of the recombinant proteins was identified by using SDS-PAGE after induction with IPTG at different dosages. Western blot assays with rabbit antiserum against the whole cell of TR/PatocⅠ of Leptospira and immunized serum with rMOMPs were used to determine the immunoreactivity and immunogenicity of the recombinant proteins. Microscopic agglutination test was used to determine the cross- agglutination titres in rabbit sera immunized with rMOMPs, and the cell adherence model of Leptospira was used to examine the blocking effects of rabbit antisera against these rMOMPs. It was found that the LipL32 gene could be found in all the 17 strains of Leptospira mentioned above with two different genotypes, i.e. LipL32/1 and LipL32/2. Amounts of expressions of rMOMP1 and rMOMP2 after IPTG accounted for 40% and 10% of the total bacterial proteins respectively. Both rMOMP1 and rMOMP2 could combine with the rabbit antiserum against leptospiral TR/PatocⅠ, and could induce the production of agglutination antibodies to these 17 strains of Leptospira with 1∶2 to 1∶64 MAT titres. The rabbit anti-rMOMP1 and anti-MOMP2 antibodies at 1∶2 to 1∶16 dilutions could efficiently block adherence of Leptospira. It concludes that all the Leptospira tested in the present study possess LipL32/1 or LipL32/2 genes, and the constructed expression system can express the rMOMP1 and rMOMP2. These recombinant proteins are showed to have good immunogenicity and satisfactory immunoreactivity.更多还原