interrogans serogroup Icterohaemorrhagiae serovar Lai strain Lai

interrogans serogroup Icterohaemorrhagiae serovar Lai SIS3 strain Lai was offered by the National Institute for the Control of Pharmaceutical and Biological Products in Beijing, China. The leptospires were cultured in Korthof liquid medium containing 8% heat-inactivated rabbit serum (RS) at 28°C. To maintain virulence, the strain was passaged intraperitoneally in

specific pathogen-free Dunkin-Hartley ICO:DH (Poc) guinea pigs (2 weeks old, each weighing about 120 g) before use, according to the description by Merien et al. and Viriyakosol et al. [44, 54]. Animal protocols were approved by the Animal Ethics Review Committee of Zhejiang University. Cell line and culture The murine mononuclear-macrophage-like cell line (J774A.1) was selleck inhibitor obtained from the American Type Culture Collection (Rockville, MD, USA). The cells were cultured in RPMI 1640 medium (GIBCO,

USA), supplemented with 10% heat-inactivated fetal calf serum (FCS) (GIBCO), 100 U/ml penicillin and 100 μg/ml streptomycin (Sigma, USA) at 37°C in an atmosphere of 5% CO2. PCR and sequencing Genomic DNA of L. interrogans strain Lai was extracted using Bacterial Genomic DNA Extraction Kit (BioColor, China). Plasmid pUC19, which has an ampicillin resistant gene (bla) cassette including promotor in E. coli DH5a, was prepared by Mini-plasmid Rapid Isolation Kit (BioDev, China). Primers for amplifications of the fliY and bla genes are shown in Table 2. A commercial PCR Kit (TaKaRa, China) was used to amplify the fliY and bla genes. The products were detected on 1.5% ethidium

bromide pre-stained agarose gel by electrophoresis, Thiamine-diphosphate kinase purified using PCR Product Purification Kit (BioColor), and ligated into plasmid pUCm-T using T-A Cloning Kit (BioColor) to form recombinant plasmids pUCm-T fliY . pUCm-T bla sequencing was performed by Invitrogen Co. Ltd in China. Table 2 Primer information for amplification of the fliY and bla genes. Gene Primer sequence (5′-3′) Product size fliY F: GCC GGA TCC (BamH I) ATG GGT GAA GGT TCC CTA TCA CAG 1065 bp   R: GCC AAG CTT (Hind III) TCA CTT ACC CTC CGG CTT AAT CCG   bla F: GCC AGA TCT (Bgl II) TCT AAA TAC ATT CAA ATA TGT 954 bp   R: GCC AGA TCT (Bgl II) CTT GGT CTG ACA GTT ACC AAT   fliP F: ATG AAA ATG AGA CAT AAA 804 bp   R: TCA TTT ATA ACT CCT TAC   fliQ F: ATG ACG GAA TTA GAC GTT ATG 264 bp   R: CTA AAA TTT TTC GAT CAT CAA   F: forward primer, R: reverse primer. Expression, purification and immunization of recombinant FliY pUCm-T fliY and expression vector pET32a (Novagen, USA) were digested with BamH I and Hind III, respectively. The recovered fliY segment was ligated into linearized pET32a using T4 DNA ligase (TaKaRa), and then transformed into E. coli BL21DE3 (Novagen) to form E. coli BL21DE3pET32a-fliY . Recombinant FliY (rFliY) was expressed under inducement of 0.5 mM IPTG for 4 h at 37°C. The expressed rFliY was extracted by Ni-NTA affinity chromatography and the purity of rFliY was determined by SDS-PAGE.

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