In were treated as above and probed with rabbit serum recognizing LipL32. The data is representation of four experiments performed separately. The identities of individual proteins are indicated on the right, and the positions of molecular mass standard (in kilodaltons) are indicated on the left. doi:10.1371/journal.pone.0051025.gouter-membrane permeabilization methods other than methanol fixation/permeabilization were employed to eliminate the possibility that antibodies for LipL32 recognize methanol-denaturated form of Fexinidazole biological activity protein more efficiently. For permeabilization by PBS, cells were resuspended in PBS, vortexed for 30 sec and centrifuged at 14,0006 g for 5 min at room temperature, repeating this procedure one more time before adding a 1-ml suspension of 56108 spirochetes to each well of Lab-Tek Two-Well Chamber Slides (Nalge Nunc, Naperville, IL) and incubated at 30uC for 80 min to adhere cells. For permeabilization by EDTA, cells were resuspended in PBS+ 2 mM EDTA and to Lab-Tek Two-Well Chamber Slides. For permeabilization by shear force, cells were resuspended in PBS and pressed through a 28 5/8 gauge needle with a syringe repeating the process four times before adding suspension Two-Well Chamber Slides. For these permeabilization methods, bacteria were fixed to the glass slides by incubation for 40 min at 30uC in 2 paraformaldehyde in PBS-5 mM MgCl2. Antibodies were diluted in blocking buffer (Difco Leptospira Enrichment EMJH, BD, Sparks, MD) as follows: rabbit serum recognizing LipL32 1:800, affinity-purified antibodies from leptospirosis patient serum recognizing LipL32 1:300, monoclonal antibodies for LipL32 1:800, rabbit sera recognizing OmpL54 1:50, and FlaA2 1:600. Normal human serum was diluted 1:300. Alexa Fluor 488-labeled goat anti-rabbit IgG, goat anti-mouse IgG 23115181 or goat anti-human 23977191 IgG (Invitrogen/Molecular Probes, Eugene, OR) diluted 1:2000 and fluorescent nucleic acid stain, 496diamidino-2-phenyl-indole dihydrochloride (DAPI) (Invitrogen/ Molecular Probes) diluted to a final concentration of 0.25 mg/ml in blocking buffer were used to detect antibody binding and the presence of spirochetes, respectively.olysis in our laboratory had included LipL32 as positive control. Surprisingly, LipL32 was not digested by Proteinase K at concentrations capable of digesting surface-exposed proteins OmpL47 and OmpL37 (Fig. 1A). To eliminate the possibility that LipL32 is intrinsically resistant to Proteinase K cleavage, intact and lysed leptospiral cells were subjected to proteolysisResults Surface proteolysis does not degrade LipLSurface proteolysis experiments involving incubation of intact leptospires with Proteinase K were performed to assess surface exposure of leptospiral proteins. Based on the assumption that LipL32 is a surface-exposed 115103-85-0 site lipoprotein, previous surface proteFigure 2. Purification and specificity of LipL32 antibodies from leptospirosis patient sera. (A) Affinity purification of LipL32-specific antibodies. Recombinant LipL32 [17] was coupled to an AminoLink Plus column. Pooled convalescent sera from 23 individuals with laboratoryconfirmed leptospirosis was added to the LipL32-affinity column. The chromatography products were analyzed by gel electrophoresis (BisTris 4?2 NuPage gel, Novex), and Coomassie G250 staining. Abbreviations: LeptoPS, leptospirosis patient sera (pooled); FT, flowthrough fraction; W, fraction after washing with PBS; E1-E4, eluted IgG fractions. (B) Extract of 16108 leptospires (lane WC) or 0.In were treated as above and probed with rabbit serum recognizing LipL32. The data is representation of four experiments performed separately. The identities of individual proteins are indicated on the right, and the positions of molecular mass standard (in kilodaltons) are indicated on the left. doi:10.1371/journal.pone.0051025.gouter-membrane permeabilization methods other than methanol fixation/permeabilization were employed to eliminate the possibility that antibodies for LipL32 recognize methanol-denaturated form of protein more efficiently. For permeabilization by PBS, cells were resuspended in PBS, vortexed for 30 sec and centrifuged at 14,0006 g for 5 min at room temperature, repeating this procedure one more time before adding a 1-ml suspension of 56108 spirochetes to each well of Lab-Tek Two-Well Chamber Slides (Nalge Nunc, Naperville, IL) and incubated at 30uC for 80 min to adhere cells. For permeabilization by EDTA, cells were resuspended in PBS+ 2 mM EDTA and to Lab-Tek Two-Well Chamber Slides. For permeabilization by shear force, cells were resuspended in PBS and pressed through a 28 5/8 gauge needle with a syringe repeating the process four times before adding suspension Two-Well Chamber Slides. For these permeabilization methods, bacteria were fixed to the glass slides by incubation for 40 min at 30uC in 2 paraformaldehyde in PBS-5 mM MgCl2. Antibodies were diluted in blocking buffer (Difco Leptospira Enrichment EMJH, BD, Sparks, MD) as follows: rabbit serum recognizing LipL32 1:800, affinity-purified antibodies from leptospirosis patient serum recognizing LipL32 1:300, monoclonal antibodies for LipL32 1:800, rabbit sera recognizing OmpL54 1:50, and FlaA2 1:600. Normal human serum was diluted 1:300. Alexa Fluor 488-labeled goat anti-rabbit IgG, goat anti-mouse IgG 23115181 or goat anti-human 23977191 IgG (Invitrogen/Molecular Probes, Eugene, OR) diluted 1:2000 and fluorescent nucleic acid stain, 496diamidino-2-phenyl-indole dihydrochloride (DAPI) (Invitrogen/ Molecular Probes) diluted to a final concentration of 0.25 mg/ml in blocking buffer were used to detect antibody binding and the presence of spirochetes, respectively.olysis in our laboratory had included LipL32 as positive control. Surprisingly, LipL32 was not digested by Proteinase K at concentrations capable of digesting surface-exposed proteins OmpL47 and OmpL37 (Fig. 1A). To eliminate the possibility that LipL32 is intrinsically resistant to Proteinase K cleavage, intact and lysed leptospiral cells were subjected to proteolysisResults Surface proteolysis does not degrade LipLSurface proteolysis experiments involving incubation of intact leptospires with Proteinase K were performed to assess surface exposure of leptospiral proteins. Based on the assumption that LipL32 is a surface-exposed lipoprotein, previous surface proteFigure 2. Purification and specificity of LipL32 antibodies from leptospirosis patient sera. (A) Affinity purification of LipL32-specific antibodies. Recombinant LipL32 [17] was coupled to an AminoLink Plus column. Pooled convalescent sera from 23 individuals with laboratoryconfirmed leptospirosis was added to the LipL32-affinity column. The chromatography products were analyzed by gel electrophoresis (BisTris 4?2 NuPage gel, Novex), and Coomassie G250 staining. Abbreviations: LeptoPS, leptospirosis patient sera (pooled); FT, flowthrough fraction; W, fraction after washing with PBS; E1-E4, eluted IgG fractions. (B) Extract of 16108 leptospires (lane WC) or 0.