Outer Membrane Protein Preparations Research Articles

Functional characterization of a broad and potent neutralizing monoclonal antibody directed against outer membrane protein (OMP) of Salmonella typhimurium.

In the present study, we have generated a murine monoclonal antibody (mAb) named Sal-06 by using the crude outer membrane protein preparation of Salmonella enteric subsp. enterica serovar Typhimurium ATCC 14028 strain as antigen. Sal-06mAb belonging to IgG1 isotype demonstrated broad cross-reactivity to standard and isolated strains of genus Salmonella and others such as Escherichia coli, Klebsiella pneumonia, and Proteus mirabilis. Cross-reactivity across several bacterial genera indicated that the epitopes reactive to Sal-06mAb are conserved among these members. Neutralizing effects of Sal-06mAb on Salmonella growth and survival was evaluated in vitro using bacteriostatic and bactericidal activity with and without complement and bacterial invasion inhibition assay. Sal-06mAb demonstrated a bacteriostatic effect on the growth of S. typhimurium ATCC 14028 strain which is both time and concentration (of mAb) dependent. It was also found that the bacterial growth inhibition was complement independent. When the bacterial cells were preincubated with Sal-06mAb, it reduced the adherence and invasion of bacterial cells into A549 epithelial cell line. This was confirmed by CFU count analysis, phase contrast, and fluorescence microscopy. Scanning electron microscope (SEM) imaging confirmed the antimicrobial effects of Sal-06mAb on S. typhimurium ATCC 14028. The development of broadly reactive and cross protective Sal-06mAb opens new possibilities for immunotherapy of sepsis caused by Gram-negative Enterobacteriaceae members.

Proteomic and bioinformatic analyses of putative Mannheimia haemolytica secretome by liquid chromatography and tandem mass spectrometry

Mannheimia haemolytica is a major bacterial contributor to bovine respiratory disease complex that costs the livestock industry a billion dollars a year in USA. Commercial vaccines are only partially efficacious under field conditions. Earlier studies found that outer membrane protein preparations and culture supernatants can induce immune responses that enhance resistance to challenge by M. haemolytica strains. The objective of this study was to characterize secretome of two M. haemolytica stains grown under two different media. Bacteria-free concentrated supernatants from M. haemolytica culture was subjected to LC–MS/MS. The secretome of M. haemolytica from both strains yielded 923 proteins. Using bioinformatic tools, 283 were identified as secreted proteins. Further breakdown of 283 proteins showed that 114 (40.2%), 184 (65.0%), 138(48.7%), 151 (53.3%) and 172 (60.7%) were characterized as secreted proteins by SignalP 4.1, SecretomeP 2.0, LipoP, Phobius, and PRED-TAT, respectively. A total of 95 (33.56%) proteins were characterized as being secreted via non-classical pathway as opposed to the majority that were secreted in signal peptide dependent pathway. The demonstrated proteins include all previously immunologically characterized M. haemolytica proteins. The potential of using secretome analysis in the design and development of a multivalent vaccine is discussed.

Characterization and Different Antigenic Preparations ofP. multocidaAlong with their Quantitative and Qualitative Analysis

Pasteurella multocida is a causative agent of a number of economically important diseases in livestock. Due to the fatal nature of the disease, there is urgent need for rapid diagnosis so that appropriate therapeutic and preventive measures could be undertaken. A study was designed to extract different antigens of P. multocida capsular type A and B which included whole bacterium, Capsular antigen, Outer membrane proteins (OMPs) and Lipopolysaccharides (LPS). Bacteria were grown on brain heart infusion broth and capsular antigen was separated by fractional precipitation with addition of polar organic solvents yielding capsular polysaccharide. OMPs were extracted by ultracentrifugation of the supernatant obtained from bacterial broth by addition of HEPES Buffer containing Sodium Lauryl Sarcosinate detergent and the detergent insoluble OMP enriched fractions were obtained. Whole cell antigen was obtained by centrifugation of sonicated P. multocida suspended in HEPES buffer. LPS was extracted by formalinized saline killing of bacteria followed by ultracentrifugation. Total protein concentration was found to be 8.97 mg/ml and 5.67 mg/ml for OMP capsular type A & OMP type B respectively, while for WCL it was 22.38 mg/ml& 26.89 mg/ml. Carbohydrate estimation of capsular type A & type B of LPS and capsular polysaccharide concentrations were estimated to be 188.32 μg/ml, 330.71 μg/ml and 4.08 mg/ml, 2.38 mg/ml respectively. OMPs and whole cell lysate extracted were subjected to discontinuous SDS-PAGE. Nine polypeptides of MW ranging from 15–100 kDa from OMPs preparation & fifteen polypeptides of MW ranging from 25–98 kDa from whole cell lysate were visualised.

Detection of the antibacterial effect of essential oils on outer membrane proteins of Pseudomonas aeruginosa by lab‐on‐a‐chip and MALDI‐TOF/MS

ABSTRACTIn bacteria, structural changes of outer membrane protein (OMP) composition may have an effect on the adhesive ability and pathogenic properties of the organisms. Pseudomonas aeruginosa can develop an intrinsic resistance to a wide range of biocides, which is associated with the nature of its outer membrane. The aim of our study was to examine how the essential oils of cinnamon bark and clove modify the OMP composition of the human pathogen P. aeruginosa strains and to identify the structure of proteins that are considerably changed after incubation with essential oils. Chemical composition of the oils was analysed by using gas chromatography and gas chromatography–mass spectrometry. Eugenol (83.7%) was the main component of the clove oil, while trans‐cinnamic aldehyde (73.2%) was the main constituent in cinnamon bark oil. Values for the minimum inhibitory concentration (MIC) of the oils were determined by a modified tube dilution method. The oils were administered to the culture at concentrations of 0.5 × MIC and 2 × MIC and incubated for 60 min. After OMP preparation, the structure of proteins was analysed by MALDI‐TOF/MS. Cinnamon and clove oil could influence the OMP composition of Pseudomonas strains. Proteins with molecular weights of 42.7 kDa and 79.4 kDa disappeared after treatment with cinnamon and clove oil, respectively. Quantitative changes in the protein profile may contribute to the explanation of the antibacterial effect of cinnamon bark and clove essential oils on pathogenic Pseudomonas strains. Copyright © 2013 John Wiley & Sons, Ltd.

Immunological Characterisation of Outer Membrane Proteins (OMPs) ofSalmonella entericaSerovar Gallinarum

Fowl typhoid caused by Salmonella enterica serovar Gallinarum remains to be a major problem for poultry health worldwide. The emergence of multidrug-resistant strains of Salmonella with increased virulence and survivability, leading to increased morbidity and mortality, has further complicated its management. Presently available vaccines against fowl typhoid have less-than-desired efficacy and unacceptable side effects, making it pertinent to search for new immunogens suitable for vaccine formulation. The outer membrane proteins (OMPs) of Salmonella have been considered as possible candidates for protection against typhoid. The present study was conducted to characterise the OMPs of Salmonella enterica serovar Gallinarum using immunodiffusion and western blot techniques. Presence of three precipitation lines against OMP preparation in immunodiffusion test indicated the presence of at least three immunogenic OMPs in S. Gallinarum. Further, western blot analysis revealed OMP 40 as one of the most immunopotent antigen. This study suggests that OMP 40 may be the suitable target for the development of vaccine formulation against fowl typhoid.

Study of Yersinia pseudotuberculosis antigenic structure to obtain a sensitin for design of species-specific diagnostic kits

A method for isolation of outer membrane proteins from Yersinia pseudotuberculosis, which are perspective for further application as sensitin for design of species-specific pseudotuberculosis antigenic diagnostic kits, has been modified. Common species-specific antigens of nine Y. pseudotuberculosis serovars (with molecular weight from 80.62 to 12.2 kDa) were detected by SDS-PAAGE electrophoresis and immunoblotting of the outer-membrane protein preparations. These antigens react with neither the rabbit experimental antiplague antiserum nor antiserum to 39 Y. enterocolitica serovars and normal rabbit serum.

Characterization of surface proteins of Cronobacter muytjensii using monoclonal antibodies and MALDI-TOF Mass spectrometry

BackgroundCronobacter spp. is a newly emerging pathogen that causes meningitis in infants and other diseases in elderly and immunocompromised individuals. This study was undertaken to investigate surface antigenic determinants in Cronobacter spp. using monoclonal antibodies (MAbs) and MALDI-TOF Mass spectrometry.ResultsSpleenocytes from mice that were immunized with heat-killed (20 min, 80°C) Cronobacter cells were fused with SP2 myeloma cells. Five desirable MAbs (A1, B5, 2C2, C5 and A4) were selected. MAbs A1, B5, 2C2 and C5 were of IgG2a isotype while A4 was an IgM. Specificity of the MAbs was determined by using immunoblotting with outer membrane protein preparations (OMPs) extracted from 12 Cronobacter and 6 non-Cronobacter bacteria. All MAbs recognized proteins with molecular weight ranging between 36 and 49 kDa except for one isolate (44) in which no OMPs were detected. In addition, MAbs recognized two bands (38-41 kDa) in four of the non-Cronobacter bacteria. Most of the proteins recognized by the MAbs were identified by MALDI-TOF peptide sequencing and appeared to be heterogeneous with the identities of some of them are still unknown. All MAbs recognized the same epitope as determined by an additive Index ELISA with their epitopes appeared to be conformational rather than sequential. Further, none of the MAbs recognized purified LPS from Cronobacter spp. Specificity of the MAbs toward OMPs was further confirmed by transmission electron microscopy.ConclusionsResults obtained in this study highlight the immunological cross-reactivity among Cronobacter OMPs and their Enterobacteriaceae counterparts. Nevertheless, the identity of the identified proteins appeared to be different as inferred from the MALDI-TOF sequencing and identification.

Identification of immunogenic proteins associated with protection against haemorrhagic septicaemia after vaccination of calves with a live-attenuated aroA derivative of Pasteurella multocida B:2

Pasteurella multocida serotype B:2 is the causative agent of haemorrhagic septicaemia (HS), a fatal disease of cattle and buffaloes. As a step towards the identification of individual antigens that may protect against HS, proteins present in a sonicated cell extract (SCE) and outer-membrane protein (OMP) preparation of a wild-type P. multocida serotype B:2 were investigated by immunoblotting with sera from calves which had been protected against challenge with a virulent strain of P. multocida B:2 by vaccination with a live-attenuated aroA derivative of the challenge strain. Five proteins in SCE, of approximately 50, 37, 30, 26 and 16kDa, were recognised by the sera. In an OMP preparation, two bands, at 37 and 50kDa, were recognised as strongly immunogenic. Mass spectrometry analysis of proteins corresponding in size to those detected by immunoblotting identified the 37kDa band as OmpA, but the band at 50kDa was not identified with certainty. A major 30kDa OMP, identified as OmpH, was not strongly immunogenic.

Selection, characterization, and application of DNA aptamers for the capture and detection of Salmonella enterica serovars

Sensitive and specific pre-analytical sample processing methods are needed to enhance our ability to detect and quantify food borne pathogens from complex food and environmental samples. In this study, DNA aptamers were selected and evaluated for the capture and detection of Salmonella enterica serovar. Typhimurium. A total of 66 candidate sequences were enriched against S. Typhimurium outer membrane proteins (OMPs) with counter-selection against Escherichia coli OMPs and lipopolysaccharides (LPS). Specificity of the selected aptamers was evaluated by gel-shift analysis against S. Typhimurium OMP. Five Salmonella-specific aptamer candidates were selected for further characterization. A dilution-to-extinction capture protocol using pure cultures of S. Typhimurium further narrowed the field to two candidates (aptamers 33 and 45) which showed low-end detection limits of 10–40 CFU. DNase protection assays applied to these aptamers confirmed sequence-specific binding to S. Typhimurium OMP preparations, while South-Western blot analysis combined with mass spectrometry identified putative membrane proteins as targets for aptamer binding. Aptamer 33 was bound to magnetic beads and used for the capture of S. Typhimurium seeded into whole carcass chicken rinse samples, followed by detection using quantitative real-time RT-PCR. In a pull-down assay format, detection limits were 10 1–10 2 CFU S. Typhimurium/9 mL rinsate, while in a recirculation format, detection limits were 10 2–10 3 CFU/25 mL rinsate. Reproducible detection at <10 1 S. typhimurium CFU/g was also achieved in spike-and-recovery experiments using bovine feces. The pull-down analysis using aptamer 33 was validated on 3 naturally infected chicken litter samples confirming their applicability in the field. This study demonstrates the applicability of Salmonella specific aptamers for pre-analytical sample processing as applied to food and environmental sample matrices.

Protein expression by Aeromonas hydrophila during growth in vitro and in vivo

Expression of Aeromonas hydrophila cellular and extracellular products (ECPs) was examined following culture of the bacterium in vitro, in Tryptic Soy Broth (TSB), and in vivo, in dialysis tubing placed within the peritoneal cavity of common carp ( Cyprinus carpio L.). Whole cell (WC), outer membrane proteins (OMPs) and ECP components of the bacteria were analysed by 1 dimensional sodium dodecyl sulphate-polyacrylamide gel electrophoresis (1D SDS-PAGE). Additionally, 2D SDS-PAGE was used to analyse WC preparations. The aim of the study was to identify unique and common proteins up-regulated in vivo. Unique bands were seen in the 1D gels at 58 and 55 kDa for WC and OMP preparations, respectively, for all the four virulent and two avirulent isolates cultured in vivo. Bands of increased intensity were also observed at 70, 55, 50 and 25 kDa with WC preparations for all virulent isolates cultured in vivo. Analysis of WC by 2D SDS-PAGE revealed that bacteria cultured in vivo expressed a number of unique spots, mostly between 30 and 80 kDa with pI values ranging from 5.0 to 6.0. The unique proteins identified in vivo may be involved in the virulence of the bacterium and their potential as vaccine candidates is currently being investigated.

Biochemical characterization of the enterotoxigenic Escherichia coli LeoA protein

Enterotoxigenic Escherichia coli (ETEC) causes enterotoxin-induced diarrhoea and significant mortality. The molecular mechanisms underlying how the heat-labile enterotoxin (LT) is secreted during infection are poorly understood. ETEC produce outer-membrane vesicles (OMVs) containing LT that are endocytosed into host cells. Although OMV production and protein content may be a regulated component of ETEC pathogenesis, how LT loading into OMVs is regulated is unknown. The LeoA protein plays a role in secreting LT from the bacterial periplasm. To begin to understand the function of LeoA and its role in ETEC H10407 pathogenesis, a site-directed mutant lacking the putative GTP-binding domain was constructed. The ability of wild-type and mutant LeoA to hydrolyse GTP in vitro was quantified. This domain was found to be responsible for GTP binding; it is important to LeoA's function in LT secretion, and may play a modest role in the formation and protein content of OMVs. Deletion of leoA reduced the abundance of OmpX in outer-membrane protein preparations and of LT in OMVs. Immunoprecipitation experiments revealed that LeoA interacts directly with OmpA, but that the GTP-binding domain is non-essential for this interaction. Deletion of leoA rendered ETEC H10407 non-motile, through apparent periplasmic accumulation of FliC.

Cellular Recognition of Trimyristoylated Peptide or Enterobacterial Lipopolysaccharide via Both TLR2 and TLR4

Evidence for specific and direct bacterial product recognition through toll-like receptors (TLRs) has been emphasized recently. We analyzed lipopeptide analogues and enterobacterial lipopolysaccharide (eLPS) for their potential to activate cells through TLR2 and TLR4. Whereas bacterial protein palmitoylated at its N-terminal cysteine and N-terminal peptides derived thereof are known to induce TLR2-mediated cell activation, a synthetic acylhexapeptide mimicking a bacterial lipoprotein subpopulation for which N-terminal trimyristoylation is characteristic (Myr(3)CSK(4)) activated cells not only through TLR2 but also through TLR4. Conversely, highly purified eLPS triggered cell activation through overexpressed TLR2 in the absence of TLR4 expression if CD14 was coexpressed. Accordingly, TLR2(-/-) macrophages prepared upon gene targeting responded to Myr(3)CSK(4) challenge, whereas TLR2(-/-)/TLR4(d/d) cells were unresponsive. Through interferon-gamma (IFNgamma) priming, macrophages lacking expression of functional TLR4 and/or MD-2 acquired sensitivity to eLPS, whereas TLR2/TLR4 double deficient cells did not. Not only TLR2(-/-) mice but also TLR4(-/-) mice were resistant to Myr(3)CSK(4) challenge-induced fatal shock. d-Galactosamine-sensitized mice expressing defective TLR4 or lacking TLR4 expression acquired susceptibility to eLPS-driven toxemia upon IFNgamma priming, whereas double deficient mice did not. Immunization toward ovalbumin using Myr(3)CSK(4) as adjuvant was ineffective in TLR2(-/-)/TLR4(-/-) mice yet effective in wild-type, TLR2(-/-), or TLR4(-/-) mice as shown by analysis of ovalbumin-specific serum Ig concentration. A compound such as Myr(3)CSK(4) whose stimulatory activity is mediated by both TLR2 and TLR4 might constitute a preferable adjuvant. On the other hand, simultaneous blockage of both of the two TLRs might effectively inhibit infection-induced pathology.

Identification of a Novel Two-Partner Secretion Locus in Moraxella catarrhalis

Although Moraxella catarrhalis continues to be a significant cause of disease in both children and adults, the steps involved in pathogenesis remain poorly understood. We have identified three open reading frames in the M. catarrhalis genome that encode homologues of the two-partner secretion system (TPS). The sequenced M. catarrhalis hemagglutinin-like locus of strain 7169 has a unique gene organization composed in the order of mchA1, mchB, and mchA2, where mchA1 is divergent. MchA1 and MchA2 are 74% identical at the amino acid level and diverge only in the C-terminal regions. The TPS motif identified in the common N-terminal regions of MchA1 and MchA2 was found to be homologous to the filamentous hemagglutinin of Bordetella pertussis, and MchB has homology to other TpsB transporters. The presence of MchA1 and MchA2 in outer membrane protein preparations and concentrated culture supernatants (CCSs) of strain 7169 was confirmed by immunoblotting using specific antisera. Nanoscale liquid chromatography-tandem mass spectrometry peptide sequencing of the antibody-reactive bands from the CCSs was performed and demonstrated that 13 different peptides mapped to identical regions of MchA1 and MchA2. Quantitative adherence assays revealed a decrease of binding to primary normal human bronchial epithelial cells by the mch mutants 7169mchB and 7169mchA1A2B compared to that by the wild-type strain. These studies show that MchA1, MchA2, and MchB are components of a novel TPS identified in M. catarrhalis and suggest that these proteins may be involved in colonization.

Detection of Iss and Bor on the surface of Escherichia coli

To confirm the presence of Iss and Bor on the outer membrane of Escherichia coli using Western blots of outer membrane protein (OMP) preparations and fluorescence microscopy, and explore the use of fluorescence microscopy for the detection of avian pathogenic E. coli (APEC) and diagnosis of avian colibacillosis. Knockout mutants of iss and bor were created using a one-step recombination of target genes with PCR-generated antibiotic resistance cassettes. Anti-Iss monoclonal antibodies (Mabs) that cross-react with Bor protein were used to study the mutants relative to the wild-type organism. These Mabs were used as reagents to study OMP preparations of the mutants with Western blotting and intact E. coli cells with fluorescence microscopy. Iss and Bor were detected in Western blots of OMP preparations of the wild type. Also, Iss was detected on Deltabor mutants, and Bor was detected on Deltaiss mutants. Iss and Bor were also detected on the surface of the intact, wild-type cells and mutants using fluorescence microscopy. These results demonstrate that Bor and Iss are exposed on E. coli's outer membrane where they may be recognized by the host's immune system. To our knowledge, this is the first report confirming Iss' location in the outer membrane of an E. coli isolate. Such surface exposure has implications for the use of these Mabs for APEC detection and colibacillosis control.

Genomic and proteomic approaches to vaccine candidate identification for Anaplasma marginale

Outer membrane protein preparations have been demonstrated to elicit protective immunity for Anaplasma marginale. Attempts to recreate this protective immunity using known surface proteins have been unsuccessful; therefore, novel outer membrane proteins have been searched for using a proteomic/genomic approach. Annotation of the whole genome sequence identified 62 outer membrane protein candidates based on sequence similarity to known surface proteins. In a proteomics approach for the identification of immunostimulatory outer membrane proteins, outer membrane preparations that were separated on 2D gels were used to immunize calves . Antisera from the calves were used to detect immunoreactive proteins, which were then selected and subjected to mass spectrometric analyses. These data were mapped back to the annotated A. marginale genome and have identified several new outer membrane proteins that are vaccine candidates.

Differentiation of outer membrane proteins from Salmonellaenterica serotypes using Fourier transform infrared spectroscopy and chemometrics

To differentiate between outer membrane proteins (OMPs) from six Salmonellaenterica serotypes using a Fourier transform infrared (FTIR) spectroscopy method and chemometrics. The OMPs from Salmonella serotypes (Typhimurium, Enteritidis, Thomasville, Hadar, Seftenberg and Brandenburg) were isolated using a sarcosyl extraction method. OMP profiles on SDS-PAGE exhibited two or three bands between 48 and 54 kDa. Spectra of 10 microl of OMP preparations (5 mg ml(-1)) dried on a gold reflective slide were collected using 128 scans at 4 cm(-1) resolution and units of log (1/R) and analyzed using canonical variate analysis (CVA) and linear discriminant analysis (LDA). The CVA of Salmonella OMP spectra in the 1800-1500 cm(-1) region separated the serotypes and LDA provided a 100% correct classification. The use of a FTIR method combined with chemometrics provided better differentiation of Salmonella OMPs than the OMP pattern analysis by SDS-PAGE. This is the first study to demonstrate that spectra of OMP extracts from Salmonella serotypes can be used for 100% correct classification of the serotypes studied.

NontypeableHaemophilus influenzaeAdheres to Intercellular Adhesion Molecule 1 (ICAM-1) on Respiratory Epithelial Cells and Upregulates ICAM-1 Expression

Nontypeable Haemophilus influenzae (NTHI) is an important respiratory pathogen. NTHI initiates infection by adhering to the airway epithelium. Here, we report that NTHI interacts with intracellular adhesion molecule 1 (ICAM-1) expressed by respiratory epithelial cells. A fourfold-higher number of NTHI bacteria adhered to Chinese hamster ovary (CHO) cells transfected with human ICAM-1 (CHO-ICAM-1) than to control CHO cells (P < or = 0.005). Blocking cell surface ICAM-1 with specific antibody reduced the adhesion of NTHI to A549 respiratory epithelial cells by 37% (P = 0.001) and to CHO-ICAM-1 cells by 69% (P = 0.005). Preincubating the bacteria with recombinant ICAM-1 reduced adhesion by 69% (P = 0.003). The adherence to CHO-ICAM-1 cells of NTHI strains deficient in the adhesins P5, P2, HMW1/2, and Hap or expressing a truncated lipooligosaccharide was compared to that of parental strains. Only strain 1128f-, which lacks the outer membrane protein (OMP) P5-homologous adhesin (P5 fimbriae), adhered less well than its parental strain. The numbers of NTHI cells adhering to CHO-ICAM-1 cells were reduced by 67% (P = 0.009) following preincubation with anti-P5 antisera. Furthermore, recombinant ICAM bound to an OMP preparation from strain 1128f+, which expresses P5, but not to that from its P5-deficient mutant, confirming a specific interaction between ICAM-1 and P5 fimbriae. Incubation of respiratory epithelial cells with NTHI increased ICAM-1 expression fourfold (P=0.001). Adhesion of NTHI to the respiratory epithelium, therefore, upregulates the expression of its own receptor. Blocking interactions between NTHI P5 fimbriae and ICAM-1 may reduce respiratory colonization by NTHI and limit the frequency and severity of NTHI infection.

Antibodies against human muscle enolase recognize a 45-kDa bacterial cell wall outer membrane enolase-like protein

Enolase, is a glycolytic enzyme ubiquitous in higher organisms, where it forms tissue specific dimers of isoforms, also found in the cytoplasm of fermentative bacteria. The aim of this work was to identify enolase-like proteins in the cell wall of some Gram-negative bacteria using antibodies against human β-enolase, an isoenzyme specific to skeletal and heart muscles. Cell wall outer membrane protein (OMP) preparations were obtained from 9 strains of Enterobacteriaceae and one of Pseudomonas aeruginosa. Specific enzymatic enolase activity was detected in the supernatant fractions of cytosolic and inner membrane material, but not in purified OMP preparations. Rabbit polyclonal antibodies specific against human β-enolase were prepared and purified using immobilized human β-enolase in affinity chromatography. In SDS–polyacrylamide gel electrophoresis and immunoblotting assay of purified OMP preparations, rabbit anti-enolase antibody interacted specifically with a few OMPs, of which a 45-kDa band also interacted with human sera of patients presenting Buerger disease and atherosclerosis. The most distinct interaction of human sera was observed with a 45-kDa OMP of Klebsiella pneumoniae. This protein was further isolated from K. pneumoniae cell mass in two ways, namely preparative SDS–polyacrylamide gel electrophoresis and specific affinity chromatography using immobilized affinity-purified rabbit antibody raised against human β-enolase. The data obtained from tandem mass spectrometry tryptic peptide analysis and sequence comparison of human and bacterial enolases using protein databases, could reveal the similarity in the epitopes between membrane enolase-like protein from Klebsiella and human β-enolase. The results show that the protein present in all studied strains has a common epitope on human β-enolase. These data raise the question whether such a bacterial protein might be a marker for detecting and monitoring damage to skeletal and heart muscles.

Characterization of the Salmonella typhimurium proteome by semi-automated two dimensional HPLC-mass spectrometry: detection of proteins implicated in multiple antibiotic resistance.

The proteome of Salmonella enterica serovar Typhimurium was characterized by 2-dimensional HPLC mass spectrometry to provide a platform for subsequent proteomic investigations of low level multiple antibiotic resistance (MAR). Bacteria (2.15 +/- 0.23 x 10(10) cfu; mean +/- s.d.) were harvested from liquid culture and proteins differentially fractionated, on the basis of solubility, into preparations representative of the cytosol, cell envelope and outer membrane proteins (OMPs). These preparations were digested by treatment with trypsin and peptides separated into fractions (n = 20) by strong cation exchange chromatography (SCX). Tryptic peptides in each SCX fraction were further separated by reversed-phase chromatography and detected by mass spectrometry. Peptides were assigned to proteins and consensus rank listings compiled using SEQUEST. A total of 816 +/- 11 individual proteins were identified which included 371 +/- 33, 565 +/- 15 and 262 +/- 5 from the cytosolic, cell envelope and OMP preparations, respectively. A significant correlation was observed (r2 = 0.62 +/- 0.10; P < 0.0001) between consensus rank position for duplicate cell preparations and an average of 74 +/- 5% of proteins were common to both replicates. A total of 34 outer membrane proteins were detected, 20 of these from the OMP preparation. A range of proteins (n = 20) previously associated with the mar locus in E. coli were also found including the key MAR effectors AcrA, TolC and OmpF.

Evidence for naturally acquired T cell-mediated mucosal immunity to Neisseria meningitidis.

Naturally acquired protective immunity against Neisseria meningitidis is thought to partially explain the disparity between the high levels of carriage in the human nasopharynx and the rare incidence of disease. To investigate this immunity to Neisseria meningitidis at the mucosal level, in vitro cellular responses to outer membrane vesicle preparations derived from this pathogen were examined using mononuclear cells from the palatine tonsils of adults and children. Characterization of these responses was achieved by depletion of CD45RA(+), CD45RO(+), and CD19(+) populations and outer membrane vesicles derived from isogenic mutants expressing different serosubtypes of the major outer membrane protein, porin A (PorA), no PorA and membrane preparations from a mutant with no LPS (LpxA(-)). The magnitude of cellular proliferative responses against the outer membrane vesicles were strongly associated with age and were largely T cell mediated, involving both CD45RO(+) and CD45RA(+) T cell phenotypes. Responses were not dependent on LPS but consisted of both PorA cross-specific and non-PorA-dependent responses. Cellular immunity against Neisseria meningitidis was found to be frequently associated with systemic IgG Abs but was not associated with serum bactericidal Abs. For the first time our results demonstrate an age-associated acquisition of mucosal T effector/memory cell responses to Neisseria meningitidis. This mucosal cellular immunity can be present in the absence of serum bactericidal Abs, a classical marker of protective immunity.