Outer Membrane Protein Extracts Research Articles

Pro-inflammatory cytokines and reproductive hormone responses in bucks post-challenge with Mannheimia haemolytica A2 and its outer membrane protein.

The lipopolysaccharide (LPS) endotoxin and outer membrane protein (OMP) are among the virulence factors of Gram-negative bacteria responsible for inducing pathogenicity in the infected host. OMP and LPS occur on the outer membrane of M. haemolytica A2, the primary aetiological agent of pneumonic mannheimiosis in small ruminants. While the LPS is known to mediate Gram-negative bacterial infection by activating downstream inflammatory pathways, the potential role of OMP during inflammatory responses remained unclear. Hence, this study determined the effect of the OMP of M. haemolytica A2 on the serum concentration of pro-inflammatory cytokines and the male reproductive hormones (testosterone and Luteinizing Hormone). We randomly assigned twelve bucks to three groups (n = 4 bucks each): Group 1 was challenged with 2mL PBS buffer (pH 7.0) intranasally; Group 2 received 2mL of 1.2 X 109CFU/mL whole M. haemolytica A2 intranasally; and Group 3 received 2mL of OMP extract obtained from 1.2 X 109CFU/mL M. haemolytica A2 intramuscularly. Serum samples collected at pre-determined intervals were used for the quantitative determination of the pro-inflammatory cytokines (IL-1β, IL-6, and TNFα) and reproductive hormones (testosterone and LH) using commercial sandwich enzyme-linked immunosorbent assay (ELISA). The serum concentration of IL1β was initially increased within the first-hour post-challenge in Groups 2 and 3, followed by a significant decrease in concentration at 21d and 35d (p < 0.05) in Group 3. Only mild fluctuations in IL-6 occurred in group 2, as opposed to the 1.7-fold rapid increase in TNFα within 2h post-challenge before decreasing at 6h. An increase in pro-inflammatory cytokines was accompanied by an acute febrile response of 39.5 ± 0.38°C (p < 0.05) at 2h and 40.1 ± 0.29°C (p < 0.05) at 4h in Group 2 and Group 3, respectively. Serum testosterone decreased significantly (p < 0.05) in both treatment groups but remained significantly (p > 0.05) lower than in Group 1 throughout the study. There was a moderate negative association between testosterone and IL1β (r = -0.473; p > 0.05) or TNFα (r = -0.527; p < 0.05) in Group 2. Serum LH also showed moderate negative associations with TNFα in Group 2 (r = -0.63; p < 0.05) and Group 3 (r = -0.54; p > 0.05). The results of this study demonstrated that M. haemolytica A2 and its OMP produced marked alterations in serum levels of pro-inflammatory cytokines and male reproductive hormones. The negative correlations between serum testosterone and inflammatory cytokines would suggest the potential role of OMP in causing male infertility by mediating innate inflammatory responses to suppress testosterone production in bucks.

Extraction of Outer Membrane Proteins of Proteus Mirabilis Isolated From Urinary Tract Infections and their Immunological Effect In Vitro

300 urine samples were collected from patients visiting Fallujah city hospitals (consulting clinicsof Fallujah Teaching Hospital and Women and Children Hospital) for the period from 1/9/2020 to30/12/2020, of different ages and for both sexes. The results showed that out of 300 urine samples were244(81.33%) A sample with a positive result for bacterial culture, and it was found there were highsignificant differences between the positive and negative cultures. Females and males (64.70) (35.29),respectively.Isolates of Proteus mirabilis were diagnosed by observing the cultivar (colonies) and microscopic(bacterial cells) characteristics, biochemical tests and diagnostics with Vitek device. Antibiotic sensitivitywere done at 12 types, Antibiotic resistance wre vary from Cefotaxime, Rifampicin, Ceftriaxon (100%),Cefixime, Ciprofloxacin (76.4%), Levofloxacin (64.7%), Nitrofurantoin (58.8%), Gentamicin (52.9%),Amikacin, Nalidixic acid (35.2%) (17.6%) Imipenem (11.7%).Extraction and partial purification of outer membrane proteins (OMPs) from the most antibioticresistantisolate using lysozyme, DNase, RNase, and N-Lauroyl-Sarcosinate enzymes. associated withthe ion exchanger.To study the effect of the antigen of outer membrane proteins, some immunoassays were performedin vitro and the following results appeared: The use of concentrations (100, 50, 25) of OMPs antigenled to low significant of lymphocyte viability percentage (96.66, 97.66,98.0), respectively compared toWith the negative control (99.66), the concentrations (100,50)% significantly reduced the percentageof survival of PMNs cells (97.66,98.33), respectively, compared with the control (99.66), while theconcentration of 25 did not affect the survival of PMNs cells (99.66). The above concentrations showeda low significant in the diameter of the migration circuit of PMNs cells (8.830,10.59,12.21) comparedwith the negative control (15.21), while these concentrations led to a high significant in the percentageof formazone-forming PMNs cells (64.66,58.0,47.0) compared with the control (36.66). ) and a highsignificant in the sensitivity of lymphocytes (4.0,3.39,1.87), as the absorption spectrum values forconcentrations (100,50,25) reached (0.92,0.74,0.41), respectively, compared with the negative control(0.22) and the positive control (1.53). The concentrations of the used proteins increased the phagocyticindex (PI) of PMN cells ,The phagocytosis coefficient was high significantly with time until it reached itsmaximum at 90 minutes, and from the statistical analysis it was found that the phagocytosis coefficientincreases with increasing concentration of proteins.

Comparision of iron-regulated outer membrane proteins (IrOMP) and iron-sufficient outer membrane proteins (IsOMP) of Pasteurella multocida strains of porcine origin

An investigation was carried out to compare the effect of growth of P. multocida type A of pig origin in iron restricted and in iron sufficient media on the basis of their outer membrane protein extract. Pasteurella multocida serotype A was cultured in two ways. In one process only BHI medium was used and on the other process same medium was used which was supplemented with 2, 2’- Dipyridyl (iron-restricted medium). Both these cultures were used to obtain Outer Membrane Proteins (OMPs) by extraction of bacterial cells with 1% Sarcosyl. Separation of the OMPs in SDS-PAGE showed that OMPs were mixture of protein fraction with molecular weight ranging from 110 to 22.6 kDa in case of iron-restricted OMP and 47.3 to 29.9 kDa in case of iron sufficient OMP. The OMP with molecular masses 29.9 kDa grew in both iron-restricted as well as in iron sufficient medium.

Preliminary Extraction and Identification of the 44.5 kDa Outer Membrane Proteins Isolated from Bovine Fusobacterium necrophorum (AB)

Fusobacterium necrophorum (AB) in the pharynx, respiratory tract, female reproductive tract or urinary system is the causative agent of footrot and hepatic abscesses in animals and acute Lemierre's syndrome in humans. Current methods do not effectively protect animals and humans against F. necrophorum (AB). The outer membrane proteins (OMP) of F. necrophorum (AB) can be used as new material to protect against the diseases induced by F. necrophorum (AB). The aim of this study was to extract OMP and examine the immunogenic response of OMP. The preliminary extraction of OMP of F. necrophorum (AB) was identified by SDS-PAGE and stained by Coomassie Brilliant Blue R-250 (CB B R-250) and silver staining methods. The results showed that only a major band of 44.5kDa was observed when staining the gel using CB B R-250. This band represented the target protein. In contrast, many small bands were observed by the silver staining method. The OMP also exhibited immune biological activities according to western blot analysis. The brightest band among the multi-banding observed was the OMP. Thus, the OMP was obtained and had immunogenic activity. The results provide a new direction to protect animals and humans against F. necrophorum (AB) in the clinical setting.

Identification of Yersinia pestis and Escherichia coli Strains by Whole Cell and Outer Membrane Protein Extracts with Mass Spectrometry-Based Proteomics

Whole cell protein and outer membrane protein (OMP) extracts were compared for their ability to differentiate and delineate the correct database organism to an experimental sample and for the degree of dissimilarity to the nearest neighbor database organism strains. These extracts were isolated from pathogenic and nonpathogenic strains of Yersinia pestis and Escherichia coli using ultracentrifugation and a sarkosyl extraction method followed by protein digestion and analysis using liquid chromatography tandem mass spectrometry (MS). Whole cell protein extracts contain many different types of proteins resident in an organism at a given phase in its growth cycle. OMPs, however, are often associated with virulence in Gram-negative pathogens and could prove to be model biomarkers for strain differentiation among bacteria. The mass spectra of bacterial peptides were searched, using the SEQUEST algorithm, against a constructed proteome database of microorganisms in order to determine the identity and number of unique peptides for each bacterial sample. Data analysis was performed with the in-house BACid software. It calculated the probabilities that a peptide sequence assignment to a product ion mass spectrum was correct and used accepted spectrum-to-sequence matches to generate a sequence-to-bacterium (STB) binary matrix of assignments. Validated peptide sequences, either present or absent in various strains (STB matrices), were visualized as assignment bitmaps and analyzed by the BACid module that used phylogenetic relationships among bacterial species as part of a decision tree process. The bacterial classification and identification algorithm used assignments of organisms to taxonomic groups (phylogenetic classification) based on an organized scheme that begins at the phylum level and follows through the class, order, family, genus, and species to the strain level. For both Gram-negative organisms, the number of unique distinguishing proteins arrived at by the whole cell method was less than that of the OMP method. However, the degree of differentiation measured in linkage distance units on a dendrogram with the OMP extract showed similar or significantly better separation than the whole cell protein extract method between the sample and correct database match compared to the next nearest neighbor. The nonpathogenic Y. pestis A1122 strain used does not have its genome available, and thus, data analysis resulted in an equal similarity index to the nonpathogenic 91001 and pathogenic Antiqua and Nepal 516 strains for both extraction methods. Pathogenic and nonpathogenic strains of E. coli were correctly identified with both protein extraction methods, and the pathogenic Y. pestis CO92 strain was correctly identified with the OMP procedure. Overall, proteomic MS proved useful in the analysis of unique protein assignments for strain differentiation of E. coli and Y. pestis. The power of bacterial protein capture by the whole cell protein and OMP extraction methods was highlighted by the data analysis techniques and revealed differentiation and similarities between the two protein extraction approaches for bacterial delineation capability.

Application of Fourier Transform Infrared Spectroscopy and Chemometrics for Differentiation of Salmonella enterica Serovar Enteritidis Phage Types

Fourier transform infrared (FT-IR) spectroscopy and chemometric techniques were used to discriminate five closely related Salmonella enterica serotype Enteritidis phage types, phage type 1 (PT1), PT1b, PT4b, PT6, and PT6a. Intact cells and outer membrane protein (OMP) extracts from bacterial cell membranes were subjected to FT-IR analysis in transmittance mode. Spectra were collected over a wavenumber range from 4,000 to 600 cm(-1). Partial least-squares discriminant analysis (PLS-DA) was used to develop calibration models based on preprocessed FT-IR spectra. The analysis based on OMP extracts provided greater separation between the Salmonella Enteritidis PT1-PT1b, PT4b, and PT6-PT6a groups than the intact cell analysis. When these three phage type groups were considered, the method based on OMP extract FT-IR spectra was 100% accurate. Moreover, complementary local models that considered only the PT1-PT1b and PT6-PT6a groups were developed, and the level of discrimination increased. PT1 and PT1b isolates were differentiated successfully with the local model using the entire OMP extract spectrum (98.3% correct predictions), whereas the accuracy of discrimination between PT6 and PT6a isolates was 86.0%. Isolates belonging to different phage types (PT19, PT20, and PT21) were used with the model to test its robustness. For the first time it was demonstrated that FT-IR analysis of OMP extracts can be used for construction of robust models that allow fast and accurate discrimination of different Salmonella Enteritidis phage types.

Immunoproteomics of extracellular proteins of theAeromonas hydrophilaChina vaccine strain J-1 reveal a highly immunoreactive outer membrane protein

Aeromonas hydrophila is a gram-negative bacterium that can infect a variety of aquatic and terrestrial animals. It is essential to develop a vaccine to reduce the economic losses caused by this bacterium in aquaculture worldwide. Here, an immunoproteomic assay was used to identify the immunogenic extracellular proteins of the Chinese vaccine strain J-1. Ten unique immunogenic proteins were identified from the two-dimensional electrophoresis immunoblot profiles by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS) or MALDI-TOF-TOF-MS. One protein of interest, Omp38, was detected by antisera on two-dimensional immunoblots, suggesting that it might be located both extracellularly and in the membrane. In exploring the potential of Omp38 as a vaccine candidate in fish, we found the omp38 gene to be prevalent by PCR among different (36/48) A. hydrophila isolates. The recombinant Omp38 induced a strong antibody response in rabbits, and the polyclonal antibody could recognize a band of approximately 38 kDa in the immunoblots of outer membrane protein extracts from most (24/40) of the A. hydrophila strains, including different predominant serotypes in China. These results indicated that the outer membrane antigen identified in this study could be developed as a vaccine candidate to induce protective immunity against A. hydrophila infection.

The interaction ofBacteroides fragiliswith components of the human fibrinolytic system

Bacteroides fragilis is a minor component of the intestinal microbiota and the most frequently isolated from intra-abdominal infections and bacteremia. Previously, our group has shown that molecules involved in laminin-1 (LMN-1) recognition were present in outer membrane protein extracts of B. fragilis MC2 strain. One of these proteins was identified and showed 98% similarity to a putative B. fragilis plasminogen-binding protein precursor, deposited in the public database. Thus, the objective of this work was to overexpress and further characterize this novel adhesin. The ability of B. fragilis MC2 strain and purified protein to convert plasminogen into plasmin was tested. Our results showed that B. fragilis strain MC2 strain adhered to both LMN-1 and plasminogen and this adhesion was inhibited by either LMN-1 or plasminogen. Regarding the plasminogen activation activity, both the whole bacterial cell and the purified protein converted plasminogen into plasmin similar to streptokinase used as a positive control. Bacterial receptors that recognize plasminogen bind to it and enhance its activation, transforming a nonproteolytic bacterium into a proteolytic one. We present in vitro evidence for a pathogenic function of the plasminogen receptor in promoting adherence to laminin and also the formation of plasmin by B. fragilis.

Heterologous protective immunization elicited in mice by Pasteurella multocida fur ompH.

Different strategies have been developed to produce vaccines against Pasteurella multocida. The approach described herein involves overexpression on the bacterial cell surface of Fur-regulated IROMPs (iron-regulated outer-membrane proteins). Accordingly, the ability of fur mutants to promote heterologous protection was examined in a Swiss mouse animal model. Twofur mutants derived from P. multocida were isolated, one of which was also defective in the OmpH protein. In mice challenged with virulent P. multocida, outer-membrane protein (OMP) extracts of fur cells conferred the same protection as obtained with wild-type cells grown in iron-depleted medium. Total protection was achieved with 40 microg of OMP extract from the fur ompH mutant. Mice administered heat-inactivated fur ompH cells were 60% cross-protected. The presence of a galE mutation in these cells did not further increase the protection level. Additionally, cell disruption by sonication provoked a higher level of protection than conferred by heat-treated cells. Taken together, the results showed that P. multocida fur ompH cells offer a simple and suitable approach for cross-protecting animals against infection with P. multocida.

Outer-membrane proteomic maps and surface-exposed proteins of Legionella pneumophila using cellular fractionation and fluorescent labelling

Bacterial surface-associated proteins play crucial roles in host-pathogen interactions and pathogenesis. The identification of these proteins represents an important goal of bacterial proteomics for vaccine development, but also for environmental concerns such as microbial biosensing. Here, we developed such an approach for Legionella pneumophila, a bacterium that causes severe pneumonia. We propose a complementary strategy consisting of (1) a fluorescent labelling of surface-exposed proteins in parallel with (2) a fractionation of the outer-membrane protein extract. These two distinct protein populations were subsequently separated using two-dimensional gel electrophoresis and characterised by mass spectrometry. Within these populations, we found proteins which were expected for the compartments studied, but also a great number of proteins never experimentally described, and also a non-negligible fraction of proteins never described in these fractions. These data provided new routes of inspection for transport and host recognition for Legionella pneumophila. In addition, these results on the membranome and surfaceome show that Legionella in the stationary phase of growth possesses the major determinants to infect host cells.

Azospirillum brasilense Sp7 produces an outer-membrane lectin that specifically binds to surface-exposed extracellular polysaccharide produced by the bacterium

Azospirillum sp promotes the growth of many important crop plants. We demonstrated lectin binding activity in outer-membrane protein extracts of A. brasilense Sp7 by hemagglutination assays. The lectin specifically recognised the exopolysaccharide (EPS) produced by aggregated cells. Affinity chromatography using EPS-Sepharose was used to identify a 67 kDa outer-membrane lectin (OML) that recognised a binding region in the extracellular polysaccharide. Results show the specific recognition and binding between EPS and OML. The potential relationship between cell-to-cell aggregation and the OML-EPS interaction is discussed.

Reduced renal Na+-K+-Cl- co-transporter activity and inhibited NKCC2 mRNA expression by Leptospira shermani: from bed-side to bench

Renal involvement is common in leptospirosis. Interstitial nephritis with interstitial oedema and mononuclear cellular infiltration are the usual findings. Clinically, non-oligouric acute renal failure, hypokalaemia and sodium wasting appear frequently in leptospirosis. The outer membrane protein from leptospira has been thought to be responsible for the disorder. However, the exact mechanisms of renal involvement are still unclear. To address these questions, we first performed detailed in vivo clearance tests in three patients with leptospirosis (Leptospira shermani) and hypokalaemia to define the tubular lesion. These tests indicated a defective Na(+)-K(+)-Cl(-) co-transporter and a poor response to furosemide infusion. We performed further in vitro studies in a model of medullary thick ascending limb (mTAL) cultured cells derived from normal mouse. Outer membrane protein extract from L.shermani (0.3 microg/ml) inhibited Na(+)-K(+)-Cl(-) co-transporter activity in mTAL cells (control, 10.15+/-0.52; L.shermani, 6.47+/-0.47 nmol/min/mg protein). The basolateral Na(+)-K(+) ATPase remained intact. Reverse transcription-polymerase chain reaction (RT-PCR) further revealed that the outer membrane protein extract from L.shermani downregulated Na(+)-K(+)-Cl(-) co-transporter (mNKCC2) mRNA expression. These changes were dose dependent and could be reversed by the antibody against outer membrane protein extract from L.shermani. Experiments with a less pathogenic strain of leptospira (L.bratislava) and Escherichia coli did not affect Na(+)-K(+)-Cl(-) co-transporter activity. We conclude that L.shermani leptospirosis downregulates mNKCC2 mRNA expression and inhibits Na(+)-K(+)-Cl(-) co-transporter activity in TAL cells. These alterations may explain the observed electrolyte disorders in leptospirosis.

Leptospira outer membrane protein activates NF-kappaB and downstream genes expressed in medullary thick ascending limb cells.

Tubulointerstitial nephritis is the main manifestation of acute renal damage caused by leptospirosis, but the mechanism remains unexplored. Patients infected with LEPTOSPIRA: shermani in Taiwan disclosed tubular dysfunction particularly in the medullary thick ascending limb of loop of Henle (mTAL), and the related renal damage seems to be underestimated. To elucidate the mechanism of tubular damage, outer membrane protein extract from LEPTOSPIRA: was administered to a model of cultured mTAL cells derived from normal mice. The addition of outer membrane protein extract from L. shermani to cultured mTAL cells induced a significant nuclear DNA binding of the NF-kappa B transcription factor by electrophoresis mobility shift assay. Forty-eight h after adding the outer membrane protein extract (0.2 microg/ml) to the cultured cells, the expression of inducible nitric oxide mRNA increased by 4.2-fold, monocyte chemoattractant protein-1 by 3-fold, and tumor necrosis factor-alpha by 2.4-fold when compared with untreated cells examined by reverse transcription competitive-PCR. Supernatant nitrite, monocyte chemoattractant protein-1, and tumor necrosis factor-alpha protein levels also increased by 1.8-, 7.1-, and 5-fold, respectively. An antiserum raised against L. shermani largely prevented these effects. Outer membrane protein extract from L. bratislava induced fewer effects than L. shermani, and the avirulent nonpathogenic L. biflexa serovar patoc did not induce significant effects in the mTAL cells. In conclusion, L. shermani infection may cause mTAL cell damage and inflammation through the NF-kappa B-associated pathway. Findings of this study may be important in understanding the pathogenesis of tubulointerstitial nephritis caused by these organisms.

Purification of Integral Outer-Membrane Protein OmpC, a Surface Antigen from Salmonella typhi for Structure–Function Studies: A Method Applicable to Enterobacterial Major Outer-Membrane Protein

Extraction of the outer-membrane porin, OmpC, from Salmonella typhi Ty21a was done by using a modified salt-extraction procedure. It was possible to extract only the major outer-membrane protein (OMP) from the crude membrane using this method. Aberrant lipopolysaccharide (LPS) production in the galE mutant Ty21a has resulted in more isoforms of OmpC and subsequently led to anomalous mobility in SDS-PAGE. The purity of the preparation was confirmed by denaturing urea SDS-PAGE and N-terminal sequencing. The major OMP extracts had LPS of both bound and free forms. The free form of LPS could be removed by gel filtration and the bound form, largely, was removed using ion-exchange chromatography and by passing through ultrafiltration devices. This method has been used to extract the native trimer of OmpC, the major OMP, in a large scale, for structure–function studies. S. typhi Ty21a OmpC preparation yielded reproducible diffraction-quality crystals. Extracts of porin from wild-type Escherichia coli HB101, grown under high osmolarity conditions, showed a single species of OMP on SDS-PAGE. This suggests the possible application of the method to other gram-negative bacterial porins.

Apoptotic effect of outer-membrane proteins from Campylobacter jejuni on chicken lymphocytes.

Campylobacter jejuni is a significant cause of food-borne diseases in humans. The bacterium is considered a commensal organism in chickens, and it can heavily colonize chickens without causing inflammation. Poultry may be the major reservoir for the human infection in developed countries. Here we show that an outer-membrane protein extract prepared from the bacteria caused apoptosis of chicken lymphocytes detected in vitro with the terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling assay that preferentially labels individual apoptotic cells. Blood- and spleen-lymphocytes from different-aged chickens displayed a significantly greater percentage of apoptotic cells after culture with the outer-membrane proteins from C. jejuni than controls treated with phosphate-buffered saline, chicken ovalbumin, or outer-membrane proteins prepared from E. coli strain BL21. The C. jejuni extract also produced apoptosis of chicken lymphoblastoid tumor cell lines. Apoptosis was blocked by pretreating the extract with proteinase K or antiserum against outer-membrane proteins. The results suggest that C. jejuni may be capable of achieving immune avoidance in chickens by causing apoptosis of lymphocytes.

Antigenically stable 35 kDa outer membrane protein of Salmonella

Outer membrane protein (OMP) extracts from Salmonella species representing seven serogroups were examined by SDS‐PAGE followed by immunoblotting. Two major proteins with apparent molecular weight of 24 and 35 kDa were identified. The latter protein was present only in Salmonella. Immunoblotting with a monoclonal antibody (MAb) 1D6 (IgA) demonstrated the 35 kDa OMP contains an antigen common for all tested Salmonella species with the exception of atypical species such as S. arizona. The type of growth media had no effect on the antigenicity of 35 kDa protein. However, the electrophoretic appearance of the 35 kDa protein was influenced by heat‐treatment. Analysis of OMP extracts by SDS‐PAGE and immunoblotting without heat‐treatment revealed that MAb 1D6 bound several isoforms of this protein, a major form at 28 kDa and about eight minor forms in the range between 34 and 40 kDa. None of these forms contained carbohydrate moieties that may be responsible for the polymorphic appearance of the protein. These forms were converted to a single form by heat‐treatment at 100°C indicating that the 35 kDa OMP is most likely a heat‐modifiable protein. Furthermore, extended heat‐treatment (121°C, 15 min) did not affect the antigenicity of the 35 kDa OMP. Electron microscopy studies revealed that the 35 kDa OMP is exposed on a surface of the bacterial cells, although the frequency of epitopes recognized by the Mab 1D6 was low as can be inferred from the low number of gold particles attached to the cells.

Identification and molecular cloning of a gene encoding a fibronectin-binding protein (CadF) from Campylobacter jejuni.

Campylobacter jejuni, a Gram-negative bacterium, is a common cause of gastrointestinal disease. By analogy with other enteric pathogens such as Salmonella and Shigella, the ability of C. jejuni to bind to host cells is thought to be essential in the pathogenesis of enteritis. Scanning electron microscopy of infected INT407 cells suggested that C. jejuni bound to a component of the extracellular matrix. Binding assays using immobilized extracellular matrix proteins and soluble fibronectin showed specific and saturable binding of fibronectin to C. jejuni. Ligand immunoblot assays using 125I-labelled fibronectin revealed specific binding to an outer membrane protein with an apparent molecular mass of 37 kDa. A rabbit antiserum, raised against the gel-purified protein, reacted with a 37 kDa protein in all C. jejuni isolates (n = 15) as tested by immunoblot analysis. Antibodies present in convalescent serum from C. jejuni-infected individuals also recognized a 37 kDa protein. The gene encoding the immunoreactive 37kDa protein was cloned and sequenced. Sequencing of overlapping DNA fragments revealed an open reading frame (ORF) that encodes a protein of 326 amino acids with a calculated molecular mass of 36872Da. The deduced amino acid sequence of the ORF exhibited 52% similarity and 28% identity to the root adhesin protein from Pseudomonas fluorescens. Isogenic C. jejuni mutants which lack the 37 kDa outer membrane protein, which we have termed CadF, displayed significantly reduced binding to fibronectin. Biotinylated fibronectin bound to a protein with an apparent molecular mass of 37 kDa in the outer membrane protein extracts from wild-type C. jejuni as judged by ligand-binding blots. These results indicate that the binding of C. jejuni to fibronectin is mediated by the 37 kDa outer membrane protein which is conserved among C. jejuni isolates.

Immunological cross reactivity of eaeA (intimin) from E. coli that cause attaching and effacing lesions in humans and rabbits.

A number of enteric diarrheal pathogens, including Hafnia alvei, enteropathogenic (EPEC) and enterohemmorrhagic (EHEC) Escherichia coli in humans, Citrobacter rodentium in mice and REPEC (rabbit EPEC) have the ability to induce major histopathologic changes on intestinal epithelial cells. These attaching and effacing (A/E) lesions are characterized by effacement of microvilli and marked cytoskeletal re-arrangements, including “pedestal” formation around the bacteria and accumulation of polymerized actin in the area of close attachment. The ability of these bacteria to form close attachment is mediated by intimin, a ~100 kDa outer membrane protein (OMP) believed to mediate close attachment, probably through binding of the C-terminal region of the protein to intestinal receptors. Intimin shows some sequence similarity to invasin, an OMP of Yersinia spp., responsible for mediating cell invasion. Sequence comparisons of RDEC-l(REPEC) intimin to intimins from EPEC O127:H6 and EHEC O157:H7 show ~90% homology at the amino terminal region, but only 65% homology at the carboxy terminal region of the protein. It is this divergent C-terminal region of the protein which is believed to play a role in the biological activity of intimin. To determine whether intimin from other E. coli are related to RDEC-1 intimin, antisera to the C-terminal region of RDEC-1 intimin was used to screen OMP extracts from a variety of E. coli isolates.

Heterogeneity in phenotypic and genotypic characteristics among strains of Hafnia alvei.

Hafnia alvei is an emerging human pathogen associated with sporadic cases and outbreaks of diarrhea. Bangladeshi isolates of H. alvei possess the Escherichia coli attaching and effacing (eaeA) gene and demonstrate an attaching and effacing phenotype. In the present study we examined 11 Canadian H. alvei isolates and strain 19,982 from Bangladesh to determine if the formation of attaching and effacing lesions is a property shared among multiple isolates. Attaching and effacing lesions were detected by induction of tyrosine kinase protein phosphorylation and cytoskeletal rearrangements in infected tissue culture epithelial cells with immunofluorescence microscopy and by the examination of infected cells with transmission electron microscopy. The presence of the eaeA gene was examined by PCR and colony blot hybridization. Profiles of outer membrane protein extracts, chromosomal macrorestriction fragments, and plasmids were also examined. Accumulation of host phosphotyrosine proteins and rearrangement of the cytoskeletal protein alpha-actinin were both observed in HEp-2 cells infected with H. alvei 19,982. In contrast, none of the other 11 clinical H. alvei isolates demonstrated either of these responses, nor did they form attaching and effacing lesions under electron microscopy. Consistent with the absence of the attaching and effacing phenotype, these clinical isolates did not possess the eaeA gene. The outer membrane protein profiles of all the Canadian isolates were identical but differed from that of H. alvei 19,982. Pulsed-field gel electrophoresis and plasmid profile analyses of the clinical H. alvei isolates differed substantially from those of the Bangladeshi strain. These results indicate that there is heterogeneity among H. alvei strains with respect to signal transduction, attaching and effacing adhesion, outer membrane constituents, and genotype. Epidemiological studies on enteropathogenic H. alvei thus need to go beyond simple species designations and require specific identification of the virulent clones.

Efficacy of various vaccines against pneumonic pasteurellosis in cattle: a meta-analysis

The objective of this study was to compare the protective efficacy induced by various experimental and commercial vaccines used in the past 12 years (1982–1994) against bovine pneumonic pasteurellosis. All studies using an experimental-challenge model to evaluate protective efficacy induced by vaccine preparations were identified using a combination of VETCD, CAB, and MEDLINE searches. A total of 72 trials were identified in 27 studies. Age groups of animals used, sample sizes used, vaccine types, route of vaccination, dose of vaccine, adjuvant types, booster times, time of challenge since first vaccination, challenge methods, challenge doses, challenge route, observation times postchallenge, and raw mean lung-lesion scores (defined as percent lung involved) were extracted from each publication and used in the analysis. Vaccine types were grouped into 11 categories as controls, live, potassium thiocyanate (KSCN) extract, phosphate buffered saline extract (PBSE), 30 kDa recombinant protein, bacterin, streptomycin dependent live (Sm D live), sodium salicylate extract (SSE), sarkosyl outer membrane protein extract (sarkosyl OMP), or culture supernatant (CS) categories based on the subunit content in each preparation. In a second analysis, the chemically altered live vaccine was grouped together with live Sm D group as modified live vaccines. The leastsquares means of the postchallenge lung-lesion scores of each vaccine type were then compared after controlling for all the above-mentioned variables in an analysis of variance using Fischer's protected least significant difference. The statistical analysis was done using the general linear models procedure of Statistical Analysis Systems Institute Inc.. Protective indices for each vaccine type were calculated as a function of independent probabilities of protection among vaccinates and controls. The protective indices of each vaccine type were then compared in a similar model. Cattle vaccinated with live vaccines had the smallest lung-lesion scores (9 ± 8) which significantly differed from that of controls (44 ± 8), bacterins (23 ± 6), and live Sm D (38 ± 12) or modified live (31 ± 10). KSCN extract (9 ± 10), bacterin, and CS (20 ± 9) also had significantly lower ( P < 0.05) lung-lesion scores compared to controls. The CS and KSCN vaccines showed a significantly ( P < 0.05) better protective index (PI) (0.70 and 0.68 respectively) than bacterins (0.50) or bacterin + CS (0.44) vaccines. Saline extract and live vaccines had better ( P < 0.05) PI (0.60 and 0.70 respectively) compared to bacterins.