Heat shock- and alkaline pH-induced proteins of Campylobacter jejuni: characterization and immunological properties

Robust immunity induced by multi-epitope DnaK peptides, potential vaccine candidates against Salmonella: An in vitro study

Enteric fever is a common yet serious issue, most troublesome in underdeveloped and developing nations affecting all age group primarily children. Pitfalls of existing vaccines along with rapidly rising Multi-Drug-Resistant Salmonella strains necessitate the need for the development of new vaccine candidates having potential to provide complete protection. Several vaccine strategies are being pursued to stimulate protective immunity against typhoid, including conjugate vaccines for the elicitation of cellular and humoral responses as both arms of immunity are essential for complete protection. Bacterial HSPs are highly immunogenic to produce humoral and cellular immune responses. In this study, we are reporting in vitro immunostimulatory activity of immunodominant multi-epitope protective antigenic DnaK peptides identified earlier by immunoinformatics approach. Remarkable increase in antibody titer, lymphocyte proliferation, cytokines and NO level with individual /mixture of DnaK peptides as compared to control demonstrate immunogenic potential of these peptides that effectively augments both humoral and cellular immune responses. None of the peptides cause any hemolysis in human RBCs. Overall; our findings strongly elucidate the immune-stimulatory potential of DnaK peptides to be explored as potent vaccine candidates against multiple pathogens.

Genome-Wide Identification of Host-Segregating Epidemiological Markers for Source Attribution in Campylobacter jejuni

Campylobacter is among the most common worldwide causes of bacterial gastroenteritis. This organism is part of the commensal microbiota of numerous host species, including livestock, and these animals constitute potential sources of human infection. Molecular typing approaches, especially multilocus sequence typing (MLST), have been used to attribute the source of human campylobacteriosis by quantifying the relative abundance of alleles at seven MLST loci among isolates from animal reservoirs and human infection, implicating chicken as a major infection source. The increasing availability of bacterial genomes provides data on allelic variation at loci across the genome, providing the potential to improve the discriminatory power of data for source attribution. Here we present a source attribution approach based on the identification of novel epidemiological markers among a reference pan-genome list of 1,810 genes identified by gene-by-gene comparison of 884 genomes of Campylobacter jejuni isolates from animal reservoirs, the environment, and clinical cases. Fifteen loci involved in metabolic activities, protein modification, signal transduction, and stress response or coding for hypothetical proteins were selected as host-segregating markers and used to attribute the source of 42 French and 281 United Kingdom clinical C. jejuni isolates. Consistent with previous studies of British campylobacteriosis, analyses performed using STRUCTURE software attributed 56.8% of British clinical cases to chicken, emphasizing the importance of this host reservoir as an infection source in the United Kingdom. However, among French clinical isolates, approximately equal proportions of isolates were attributed to chicken and ruminant reservoirs, suggesting possible differences in the relative importance of animal host reservoirs and indicating a benefit for further national-scale attribution modeling to account for differences in production, behavior, and food consumption.IMPORTANCE Accurately quantifying the relative contribution of different host reservoirs to human Campylobacter infection is an ongoing challenge. This study, based on the development of a novel source attribution approach, provides the first results of source attribution in Campylobacter jejuni in France. A systematic analysis using gene-by-gene comparison of 884 genomes of C. jejuni isolates, with a pan-genome list of genes, identified 15 novel epidemiological markers for source attribution. The different proportions of French and United Kingdom clinical isolates attributed to each host reservoir illustrate a potential role for local/national variations in C. jejuni transmission dynamics.

Stress response and virulence of heat-stressed Campylobacter jejuni

Thermotolerant Campylobacter spp. frequently cause bacterial gastroenteritis in humans commonly infected through the consumption of undercooked poultry meat. We examined Campylobacter jejuni heat-stress responses in vitro after exposure to 48°C and 55°C. The in vivo modulation of its pathogenicity was also investigated using BALB/c mice intravenously infected with stressed C. jejuni. Regardless of the bacterial growth phase, the culturability and viability of C. jejuni in vitro was reduced after exposure to 55°C. This correlated with the altered protein profile and decreased virulence properties observed in vivo. Heat stress at 48°C elicited the transition to more resistant bacterial forms, independent of morphological changes or the appearance of shorter spiral and coccoid cells. This treatment did not cause marked changes in bacterial virulence properties in vivo. These results indicated that the characteristics and pathogenicity of C. jejuni in response to heat stress are temperature dependent. Further studies on the responses of C. jejuni to stresses used during food processing, as well as the modulation of its virulence, are important for a better understanding of its contamination and infective cycle, and will, thus, contribute to improved safety in the food production chain.

Cloning, expression, and antigenicity of 14 proteins from Campylobacter jejuni

Fourteen Campylobacter jejuni genes--porA, cadF, omp18, dnaK, flaC, peb1, peb2, peb3, peb4, ahpC, groEL, tuF, hipO, and Cj0069--were cloned and expressed in Escherichia coli BL21. The recombinant proteins were purified on histidine (His) and glutathione S-transferase (GST) trap columns using the ÄKTA Explorer 100 System. Recombinant proteins were visualized using sodium dodecyl sulfate-polyacrylamide gel electrophoresis and identified using matrix-assisted laser desorption ionization time-of-flight mass spectrometry. The antigenicities of these recombinant proteins were assessed by Western blotting and enzyme-linked immunosorbent assays with anti-C. jejuni immune rabbit sera. Four recombinant proteins, including rGST-PorA, rHis-CadF, rGST-GroEL, and rGST-TuF, demonstrated reactions with both anti-serum and preimmune serum, while rHis-DnaK, rGST-FlaC, rGST-PEB2, rGST-PEB3, rGST-PEB4, and rGST-HipO showed variable antigenicity characteristics to the anti-sera derived from different C. jejuni strains. rHis-Omp18, rHis-PEB1, and rGST-AhpC demonstrated universal and specific antigenities with the entire anti-sera panel tested in this present study, while recombinant rGST-Cj0069 and rHis-DnaK did not react with any of the anti-C. jejuni sera tested. In conclusion, rGST-AhpC may be useful as a potential serodiagnostic antigen for C. jejuni infection.

The hrcA and hspR regulons of Campylobacter jejuni

The human pathogen Campylobacter jejuni has a classic heat shock response, showing induction of chaperones and proteases plus several unidentified proteins in response to a small increase in growth temperature. The genome contains two homologues to known heat shock response regulators, HrcA and HspR. Previous work has shown that HspR controls several heat-shock genes, but the hrcA regulon has not been defined. We have constructed single and double deletions of C. jejuni hrcA and hspR and analysed gene expression using microarrays. Only a small number of genes are controlled by these two regulators, and the two regulons overlap. Strains mutated in hspR, but not those mutated in hrcA, showed enhanced thermotolerance. Some genes previously identified as being downregulated in a strain lacking hspR showed no change in expression in our experiments.

Metabolite and transcriptome analysis of Campylobacter jejuni in vitro growth reveals a stationary-phase physiological switch

Campylobacter jejuni is a prevalent cause of food-borne diarrhoeal illness in humans. Understanding of the physiological and metabolic capabilities of the organism is limited. We report a detailed analysis of the C. jejuni growth cycle in batch culture. Combined transcriptomic, phenotypic and metabolic analysis demonstrates a highly dynamic ‘stationary phase’, characterized by a peak in motility, numerous gene expression changes and substrate switching, despite transcript changes that indicate a metabolic downshift upon the onset of stationary phase. Video tracking of bacterial motility identifies peak activity during stationary phase. Amino acid analysis of culture supernatants shows a preferential order of amino acid utilization. Proton NMR (1H-NMR) highlights an acetate switch mechanism whereby bacteria change from acetate excretion to acetate uptake, most probably in response to depletion of other substrates. Acetate production requires pta (Cj0688) and ackA (Cj0689), although the acs homologue (Cj1537c) is not required. Insertion mutants in Cj0688 and Cj0689 maintain viability less well during the stationary and decline phases of the growth cycle than wild-type C. jejuni, suggesting that these genes, and the acetate pathway, are important for survival.

Global transcriptome analysis of Tropheryma whipplei in response to temperature stresses

Tropheryma whipplei, the agent responsible for Whipple disease, is a poorly known pathogen suspected to have an environmental origin. The availability of the sequence of the 0.92-Mb genome of this organism made a global gene expression analysis in response to thermal stresses feasible, which resulted in unique transcription profiles. A few genes were differentially transcribed after 15 min of exposure at 43 degrees C. The effects observed included up-regulation of the dnaK regulon, which is composed of six genes and is likely to be under control of two HspR-associated inverted repeats (HAIR motifs) found in the 5' region. Putative virulence factors, like the RibC and IspDF proteins, were also overexpressed. While it was not affected much by heat shock, the T. whipplei transcriptome was strongly modified following cold shock at 4 degrees C. For the 149 genes that were differentially transcribed, eight regulons were identified, and one of them was composed of five genes exhibiting similarity with genes encoding ABC transporters. Up-regulation of these genes suggested that there was an increase in nutrient uptake when the bacterium was exposed to cold stress. As observed for other bacterial species, the major classes of differentially transcribed genes encode membrane proteins and enzymes involved in fatty acid biosynthesis, indicating that membrane modifications are critical. Paradoxically, the heat shock proteins GroEL2 and ClpP1 were up-regulated. Altogether, the data show that despite the lack of classical regulation pathways, T. whipplei exhibits an adaptive response to thermal stresses which is consistent with its specific environmental origin and could allow survival under cold conditions.

Survival and stress induced expression of groEL and rpoD of Campylobacter jejuni from different growth phases

Although Campylobacter jejuni is the leading cause of bacterial diarrhoeal disease in humans worldwide, its potential to adapt to the stressful conditions and survive in extra-intestinal environment is still poorly understood. We tested the effect of heat shock (55 degrees C, 3 min) and oxidative stress (3 mM H2O2 for 10 min or prolonged incubation at atmosphere oxygen concentration) on non-starved and starved cells of Campylobacter jejuni from different growth phases. Viability as assessed with the Bacterial Viability Kit LIVE/DEAD BacLighttrade mark dying before fluorescent microscopy and culturability of the cells (CFU ml(-1)) from both growth phases showed that starvation increased heat but not oxidative resistance. High temperature and oxidative stress invoked quick transformation from culturable spiral shaped to nonculturable spiral and coccoid cells. Despite physiological changes of the cells we were not able to document clear differences in the expression of heat shock and starvation genes (dnaK, htpG, groEL), oxidative (ahpC, sodB), virulence (flaA) and housekeeping genes (16S rRNA, rpoD) after heat treatment (55 degrees C, 3 min) or oxidative stresses applied. When starving, no induction of expression of any of these genes was noticed, chloramphenicol had no influence on their gene expression. Quantitative real-time PCR analyses showed that at least 10-20 min of heat shock was necessary to evidently increase the amount of groEL and rpoD transcripts.

Environmental survival mechanisms of the foodborne pathogen Campylobacter jejuni

Campylobacter spp. continue to be the greatest cause of bacterial gastrointestinal infections in humans worldwide. They encounter many stresses in the host intestinal tract, on foods and in the environment. However, in common with other enteric bacteria, they have developed survival mechanisms to overcome these stresses. Many of the survival mechanisms used by Campylobacter spp. differ from those used by other bacteria, such as Escherichia coli and Salmonella spp. This review summarizes the mechanisms by which Campylobacter spp. adapt to stress conditions and thereby increase their ability to survive on food and in the environment.

Use of genome-wide expression profiling and mutagenesis to study the intestinal lifestyle of Campylobacter jejuni

Campylobacter jejuni is the most common bacterial cause of diarrhea worldwide. To colonize the gut and cause infection, C. jejuni must successfully compete with endogenous microbes for nutrients, resist host defenses, persist in the intestine, and ultimately infect the host. These challenges require the expression of a battery of colonization and virulence determinants. In this study, the intestinal lifestyle of C. jejuni was studied using whole-genome microarray, mutagenesis, and a rabbit ileal loop model. Genes associated with a wide range of metabolic, morphological, and pathological processes were expressed in vivo. The in vivo transcriptome of C. jejuni reflected its oxygen-limited, nutrient-poor, and hyperosmotic environment. Strikingly, the expression of several C. jejuni genes was found to be highly variable between individual rabbits. In particular, differential gene expression suggested that C. jejuni extensively remodels its envelope in vivo by differentially expressing its membrane proteins and by modifying its peptidoglycan and glycosylation composition. Furthermore, mutational analysis of seven genes, hspR, hrcA, spoT, Cj0571, Cj0178, Cj0341, and fliD, revealed an important role for the stringent and heat shock response in gut colonization. Overall, this study provides new insights on the mechanisms of gut colonization, as well as possible strategies employed by Campylobacter to resist or evade the host immune responses.

Determination of toxicity of Campylobacter jejuni isolated from humans and from poultry carcasses acquired at various stages of production

AIM

The research focused on the determination of the toxicity variation associated with Campylobacter jejuni isolated from humans and chickens.

METHODS AND RESULTS

Campylobacter jejuni isolates were obtained from chicken carcasses and from humans exhibiting symptoms of campylobacteriosis. Using HeLa cells as the in vitro model, toxicity was determined for each isolate. The mean toxicity level of the chicken isolates was significantly lower than that of the human isolates (P < 0.001). There was a wide range of toxicity in C. jejuni isolated from chickens and the percentage of isolates exhibiting low toxicity remaining relatively constant. All C. jejuni isolates from humans possessed either medium or high levels of toxicity.

CONCLUSIONS

All wildtype C. jejuni isolates obtained from poultry carcasses may not be equally important as a human foodborne pathogen.

SIGNIFICANCE AND IMPACT OF STUDY

Campylobacter jejuni remains a primary foodborne pathogen and increased efforts are needed to determine the impact of wildtype isolates in causing human illness. The present research indicates that all isolates may not be equally important in regards to disease potential. The information found should be included in efforts to develop C. jejuni detection, control and infection modelling.

The Mycobacterium tuberculosis chaperonin 10 monomer exhibits structural plasticity

The conditions which favor dissociation of oligomeric Mycobacterium tuberculosis chaperonin 10 and the solution structure of the monomer were studied by analytical ultracentrifugation, size exclusion chromatography, fluorescence, and circular dichroism spectroscopies. At neutral pH and in the absence of divalent cations, the protein is fully monomeric below approximately a 4.7 microM concentration. Under these conditions the monomer forms completely unfolded and partially folded conformers which are in equilibrium with each other. One conformer accumulates over the others which is stable within a very narrow range of temperatures. It contains a beta-sheet-structured C-terminal half and a mostly disordered N-terminal half. Other components of the equilibrium include partially helical structures which do not completely unfold at high temperature or under strong acidic conditions. Complete unfolding of the monomer occurs in the presence of denaturants or below 14 degrees C. Cold-denaturation is detected at an unusually high temperature and this may be due to the concentration of hydrophobic residues, which is larger in chaperonins than in other globular proteins. Finally, the monomer self-associates in the pH range 5.8-2.9, where it forms small oligomers. A structure-activity relationship was investigated with the sequences known to be involved in the various biological activities of the monomer.

Planktonic or biofilm growth affects survival, hydrophobicity and protein expression patterns of a pathogenic Campylobacter jejuni strain

The effect of planktonic or biofilm modes of growth on survival, hydrophobicity and cellular protein expression patterns of a pathogenic Campylobacter jejuni strain were determined. This was achieved by growing the strain in brain heart infusion broth (with 1% yeast extract), or attached to glass beads in the same medium, at 37 degrees C for 48 h under microaerophilic conditions. Cells from the broth or the bead surfaces were stored at different temperatures (4, 10, 25 and 37 degrees C) for 28 days in phosphate buffered saline (PBS) and monitored at appropriate time intervals for culturable numbers and hydrophobicity by standard methods. In addition, cells were inoculated onto the surface of two processed meat products (a bologna and a summer sausage) vacuum packaged and stored at 4 degrees C for 28 days. Numbers of culturable cells were monitored at appropriate time intervals by standard methods. Cells from the broth or the bead surfaces were also examined for protein expression using two-dimensional protein electrophoresis. Results indicated that numbers of culturable cells in phosphate buffered saline decreased from approximately 6 log colony forming units (cfu) g(-1) to undetectable levels within 14-day storage in a temperature dependent manner. Hydrophobicity of broth grown cells decreased from 15% to 0% adherence to xylene over the same time in a temperature independent manner. Cells grown in a biofilm mode initially displayed a <0.3% adherence to xylene which was maintained during storage. Furthermore, cells grown in the biofilm mode decreased in number more rapidly on storage in buffer than their counterparts grown in broth. Numbers of culturable cells on meat decreased from approximately 5 log cfu g(-1) to undetectable levels within 14-day storage in a product dependent manner, with the most rapid decrease observed for the more acidic summer sausage. Cells grown in a biofilm mode decreased in number more rapidly on storage than broth grown cells. The protein expression patterns differed between planktonic and biofilm cells with seven unique and 12 up-regulated protein spots expressed in a growth mode specific manner. A number of the differentially expressed spots were tentatively identified, by comparison to existing literature, as surface- and stress-associated proteins. Despite the elicitation of some putative stress proteins, this study importantly indicates that biofilm cells of C. jejuni are less resistant to stress than their planktonic counterparts and may lack a sophisticated adaptive stress-resistance response. These findings have implication in determining the risks of infection associated with C. jejuni contamination on food.

Mycobacterium tuberculosis chaperonin 10 is secreted in the macrophage phagosome: is secretion due to dissociation and adoption of a partially helical structure at the membrane?

To confirm that Mycobacterium tuberculosis chaperonin 10 (Cpn10) is secreted outside the live bacillus, infected macrophages were examined by electron microscopy. This revealed that the mycobacterial protein accumulates both in the wall of the bacterium and in the matrix of the phagosomes in which ingested mycobacteria survive within infected macrophages. To understand the structural implications underlying this secretion, a structural study of M. tuberculosis Cpn10 was performed under conditions that are generally believed to mimic the membrane environment. It was found that in buffer-organic solvent mixtures, the mycobacterial protein forms two main species, namely, a partially helical monomer that prevails in dilute solutions at room temperature and a dimer that folds into a beta-sheet-dominated structure and prevails in either concentrated protein solutions at room temperature or in dilute solutions at low temperature. A partially helical monomer was also found and was completely associated with negatively charged detergents in a micelle-bound state. Remarkably, zwitterionic lipids had no effect on the protein structure. By using N- and C-truncated forms of the protein, the C- and N-terminal sequences were identified as possessing an amphiphilic helical character and as selectively associating with acidic detergent micelles. When the study was extended to other chaperonins, it was found that human Cpn10 is also monomeric and partially helical in dilute organic solvent-buffer mixtures. In contrast, Escherichia coli Cpn10 is mostly dimeric and predominately beta-sheet in both dilute and concentrated solutions. Interestingly, human Cpn10 also crosses biological membranes, whereas the E. coli homologue is strictly cytosolic. These results suggest that dissociation to partially helical monomers and interaction with acidic lipids may be two important steps in the mechanism of secretion of M. tuberculosis Cpn10 to the external environment.

Gene expression profile of Campylobacter jejuni in response to growth temperature variation

The foodborne pathogen Campylobacter jejuni is the primary causative agent of gastroenteritis in humans. In the present study a whole genome microarray of C. jejuni was constructed and validated. These DNA microarrays were used to measure changes in transcription levels over time, as C. jejuni cells responded to a temperature increase from 37 to 42 degrees C. Approximately 20% of the C. jejuni genes were significantly up- or downregulated over a 50-min period after the temperature increase. The global change in C. jejuni transcriptome was found to be essentially transient, with only a small subset of genes still differentially expressed after 50 min. A substantial number of genes with a downregulated coexpression pattern were found to encode for ribosomal proteins. This suggests a short growth arrest upon temperature stress, allowing the bacteria to reshuffle their energy toward survival and adaptation to the new growth temperature. Genes encoding chaperones, chaperonins, and heat shock proteins displayed the most dramatic and rapid upregulation immediately after the temperature change. Interestingly, genes encoding proteins involved in membrane structure modification were differentially expressed, either up- or downregulated, suggesting a different protein membrane makeup at the two different growth temperatures. Overall, these data provide new insights into the primary response of C. jejuni to surmount a sudden temperature upshift, allowing the bacterium to survive and adapt its transcriptome to a new steady state.

Hsp60 specific antibodies in egg yolks from laying hens naturally infected with Salmonella enterica subspecies enterica serovar Enteritidis

Heat shock protein (Hsp) 60 of Salmonella appears to be involved in pathogenesis of infectious processes and host immune responses. Eggs of laying hens from two Salmonella Enteritidis naturally infected flocks (I--acute outbreak of infection; II--occasional bacteria excretion) and one control flock (III) were tested for the presence of yolk antibodies (IgY) against Hsp60 by applying enzyme-linked immunosorbent assay (ELISA). The levels of specific immunoglobulins were related to those against lipopolysaccharide (LPS) and flagellin. the antigens of the established immunological importance in S. Enteritidis infections. Within flock III, the antibody concentrations were consistently low. Elevated levels were detected in eggs from two infected flocks. Levels of specific IgY measured for flock I were higher than those in flock II; the greatest difference was observed for anti-Hsp60. This report indicates a probable important role of Hsp60 as a target of the hens' immune response, especially during the acute phase of S. Enteritidis infection.

Environmental regulation of Campylobacter jejuni major outer membrane protein porin expression in Escherichia coli monitored by using green fluorescent protein

Porins allow exchanges between bacteria and their environment. In the gram-negative food-borne pathogen Campylobacter jejuni two porins, major outer membrane protein (MOMP) and Omp50, have been identified. MOMP is synthesized at a very high level under laboratory culture conditions, suggesting that its promoter functions very efficiently under these conditions. In Campylobacter samples, we observed that MOMP porin expression increased at a high temperature (42 degrees C) or a high pH (pH 8.5) compared to expression at a low temperature (31 degrees C) or an acidic pH (pH 5.5). To study the regulation of MOMP expression at the transcriptional level, we constructed an momp-gfp fusion in which gfp expression was put under the control of the momp promoter. Interestingly, we observed the same pattern of regulation in Escherichia coli, as monitored by green fluorescent protein production, that was found in CAMPYLOBACTER: The ranges of pH and temperature tested are physiologically relevant, because they can be found in the digestive tracts of both birds and humans, which are both colonized by CAMPYLOBACTER: Our results suggest that a component of the regulatory mechanism is conserved in C. jejuni and E. coli. However, medium osmolarity and sodium salicylate did not have a significant effect on C. jejuni momp promoter activity in E. coli, suggesting that major regulatory elements of E. coli porin expression do not participate in MOMP regulation. In contrast, mechanisms involving DNA supercoiling may be involved, as shown by DNA gyrase inhibition assays. These findings are a step towards determining the role of outer membrane proteins in the adaptation of C. jejuni to its environment.

Periplasmic localization of a GroES homologue in Escherichia coli transformed with groESx cloned from Legionella-like endosymbionts in Amoeba proteus

Escherichia coli MC4100 transformed with a groE homologous operon cloned from X-bacteria accumulated large amounts of the gene product when cultured at 30 or 37 degrees C. Heat shock for 10-30 min at 42 degrees C or ethanol (5%) shock for 2 h increased GroESx levels to about twice that in E. coli grown at 30 degrees C. The subcellular localization of GroESx in transformed E. coli was determined by several subcellular fractionation methods, by the analysis of extracted proteins in SDS polyacrylamide gels and by assays of marker enzymes. The GroESx protein was detected in both the periplasmic and cytoplasmic extracts and a large amount of the protein was accumulated in the periplasm. The GroEL protein and recombinant beta-galactosidase were exclusively localized in the cytoplasmic fraction, eliminating the possibility that periplasmic GroESx might be due to simple overproduction. N-terminal amino acid sequencing confirmed that the protein resolved on a 2-D gel was GroESx. This work represents the first report of the periplasmic location of GroES homologues in E. coli.

Immunogens of interest for the diagnosis of Campylobacter jejuni infections

In order to identify the C. jejuni immunogens of interest for the diagnosis of Campylobacter infections, we analyzed the humoral response of 153 patients by using complement fixation (CF) and western blot assays. A first group of 79 sera was from C. jejuni infected patients suffering from enteritis (n=16), Guillain-Barré syndrome (GBS) (n=40) and arthritis (n=23). A second group of 49 sera was from healthy blood donors and a third group consisted of 25 sera from children under 4 years old. Using the CF test, 88.6% of the C. jejuni infected patients were seropositive versus 28.5% of the healthy blood donors and none of the children. The Western blot assay allowed detection of antibodies directed against seven selected antigens ranging from 14 to 67 kDa. Three of these antigens with a molecular size of 29, 37 and 43 kDa were detected by 86.0%, 84.8% and 91.1% of the C. jejuni infected patients, respectively. These three antigens seem to be good candidates for the development of assays suitable for direct and indirect diagnosis of Campylobacter infections.

Viability and DNA maintenance in nonculturable spiral Campylobacter jejuni cells after long-term exposure to low temperatures

Survival of Campylobacter jejuni at 4 and 20 degrees C was investigated by using cellular integrity, respiratory activity, two-dimensional (2D) protein profile, and intact DNA content as indicators of potential viability of nonculturable cells. Intact DNA content after 116 days, along with cellular integrity and respiring cells, was detected for up to 7 months at 4 degrees C by pulsed-field gel electrophoresis. Most changes in 2D protein profiles involved up- or down-regulation.

Serum antibody level against GroEL type heat-shock protein of Campylobacter jejuni in patients with Guillain-Barré syndrome

Recently there has been an increase in the number of cases reported of Guillain-Barré syndrome (GBS) developed after Campylobacter jejuni infection. To investigate the role of a C.jejuni GroEL-type heat-shock protein (CjHsp60) in the infection and induction of GBS, we examined the antibody level against CjHsp60 in 27 human sera, including GBS and non-GBS patients, by an enzyme-linked immunosorbent assay. Sera from patients with C. jejuni infection, despite the development of GBS, had a higher titer of anti-CjHsp60 antibody than those of patients without the infection and healthy control subjects. The patients with C. jejuni infection followed by GBS had slightly higher levels of this antibody than did the patients with infection who did not develop GBS, but there was no statistical significance. In conclusion, CjHsp60 is found to be one of the major immunogenic antigens in actual C. jejuni infection, but no evidence that supports the direct relationship between this protein and C. jejuni-associated GBS was found in this study.

Cloning and expression of the dnaK gene of Campylobacter jejuni and antigenicity of heat shock protein 70

Campylobacter jejuni is a leading cause of infectious diarrhea throughout the world. In addition, there is growing evidence that Guillain-Barré syndrome, an inflammatory demyelinating disease of the peripheral nervous system, is frequently preceded by C. jejuni infection. In the present study, the hrcA-grpE-dnaK gene cluster of C. jejuni was cloned and sequenced. The dnaK gene consists of an open reading frame of 1,869 bp and encodes a protein with a high degree of homology to other bacterial 70-kDa heat shock proteins (HSPs). The overall percentages of identity to the HSP70 proteins of Helicobacter pylori, Borrelia burgdorferi, Chlamydia trachomatis, and Bacillus subtilis were calculated to be 78.1, 60.5, 57.2, and 53. 8%, respectively. Regions similar to the Escherichia coli sigma70 promoter consensus sequence and to a cis-acting regulatory element (CIRCE) are located upstream of the hrcA gene. Following heat shock, a rapid increase of dnaK mRNA was detectable, which reached its maximum after 20 to 30 min. A 6-His-tagged recombinant DnaK protein (rCjDnaK-His) was generated in E. coli, after cloning of the dnaK coding region into pET-22b(+), and purified by affinity and gel filtration chromatography. Antibody responses to rCjDnaK-His were significantly elevated, compared to those of healthy individuals, in about one-third of the serum specimens obtained from C. jejuni enteritis patients.

Cloning and expression of the Campylobacter jejuni lon gene detected by RNA arbitrarily primed PCR

Fingerprinting of RNA by arbitrarily primed PCR was used to identify a heat-inducible gene in Campylobacter jejuni. Comparing RNA fingerprints from C. jejuni cells before and after 20 min of heat shock at 48 degrees C, a differentially amplified PCR product was identified which displayed a high degree of homology to bacterial lon genes. By screening C. jejuni genomic libraries, the entire lon gene was cloned and sequenced. It encodes a protein of 791 amino acids with a calculated molecular mass of 90.2 kDa. Alignment of the Lon amino acid sequence with that of other bacterial species revealed an overall identity of up to 56.6% (Helicobacter pylori). Northern and RNA dot blot experiments confirmed heat induction of the C. jejuni lon gene, revealing a maximum 6-8-fold increase in the level of specific mRNA.

Enhanced levels of Staphylococcus aureus stress protein GroEL and DnaK homologs early in infection of human epithelial cells

Antibodies to Staphylococcus aureus heat shock proteins (Hsps) are present in the sera of patients with S. aureus endocarditis (M. W. Qoronfleh, W. Weraarchakul, and B. J. Wilkinson, Infect. Immun. 61:1567-1570, 1993). Although these proteins are immunogenic, their role in infection has not been established. We developed a cell culture system as a model to examine the potential involvement of staphylococcal Hsps in the initial events of infection. This study supports a model in which a clinical endocarditis isolate responds to host cell signals by selectively regulating the synthesis of numerous proteins, including the stress proteins Hsp60 (GroEL homolog) and Hsp70 (DnaK homolog) and a unique 58-kDa protein.

Immune responses to stress proteins: applications to infectious disease and cancer

Heat shock proteins, or stress proteins have been identified as part of a highly conserved cellular defence mechanism mediated by multiple, distinct gene families and corresponding gene products. As intracellular chaperones, stress proteins participate in many essential biochemical pathways of protein maturation and function active during times of stress and during normal cellular homeostasis. In addition to their well-characterized role as protein chaperones, stress proteins are now realized to possess another important biological property: immunogenicity. Stress proteins are now understood to play a fundamental role in immune surveillance of infection and malignancy and this body of basic research has provided a framework for their clinical application. As key targets of both humoral and cellular immunity during infection, stress proteins have accordingly received considerable research interest as prophylactic vaccines for infectious disease applications. The unique and potent immunostimulatory properties of stress proteins have similarly been applied to the development of new approaches to cancer therapy, including both protein and gene-based modalities.

Induction and characterization of heat shock proteins of Salmonella typhi and their reactivity with sera from patients with typhoid fever

The heat shock protein (HSP) response of Salmonella typhi following exposure to elevated growth temperatures was studied. Three major proteins with molecular sizes of 58, 68, and 88 kDa were abundantly expressed when S. typhi cells were shifted from 37 to 45 degrees C and to 55 degrees C. These proteins were also constitutively expressed at 37 degrees C. Western blotting and immunoprecipitation studies with anti-HSP monoclonal antibodies revealed that the 58- and 68-kDa proteins were analogous to the GroEL and DnaK proteins, respectively, of Escherichia coli. These HSPs are also abundantly present in the outer membrane fraction of disrupted cells and, to a lesser extent, in the cytosol. Immunoblotting experiments with sera from patients with a culture-positive diagnosis of typhoid fever showed the presence of antibodies to these HSPs. Nine of twelve sera reacted with the 58-, 68-, and 88-kDa proteins, while three sera reacted only with the 68- and 88-kDa proteins. All 10 sera from healthy individuals showed no binding to these HSPs. In light of the well-documented roles of HSPs in the pathogenesis of microbial infections and as immunodominant antigens, these findings may be relevant for a better understanding of disease processes and for the future development of diagnostic and preventive strategies.

Alteration of gonococcal protein expression in acidic culture

We grew Neisseria gonorrhoeae under acidic, neutral, and alkaline conditions and noted altered expression of at least 12 outer membrane proteins between 31 and 100 kDa in size. One protein whose expression was upregulated under acidic conditions was gonococcal heat shock protein 63. These proteins may contribute to the pathogenesis of gonorrhea in the urogenital tract.

The purification of a GroEL-like stress protein from aerobically adapted Campylobacter jejuni

From plate cultures of Campylobacter jejuni grown in room air a particulate protein of 62 kDa was isolated by ion-exchange chromatography. The protein had a square shape from the side view but when viewed from the top it had a star-shaped structure. The molecular size of the whole particle determined by gel filtration was 850 kDa which suggested the presence of 14 subunits of 62 kDa in each particle. The N-terminal 37 amino residues showed more than 80% homology with the sequence of these heat shock protein (HSP) 60 homologs of Chlamydia trachomatis, Helicobacter pylori, and Escherichia coli (GroEL). This protein is immunologically cross-reactive with the antiserum for the 60-kDa HSP of Yersinia enterocolitica. Production of the 62-kDa protein increased under heat stress and growth in an aerobic atmospheric environment. From these observations we concluded that the 62-kDa protein is a Campylobacter stress protein (Cj62) which belongs to the HSP 60 family.