Monoclonal antibodies directed against the flagella of Campylobacter jejuni: production, characterization and lack of effect on the colonization of infant mice

Murine Models for the Investigation of Colonization Resistance and Innate Immune Responses in Campylobacter Jejuni Infections

Human infections with the food-borne pathogen Campylobacter jejuni are progressively increasing worldwide and constitute a significant socioeconomic burden to mankind. Intestinal campylobacteriosis in humans is characterized by bloody diarrhea, fever, abdominal pain, and severe malaise. Some individuals develop chronic post-infectious sequelae including neurological and autoimmune diseases such as reactive arthritis and Guillain-Barré syndrome. Studies unraveling the molecular mechanisms underlying campylobacteriosis and post-infectious sequelae have been hampered by the scarcity of appropriate experimental in vivo models. Particularly, conventional laboratory mice are protected from C. jejuni infection due to the physiological colonization resistance exerted by the murine gut microbiota composition. Additionally, as compared to humans, mice are up to 10,000 times more resistant to C. jejuni lipooligosaccharide (LOS) constituting a major pathogenicity factor responsible for the immunopathological host responses during campylobacteriosis. In this chapter, we summarize the recent progress that has been made in overcoming these fundamental obstacles in Campylobacter research in mice. Modification of the murine host-specific gut microbiota composition and sensitization of the mice to C. jejuni LOS by deletion of genes encoding interleukin-10 or a single IL-1 receptor-related molecule as well as by dietary zinc depletion have yielded reliable murine infection models resembling key features of human campylobacteriosis. These substantial improvements pave the way for a better understanding of the molecular mechanisms underlying pathogen-host interactions. The ongoing validation and standardization of these novel murine infection models will provide the basis for the development of innovative treatment and prevention strategies to combat human campylobacteriosis and collateral damages of C. jejuni infections.

Reducing Campylobacter jejuni colonization of poultry via vaccination

Campylobacter jejuni is a leading bacterial cause of human gastrointestinal disease worldwide. While C. jejuni is a commensal organism in chickens, case-studies have demonstrated a link between infection with C. jejuni and the consumption of foods that have been cross-contaminated with raw or undercooked poultry. We hypothesized that vaccination of chickens with C. jejuni surface-exposed colonization proteins (SECPs) would reduce the ability of C. jejuni to colonize chickens, thereby reducing the contamination of poultry products at the retail level and potentially providing a safer food product for consumers. To test our hypothesis, we injected chickens with recombinant C. jejuni peptides from CadF, FlaA, FlpA, CmeC, and a CadF-FlaA-FlpA fusion protein. Seven days following challenge, chickens were necropsied and cecal contents were serially diluted and plated to determine the number of C. jejuni per gram of material. The sera from the chickens were also analyzed to determine the concentration and specificity of antibodies reactive against the C. jejuni SECPs. Vaccination of chickens with the CadF, FlaA, and FlpA peptides resulted in a reduction in the number of C. jejuni in the ceca compared to the non-vaccinated C. jejuni-challenged group. The greatest reduction in C. jejuni colonization was observed in chickens injected with the FlaA, FlpA, or CadF-FlaA-FlpA fusion proteins. Vaccination of chickens with different SECPs resulted in the production of C. jejuni-specific IgY antibodies. In summary, we show that the vaccination of poultry with individual C. jejuni SECPs or a combination of SECPs provides protection of chickens from C. jejuni colonization.

Immunity to Campylobacter: its role in risk assessment and epidemiology

Acquired immunity is an important factor in the epidemiology of campylobacteriosis in the developing world, apparently limiting symptomatic infection to children of less than two years. However, also in developed countries the highest incidence is observed in children under five years and the majority of Campylobacter infections are asymptomatic, which may be related to the effects of immunity and/or the ingested doses. Not accounting for immunity in epidemiological studies may lead to biased results due to the misclassification of Campylobacter-exposed but apparently healthy persons as unexposed. In risk assessment studies, health risks may be overestimated when immunity is neglected.

Characterization of genetically matched isolates of Campylobacter jejuni reveals that mutations in genes involved in flagellar biosynthesis alter the organism's virulence potential

Phenotypic and genotypic evidence suggests that not all Campylobacter jejuni isolates are pathogenic for humans. We hypothesized that differences in gene content or gene expression alter the degree of pathogenicity of C. jejuni isolates. A C. jejuni isolate (Turkey) recovered from a turkey and a second C. jejuni isolate (CS) recovered from a chicken differed in their degrees of in vitro and in vivo virulence. The C. jejuni Turkey isolate invaded INT 407 human epithelial cells and secreted the Cia (Campylobacter invasion antigen) proteins, while the C. jejuni CS isolate was noninvasive for human epithelial cells and did not secrete the Cia proteins. Newborn piglets inoculated with the C. jejuni Turkey isolate developed more severe clinical signs of campylobacteriosis than piglets inoculated with the C. jejuni CS isolate. Additional work revealed that flagellin was not expressed in the C. jejuni CS isolate. Microarray and real-time reverse transcription-PCR analyses revealed that all flagellar class II genes were significantly downregulated in the C. jejuni CS isolate compared to the C. jejuni Turkey isolate. Finally, nucleotide sequencing of the flgR gene revealed the presence of a single residue that was different in the FlgR proteins of the C. jejuni Turkey and CS isolates. Complementation of the C. jejuni CS isolate with a wild-type copy of the flgR gene restored the isolate's motility. Collectively, these findings support the hypothesis that critical differences in gene content or gene expression can alter the pathogenic potential of C. jejuni isolates.

Correlation Between In Vitro Secretion of Virulence-Associated Proteins of Campylobacter jejuni and Colonization of Chickens

The mechanisms used by Campylobacter jejuni to colonize the (chicken) intestinal tract have not been defined. In this study, we obtained evidence that in the presence of chicken serum and mucus, C. jejuni secreted proteins that may play a role in the colonization of chicken gut (Campylobacter invasion antigen = Cia). C. jejuni strains NCTC11168V1 and 81-176, as well as an NCTC11168V1 flaA mutant, were found to colonize intestinal tract and secrete proteins in the presence of chicken mucus, chicken serum, or fetal bovine serum in cell culture-conditioned medium. C. jejuni strain NCTC11168V26, which was observed to be a poor colonizer compared with the other C. jejuni isolates, did not secrete Cia proteins. Secreted proteins were also recognized by Western immunoblot using sera from birds that had been colonized by C. jejuni. These data suggest that C. jejuni secretes Cia proteins during colonization of chicken gut and that these Cia proteins play an important role in colonization.

Secretion of virulence proteins from Campylobacter jejuni is dependent on a functional flagellar export apparatus

Campylobacter jejuni, a gram-negative motile bacterium, secretes a set of proteins termed the Campylobacter invasion antigens (Cia proteins). The purpose of this study was to determine whether the flagellar apparatus serves as the export apparatus for the Cia proteins. Mutations were generated in five genes encoding three structural components of the flagella, the flagellar basal body (flgB and flgC), hook (flgE2), and filament (flaA and flaB) genes, as well as in genes whose products are essential for flagellar protein export (flhB and fliI). While mutations that affected filament assembly were found to be nonmotile (Mot-) and did not secrete Cia proteins (S-), a flaA (flaB+) filament mutant was found to be nonmotile but Cia protein secretion competent (Mot-, S+). Complementation of a flaA flaB double mutant with a shuttle plasmid harboring either the flaA or flaB gene restored Cia protein secretion, suggesting that Cia export requires at least one of the two filament proteins. Infection of INT 407 human intestinal cells with the C. jejuni mutants revealed that maximal invasion of the epithelial cells required motile bacteria that are secretion competent. Collectively, these data suggest that the C. jejuni Cia proteins are secreted from the flagellar export apparatus.

Immunoproliferative small intestinal disease associated with Campylobacter jejuni

BACKGROUND

Immunoproliferative small intestinal disease (also known as alpha chain disease) is a form of lymphoma that arises in small intestinal mucosa-associated lymphoid tissue (MALT) and is associated with the expression of a monotypic truncated immunoglobulin alpha heavy chain without an associated light chain. Early-stage disease responds to antibiotics, suggesting a bacterial origin. We attempted to identify a causative agent.

METHODS

We performed polymerase chain reaction (PCR), DNA sequencing, fluorescence in situ hybridization, and immunohistochemical studies on intestinal-biopsy specimens from a series of patients with immunoproliferative small intestinal disease.

RESULTS

Analysis of frozen intestinal tissue obtained from an index patient with immunoproliferative small intestinal disease who had a dramatic response to antibiotics revealed the presence of Campylobacter jejuni. A follow-up retrospective analysis of archival intestinal-biopsy specimens disclosed campylobacter species in four of six additional patients with immunoproliferative small intestinal disease.

CONCLUSIONS

These results indicate that campylobacter and immunoproliferative small intestinal disease are associated and that C. jejuni should be added to the growing list of human pathogens responsible for immunoproliferative states.

Long-term antibody responses following human infection with Campylobacter jejuni

Epidemiological evidence suggests prior infection of humans by Campylobacter jejuni leads to protection against disease following further exposure. It is known that infections elicit strong antibody responses following the onset of disease and that antibody levels are elevated in putatively immune populations. To determine if systemic and mucosal antibodies induced by a confirmed infection remain at elevated levels for prolonged periods, repeat serum, saliva and urine samples were taken from campylobacter patients from 1 week and up to a year postinfection. Antibodies were monitored by ELISAs using three different antigen preparations: acid-glycine extracts (AE) of C. jejuni strain 81116 and an aflagellate mutant (R2), and a whole-cell R2 sonicate, and by Western blotting. Levels of serum IgG antibodies against 81116AE and R2 sonicate, but not R2AE, remained significantly raised over time when compared to a comparison population. Serum anti-sonicate IgA antibody levels were initially significantly raised but decreased over time to levels similar to the comparison group. There were no significant differences in levels of salivary IgA against the AEs. Anti-sonicate salivary IgA and IgG levels were initially significantly higher than in the comparison group. Both declined over time but the IgG levels remained significantly higher. Significant correlations were seen between serum IgG levels and age and duration of illness. Serum antibodies against flagellin, 40 kDa and 29 kDa antigens were still detectable in most patients up to a year postinfection, as were salivary antibodies to flagellin, the major outer-membrane protein and a 40 kDa antigen.

Restriction fragment length polymorphism of polymerase chain reaction products applied to the differentiation of poultry campylobacters for epidemiological investigations

A technique for subtyping Campylobacter jejuni isolates has been developed by using the restriction fragment length polymorphism (RFLP) of polymerase chain reaction (PCR) products of the flaA and flaB genes. The technique was validated by using strains representing 28 serotypes of C jejuni and it may also be applied to C coli. From these strains 12 distinct RFLP profiles were observed but there was no direct relationship between the RFLP profile and the serotype. One hundred and thirty-five campylobacter isolates from 15 geographically distinct broiler flocks were investigated. All the isolates could be subtyped by using the RFLP method. Isolates from most of the flocks had a single RFLP profile despite data indicating that several serotypes were involved. Although it is possible that further restriction analysis may have demonstrated profile variations in these strains, it is more likely that antigenic variation can occur within genotypically related campylobacters. As a result, serotyping may give conflicting information for veterinary epidemiological purposes. This RFLP typing scheme appears to provide a suitable tool for the investigation of the sources and routes of transmission of campylobacters in chickens.

Functions of bacterial flagella

Many bacterial species are motile by means of flagella. The structure and implantation of flagella seems related to the specific environments the cells live in. In some cases, the bacteria even adapt their flagellation pattern in response to the environmental conditions they encounter. Swarming cell differentiation is a remarkable example of this phenomenon. Flagella seem to have more functions than providing motility alone. For many pathogenic species, studies have been performed on the contribution of flagella to the virulence, but the result is not clear in all cases. Flagella are generally accepted as being important virulence factors, and expression and repression of flagellation and virulence have in several cases been shown to be linked. Providing motility is always an important feature of flagella of pathogenic bacteria, but adhesive and other properties also have been attributed to these flagella. In nonpathogenic bacterial colonization, flagella are important locomotive and adhesive organelles as well. In several cases where competition between several bacterial species exists, motility by means of flagella is shown to provide a specific advantage for a bacterium. This review gives an overview of studies that have been performed on the significance of flagellation in a wide variety of processes where flagellated bacteria are involved.

Analysis of flagellin gene expression in flagellar phase variants of Campylobacter jejuni 81116

Flagella production in Campylobacter jejuni 81116 is subject to phase variation; the bacterium is able to switch its flagellum synthesis, and thereby its motility, on and off. Under standard laboratory growth conditions flagellar phase variants can be maintained as stable, pure cultures. We found conditions that efficiently induced a phase shift in vitro. The flaA gene but not the flaB gene is subject to the on and off switch. Minor amounts of FlaB are still present in aflagellate cells. We previously showed that flagellin gene expression in phase variants was regulated at the transcriptional level. Here, sequence data prove that abolishment of flaA transcription is not caused by DNA rearrangements or mutations within the flagellin locus. Since flaA is preceded by a typical sigma 28 promoter a C. jejuni sigma 28 homolog could play a role in regulation of flaA gene expression but such a gene or protein could not be detected. However, in vitro transcription could be detected using sigma 28-holoenzyme preparations from Bacillus subtilis. Possible regulatory mechanisms that may control flagellar phase variation in Campylobacter are discussed.

Differential flagellin expression in a flaA flaB+ mutant of Campylobacter jejuni

Campylobacter jejuni 81116 has two genes coding for flagellin, flaA and flaB. Fully motile wild-type C. jejuni bacteria express the flaA gene, with no flaB message being detected. A nonmotile flaA flaB+ mutant, R1, produced detectable levels of flagellin B which was incorporated into truncated flagella. After R1 had invaded INT-407 cells, a variant with increased motility, R1-V2, was isolated. R1-V2 produced full-length flagella and an increased amount of flagellin B. Transcriptional analysis showed that R1-V2 contained more flaB mRNA than its parental strain, R1. The flaB gene promoter sequence and primer extension experiments confirmed that transcription of the flaB gene is initiated from a sigma 54 promoter. Neither the promoter sequence nor the coding sequence of flaB had changed in R1-V2. In contrast to R1, R1-V2 no longer produced (truncated) flaA mRNA. The sigma 28 flaA promoter sequence was not changed in R1-V2. We propose that expression of the two flagellin genes in C. jejuni 81116 is regulated at the transcriptional level, in such a way that predominantly one gene at a time is transcribed. We compared the levels of invasiveness of the wild-type strain, R1, and R1-V2 for INT-407 cells. The shift in expression from flaA to flaB occurred not only during invasion assays but also under different conditions in the absence of eukaryotic cells.

Biochemical and antigenic properties of the Campylobacter flagellar hook protein

The flagellar filament-hook complex was removed from Campylobacter cells by shearing and was purified by differential solubilization and ultracentrifugation at pH 11 followed by cesium chloride buoyant density ultracentrifugation. Flagellar filaments were then dissociated in 0.2 M glycine-HCl (pH 2.2), and purified hooks were collected by ultracentrifugation. The hooks (105 by 24 nm) each displayed a conical protrusion at the proximal end, a concave cavity at the distal end, and helically arranged subunits. The apparent subunit molecular weight of the hook protein of seven of the eight Campylobacter strains studied was 92,500, while that of the other was 94,000. N-terminal amino acid analysis of the hook protein of two strains of Campylobacter coli and one strain of Campylobacter jejuni demonstrated that the first 15 residues were identical. Amino acid composition analysis showed that the Campylobacter hook protein contained 35.7% hydrophobic and 9.5% basic residues. Isoelectric focusing determined that the hook protein was acidic, with a pI of 4.9. Comparisons with the Salmonella and Caulobacter hook protein compositions and N-terminal amino acid sequences indicated that the Campylobacter protein was related, but more distantly than these two proteins were to each other. Immunochemical analysis with four different antisera and a panel of eight strains showed that serospecific epitopes were immunodominant. The Campylobacter hook proteins carried both cross-reactive and specific non-surface-exposed epitopes, as well as serospecific epitopes which were exposed on the surface of the assembled hook. One class of these surface-exposed hook epitopes was shared with serospecific flagellin epitopes and may involve posttranslational modification, while the second class of epitopes was hook specific and not shared with flagellin.

Analysis of the role of flagella in the heat-labile Lior serotyping scheme of thermophilic Campylobacters by mutant allele exchange

Flagellin mutations originally constructed in Campylobacter coli VC167 (serotype LIO8) by a gene replacement mutagenesis technique (P. Guerry, S. M. Logan, S. Thornton, and T. J. Trust, J. Bacteriol. 172:1853-1860, 1990) were moved from the original host into Campylobacter strains of a number of other Lior serogroups by a natural transformation procedure. This is the first report of the use of this transformation method to transfer a mutated locus among Campylobacter strains. Flagellin mutants were constructed in a number of heat-labile LIO serotypes and were serotyped and analyzed by immunoelectron microscopy with LIO typing antisera. In six cases, isogenic nonflagellated mutants were able to be serotyped in the same serogroup as their parent, and immunogold electron microscopy confirmed that antibodies in the typing antisera bound to components on the surface of both parent and mutant cells. However, in only one case, a strain belonging to serogroup LIO4, was a nonflagellated mutant untypeable, and immunogold electron microscopy showed that antibodies bound to the flagella filament of the parent but not to the cell surface. Furthermore, after introduction and expression as a flagellar filament of a LIO8 flagellin gene in this mutant, the strain could not be serotyped. These results indicate that a nonflagellar antigen is often the serodeterminant in the heat-labile Lior serotyping scheme.

Inactivation of Campylobacter jejuni flagellin genes by homologous recombination demonstrates that flaA but not flaB is required for invasion

The role of the Campylobacter jejuni flagella in adhesion to, and penetration into, eukaryotic cells was investigated. We used homologous recombination to inactivate the two flagellin genes flaA and flaB of C. jejuni, respectively. Mutants in which flaB but not flaA is inactivated remain motile. In contrast a defective flaA gene leads to immotile bacteria. Invasion studies showed that mutants without motile flagella have lost their potential to adhere to, and penetrate into, human intestinal cells in vitro. Invasive properties could be partially restored by centrifugation of the mutants onto the tissue culture cells, indicating that motility is a major, but not the only, factor involved in invasion.

Significance of flagella in colonization resistance of rabbits immunized with Campylobacter spp

Cross-protection among different Lior and Penner serogroups of Campylobacter spp. was studied. Rabbits were orally immunized by gastric feeding with Campylobacter spp., and 27 to 30 days later, they were challenged with matched or unmatched serogroups by the removable intestinal tie adult rabbit diarrhea (RITARD) procedure. When immunized animals were challenged with different Lior serotypes, no protection against colonization was seen; however, when challenged with homologous Lior serogroups, protection was demonstrated. Immune animals were colonized for an average of 1 day or less versus at least 6 days for nonimmune animals. Rabbits challenged with matched Penner-unmatched Lior strains showed only marginal protection. Our study also demonstrated that flagella are important in initiating colonization and eliciting protective immunity. Campylobacter coli VC167B3, an isogenic, nonflagellated mutant, did not colonize rabbits regardless of the route of administration. Single feeding of the mutant strain did not protect the host, whereas three feedings, 48 h apart, resulted in complete protection against the flagellated parent strain. When mutant strain immunized rabbits were challenged with other strains of the same Lior serotype, marginal protection was obtained. Immunogold labeling indicated that there is one or more antigens on the cell surface of the nonflagellated mutant which reacts with a polyclonal antiserum from organisms of the same Lior serogroup. These data implicated the flagellum as the cross-strain protective component of the Lior antigen complex.

Localization of immunogenic regions on the flagellin proteins of Campylobacter jejuni 81116

The purpose of this study was to localize antigenic regions on the flagellin protein of Campylobacter jejuni 81116. This strain has two flagellin genes, flaA and flaB, which are 95% identical; only flaA seems to be expressed in motile C. jejuni 81116 cells. Fragments of flaA and flaB were cloned in the bacterial expression vector pEX, and the expression products were incubated with flagellin-specific antibodies. Monoclonal antibodies to broadly cross-reactive epitopes recognized fragments that are located in the termini (CF16 and CF17) and in the center (CF15) of both flagellin A and B proteins. Most of the serotype-specific monoclonal antibodies (CF1, CF2, CD3, CF4, and CF13) reacted with only the center of flagellin A in an area where flagellin A and B differ in 6 amino acid residues. The epitopes in this area were further characterized by competitive binding experiments. The charge and molecular weight microheterogeneity of flagellin, as determined by two-dimensional gel electrophoresis, were unrelated to the expression of both flagellin genes or parts thereof.

Antigenicity of fractions of Helicobacter pylori prepared by fast protein liquid chromatography and urease captured by monoclonal antibodies

The antigenicity of Helicobacter pylori protein fractions separated by fast protein liquid chromatography size exclusion was investigated by EIA with sera from patients of well defined Helicobacter pylori status. The antigenic material of Helicobacter pylori was confined to fractions 8 and 14 to 21. Urease containing fractions (14/15) and flagella containing fractions (17/18) were identified. Fraction 8 non-specifically bound human immunoglobulin as demonstrated by the binding of Helicobacter pylori negative sera. The remaining fractions 14 to 21 when used individually as EIA antigens were 91-100% specific, however fractions 16 to 19 showed a reduced sensitivity (78%) compared with the acid extract (95%). The urease fractions were 91% sensitive. Purified urease antigen captured by antiurease monoclonal antibodies was 83% sensitive and 93.3% specific.

Polynucleotide sequence relationships among flagellin genes of Campylobacter jejuni and Campylobacter coli

DNA probes that encode a complete flagellin gene and various internal regions of the Campylobacter coli VC167 flagellin genes were hybridized to 30 strains of C. coli or C. jejuni from 20 different Lior serogroups. The results indicated a high overall degree of homology among all of the strains examined. Although the most variable regions occurred within the middle of the gene, significant DNA homology was observed among many serogroups in this region of the molecule.

Infection of adult Syrian hamsters with flagellar variants of Campylobacter jejuni

Two variants of Campylobacter jejuni IN1 differing in the expression of flagella, IN1 (Fla+ Mot+, wild type) and IN1-NM (Fla- Mot-), were tested for their ability to establish infection in adult hamsters. Animals were challenged intracecally with 2 X 10(9) to 5 X 10(10) CFU and monitored for evidence of infection. None of the challenged animals developed illness. There was a significant difference, however, in the ability of IN1 to infect hamsters (35 of 43) compared with that of IN1-NM (1 of 42) (P less than 0.01). Additionally, eight animals challenged with IN1-NM excreted only the campylobacters of Fla+ phenotype, which were shown to be identical with the parental Fla+ Mot+ type. Both groups of animals developed serum immunoglobulin G antibodies to outer membrane proteins of IN1 as measured by an enzyme-linked immunosorbent assay; however, only animals that excreted Fla+ organisms developed antiflagellin antibodies. In vitro reversibility from Fla+ to Fla- occurred with a frequency of 9.2 X 10(-6) per cell per generation; however, reversion from Fla- to Fla+ could not be detected in vitro. Further characterization of IN1-NM showed that it produced a cytoplasmic 62K flagellin subunit protein, but this protein lacked six epitopes detected in IN1 and also differed in its two-dimensional gel electrophoresis pattern. The results of these studies support the concept that an intact flagellum is necessary for intestinal infection with C. jejuni and that this model may be useful for studying the immune response to C. jejuni.

Genomic organization and expression of Campylobacter flagellin genes

Campylobacter coli VC167, which undergoes an antigenic flagellar variation, contains two full-length flagellin genes, flaA and flaB, that are located adjacent to one another in a tandem orientation and are 91.5% homologous. The gene product of flaB, which has an Mr of 58,946, has 93% sequence homology to the gene product of flaA, which has an Mr of 58,916 (S. M. Logan, T. J. Trust, and P. Guerry, J. Bacteriol. 171:3031-3038, 1989). Mutational analyses and primer extension experiments indicated that the two genes are transcribed under the control of distinct promoters but that they are expressed concomitantly in the same cell, regardless of the antigenic phase of flagella being produced. The flaA gene, which was expressed at higher levels than the flaB gene in both phases, was transcribed from a typical sigma 28-type promoter, whereas the flaB promoter was unusual. A mutant producing only the flaB gene product did not synthesize a flagellar filament and was nonmotile. Southern blot analysis indicated that flagellar antigenic variation involves a rearrangement of flagellin sequence information rather than the alternate expression of the two distinct genes.

Detection of salmonellas in animal feeds by electrical conductance

A comparison was made between standard culture methods and electrical conductance using a Malthus AT Microbiological Analyser for the examination of animal feeds for salmonella. Conductance testing with a selenite cystine/trimethylamine-N-oxide/dulcitol medium resulted in the detection of salmonellas in 49 of 55 known positive animal feeds, 13 of 19 spiked feed samples and 36 of 47 salmonella cultures. Testing with a lysine decarboxylase/glucose medium gave significantly better results (P less than 0.05) than with selenite cystine medium but five lysine decarboxylase negative strains of salmonella were undetected. When both media were used in parallel all salmonella positive samples were detected. No difference was found between preenrichment in buffered peptone water containing trimethylamine/mannitol and that containing lysine/glucose. Positive detection criteria for selenite medium of conductance peak at greater than or equal to 500 microsiemens (microS) with a rate of change of greater than or equal to 60 microS/h or 400-499 microS with a rate of change of greater than or equal to 40 microS/h and for lysine medium with a peak of greater than or equal to 100 microS have been established. The method offers savings in media and operating costs over conventional standard culture methods, provides results within 48 h and is recommended for statutory feed monitoring purposes.

In vivo antigenic variation of Campylobacter flagellin

Campylobacter coli VC167 cells producing either antigenic phase 1 (P1) or phase 2 (P2) flagellins (as determined by characteristic protein and DNA patterns) were used to infect rabbits by the removable intestinal tie-adult rabbit diarrhea (RITARD) procedure. Rabbits infected with P2 cells shed predominantly P2 cells throughout the infection; in rabbits infected with P1 cells, a transition of fecal isolates from P1 to P2 was observed.

A two-year study of the distribution of 'thermophilic' campylobacters in human, environmental and food samples from the Reading area with particular reference to toxin production and heat-stable serotype

The incidence of 'thermophilic' campylobacters in foods and environmental samples has been studied over a two-year period. Of 781 environmental samples, 529 (67%) were found to contain campylobacters, and campylobacters were isolated from 835 (39%) of 2116 food samples. Sewage was almost always contaminated with campylobacters (96.6% of samples) and of the food samples both poultry (55.5%) and offal (47.0%) were commonly contaminated. Determination of the heat-stable serotypes of all strains isolated from these sources and of 921 strains isolated from human faeces showed that there was a wide distribution of serotypes in most types of sample. Serotype Pen 2 was the commonest type found in human faeces (18.9%) and it was also commonest in offal (21.3%), beef (40.0%), sewage (17.7%) and was the third commonest type in poultry. A comparison of culture media and conditions for optimal production of both cytotoxic and cytotonic enterotoxins showed that Brucella Broth incubated under microaerobic conditions for 24 h at 42 degrees C was suitable for both toxins. Detection of cytotoxic activity was most sensitive using HeLa cells. The sensitivities of two ELISA systems and a Chinese Hamster Ovary tissue culture assay for detection of cytotonic enterotoxin were comparable. Not all strains isolated from cases of enteritis in human beings produced toxin; 23.1% produced cytotonic enterotoxin and 17.5% produced cytotoxin. There was no correlation between serotype and toxin production. The wide distribution of campylobacters, indistinguishable from those isolated from cases of enteritis in human beings, leads us to conclude that simplistic statements suggesting that one particular type of food is primarily responsible for cases of human disease should not be made.

In vitro binding of Campylobacter jejuni surface proteins to murine small intestinal cell membranes

Surface proteins of nine Campylobacter jejuni strains belonging to three different serovia were extracted with lysozyme/ethylenediamine-tetraacetic acid. The preparations bound to isolated murine small intestinal cells and to a membrane fraction (MF) of isolated brush borders obtained by detergent treatment with Triton X-100 and Nonidet P40. Binding was demonstrated by an enzyme-linked immunosorbent assay procedure. Using lipopolysaccharide (LPS)- and flagella-specific antisera the contribution of flagella and LPS, present in the protein preparations, to the total binding to MF was investigated. Only up to approximately 10% of the total binding of each strain was found to be mediated by LPS, 10%-33% of binding was flagella dependent. The preparations of four strains (serovar HS2) bound in a trypsin-sensitive manner (45%-85% reduction), while the others (serovaria HS1 and HS13) were hardly influenced by trypsin treatment. Binding to MF was not impaired by preincubation of the bacterial surface protein preparations with several sugars and lectins.

Evidence for posttranslational modification and gene duplication of Campylobacter flagellin

A gene encoding a flagellin protein of Campylobacter coli VC167 has been cloned and sequenced. The gene was identified in a pBR322 library by hybridization to a synthetic oligonucleotide probe corresponding to amino acids 4 to 9 of the N-terminal sequence obtained by direct chemical analysis (S. M. Logan, L. A. Harris, and T. J. Trust, J. Bacteriol. 169:5072-5077, 1987). The DNA was sequenced and shown to contain an open reading frame encoding a protein with a molecular weight of 58,945 and a length of 572 amino acids. The deduced amino acid sequence was identical to the published N-terminal amino acid sequence of VC167 flagellin and to four internal regions whose partial sequences were obtained by direct chemical analysis of two tryptic and two cyanogen bromide peptides of VC167 flagellin. The C. coli flagellin protein contains posttranslationally modified serine residues, most of which occur within a region containing two 9-amino-acid repeating peptides separated by 34 unique amino acids. Comparisons with the sequences of flagellins from other bacterial species revealed conserved residues at the amino- and carboxy-terminal regions. Hybridization data suggest the presence of a second flagellin copy located adjacent to the first on the VC167 chromosome.

Flagellin expression in Campylobacter jejuni is regulated at the transcriptional level

Campylobacter jejuni 81116 is able to switch flagellum formation on and off. To study the expression of flagellin, the main component of flagella, an expression library of C. jejuni DNA was constructed in lambda gt11. Screening of this library with a flagellin-specific antiserum resulted in a clone producing a beta-galactosidase-flagellin fusion protein; it contained a DNA insert of 850 base pairs and coded for about 15 kilodaltons of the flagellin, corresponding to 410 base pairs of the flagellin gene. To study the regulation of the on-and-off switch of flagellum production, a nonmotile variant was isolated from semisolid medium. Western blots (immunoblots) showed the absence of flagellin in the nonmotile form. Southern blots of digested DNA of both motile, flagellate bacteria and nonmotile, aflagellate bacteria were identical, while Northern (RNA) blot analysis showed the absence of flagellin mRNA in the aflagellate form. Thus, it is concluded that reversible flagellin expression is regulated at the transcriptional level. Southern blots suggest that more than one flagellin gene is present. The structure and function of campylobacter flagellin can now be further investigated at the DNA level.

Antigenic analysis of Campylobacter species and an intracellular Campylobacter-like organism associated with porcine proliferative enteropathies

Whole-cell and outer membrane preparations of Campylobacter mucosalis, C. hyointestinalis, C. jejuni, and C. coli isolated from porcine intestines were compared with preparations of intracellular Campylobacter-like organisms extracted directly from the lesions of pigs with proliferative enteropathy. By gradient polyacrylamide gel electrophoresis, outer membrane and total protein profiles of C. mucosalis, C. hyointestinalis, C. jejuni, and C. coli were significantly different from each other and from those of the Campylobacter-like organisms. Immunoblotting of these preparations with rabbit antisera or monoclonal antibodies prepared against the intracellular Campylobacter-like organisms showed strong reactions only with a 25,000- to 27,000-molecular-weight component of preparations of the intracellular organisms. Antisera to cultivable Campylobacter species isolates did not react with preparations of intracellular organisms. Isoelectric focusing of sonicated preparations showed protein profile differences and an immune-reactive component in the intracellular organisms with a pI of 4.5. This study suggests that the intracellular Campylobacter-like organism associated with proliferative enteropathy may be a novel bacterium with significant antigenic differences from the Campylobacter species previously associated with the disease.

MHC class I and class II antigen expression in normal human corneas and in corneas from cases of herpetic keratitis

The expression of HLA class I and class II antigens in corneas from normal donors and patients with quiescent herpetic keratitis was investigated using specific monoclonal antibodies. Keratocytes from diseased corneas showed aberrant expression of HLA class I and class II (DR, DP and DQ) antigens. The expression of HLA antigens in these corneas was not associated with immune cell infiltrates or viral antigens.

Characterization of flagella purified from enterohemorrhagic, vero-cytotoxin-producing Escherichia coli serotype O157:H7

Escherichia coli of the serotype O157:H7 has recently been isolated in human fecal specimens in association with sporadic cases and outbreaks of hemorrhagic colitis and with the hemolytic uremic syndrome. The aim of this study was to characterize the flagellin protein subunit constituents of flagellar filaments from E. coli O157:H7 strain CL-56. Flagellin isolated from a reference Salmonella enteritidis strain was used for comparison. Flagella were dissociated by incubation of bacteria under acidic conditions, centrifugation, and differential ammonium sulfate precipitation. Reconstituted flagellar filaments were demonstrated by three complementary methods: transmission electron microscopy, antigenic reactivity with H7 antiserum by a dot blot immunoassay, and immunogold localization of antiserum raised to the purified antigen to intact flagella on whole E. coli O157:H7. On sodium dodecyl sulfate-polyacrylamide gels flagellin proteins from E. coli O157:H7 demonstrated an apparent Mr of 66,000. The isoelectric point of E. coli O157:H7 flagellin was 5.42. By immunoblotting, H7 flagellin proteins were shown to be immunogenic. They induced a systemic immune response both in rabbits challenged with whole bacteria and in a human previously infected with E. coli O157:H7.

Protection against Campylobacter jejuni infection in suckling mice by anti-flagellar antibody

We obtained two monoclonal antibodies of IgM class and IgA class of immunoglobulin prepared from mouse spleen cells immunized with crude flagellar preparation, and a polyclonal antibody raised against purified flagellin monomer of Campylobacter jejuni in a rabbit. The specificity of the reaction of these antibodies for flagellar filament was confirmed by Western blotting and by immunoelectron microscopy. These antibodies caused agglutination of the bacteria and inhibited the motility of the bacteria. When a strain of C. jejuni was treated with IgM class monoclonal antibody before being inoculated into suckling mice, it reduced colonization of the intestinal tract by this bacteria. Inhibition of the colonization by IgA class monoclonal antibody was less effective than that of IgM class, and the polyclonal antibody consisting mostly of IgG class immunoglobulin was without effect.

Antigenic variation of Campylobacter flagella

Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of flagella dissociated from strains of Campylobacter coli and Campylobacter jejuni belonging to the heat-labile serogroup LIO 8 showed that some strains were capable of producing flagellin subunits of two different molecular weights (MrS), 59,500 and 61,500. Immunoelectron microscopy of cultures of the type strain of this serogroup, C. coli VC167, showed the presence of two flagellum filaments of different antigenic specificity. Epitopes on the surface of one of these flagella bound antibodies in LIO 8 typing antiserum, and Western blotting (immunoblotting) and immunoprecipitation showed that the flagellum was composed of flagellin of Mr 61,500. The other flagellum antigenic type did not bind LIO 8 antibodies but did possess serospecific epitopes which bound a second polyclonal antiserum, LAH2. This second antigenic flagellum type was composed of the Mr 59,500 flagellin. Cells producing either of the flagellum antigenic types serotyped as LIO 8, indicating that flagella composed of the Mr 61,500 flagellin do not carry the serological determinants for this serogroup. The ability of C. coli VC167 to produce these flagella of different subunit MrS was shown to represent a bidirectional antigenic variation. When measured in culture medium, the phase 1-to-phase 2 transition occurred at a rate of approximately 2.0 x 10(-5) per cell per generation, and the phase 2-to-phase 1 transition occurred at a rate of 1.2 x 10(-6) per cell per generation.