Cloning and characterization of Treponema hyodysenteriae antigens and protection in a CF-1 mouse model by immunization with a cloned endoflagellar antigen

Brachyspira hyodysenteriae and B. pilosicoli Proteins Recognized by Sera of Challenged Pigs

The spirochetes Brachyspira hyodysenteriae and B. pilosicoli are pig intestinal pathogens that are the causative agents of swine dysentery (SD) and porcine intestinal spirochaetosis (PIS), respectively. Although some inactivated bacterin and recombinant vaccines have been explored as prophylactic treatments against these species, no effective vaccine is yet available. Immunoproteomics approaches hold the potential for the identification of new, suitable candidates for subunit vaccines against SD and PIS. These strategies take into account the gene products actually expressed and present in the cells, and thus susceptible of being targets of immune recognition. In this context, we have analyzed the immunogenic pattern of two B. pilosicoli porcine isolates (the Spanish farm isolate OLA9 and the commercial P43/6/78 strain) and one B. hyodysenteriae isolate (the Spanish farm V1). The proteins from the Brachyspira lysates were fractionated by preparative isoelectric focusing, and the fractions were analyzed by Western blot with hyperimmune sera from challenged pigs. Of the 28 challenge-specific immunoreactive bands detected, 21 were identified as single proteins by MS, while the other 7 were shown to contain several major proteins. None of these proteins were detected in the control immunoreactive bands. The proteins identified included 11 from B. hyodysenteriae and 28 from the two B. pilosicoli strains. Eight proteins were common to the B. pilosicoli strains (i.e., elongation factor G, aspartyl-tRNA synthase, biotin lipoyl, TmpB outer membrane protein, flagellar protein FlaA, enolase, PEPCK, and VspD), and enolase and PEPCK were common to both species. Many of the identified proteins were flagellar proteins or predicted to be located on the cell surface and some of them had been previously described as antigenic or as bacterial virulence factors. Here we report on the identification and semiquantitative data of these immunoreactive proteins which constitute a unique antigen collection from these bacteria.

Swine dysentery: aetiology, pathogenicity, determinants of transmission and the fight against the disease

Swine Dysentery (SD) is a severe mucohaemorhagic enteric disease of pigs caused by Brachyspira hyodysenteriae, which has a large impact on pig production and causes important losses due to mortality and sub-optimal performance. Although B. hyodysenteriae has been traditionally considered a pathogen mainly transmitted by direct contact, through the introduction of subclinically infected animals into a previously uninfected herd, recent findings position B. hyodysenteriae as a potential threat for indirect transmission between farms. This article summarizes the knowledge available on the etiological agent of SD and its virulence traits, and reviews the determinants of SD transmission. The between-herds and within-herd transmission routes are addressed. The factors affecting disease transmission are thoroughly discussed, i.e., environmental survival of the pathogen, husbandry factors (production system, production stage, farm management), role of vectors, diet influence and interaction of the microorganism with gut microbiota. Finally, prophylactic and therapeutic approaches to fight against the disease are briefly described.

Identification of the gene encoding BmpB, a 30 kDa outer envelope lipoprotein of Brachyspira (Serpulina) hyodysenteriae, and immunogenicity of recombinant BmpB in mice and pigs

A gene encoding a 30kDa outer envelope protein of the intestinal spirochaete Brachyspira (Serpulina) hyodysenteriae, was cloned and expressed in Escherichia coli strain XLOLR. Five phagemids containing DNA inserts encoding the protein were established and one clone (pSHA) was sequenced. An 816bp hypothetical open reading frame (ORF) was identified, with a potential ribosome binding site (AGGAG), and putative -10 (TATAAT) and -35 (TTGAAA) promoter regions upstream from the ATG start of the ORF. A 12bp inverted repeat sequence, possibly serving as a transcription terminator, was identified downstream from the TAA stop codon. Analysis of the amino acid sequence identified a 19 residue hydrophobic signal peptide, incorporating a potential signal peptidase cleavage site and membrane lipoprotein lipid attachment site. Further analysis of the amino acid usage of this lipoprotein, designated BmpB, showed its possible outer membrane localisation. Comparison of the gene encoding the lipoprotein, bmpB, with GenBank nucleotide sequences showed that it has homology with the gene (plp3) encoding Plp3, an outer membrane lipoprotein of Pasteurella haemolytica (54% identity in 735bp). Comparison of the deduced amino acid sequence with the SWISS-PROT amino acid database revealed greatest homology with the outer membrane lipoproteins (Plp1, 2, 3) of P. haemolytica (34% identity in 242 aa, 37% identity in 250 aa, and 39% identity in 272 aa, respectively), and lipoproteins (rcsF and lipoprotein-28) of E. coli (40% identity in 267 aa and 36% identity in 263 aa, respectively). Three of the recombinant E. coli clones (pSHA, pSHD, and pSHE) were formalinised and used to immunise mice. A bacterin preparation of one recombinant E. coli clone (pSHA) was used to immunise pigs. Sera from these mice and pigs recognised the 30kDa lipoprotein in outer membrane preparations of B. hyodysenteriae, indicating the immunogenicity of recombinant BmpB. Sera from pigs naturally infected with B. hyodysenteriae also reacted with recombinant BmpB expressed in E. coli.

Flagellins, but not endoflagellar sheath proteins, of Treponema pallidum and of pathogen-related oral spirochetes are glycosylated

Glycosylation of the flagellar core proteins (FlaBs) was detected in Treponema pallidum Nichols and in the type or reference strains of seven oral Treponema species. In several nonmotile strains of oral treponemes, the FlaBs were undetectable by both antibody and glycan staining. In contrast, a spontaneous low-motility variant of T. vincenti poundi-related strain RitzA, OMZ 305A, lacked the flagellar sheath protein (FlaA) and the two glycan-staining FlaB bands of the wild type, but antibody labeling revealed a novel FlaB band with a lower relative molecular weight. A ca. 38-kDa component of isolated endoflagella of T. vincentii OMZ 800 was identified on Western blots as FlaA by monoclonal antibody (MAb) H9-2, which specifically labels the 37-kDa FlaA protein of T. pallidum. Glycan and H9-2 labeling patterns similar to those of T. pallidum were observed in whole-cell extracts of T. medium G7201 and of 10 strains classified as T. vincentii and as two T. vincentii-related taxons. These four groups were thus identified as cultivable pathogen (T. pallidum)-related oral spirochetes as defined by labeling with MAb H9-2. No H9-2 MAb-reactive component could be detected in T. amylovorum, T. denticola, T. maltophilum, T. pectinovorum, and the three subspecies of T. socranskii.

Presence of 22- and 17-kDa proteins reacting with sera in mice experimentally infected with Brachyspira (Serpulina) hyodysenteriae

The antibodies to B. (S.)hyodysenteriae in experimentally infected mice were detected by microscopic agglutination test (MAT) and enzyme-linked immunosorbent assay (ELISA). The reactions in MAT were serotype specific while those in ELISA were common to both strains. A further investigation with immunoblotting technique demonstrated that 22- and 17-kDa proteins reacted strongly with the sera. The proteins in ATCC 27164 strain strongly reacted with the serum from ATCC 31212 strain-infected mouse and vice versa. These proteins were sensitive to proteinase K.

Production and characterization of monoclonal antibodies against Serpulina hyodysenteriae and S. innocens and their use in serotyping

Murine monoclonal antibodies (MAbs) directed against serotypes 1, 2, 8, and 9 of Serpulina hyodysenteriae and strain B256 of Serpulina innocens were produced and characterized. A serological classification of 96 field strains of S. hyodysenteriae and 28 field strains of S. innocens isolated from pigs showing clinical signs of swine dysentery was performed by rapid dot enzyme-linked immunosorbent assay (ELISA) with the MAbs. The results indicated that the majority of the field strains of S. hyodysenteriae (69%) belonged to serotypes 8, 1, and 9, whereas only 31% of the S. innocens strains were recognized by MAb 9H7, indicating the presence of antigenic heterogeneity among S. innocens isolates. Rapid dot ELISA with type-specific MAbs was found to be specific, sensitive, and easy to perform and thus to be suitable for routine serotyping of S. hyodysenteriae and S. innocens isolates. This is the first report of MAbs being used for serotyping clinical isolates of S. hyodysenteriae and S. innocens.

Isolation of extracytoplasmic proteins from Serpulina hyodysenteriae B204 and molecular cloning of the flaB1 gene encoding a 38-kilodalton flagellar protein

Extracytoplasmic proteins were released from Serpulina (Treponema) hyodysenteriae (strain B204) by treatment of whole cells with a nonionic detergent (Tween 20). Centrifugation of the Tween 20-released proteins at 100,000 x g sedimented 10 major extracytoplasmic proteins with approximate molecular masses of 44, 43.5, 42, 39, 38, 34, 33.5, 33, 31, and 29 kDa. Treatment of the sedimented fraction with 6 M urea solubilized all of the proteins except the 39-kDa protein. Peptide sequences were obtained for the purified 42-, 39-, 38-, 34-, 31-, and 29-kDa proteins. The peptide sequences of the 42-, 38-, and 31-kDa proteins indicate that they likely are components of the periplasmic flagella. The amino-terminal peptide sequence of the 38-kDa protein was used to design an oligonucleotide probe and to clone an S. hyodysenteriae DNA fragment containing the gene encoding this protein. The predicted 290-amino-acid protein sequence derived from the cloned gene was highly homologous to those of several other bacterial flagellar proteins and is preceded by consensus sigma D nucleotide sequences found upstream of other flagellar genes. On the basis of its similarity to the FlaB proteins of other spirochetes, we propose to designate the cloned S. hyodysenteriae gene flaB1 and its encoded protein FlaB1. Vaccination of pigs with FlaB1 or its recombinant counterpart did not protect them from an experimental challenge.

A species-specific periplasmic flagellar protein of Serpulina (Treponema) hyodysenteriae

We have previously reported that a 46-kDa protein present in an outer membrane protein preparation seemed to be a species-specific antigen of Serpulina hyodysenteriae (Z. S. Li, N. S. Jensen, M. Bélanger, M.-C. L'Espérance, and M. Jacques, J. Clin. Microbiol. 30:2941-2947, 1992). The objective of this study was to further characterize this antigen. A Western blot (immunoblot) analysis and immunogold labeling with a monospecific antiserum against this protein confirmed that the protein was present in all S. hyodysenteriae reference strains but not in the nonpathogenic organism Serpulina innocens. The immunogold labeling results also indicated that the protein was associated with the periplasmic flagella of S. hyodysenteriae. N-terminal amino acid sequencing confirmed that the protein was in fact a periplasmic flagellar sheath protein. The molecular mass of this protein, first estimated to be 46 kDa by Western blotting, was determined to be 44 kDa when the protein was evaluated more precisely by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and the protein was glycosylated, as determined by glycoprotein staining and also by N-glycosidase F treatment. Five other periplasmic flagellar proteins of S. hyodysenteriae, which may have been the core proteins and had molecular masses of 39, 35, 32, 30, and 29 kDa, were antigenically related and cross-reacted with the periplasmic flagellar proteins of S. innocens. Finally, serum from a pig experimentally infected with S. hyodysenteriae recognized the 44-kDa periplasmic flagellar sheath protein. Our results suggest that the 44-kDa periplasmic flagellar sheath protein of S. hyodysenteriae is a species-specific glycoprotein antigen.

Comparison of outer-membrane fractions of Serpulina (Treponema) hyodysenteriae

Sarkosyl-insoluble fractions (outer-membrane proteins) and endoflagella (EF) fractions of Serpulina hyodysenteriae serotypes 1-7 were examined for protein differences using SDS-PAGE. Both the outer-membrane proteins (OMP) and endoflagella were also examined for antigenicity using porcine sera from acutely infected and convalescent swine. Seven major staining proteins were resolved in outer-membrane enriched fractions ranging in molecular weight between 42 and 32 kDa. A comparison of purified EF to OMP from serotype 1 and 2 isolates of Serpulina hyodysenteriae demonstrated that six of the seven OMP were actually EF. Sera from swine with acute swine dysentery identified only a portion of the proteins from both preparations. In contrast, immune sera from convalescent swine identified all the proteins in the OMP and EF preparations as well as an additional 16 kDa carbohydrate antigen.

Cloning and DNA sequence analysis of a Serpulina (Treponema) hyodysenteriae gene encoding a periplasmic flagellar sheath protein

A Serpulina (Treponema) hyodysenteriae expression library was constructed in vector lambda ZAP and screened with a polyclonal antiserum raised against S. hyodysenteriae periplasmic flagella. A single immunoreactive plaque was chosen for further analysis. The recombinant phage from this plaque contained a gene encoding the 44-kDa protein that is on the outer layer (or sheath) of the periplasmic flagella. DNA sequence analysis showed that the gene encodes a protein of 320 amino acids. The protein is homologous to the flagellar sheath proteins of Treponema pallidum and Spirochaeta aurantia but not to any other flagellar proteins. We designated the cloned S. hyodysenteriae flagellar sheath protein gene flaA and the encoded protein FlaA. The 19 N-terminal amino acid residues of FlaA constitute a signal peptide that is cleaved from the protein before assembly onto the flagella in the periplasm. Amino acid residues 20 to 38 correspond to the N-terminal amino acid sequence of the native protein. Upstream from the gene, DNA motifs that are similar to the consensus Escherichia coli -35 and -10 promoter sequences and a ribosome binding site were identified. Downstream from the gene, two inverted repeat sequences that may serve as a rho-independent transcription termination signal are present.

Molecular cloning and characterization of DNA from human intestinal spirochetes

HindIII cleaved human intestinal spirochete genomic DNA was cloned into the plasmid vector pBluescript. The inserts from three of these clones (pRB.C33, pRB.C47 and pRB.F11) successfully hybridized with DNA from the nine human intestinal spirochetes used in this study. The fourth insert (from clone pRB.A8) failed to hybridize with DNA from two of these isolates (HRM4 and HRM9), and, all four of the inserts hybridized with the M1 strain of swine intestinal spirochete Treponema innocens. Hybridization with DNA from the P18 strain of Treponema hyodysenteriae was observed only for the probe pRB.F11. No hybridization was detected with the human strain of Borrelia burgdorferi. With these probes we were thus able to demonstrate, in southern blot experiments, a restriction site polymorphism among the isolates of the human intestinal spirochetes we tested.

Analysis of outer membrane ultrastructure of pathogenic Treponema and Borrelia species by freeze-fracture electron microscopy

We analyzed the outer membrane (OM) ultrastructure of four pathogenic members of the family Spirochaetaceae by freeze fracture. The OM of Treponema pallidum subsp. pertenue contained a low intramembranous particle concentration, indicating that it contains few OM transmembrane proteins. The concave OM fracture faces of Treponema hyodysenteriae and Borrelia burgdorferi contained dense populations of particles, typical of gram-negative organisms. A relatively low concentration of particles which were evenly divided between a small and a large species was present in the concave OM fracture face of Borrelia hermsii; the convex OM fracture face contained only small particles. As for gram-negative bacteria, the convex OM fracture face particle concentrations of these pathogens were low. These spirochetes cleaved preferentially within the OM, in contrast to typical gram-negative bacteria, which tend to fracture within the inner membrane. The OM ultrastructure of T. pallidum subsp. pertenue provides an explanation for the lack of antigenicity of the treponemal surface and may reflect a mechanism by which this pathogen evades the host immune response.