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Akabane virus (AKAV), belonging to the genus Orthobunyavirus and family Peribunyaviridae, causes reproductive and congenital abnormalities in ruminants. Its envelope glycoprotein Gc is a neutralizing antigen, on which at least five distinct antigenic regions have been identified. We attempted to identify the domains using truncated recombinant AKAV Gc proteins expressed in Escherichia coli and monoclonal antibodies (mAbs) with AKAV-neutralizing activity. Dot blot analysis revealed that amino acid positions 1-97 and 189-397 (Gc

We previously developed a multiplex PCR assay for the differentiation of serovar 1a, 1b, 2 and 5 strains of Erysipelothrix rhusiopathiae. In this study, we analyzed the serovar-defining chromosomal region of a serovar 2 swine isolate, which was PCR-positive for both serovars 1a and 2 by the multiplex PCR assay. Genetic analysis of the chromosomal region revealed that, as in serovar 1a strains, the ERH_1440 gene, which is usually truncated or missing in serovar 2 strains, was intact in this strain. This paper first shows an E. rhusiopathiae serovar 2 strain possessing an intact ERH_1440 gene and suggests that care may be needed when determining the serovar of such rare strains by PCR assay.

The potential role of wild boars as a source of erysipelas infection was investigated. An ELISA test of wild boar serum samples from 41 prefectures in Japan revealed that proportions of the Erysipelothrix rhusiopathiae-positive samples were very high in all the prefectures, and the mean positive rate was 95.6% (1312/1372). Serovars of E. rhusiopathiae isolates from wild boars were similar to those of previously reported swine isolates, and all serovar isolates tested were found to be pathogenic to mice. These results suggest that wild boars in Japan constitute a reservoir of E. rhusiopathiae and may pose risks to other animals.

Anti-O-antigen antibodies, such as anti-O4 antigen IgG, induce protective immunity against Salmonella enterica serovar Typhimurium (S. Typhimurium) infection. S. Typhimurium belongs to the group O4, which can be classified into two serological variants, namely factor O5 antigen positive (O5+) and factor O5 antigen negative (O5-). In this study, we determined the protective immunity induced by anti-O4 antigen IgG against O5+ and O5- S. Typhimurium infection in a mouse model. Unexpectedly, anti-O4 antigen IgG induced protection against O5- of S. Typhimurium, but not against O5+ of S. Typhimurium. We suggest that the affinity of the O4 antigen with anti-O4 antigen IgG is stronger in the O5- S. Typhimurium compared to the O5+ S. Typhimurium. Although anti-O4 antigen IgG has the potential to protect against S. Typhimurium infection, the effects of anti-O4 antigen IgG in protection against Salmonella infection differ depending on the presence or absence of the O5 antigen.

Among the four species of the genus Erysipelothrix, Erysipelothrix rhusiopathiae is the main species that causes disease in swine and poultry and has also been isolated from human patients. Recently, E. rhusiopathiae infections in domesticated animals have increased in many countries and are also the cause of emerging wildlife disease in arctic and boreal ecosystems. Historically, E. rhusiopathiae has been differentiated from other Erysipelothrix species by their serovars, which are determined based on cell wall antigens. Serotyping of Erysipelothrix is important, as specific E. rhusiopathiae serovars (1a, 1b, and 2) are associated with disease in pigs, poultry, and humans. However, serotyping is laborious and time-consuming and requires a full set of serovar reference strains and strain-specific antiserum. In this study, to develop a conventional gel-based PCR assay that can detect the main disease-associated serovars of E. rhusiopathiae, the draft genome sequences of E. rhusiopathiae strains of serovars 1a, 1b, 2, and 5, the last of which is often isolated from wild animals, were analyzed. Primers were designed based on the serovar-specific sequences of the strains and tested for field strains isolated from extensive origins. Among two hundred and ninety-seven isolates of various serovar strains of E. rhusiopathiae and other Erysipelothrix species, the PCR assay identified serovar 1a, 1b, 2, and 5 strains of E. rhusiopathiae. This conventional gel-based PCR assay should be useful for serovar surveillance of E. rhusiopathiae isolates in domesticated and wild animals as well as in humans.

The species Erysipelothrix rhusiopathiae displays genetic heterogeneity; however, E. rhusiopathiae serovar 1a strains currently circulating in Japan exhibit remarkably low levels of genetic diversity and group into clonal sublineages of Lineage IVb (IVb-1 and IVb-2). In the present study, based on whole genome sequencing data, we designed primers for a multiplex PCR assay to simultaneously detect and differentiate the sublineages of E. rhusiopathiae strains. Among the one hundred and twenty-seven isolates of various serovar strains, including isolates from a wide range of hosts and geographic origins, the PCR assay could successfully detect and differentiate the serovar 1a strains belonging to the sublineages.

Swine erysipelas is caused by the Gram-positive pathogen Erysipelothrix rhusiopathiae. The swine erysipelas live vaccine in Japan, the E. rhusiopathiae Koganei 65-0.15 strain (Koganei), has been reported to cause arthritis and endocarditis. To develop a vaccine with increased safety, we used a virulent Fujisawa strain to construct transposon mutants for a total of 651 genes, which covered 38% of the coding sequence of the genome. We screened the mutants for attenuation by inoculating mice with 10(8) CFU of each mutant and subsequently assessed protective capability by challenging the surviving mice with 10(3) CFU (10(2) times the 50% lethal dose) of the Fujisawa strain. Of the 23 attenuated mutants obtained, 6 mutants were selected and evaluated for protective capability in pigs by comparison to that of the Koganei strain. A mutant in the ERH_0432 (tagF) gene encoding a putative CDP-glycerol glycerophosphotransferase was found to be highly attenuated and to induce humoral and cell-mediated immune responses in conventional pigs. An in-frame deletion mutant of the gene, the Δ432 mutant, was constructed, and attenuation was further confirmed in germfree piglets; three of four piglets subcutaneously inoculated with 10(9) CFU of the Δ432 mutant showed no apparent clinical symptoms, whereas all four of the Koganei-inoculated piglets died 3 days after inoculation. It was confirmed that conventional pigs inoculated orally or subcutaneously with the Δ432 strain were almost completely protected against lethal challenge infection. Thus, the tagF homolog mutant of E. rhusiopathiae represents a safe vaccine candidate that can be administered via the oral and subcutaneous routes.

The surface protective antigen (Spa) protein of Erysipelothrix rhusiopathiae is an important component in protecting pigs against swine erysipelas. The Spa protein has been antigenically divided into 3 types: SpaA, SpaB, and SpaC. Swine erysipelas vaccines are formulated with strains of serovar 1 and/or 2, both of which are SpaA-possessing serovars. The association of Spa type with E. rhusiopathiae serovar has been reported, and therefore, the determination of the Spa type and the serovar of clinical isolates are important to assess vaccine efficacy. An E. rhusiopathiae strain, designated Ireland, was isolated from a diseased pig and identified as serovar 6 by a conventional agar gel precipitation test. Sequence analysis of the chromosomal locus presumably defining the serovar antigenicity of E. rhusiopathiae revealed that the gene content and organization of the chromosomal regions of the Ireland strain were identical to those of the serovar 6 reference strain (Tuzok). Sequence analysis of the spa gene and dot blots using a SpaA-specific monoclonal antibody confirmed that, unlike the Tuzok strain possessing SpaB, the Ireland strain expressed SpaA, indicating that the Spa type is not associated with the serovar in this strain. Thus, further investigation into the association between Spa type and serovar of clinical swine isolates is warranted.

Acriflavine, an acridine dye that causes frameshift mutations, has been used to attenuate various veterinary pathogens for the development of live vaccines. Erysipelothrix rhusiopathiae Koganei 65-0.15 strain (Koganei) (serovar 1a) is the acriflavine-resistant live vaccine currently used in Japan for the control of swine erysipelas. To investigate the attenuation mechanisms of the Koganei strain, we analyzed the draft genome sequence of the Koganei strain against the reference genome sequence of the E. rhusiopathiae Fujisawa strain (serovar 1a). The sequence analysis revealed a high degree of sequence similarity between the two strains and identified a total of 98 sequence differences within 80 protein-coding sequences. Among them, insertions/deletions (indels) were identified in 9 genes, of which 7 resulted in frameshift and premature termination. To investigate whether these mutations resulted in the attenuation of the Koganei strain, we focused on the indel mutation identified in ERH_0661, an XRE family transcriptional regulator. We introduced the mutation into ERH_0661 of the Fujisawa strain and restored the mutation of the Koganei strain. Animal experiments using the recombinant strains showed that mice survived inoculation with 103 colony forming units (CFUs) (equivalent to approximately 100 50% lethal doses [LD50] of the wild-type Fujisawa) of the recombinant Fujisawa strain, and the mice became ill after inoculation with 108 CFUs of the recombinant Koganei strain. These results suggest that the transcriptional regulator ERH_0661 is involved in the virulence of E. rhusiopathiae and that the ERH_0661 mutation is partially responsible for the attenuation of the Koganei strain.

Over the past decades, Erysipelothrix rhusiopathiae strains displaying similar phenotypic and genetic profiles of the attenuated, acriflavine-resistant E. rhusiopathiae Koganei 65-0.15 strain (serovar 1a) have been frequently isolated from pigs affected with chronic erysipelas in Japan. In this study, using the conventional PCR assay that was designed to detect strain-specific single nucleotide polymorphism (SNP) sites found in the genome of the vaccine strain, we analyzed E. rhusiopathiae isolates from pigs with chronic disease in farms where the Koganei vaccine was used. Out of a total of 155 isolates, 101 isolates (65.2%) were determined to be the vaccine strain by SNP-based PCR. Among the 101 PCR-positive isolates, four isolates were found to be sensitive to acriflavine.

Erysipelothrix rhusiopathiae causes swine erysipelas, an important infectious disease in the swine industry. In Japan, the incidence of acute swine erysipelas due to E. rhusiopathiae serovar 1a has recently increased markedly. To study the genetic relatedness of the strains from the recent cases, we analyzed 34 E. rhusiopathiae serovar 1a swine isolates collected between 1990 and 2011 and further investigated the possible association of the live Koganei 65-0.15 vaccine strain (serovar 1a) with the increase in cases. Pulsed-field gel electrophoresis analysis revealed no marked variation among the isolates; however, sequencing analysis of a hypervariable region in the surface-protective antigen A gene ( spaA ) revealed that the strains isolated after 2007 exhibited the same spaA genotype and could be differentiated from older strains. Phylogenetic analysis based on genome-wide single-nucleotide polymorphisms (SNPs) revealed that the Japanese strains examined were closely related, showing a relatively small number of SNPs among them. The strains were classified into four major lineages, with Koganei 65-0.15 (lineage III) being phylogenetically separated from the other three lineages. The strains isolated after 2007 and the two older strains constituted one major lineage (lineage IV) with a specific spaA genotype (M203/I257-SpaA), while the recent isolates were further divided into two geographic groups. The remaining older isolates belonged to either lineage I, with the I203/L257-SpaA type, or lineage II, with the I203/I257-SpaA type. These results indicate that the recent increased incidence of acute swine erysipelas in Japan is associated with two sublineages of lineage IV, which have independently evolved in two different geographic regions. IMPORTANCE Using large-scale whole-genome sequence data from Erysipelothrix rhusiopathiae isolates from a wide range of hosts and geographic origins, a recent study clarified the existence of three distinct clades (clades 1, 2, and 3) that are found across multiple continents and host species, representing both livestock and wildlife, and an “intermediate” clade between clade 2 and the dominant clade 3 within the species. In this study, we found that the E. rhusiopathiae Japanese strains examined exhibited remarkably low levels of genetic diversity and confirmed that all of the Japanese and Chinese swine isolates examined in this study belong to clonal lineages within the intermediate clade. We report that spaA genotyping of E. rhusiopathiae strains is a practical alternative to whole-genome sequencing analysis of the E. rhusiopathiae isolates from eastern Asian countries.

A crucial event in the initiation of many bacterial infections is the adherence of the bacteria to host cells, and bacterial surface structures and their interactions with host cell receptors play an important role in this process. Erysipelothrix rhusiopathiae is the causative agent of swine erysipelas, which may cause acute septicemia or chronic endocarditis and polyarthritis. To study the pathogenic mechanism of the widespread vascular disease observed in the acute form of swine erysipelas, we investigated the role of phosphorylcholine (PCho), a component of the E. rhusiopathiae capsule, in bacterial adherence to porcine endothelial cells (PECs) in vitro. We found that adherence of E. rhusiopathiae strain Fujisawa to PECs was twice that of adherence to control COS-7 cells and that the adherence rates of PCho-defective mutants were approximately 30-50% lower than those of the Fujisawa strain. The adherence of the Fujisawa strain to COS-7 cells transfected with the porcine platelet-activating factor receptor (PAFR) gene, which encodes a G protein-coupled receptor that has been shown to directly bind to Streptococcus pneumoniae via PCho in the bacterial cell wall, was not enhanced. Treatment with a PAFR antagonist (WEB-2086) did not inhibit bacterial adherence to PECs. Incubation of the bacterial cells with an antibody against PCho or SpaA, a choline-binding protein anchored to PCho of the Fujisawa strain, reduced the adherence of the strain to PECs. This effect was not observed when PCho-defective mutants were used. These results suggest that E. rhusiopathiae adheres to PECs via PCho and SpaA and that the PCho-mediated adherence is independent of PAFR.

The differentiation of vaccine from non-vaccine isolates is important for disease control. Based on single nucleotide polymorphisms identified by comparison of the genomes of the Koganei 65-0.15 vaccine strain and a reference strain of Erysipelothrix rhusiopathiae, we developed a PCR assay that can differentiate the vaccine strain from field isolates.

Salmonella-specific antibodies play an important role in host immunity; however, the mechanisms of Salmonella clearance by pathogen-specific antibodies remain to be completely elucidated since previous studies on antibody-mediated protection have yielded inconsistent results. These inconsistencies are at least partially attributable to the use of polyclonal antibodies against Salmonella antigens. Here, we developed a new monoclonal antibody (mAb)-449 and identified its related immunogen that protected BALB/c mice from infection with Salmonella enterica serovar Typhimurium. In addition, these data indicate that the mAb-449 immunogen is likely a major protective antigen. Using in vitro infection studies, we also analyzed the mechanism by which mAb-449 conferred host protection. Notably, macrophages infected with mAb-449-treated S. Typhimurium showed enhanced pathogen uptake compared to counterparts infected with control IgG-treated bacteria. Moreover, these macrophages produced elevated levels of pro-inflammatory cytokine TNFα and nitric oxide, indicating that mAb-449 enhanced macrophage activation. Finally, the number of intracellular bacteria in mAb-449-activated macrophages decreased considerably, while the opposite was found in IgG-treated controls. Based on these findings, we suggest that, although S. Typhimurium has the potential to survive and replicate within macrophages, host production of a specific antibody can effectively mediate macrophage activation for clearance of intracellular bacteria.

The capsule has been implicated in the virulence of the swine pathogen Erysipelothrix rhusiopathiae , a rod-shaped, intracellular Gram-positive bacterium that has a unique phylogenetic position in the phylum Firmicutes and is a close relative of Mollicutes (mycoplasma species). In this study, we analyzed the genetic locus and composition of the capsular polysaccharide (CPS) of the Fujisawa strain of E. rhusiopathiae . Genome analysis of the Fujisawa strain revealed that the genetic locus for capsular polysaccharide synthesis ( cps ) is located next to an lic operon, which is involved in the incorporation and expression of phosphorylcholine (PCho). Reverse transcription-PCR analysis showed that cps and lic are transcribed as a single mRNA, indicating that the loci form an operon. Using the cell surface antigen-specific monoclonal antibody (MAb) ER21 as a probe, the capsular materials were isolated from the Fujisawa strain by hot water extraction and treatment with DNase, RNase, pronase, and N -acetylmuramidase SG, followed by anion-exchange and gel filtration chromatography. The materials were then analyzed by high-performance liquid chromatography, mass spectrometry, and nuclear magnetic resonance (NMR) spectroscopy. The CPS of E. rhusiopathiae is heterogeneous and consists of the major monosaccharides galacturonic acid, galactose, mannose, glucose, arabinose, xylose, and N -acetylglucosamine and some minor monosaccharides containing ribose, rhamnose, and N -acetylgalactosamine. In addition, the capsule is modified by PCho, which comigrates with the capsular materials, as determined by Western immunoblotting, and colocalizes on the cell surface, as determined by immunogold electron microscopy. Virulence testing of PCho-defective mutants in mice demonstrated that PCho is critical for the virulence of this organism.

Interleukin-18 (IL-18), which was originally called gamma interferon (IFN-γ)-inducing factor, has been shown to play an important role in innate and acquired immune responses. In this study, attenuated Erysipelothrix rhusiopathiae strains were engineered to produce porcine IL-18 (poIL-18) and evaluated for their potential immunostimulatory effect in animals. Recombinant poIL-18 was successfully expressed in the recombinant E. rhusiopathiae strains YS-1/IL-18 and KO/IL-18. The culture supernatant of YS-1/IL-18 was confirmed to induce IFN-γ production in murine splenocytes in vitro , and this production was inhibited by incubation with anti-poIL-18 monoclonal antibodies. Furthermore, more IFN-γ production was induced upon stimulation of splenocytes with concanavalin A for splenocytes from mice that were intraperitoneally inoculated with YS-1/IL-18 than for splenocytes from control mice inoculated with the parent strain YS-1. Peritoneal macrophages from mice preinoculated with YS-1/IL-18 exhibited enhanced phagocytosis of Salmonella enterica subsp. enterica serovar Typhimurium compared with peritoneal macrophages from control mice preinoculated with YS-1. We also confirmed the immunostimulatory effect on humoral immune responses against antigens of E. rhusiopathiae and Mycoplasma hyopneumoniae in gnotobiotic pigs that were orally preinoculated with KO/IL-18. Thus, these results provide evidence that E. rhusiopathiae is a promising vector for the expression of host cytokines and suggest the potential utility of E. rhusiopathiae vector-encoded cytokines in the activation of host innate and acquired immune responses.

Erysipelothrix rhusiopathiaeis a Gram-positive bacterium that represents a new class,Erysipelotrichia, in the phylumFirmicutes. The organism is a facultative intracellular pathogen that causes swine erysipelas, as well as a variety of diseases in many animals. Here, we report the first complete genome sequence analysis of a member of the classErysipelotrichia. TheE. rhusiopathiaegenome (1,787,941 bp) is one of the smallest genomes in the phylumFirmicutes. Phylogenetic analyses based on the 16S rRNA gene and 31 universal protein families suggest thatE. rhusiopathiaeis phylogenetically close toMollicutes, which comprisesMycoplasmaspecies. Genome analyses show that the overall features of theE. rhusiopathiaegenome are similar to those of other Gram-positive bacteria; it possesses a complete set of peptidoglycan biosynthesis genes, two-component regulatory systems, and various cell wall-associated virulence factors, including a capsule and adhesins. However, it lacks many orthologous genes for the biosynthesis of wall teichoic acids (WTA) and lipoteichoic acids (LTA) and thedltABCDoperon, which is responsible ford-alanine incorporation into WTA and LTA, suggesting that the organism has an atypical cell wall. In addition, likeMollicutes, its genome shows a complete loss of fatty acid biosynthesis pathways and lacks the genes for the biosynthesis of many amino acids, cofactors, and vitamins, indicating reductive genome evolution. The genome encodes nine antioxidant factors and nine phospholipases, which facilitate intracellular survival in phagocytes. Thus, theE. rhusiopathiaegenome represents evolutionary traits of bothFirmicutesandMollicutesand provides new insights into its evolutionary adaptations for intracellular survival.

Erysipelothrix rhusiopathiae causes swine erysipelas, an infection characterized by acute septicemia or chronic endocarditis and polyarthritis. Among seventeen E. rhusiopathiae serovars, determined based on heat-stable peptidoglycan antigens, serovars 1 and 2 are most commonly associated with the disease; however, the molecular basis for the association between these serovars and virulence is unknown. To search for the genetic region defining serovar 1a (Fujisawa) strain antigenicity, we examined the 15-kb chromosomal region encompassing a putative pathway for polysaccharide biosynthesis, which was previously identified in the E. rhusiopathiae Fujisawa strain. Six transposon mutants of Fujisawa strain possessing a mutation in this region lost antigenic reactivity with serovar 1a-specific rabbit serum. Sequence analysis of this region in wild-type strains of serovars 1a, 1b, and 2 and serovar N, which lacks serovar-specific antigens, revealed that gene organization was similar among the strains and that serovar 2 strains showed variation. Serovar N strains displayed the same gene organization as either the serovar 1a, 1b or 2 strains and possessed certain mutations in this region. In two of the analyzed serovar N strains, restoration of the mutations via complementation with sequences derived from serovar 1a and 2 strains recovered antigenic reactivity with 1a- and 2-specific rabbit serum, respectively. Several gene mutations in this region resulted in altered capsule expression and attenuation of virulence in mice. These results indicate a functional connection between the biosynthetic pathways for the capsular polysaccharide and peptidoglycan antigens used for serotyping, which may explain variation in virulence among strains of different serovars.

Serotyping is an important element for surveillance of Salmonella. In this study, an anti-O:4 Salmonella monoclonal antibody-based competitive enzyme-linked immunosorbent assay that could identify Salmonella infection in cow, pig, horse, and chicken was developed. This detection system can therefore be useful for a wide range of animals and for humans.

We evaluated the protective efficacy of 94-kb virulence plasmid-cured, and phoP- or aroA-deficient strains of Salmonella enterica serovar Typhimurium (ΔphoP or ΔaroA S. Typhimurium) as oral vaccine candidates in BALB/c mice. Two weeks after the completion of 3 oral immunizations with 1 × 10(8) colony-forming units (CFU) of virulence plasmid-cured, and ΔphoP or ΔaroA S. Typhimurium at 10-day intervals, S. Typhimurium lipopolysaccharide (LPS)-specific mucosal secretory immunoglobulin A (s-IgA) antibody titers were detected in the cecal homogenate, bile and lung lavage fluid, but not in the intestinal lavage fluid. In addition, the increases in S. Typhimurium LPS-specific immunoglobulin G (IgG) and IgA antibody titers in the serum were also observed 2 weeks after completing 3 oral immunizations with virulence plasmid-cured, and ΔphoP or ΔaroA S. Typhimurium. The series of 3 oral immunizations protected the mice against an oral challenge with 5 × 10(8) CFU of the virulent strain of S. Typhimurium, suggesting that both the virulence plasmid-cured, and ΔphoP and ΔaroA S. Typhimurium strains are promising candidates for safe and effective live S. Typhimurium vaccines.

Erysipelothrix rhusiopathiae , the causative agent of swine erysipelas, is a facultative intracellular Gram-positive bacterium. It has been shown that animals immunized with a filtrate from E. rhusiopathiae cultures are protected against lethal challenge. In this study, we identified and characterized the extracellular proteins of E. rhusiopathiae to search for novel vaccine antigens. A concentrated culture supernatant from the E. rhusiopathiae Fujisawa strain, which has been found to induce protection in mice, was analyzed using two-dimensional electrophoresis. From more than 40 confirmed protein spots, 16 major protein spots were selected and subjected to N-terminal amino acid sequence determination, and 14 protein spots were successfully identified. The identified proteins included housekeeping proteins and other metabolic enzymes. We searched for surface-localized proteins by analyzing the genomes of two E. rhusiopathiae strains: Fujisawa and ATCC 19414. Genome analysis revealed that the ATCC 19414 strain has three putative surface-exposed c holine- b inding p roteins (CBPs): CbpA, CbpB, and CbpC. Each CBP contains a putative choline-binding domain. The CbpC gene is mutated in Fujisawa, becoming a nonfunctional pseudogene. Immunogold electron microscopy confirmed that CbpA and CbpB, as well as the majority of the metabolic enzymes examined, are associated with the cell surface of E. rhusiopathiae Fujisawa. Immunization with recombinant CbpB, but not with other recombinant CBPs or metabolic enzymes, protected mice against lethal challenge. A phagocytosis assay revealed that antiserum against CbpB promoted opsonin-mediated phagocytosis by murine macrophages in vitro . The protective capabilities of CbpB were confirmed in pigs, suggesting that CbpB could be used as a vaccine antigen.

Tonsils are important organs for mucosal immunity and are gateways for various pathogens, including bacteria and viruses. The purpose of the present study was to reveal how Erysipelothrix rhusiopathiae, the causative agent of swine erysipelas, invades the mucosal epithelium of the tonsils of pigs. Two germ-free piglets were orally infected with E. rhusiopathiae Koganei 65-0.15, an attenuated vaccine strain in Japan, and their tonsils of the soft palate were histologically examined four weeks after infection. Bacterial organisms were observed in dilated crypt lumens and a few epithelial cells of the crypt. Immunohistochemical examination revealed that some epithelial cells of the crypt were positive for cytokeratin (CK) 18, a specific marker for M cells in the Peyer's patches of pigs. Confocal laser scanning microscopy showed that bacterial antigens were present in the cytoplasm of CK 18-positive epithelial cells. Furthermore, an ultramicroscopic examination revealed that the bacteria-containing epithelial cells did not have microfolds or microvilli, both of which are characteristic of membranous epithelial cells (M cells), and that they were in close contact with intraepithelial phagocytes. Thus, the present observations suggest that the tonsillar crypt epithelium is a site of persistent infection for orally administered E. rhusiopathiae, and the bacteria exploit cytokeratin 18-positive epithelial cells of the crypts as portals of entry into the body.

Erysipelothrix rhusiopathiae Koganei 65-0.15 strain, the live swine erysipelas vaccine for subcutaneous injection, has been shown to colonize the tonsils of pigs after oral inoculation. We thus evaluated the possible use of the strain as a vector for oral vaccination against mycoplasmal pneumonia of swine. Recombinant E. rhusiopathiae strains expressing the C-terminal domain of the P97 adhesin of Mycoplasma hyopneumoniae were constructed and examined for vaccine efficacy in mice and pigs. Mice subcutaneously inoculated with the recombinant strains were protected from challenge exposure to a virulent E. rhusiopathiae. Administration of milk replacer containing recombinant E. rhusiopathiae expressing the M. hyopneumoniae protein protected pigs from death after exposure to E. rhusiopathiae and significantly reduced the severity of pneumonic lung lesions caused by infection with M. hyopneumoniae.

Erysipelothrix rhusiopathiaeis a gram-positive bacterium that causes erysipelas in animals and erysipeloid in humans. We found two adhesive surface proteins ofE. rhusiopathiaeand determined the nucleotide sequences of the genes, which were colocalized and designatedrspAandrspB. The two genes were present in all of the serovars ofE. rhusiopathiaestrains examined. The deduced RspA and RspB proteins contain the C-terminal anchoring motif, LPXTG, which is preceded by repeats of consensus amino acid sequences. The consensus sequences are composed of 78 to 92 amino acids and repeat 16 and 3 times in RspA and RspB, respectively. Adhesive surface proteins of other gram-positive bacteria, includingListeria monocytogenesadhesin-like protein,Streptococcus pyogenesprotein F2 and F2-like protein,Streptococcus dysgalactiaeFnBB, andStaphylococcus aureusCna, share the same consensus repeats. Furthermore, the N-terminal regions of RspA and RspB showed characteristics of the collagen-binding domain that was described for Cna. RspA and RspB were expressed inEscherichia colias histidine-tagged fusion proteins and purified. The recombinant proteins showed a high degree of capacity to bind to polystyrene and inhibited the binding ofE. rhusiopathiaeonto the abiotic surface in a dose dependent manner. In a solid-phase binding assay, both of the recombinant proteins bound to fibronectin, type I and IV collagens, indicating broad spectrum of their binding ability. It was suggested that both RspA and RspB were exposed on the cell surface ofE. rhusiopathiae, as were the bacterial cells agglutinated by the anti-RspA immunoglobulin G (IgG) and anti-RspB IgG. RspA and RspB were present both in surface-antigen extracts and the culture supernatants ofE. rhusiopathiaeFujisawa-SmR (serovar 1a) and SE-9 (serovar 2). The recombinant RspA, but not RspB, elicited protection in mice against experimental challenge. These results suggest that RspA and RspB participate in initiation of biofilm formation through their binding abilities to abiotic and biotic surfaces.

application/pdf, Background: Toxoplasma gondii is a highly prevalent protozoan that can infect all warm-blooded animals, including humans. Its definitive hosts are Felidae and its intermediate hosts include various other mammals and birds, including pigs. It is found in the meat of livestock which is a major source of human infection. Hence the control of toxoplasmosis in pigs is important for public health. We previously showed that dextran sulfate (DS), especially DS10 (dextran sulfate MW 10 kDa), is effective against T. gondii infection both in vitro and in mice. In this study, we asked whether DS affects T. gondii infection of pigs, one of the main animal sources of toxoplasmosis transmission to humans. Methods: Fourteen-day-old male pigs (n = 10) were infected with T. gondii and then immediately treated with different doses of DS10; clinical, pathological, and immunological analyses were performed 5 days post-infection. Results: DS10 had an inhibitory effect on toxoplasmosis in pigs. Intravenous injection of DS10 prevented the symptoms of toxoplasmosis and reduced the parasite burden and inflammation induced by T. gondii infection. High-dose DS10 (500 mu g per head) caused reversible hepatocellular degeneration of the liver; middle-dose DS10 (50 mu g per head) was effective against toxoplasmosis in pigs without causing this side effect. Conclusions: Our data suggest that middle-dose DS10 led to minimal clinical symptoms of T. gondii infection and caused little hepatocellular degeneration in our pig model, thereby demonstrating its potential as a new treatment for toxoplasmosis. These data should be very beneficial to those interested in the control of toxoplasmosis in pigs.