Induction of gamma/delta T cells in murine salmonellosis by an avirulent but not by a virulent strain of Salmonella choleraesuis.

To elucidate the relationship between the virulence of intracellular bacterium and its ability to induce gamma/delta T cells in the host during infection, we examined the differences in appearance of gamma/delta T cells in mice infected with Salmonella choleraesuis virulent strain RF-1 carrying a virulence plasmid of 50 kb, and with avirulent strain 31N-1 cured of the 50-kb plasmid. The number of gamma/delta T cells in the peritoneal cavity was increased to a significant level on day 3 after an intraperitoneal infection with a sublethal dose (5 x 10(4) colony-forming units) of avirulent strain 31N-1. On the other hand, no increase in the number of gamma/delta T cells was evident in the peritoneal cavity at any stage after infections with various doses of virulent strain RF-1, although the numbers of the bacteria were drastically increased. Similar to that seen in the peritoneal cavity, the number of gamma/delta T cells in the liver was significantly increased after an intraperitoneal infection with avirulent strain 31N-1 but not with virulent strain RF-1. The early appearing gamma/delta T cells during salmonellosis with avirulent stain 31N-1, which preferentially used V gamma 1/V delta 6, showed blastogenesis in response to purified protein derivative (PPD) derived from Mycobacterium tuberculosis. The gamma/delta T cells also responded to the peritoneal adherent cells in mice infected with avirulent strain 31N-1 6 d previously, which expressed a high level of endogenous heat-shock protein (hsp) homologous to the mycobacterial 65-kD hsp. The expression of the hsp, however, was not prominent in the adherent cells in mice infected with virulent strain RF-1. These results suggest that the gamma/delta T cells specific for PPD may play important roles in host defense against murine salmonellosis, and that the virulence of Salmonella may be inversely correlated with its ability to induce endogenous hsp in the infected macrophages, which in turn stimulate the gamma/delta T cells in the host during salmonellosis.

A practical random mutagenesis system for probiotic Lactobacillus casei using Tn5 transposition complexes.

AIMS: Despite the fact that the entire genome sequence of probiotic Lactobacillus casei has recently been available, their mechanisms of beneficial effects are poorly clarified, probably because of the lack of an efficient mutagenesis system. The aim of this study was to establish a practical random mutagenesis system of L. casei using the Tn5 transposome complexes. METHODS AND RESULTS: We optimized the conditions for transformation using a plasmid pUCYIT356-1-Not2 and then transposition reaction using Tn5 transposome system for L. casei ATCC 27139. Tn5 insertion library of this strain being consisted of 9408 mutants was constructed by repeating the mutagenesis procedure. To examine the utility of this mutagenesis system, we screened a panel of insertion mutants for nutrient requirements. Six auxotrophic mutants were isolated and their Tn5 insertion sites were determined by inverse PCR, which demonstrated that insertions occur randomly throughout the whole bacterial genome. CONCLUSIONS: Tn5 transposome system functioned efficiently to generate transposon insertion mutants of L. casei and enabled to construct useful L. casei Tn5 insertion library at optimized conditions for transformation and transposition. SIGNIFICANCE AND IMPACT OF THE STUDY: The availability of this system facilitates the study of the mechanisms of beneficial effects of L. casei for human health.

Chemical structure of glycosphingolipids isolated from Sphingomonas paucimobilis.

Two novel glycosphingolipids were isolated from Sphingomonas paucimobilis and their structures were completely elucidated. The glycosyl portion of the glycosphingolipid consists of an alpha-D-Manp-[1----2)-alpha-D-Galp-(1----6)-alpha-D-GlcpN-(1 ----4)-alpha-D- GlcpA-R tetrasaccharide. The hydrophobic residue R was found to be heterogeneous with respect to the dihydrosphingosine residue. Erythro-1,3-dihydroxy-2-amino-octadecane and erythro-1,3-dihydroxy-2-amino-cis-13,14-methyleneoctadecane were identified in comparable amounts. Both dihydrosphingosine derivatives were quantitatively substituted by an (S)-2-hydroxymyristic acid in amide linkage.

Rapid DNA typing utilizing immobilized oligonucleotide probe and a nonradioactive detection system. Application to HLA-DR typing of the Japanese population.

We established a rapid and simple method of HLA-DR genotyping, and applied it for analysis of the Japanese population. Our method includes rapid preparation of DNA samples from buccal mucosa, incorporation of biotin-dATP into DRB genes during amplification by the polymerase chain reaction, hybridization with sequence-specific oligonucleotide (SSO) probes immobilized on nylon membranes via poly (dT) tails, and detection of the hybridization signal as chemiluminescence. We carried out DR typing of 30 Japanese donors using 20 different immobilized SSO probes, and obtained unambiguous typing signals showing perfect correlation with their serologic DR types. The genotyping also enabled us to identify several DR types unique to the Japanese population, such as DRw12b (DRB1*1202), DRw14c (DRB1*1405), and serology blank type, DR'JX6' (DRB1*1403). The method presented here would be suitable for routine DR typing in tissue-typing laboratories.

The epitope structure in lipopolysaccharide recognized by the serotype 2-specific monoclonal antibody of Actinobacillus pleuropneumoniae.

The polysaccharide structure recognized by a monoclonal antibody specific to serotype 2 lipopolysaccharide of Actinobacillus pleuropneumoniae was investigated using an enzyme-linked immunosorbent assay inhibition test. Lipopolysaccharide obtained from serotype 2, strain SH-15, was hydrolysed with acetic acid to liberate the polysaccharide portion, and the polysaccharide mixture was fractionated by gel filtration. The longer polysaccharide, composed of O-antigenic polysaccharide and core, fully inhibited the binding of monoclonal antibodies to a whole cell antigen of strain SH-15, whereas the core oligosaccharide without O-polysaccharide did not. No inhibition was observed with the monosaccharides which were the components of serotype 2 LPS. Enzyme-linked immunosorbent assay inhibition ability of O-polysaccharide was completely lost only by O-deacetylation. These results demonstrate that the epitope of the serotype-specific monoclonal antibody resided in O-polysaccharide of LPS and that the O-acetyl group was essential for the epitope structure.

Extraction and characterization of lipopolysaccharide from Pseudomonas pseudomallei.

The best yield of lipopolysaccharide (LPS) of Pseudomonas pseudomallei GIFU 12046 was obtained by extraction of defatted cells by phenol/chloroform/petroleum ether. The LPS showed a smooth character on SDS-polyacrylamide gel electrophoresis and contained D-glucose, L-glycero-D-manno-heptose, and D-glucosamine as the main sugar components, and 3-hydroxypalmitic acid as an amide-linked fatty acid. The growth conditions did not affect the electrophoresis profile and chemical composition of LPS. 2-Keto-3-deoxyoctonic acid was not detectable, and mild acid hydrolysis could not liberate free lipid A, suggesting that the linkage between inner core and lipid A was stable against acid hydrolysis, and the structure of this region is similar to that of P. cepacia, which has close taxonomic relationship with P. pseudomallei.

Purification and characterization of Bordetella calmodulin-like protein.

Bordetella calmodulin-like protein was purified from culture supernatant fluid of B. pertussis, B. parapertussis and B. bronchiseptica by successive chromatography on hydroxyapatite, Toyopearl HW-50F and QAE-Toyopearl 550C columns. The purified calmodulin-like protein appeared to be homogeneous by SDS-polyacrylamide gel electrophoresis. The apparent molecular mass of calmodulin-like protein on SDS-polyacrylamide gel electrophoresis was 10 kDa, which was smaller than bovine brain calmodulin (17 kDa). The purified calmodulin-like protein activated both Bordetella adenylate cyclase and mammalian phosphodiesterase in a Ca(2+)-dependent manner. This activation was inhibited by calmodulin antagonists. The calmodulin-like protein, like calmodulin, was retained by a hydrophobic resin in the presence of Ca2+ and eluted by the addition of EDTA. These results indicated that the Bordetella calmodulin-like protein is closely related to calmodulin. As a putative calmodulin the extracellular calmodulin may be involved in Bordetella pathogenesis.

Rapid and sensitive method for detection of Salmonella strains using a combination of polymerase chain reaction and reverse dot-blot hybridization.

We have developed a reverse dot-blot hybridization assay for detection of Salmonella using Salmonella-specific oligonucleotide probes designed from the base sequence of the 16S rRNA gene (rDNA). The target fragment of 16S rDNA was amplified, and labelled with biotin by the polymerase chain reaction. The amplified fragment was hybridized with the membrane-immobilized probe and the hybridization was detected by chemiluminescence. Amplified fragments from 24 different serovars of Salmonella hybridized with the probes, whereas those of species of Enterobacteriaceae, Pseudomonas aeruginosa, Bacillus subtilis, and Staphylococcus aureus failed to hybridize. By this assay, it was possible to detect in the order of 10(4) bacteria in fish meat homogenate in 10 h.

Regional and subcellular distribution of gold in brain of gold thioglucose obese mouse.

By employing neutron activation analysis, endogenous content of gold was estimated quantitatively in discrete brain areas and in subcellular fractions of the hypothalamus of gold thioglucose (GTG) induced obese mice. The highest concentration of gold was obtained in the ventromedial hypothalamus (VMH) reaching approximately 100 ng/mg wet tissue. Significantly higher concentrations were observed in other hypothalamic subareas followed by certain limbic areas and the thalamus, while in the cerebral and the cerebellar cortex the gold concentration was very low. Subcellularly, the hypothalamic gold was principally recovered in the supernatant fraction particularly after a hyposmotic shock treatment of the crude mitochondrial fraction. Contrary to GTG, treatment with gold thiomalate (GTM) did not induce obesity in the mouse, although considerable amount of gold was observed in the VMH, a finding suggesting the existence in the VMH of at least a two step mechanisms for inducing GTG obesity. To identify the satiety neuron transmitter, an analysis of certain enzyme activities involved in the synthesis of known transmitters, such as acetylcholine or gamma-aminobutyric acid (GABA), was made in the GTG-obese mice. There were no significant changes in any of the areas functionally related to the VMH.

A conjugative plasmid pTE195 coding for drug resistance and virulence phenotypes from Salmonella naestved strain of calf origin.

Salmonella naestved strain AHI-195, of calf origin, harbors a conjugative 95 megadalton (MDa) plasmid, pTE195, which encodes resistance to tetracycline and chloramphenicol and belongs to incompatibility group FII. Moreover, DNA homology between pTE195 and the Salmonella dublin virulence plasmid pTE800 was revealed by digestion with several restriction endonucleases and confirmed by hybridization with different specific probes. These results indicate that pTE195 carries not only genes for drug resistance but also genes for virulence phenotypes such as serum resistance and mouse lethality.

Serum resistance and aerobactin iron uptake in avian Escherichia coli mediated by conjugative 100-megadalton plasmid.

A total of 115 strains of Escherichia coli isolated from chickens with colisepticemia in Japan were examined for chicken lethality and virulence factors. It was found that serum resistance and aerobactin-mediated iron uptake are the most prevalent characteristics in these strains. Among them, S-20, a representative virulent strain of serotype O2, was further studied. S-20 harbored a conjugative 100-megadalton (Mdal) plasmid, designated pKI100. Curing and reintroduction experiments showed that pKI100 encodes both serum resistance and aerobactin-mediated iron uptake, and the diminished virulence of the pKI100-cured strain was fully restored by the reintroduction of the plasmid. These results demonstrated that pKI100 is the virulence plasmid of the S-20 strain, and that serum resistance and aerobactin-mediated iron uptake are the virulence factors in E. coli strains which cause avian colibacillosis.

Identification of the cross-reacting antigen among Actinobacillus pleuropneumoniae strains of serotype 1, 9 and 11 by use of monoclonal antibodies.

Two monoclonal antibodies (MAbs), lMAb-1 and lMAb-5, against Actinobacillus pleuropneumoniae serotype 1 were obtained. In enzyme-linked immunosorbent assay-inhibition tests with whole cell antigens obtained from serotype 1 to 12 strains of A. pleuropneumoniae, lMAb-1 reacted to only a serotype 1, strain 4074. The epitope recognized by lMAb-1 was a carbohydrate sensitive to periodate oxidation and resided on capsular polysaccharide (CP) of A. pleuropneumoniae serotype 1. On the other hand, lMAb-5 reacted with serotype 1, 9 and 11 strains at the same degree and its epitope was found to be located on O-polysaccharide of serotype 1, 9 or 11 lipopolysaccharide (LPS). These results showed that CP was one of the serotype-specific antigens of A. pleuropneumoniae, and that O-polysaccharide of LPS obtained from serotype 1, 9 or 11 strain was the cross-reacting antigen among these strains.

Effect of 50 kilobase-plasmid, pKDSC50, of Salmonella choleraesuis RF-1 strain on pig septicemia.

Salmonella choleraesuis strains with and without 50-kilobase plasmid (pKDSC50) were intravenously inoculated into Yorkshire pigs. By the inoculation of 7.2 x 10(5) - 3.5 x 10(7) cells, RF-1 strain with pKDSC50, but not 31N-1 strain without the plasmid, caused a septicemia. The inoculation of 8.7 x 10(9) RF-1 cells killed pigs at 2-4 day postinfection with severe hemorrhage on the whole body. Pigs with a similar number of 31N-1 cells (8.3 x 10(9) cells), showed milder hemorrhage, and they died at 6 day postinfection. These results indicated that pKDSC50 is required for RF-1 strain to express the full virulence causing a heavy cutaneous pig septicemia.

Effect of breeding bull on the fatty acid composition of the carcass lipid in steers of a beef breed cattle.

Samples of neutral lipid were taken from the carcasses of forty-eight Japanese Black steers, the progeny from three breeding bulls, on similar planes of nutrition and of the same age, and were analysed for fatty acid composition. The breeding bull seems to significantly affect the fatty acid composition of the lipid from the thoracic subcutaneous fatty tissue and the inter- and intra-muscular fatty tissues of the Longissimus dorsi muscle. No significant correlation between breeding bull and fatty acid composition of perinephric fatty tissue was found. There was an increase in total concentration of unsaturated fatty acids from internal to external sample locations.

Characterization of monoclonal antibodies against Actinobacillus pleuropneumoniae serotype 5.

Two monoclonal antibodies against Actinobacillus pleuropneumoniae serotype 5, designated as 5MAb-1 and 5MAb-6, were characterized. Enzyme-linked immunosorbent assay-inhibition tests with whole-cell antigens obtained from strains of serotype 1 through 12 of A pleuropneumoniae revealed that 5 MAb-1 bound to only serotype-5 strains. The epitope recognized by 5MAb-1 was a carbohydrate that was sensitive to periodate oxidation and resided on the structure of beta-1,6-linked D-galactose in an O-antigen polysaccharide of serotype-5 lipopolysaccharide. Analysis of these results revealed that the O-antigen polysaccharide of lipopolysaccharide was 1 of the antigenic determinants responsible for the serotype specificity of A pleuropneumoniae. On the other hand, 5MAb-6 reacted with strains of serotype 1 through 10 in varying degrees and its epitope was located on polypeptides sensitive to proteinase K. In an immunoblotting analysis, 5MAb-6 reacted with 2 polypeptide bands, with molecular weights of approximately 41,500 and 28,000, in the outer membrane protein-rich fraction obtained from strains of serotype 1 through 10. These results indicated that outer membrane proteins from several serotype strains of A pleuropneumoniae possessed common antigenic determinants.

[Mechanism of pore formation on erythrocyte membrane by streptolysin-O].

The erythrocyte membrane damaged by streptolysin-O (SLO) was observed in negative staining electron microscopy. It was confirmed that rings took arc (c-ring), sigmoidal (s-ring) or circular (o-ring) structures, and had electron-dense centers of a diameter of 24 nm and 4.9 nm width. We found a crown structure on top of the ring in view of side projection. The ring structure was constructed by three layers of the electron lucent top which was the crown, the second dark layer, and the third, base part which embedded in the erythrocyte membrane, and the heights were 3.2, 1.6, 5.0 nm, respectively. When the ghost membrane of erythrocyte was treated with SLO, the double of the inner and outer layers of a ring were observed by the negative-staining images. The figures of rings taken by under focus showed that one ring might be constituted between the 22 and 24 pair of inner and outer molecules. Totally 44 or 48 toxin molecules might be required for one O-ring.