Masato Kanamori

Protective Effect of Colostrum in Mycoplasma pneumoniae Infection Induced in Infant Mice

The immunological responses and mechanism of maternal immunity in Mycoplasma pneumoniae infection of mice were investigated. ICR female mice, 4 weeks old, and infant mice, 2 to 4 days old, were infected with M. pneumoniae. Anti‐M. pneumoniae antibodies in serum and colostrum were determined by enzyme‐linked immunosorbent assay. The specific IgG antibody production persisted for 9 months or longer in both the young and infant mice. These infected mice were protected from rechallenge with M. pneumoniae. In addition, the infected dams conferred passive immunity on their offspring. The infant mice born to uninfected normal dams were protected from the challenge with M. pneumoniae when fed by infected foster dams. Conversely, the infant mice born to infected dams were not protected from the challenge with M. pneumoniae when the infants were fed by uninfected dams. The specific IgG antibody appeared in serum of infant mice inoculated orally with M. pneumoniae‐infected mouse serum and the infants were protected from challenge with M. pneumoniae, while the infants given protein A‐absorbed serum were not protected from the challenge. These results suggest that one of the factors involved in the resistance of infant mice to M. pneumoniae infection is the specific IgG antibody present in the colostrum rather than the result of transplacental transfer.

Shigella dysenteriae strains possessing a new serovar isolated from imported diarrheal cases in Japan

Two Shigella strains (93-119 and 95-619) isolated from stool cultures of imported diarrheal cases in Japan, did not react to any antisera of the established SHigella serovars. These strains had the typical biochemical characteristics of Shigella dysenteriae, and were biochemically identical to each other. Both strains were positive in the Serény test and other tests for invasiveness; these indicate that they can cause shigellosis in humans. The results of antigenic analysis showed that they did not belong to any of the recognized or provisional serovars, and were serologically indistinguishable. Strain 93-119 is designated as the test strain for this new serovar.

Chemical and Immunochemical Characterization of Polysaccharides of Sasa Veitchii Leaves

A hot water extract of Sasa veitchii is a health-promoting food in general use. To analyze the structure and function of the polysaccharide fraction of the extract, a macromolecular fraction was obtained by dialysis (HMF) and two polysaccharide fractions (NPS and APS) were separated by DEAE-Sephadex chromatography. HMF strongly reacted with human sera and immunoglobulin preparations. All of the IgM, IgG, and IgA classes of antibodies were reacted with HMF. Comparing the reactivity of NPS and APS, NPS showed significantly stronger reactivity to the sera. From physicochemical analysis, their molecular weights are 20,000 and 8,000, respectively. Sugar analyses of the acid hydrolysates indicated rhamnose, arabinose, xylose, mannose, glucose, and galactose in the molar ratio of 1.0 : 2.3 : 1.5 : 3.8 : 0.6 : 5.3 for NPS and 1.0 : 3.0 : 2.6 : 0.8 : 6.3 : 3.0 for APS, and suggested major differences in the ratio of hexoses. APS also contained 2.6% galacturonic acid. Methylation analyses suggested that 1) both NPS and APS have a highly branched structure, 2) only NPS contains galactofuranose residue at the non-reducing terminal. Partial acid hydrolysis of HMF and subsequent dialysis recovered a high molecular weight fraction, but the resulting product had significantly low immunochemical reactivity. Considering the physicochemical and immunochemical analyses, the major epitope structure of NPS was suggested to be galactofuranose residues. Immunochemical reactivity of the polysaccharide is a key molecular mechanism for the health promoting activity of S. veitchii.

Effects of Homologous O-Antibody on Host Responses to Lipopolysaccharide from Yersinia enterocolitica : Neutralization of Its Pyrogenicity

The pyrogenic activity of lipopolysaccharide (LPS) obtained from Yersinia enterocolitica was neutralized by the homologous O‐antiserum at the optimal antigen/antibody ratio. The level of neutralization in either antigen excess or extreme antibody excess was significantly lower than that at the optimal ratio. These facts suggested that the structure of the so‐called “lattice” of LPS/antibody complex might influence the neutralization of pyrogenic activity. Moreover, when LPS was gradually added to the antiserum to reach the optimal antigen/antibody ratio, the pyrogenic activity of LPS was only slightly neutralized by the antibody. The similar event to Danysz phenomenon that has been known in the diphtheria toxin‐antitoxin system was also observed in the LPS‐anti‐LPS system.

Aeromonas hydrophila の主要O群株からの耐熱性リパーゼ遺伝子の検出

On the basis of DNA hybridization data and phenotypes, most pathogenic strains of Aeromonas hydrophila are grouped into hybridization group 1 (HG1). These pathogenic strains secret the theromostable lipase, and its gene (lipAH) has been cloned and sequenced. The present study was performed to identify the pathogenic strains of A. hydrophila by the polymerase chain reaction (PCR) technique to detect the lipAH. Synthetic oligonucleotide primers (lipAH-ns-1 and -na-1) were used in the PCR. The PCR identified 80% of lipAH-positive strains, consisting of seven of the 11 O11 strains (64%), 13 of the 15 O16 strains (87%) and 25 of the 30 O34 strains (83%) in clinical isolates of A. hydrophila used in this study.

Immunochemical Cross-Reactivity of β-Glucan in the Medicinal Plant, Sasa veitchii (Japanese Folk Medicine Kumazasa), and Medicinal Mushrooms.

Fungal β-glucan is a representative pathogen-associated molecular pattern from mushroom, yeast, and fungi and stimulates innate as well as acquired immune systems. This β-glucan is widely applied in functional food to enhance immunity. Humans and animals generally become sensitized to this β-glucan and gradually produce specific antibodies to β-glucans. The extracts of plants have been used as folk medicine and are reported to possess various biological activities that are beneficial for human health, such as antitumor, antiallergic, and anti-inflammatory activities. In the present study, the immunochemical cross-reactivity of Sasa extract and fungal β-glucan was analyzed. We found that the anti-β-glucan antibody in human sera strongly cross-reacted with the Sasa extract. This result strongly suggested that plant extracts modulate the immunostimulating effects of medicinal mushrooms. The cooperative effects of plants and mushrooms may be an important issue for functional foods.

[Increasing nalidixic-acid-resistance in Salmonella strains isolated from sporadic cases in Tokyo].

A total of 118 nalidixic-acid (NA)-resistant Salmonella strains consisting of 68 domestic strains and 50 imported strains isolated during 1988-1998 in Tokyo were examined regarding their annual incidence, serovars, drug-resistance patterns, and minimum inhibitory concentrations(MIC) to fluoroquinolones (NFLX, OFLX, ENX, and CPFX). NA-resistant strains accounted for 1.3% of all Salmonella (5,302 strains) isolated from domestic cases, and 2.5% of all Salmonella (1,981 strains) isolated from imported cases. The incidence of NA-resistant strains has increased since 1995, and it has been remarkable in imported cases. The results of the serotyping showed that the NA-resistant strains were classified into 25 serovars, excluding untypable strains. Among those, S. Enteritidis (21 strains), S. Blockley (13 strains), S. Litchifield (13 strains), S. Typhimurium (13 strains), S. Hadar (9 strains), and S. Virchow (8 strains) were predominant. Drug-resistance patterns of NA-resistant strains, including other drugs (CP, TC, SM, KM, ABPC, ST, FOM, and NFLX) tested varied among the 26 types. Among those, multidrug-resistant strains accounted for 61.9% (73 strains), and one strain among them was high-resistant to NFLX. MIC distribution of NA-resistant strains to fluoroquinolones showed that the ranges of all drugs were 4-128 times higher than NA-sensitive strains used for controls.