To establish infections, viruses use various strategies to suppress the host defense mechanism, such as interferon (IFN)-induced antiviral state. We found that cells infected with a wild strain of measles virus (MeV) displayed nearly complete suppression of IFN-alpha-induced antiviral state, but not IFN-gamma-induced state. This phenomenon is due to the suppression of IFN-alpha-inducible gene expression at a transcriptional level. In the IFN-alpha signal transduction pathway, Jak1 phosphorylation induced by IFN-alpha is dramatically suppressed in MeV-infected cells; however, phosphorylation induced by IFN-gamma is not. We performed immunoprecipitation experiments using antibodies against type 1 IFN receptor chain 1 (INFAR1) and antibody against RACK1, which is reported to be a scaffold protein interacting with type I IFN receptor chain 2 and STAT1. These experiments indicated that IFNAR1 forms a complex containing the MeV-accessory proteins C and V, RACK1, and STAT1 in MeV-infected cells but not in uninfected cells. Composition of this complex in the infected cells altered little by IFN-alpha treatment. These results indicate that MeV suppresses the IFN-alpha, but not IFN-gamma, signaling pathway by inhibition of Jak1 phosphorylation. Our data suggest that functional disorder of the type I IFN receptor complex is due to "freezing" of the receptor through its association with the C and/or V proteins of MeV.

Helicobacter pylori is recognized as an etiological agent of gastroduodenal diseases. H. pylori produces various toxic substances, including lipopolysaccharide (LPS). However, H. pylori LPS exhibits extremely weakly endotoxic activity compared to the typical LPS, such as that produced by Escherichia coli, which acts through Toll-like receptor 4 (TLR4) to induce inflammatory molecules. The gastric epithelial cell lines MKN28 and MKN45 express TLR4 at very low levels, so they show very weak interleukin-8 (IL-8) production in response to E. coli LPS, but pretreatment with H. pylori LPS markedly enhanced IL-8 production induced by E. coli LPS by upregulating TLR4 via TLR2 and the MEK1/2-ERK1/2 pathway. The transcription factor NF-Y was activated by this signal and promoted transcription of the tlr4 gene. These MEK1/2-ERK1/2 signal-mediated activities were more potently activated by LPS carrying a weakly antigenic epitope, which is frequently found in gastric cancers, than by LPS carrying a highly antigenic epitope, which is associated with chronic gastritis. H. pylori LPS also augmented the proliferation rate of gastric epithelial cells via the MEK1/2-ERK1/2 pathway. H. pylori LPS may be a pathogenic factor causing gastric tumors by enhancing cell proliferation and inflammation via the MEK1/2-ERK1/2 mitogenactivated protein kinase cascade in gastric epithelial cells.

Helicobacter pylori is recognized as an etiologic agent of gastroduodenal diseases. Among toxic substances produced by H. pylori, LPS exhibits extremely low endotoxic activity as compared to the typical LPSs, such as that produced by Escherichia coli. We found that the LPS-low-responder stomach cancer cell line MKN28, which expresses Toll-like receptor 4 (TLR4) at extremely low levels, showed similar levels of interleukin-8 (IL-8) induction by H. pylori or E. coli LPS preparations. Weak IL-8 induction by H. pylori LPS preparations was suppressed by expression of a dominant negative mutant of TLR2 but not of TLR4. Data from luciferase reporter analysis indicated that cotransfection of TLR2-TLR1 or TLR2-TLR6 was required for the activation induced by H. pylori LPS preparations. In conclusion, the H. pylori LPS preparations significantly induce an inflammatory reaction via the receptor complex containing TLR2-TLR1 or TLR2-TLR6 but not that containing TLR4. The TLR2-TLR1 complex was preferentially recognized by the H. pylori LPS preparations over the TLR2-TLR6 complex. Whereas the magnitude of response to H. pylori LPS preparation was markedly less than that to E. coli LPS preparation in LPS-high-responder cells strongly expressing TLR4, it was comparable to that of E. coli LPS in low-responder cells expressing negligible amount of TLR4.

We have purified lipopolysaccharides (LPS) from 10 Helicobacter pylori clinical isolates which were selected on the basis of chemotype and antigenic variation. Data from immunoblotting of the purified LPS with sera from humans with H. pylori infection and from absorption of the sera with LPS indicated the presence of two distinct epitopes, termed the highly antigenic and the weakly antigenic epitopes, on the polysaccharide chains. Among 68 H. pylori clinical isolates, all smooth strains possessed either epitope; the epitopes were each carried by about 50% of the smooth strains. Thus, H. pylori strains can be classified into three types on the basis of their antigenicity in humans: those with smooth LPS carrying the highly antigenic epitope, those with smooth LPS carrying the weakly antigenic epitope, and those with rough LPS. Sera from humans with H. pylori infection could be grouped into three categories: those containing immunoglobulin G (IgG) antibodies against the highly antigenic epitope, those containing IgG against the weakly antigenic epitope, and those containing both specific IgGs; these groups made up about 50%, less than 10%, and about 40%, respectively, of all infected sera tested. In other words, IgG against the highly antigenic epitope were detected in more than 90% of H. pylori-infected individuals with high titers. IgG against the weakly antigenic epitope were detected in about 50% of the sera tested; however, the antibody titers were low. The two human epitopes existed independently from the mimic structures of Lewis antigens, which are known to be an important epitope of H. pylori LPS. No significant relationship between the reactivities toward purified LPS of human sera and a panel of anti-Lewis antigen antibodies was found. Moreover, the reactivities of the anti-Lewis antigen antibodies, but not human sera, were sensitive to particular ␣-L-fucosidases. The human epitopes appeared to be located on O-polysaccharide chains containing endo-␤-galactosidase-sensitive galactose residues as the backbone. Data from chemical analyses indicated that all LPS commonly contained galactose, glucosamine, glucose, and fucose (except one rough strain) as probable polysaccharide components, together with typical components of inner core and lipid A. We were not able to distinguish between the differences of antigenicity in humans by on the basis of the chemical composition of the LPS.

The virulence traits of the Escherichia coli strain associated with a waterborne diarrhea outbreak were examined. Forty-one of 75 students (ages 12 to 15) in Akita Prefecture, Japan, showed clinical symptoms. Seven E. coli Ouk:K-:H45 isolates were isolated from the patients as the causative agent of this outbreak. One isolate (EC-3605) showed the presence of E. coli attaching-and-effacing (eaeA) and enteroaggregative E. coli heatstable enterotoxin-1 (astA) genes and the absence of Shiga toxin (stx1 and stx2) genes. A polymorphic enteropathogenic E. coli (EPEC) adherence factor plasmid was detected in EC-3605 with a major structural gene deletion and a regulatory gene frameshift mutation, revealing that EC-3605 represents an atypical EPEC strain harboring the astA gene. The role that atypical EPEC strains harboring the astA gene play in human disease is unclear. Our results, along with those of others, present a possibility that these strains comprise a distinct category of diarrheagenic E. coli and that astA affects the age distribution of atypical-EPEC infection.

Past studies have shown that the cell surface lipopolysaccharides (LPSs) of the ubiquitous human gastric pathogen Helicobacter pylori (a type 1 carcinogen) isolated from people residing in Europe and North America express predominantly type 2 Lewis x (Le(x)) and Le(y) epitopes and, infrequently, type 1 Le(a), Le(b), and Le(d) antigens. This production of Lewis blood-group structures by H. pylori LPSs, similar to those found in the surfaces of human gastric cells, allows the bacterium to mimic its human niche. In this study, LPSs of H.pylori strains extracted from patients living in China, Japan, and Singapore were chemically and serologically analyzed. When compared with Western H.pylori LPSs, these Asian strains showed a stronger tendency to produce type 1 blood groups. Of particular interest, and novel observations in H.pylori, the O-chain regions of strains F-58C and R-58A carried type 1 Le(a) without the presence of type 2 Le(x), strains R-7A and H607 were shown to have the capability of producing the type 1 blood group A antigen, and strains CA2, H507, and H428 expressed simultaneously the difucosyl isomeric antigens, type 1 Le(b) and type 2 Le(y). The apparent proclivity for the production of type 1 histo-blood group antigens in Asian H.pylori LPSs, as compared with Western strains, may be an adaptive evolutionary effect in that differences in the gastric cell surfaces of the respective hosts might be significantly dissimilar to select for the formation of different LPS structures on the resident H.pylori strain.

Virulence characteristics of diarrheal outbreak-associated Escherichia coli O55:NM, O126:NM, and O111:NM were examined. The E. coli O55:NM strains were atypical enteropathogenic E. coli (EPEC), while the E. coli O126:NM and O111:NM strains should be classified as enteroaggregative E. coli (EAggEC). The contributions of EPEC and EAggEC to the human disease burden in Japan might be significantly greater than is currently appreciated.There are six categories of Escherichia coli that cause diarrhea: enterotoxigenic E. coli (ETEC), enteropathogenic E. coli (EPEC), enterohemorrhagic E. coli, enteroaggregative E. coli (EAggEC), enteroinvasive E. coli, and diffusely adherent E. coli (21). EPEC causes characteristic attaching-and-effacing lesions (A/E), which can be observed by intestinal biopsy in both human patient (19) and animal (29) models. A/E is characterized by loss of microvilli, intimate adherence of bacteria between epithelial cell membranes (27,30), and cytoskeletal changes such as actin polymerization directly beneath the adherent bacteria (15). Generally, EPEC causes infantile diarrhea in developing countries and sporadic diarrhea in developed countries (21). EAggEC, on the other hand, is an enteric pathogen defined by its distinctive aggregative or "stackedbrick" pattern of adherence to cultured human epithelial cells (22). EAggEC associates mainly with persistent diarrhea in developing countries (21). Only two reports in Japan have described diarrheal outbreaks caused by EAggEC or EPEC. Itoh et al. (11) reported the isolation of EAggEC from the stools of patients with severe diarrhea in elementary and junior high schools. Makino et al. (18) reported the isolation of EPEC from a mass outbreak. In this paper, we describe three cases of diarrheal outbreaks in Japan caused by E. coli belonging to the traditional EPEC serotype.Chromosomal DNA-embedded agarose plugs for pulsedfield gel electrophoresis (PFGE) analysis were prepared by using the CHEF Bacterial DNA Plug Kit (Bio-Rad, Hercules, Calif.) and were digested with XbaI (Nippon gene; Osaka, Japan) at a concentration of 30 U/plug for 4 h at 37°C. The plugs were applied to a 1% PFC Grade Agarose (Bio-Rad) gel. Electrophoresis was performed in 0.5ϫ Tris-Borate EDTA buffer at 14°C using a CHEF DR-II PFGE apparatus (BioRad) under the following conditions: voltage, 6 V/cm; block 1, 11 h, with initial switching time of 4 s to final switching time of 8 s; block 2, 9 h, with initial switching time of 8 s to final switching time of 50 s. The HEp-2 cell assay was performed following the method described by Craviotto et al. (4), with modifications involving 3 or 6 h of incubation (15). The E. coli isolates were examined for the presence of the following virulence genes by PCR: stx1 (Shiga toxin) and stx2 (16), eaeA (E. coli attaching and effacing) (12), bfpA (bundle-forming pilus) (9), perA (EPEC plasmid-encoded regulatory region) (8), astA (EAggEC heat-stable enterotoxin) (28), aggR (transcriptional activator for EAggEC aggregative adherence fimbria I expression) ...

A low transformation temperature (LTT) welding consumable has been developed to prevent cold cracking in high strength steel welded joints without preheating. In the LTT welded joint, the residual tensile stress is reduced by martensitic expansion of weld metal formed by the LTT consumable. In the weld cracking tests, cold cracking in the LTT weld metal is successfully prevented under high restraint conditions, but cold cracking occurs at very low joint restraint strength in case the weld metal is fully martensitic. Chemical compositions of the consumable are designed to retain austenite in martensite in the newly developed weld metal to absorb the diffusible hydrogen into the austenite to prevent cold cracking. In the newly developed LTT weld metal, cold cracking is almost fully suppressed without preheating under every joint restraint condition.