Ken-ichi Amano

Measles virus suppresses interferon-α signaling pathway: suppression of Jak1 phosphorylation and association of viral accessory proteins, C and V, with interferon-α receptor complex

Abstract 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-α-induced antiviral state, but not IFN-γ-induced state. This phenomenon is due to the suppression of IFN-α-inducible gene expression at a transcriptional level. In the IFN-α signal transduction pathway, Jak1 phosphorylation induced by IFN-α is dramatically suppressed in MeV-infected cells; however, phosphorylation induced by IFN-γ 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-α treatment. These results indicate that MeV suppresses the IFN-α, but not IFN-γ, 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.

Characterization of Enteropathogenic and Enteroaggregative Escherichia coli Isolated from Diarrheal Outbreaks

ABSTRACT 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.

Characterization of Atypical Enteropathogenic Escherichia coli Strains Harboring the astA Gene That Were Associated with a Waterborne Outbreak of Diarrhea in Japan

ABSTRACT 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 heat-stable 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.

Helicobacter pylori Lipopolysaccharides Upregulate Toll-Like Receptor 4 Expression and Proliferation of Gastric Epithelial Cells via the MEK1/2-ERK1/2 Mitogen-Activated Protein Kinase Pathway

ABSTRACT 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 mitogen-activated protein kinase cascade in gastric epithelial cells.

Class 1 Integron Containing Metallo-β-Lactamase Gene blaVIM-2 in Pseudomonas aeruginosa Clinical Strains Isolated in Japan

ABSTRACT Four blaVIM-2 gene-harboring Pseudomonas aeruginosa strains were identified. These strains possessed a class 1 integron harboring ORF1, blaVIM-2, and aacA4 gene cassettes. The transposon-mediated horizontal spread of the blaVIM-2 gene among these strains was suggested, which increases the threat that the blaVIM-2 gene will disseminate among diverse genera of bacteria.

Serological Reactivity of Sera from Scrub Typhus Patients against Weil-Felix Test Antigens

Sera from 17 patients of scrub typhus in the acute and convalescent phases were tested by indirect immunoperoxidase test, Weil‐Felix (WF) test, enzyme‐linked immunosorbent assay (ELISA), and immunoblotting. In the comparison of antibody titers between acute‐ and convalescent‐phase sera, we recognized a parallelism of increment between the titers in WF test and titers of immunoglobulin M (IgM) in ELISA against Proteus mirabilis strain OXK‐whole cells and OXK‐lipopolysaccharides (Proteus OXK‐LPS). Furthermore, IgM antibodies from almost all of WF test‐positive sera recognized LPS from Proteus OXK in immunoblotting. Based on these results, it was concluded that IgM antibody rather than IgG may participate in WF test, and that Proteus OXK‐LPS may have one of antigenic epitopes common to the components of R. tsutsugamushi.

Isolation and Characterization of the Measles Virus Strains with Low Hemagglutination Activity

Six measles virus strains were isolated from clinical specimens. They differed from a prototype strain in being incapable to grow in cell lines derived from monkey kidney and having a slower electrophoretic mobility of the hemagglutinin protein and a very low hemagglutination activity.

Structures of the O-antigens of Proteus bacilli belonging to OX group (serogroups O1–O3) used in Weil-Felix test

Structures of the O‐specific polysaccharide chains of lipopolysaccharides from Proteus group OX strains (serogroups O1–O3) used as antigens in Weil‐Felix test for diagnosis of rickettsiosis, were established. From them, the acid‐labile polysaccharide of Proteus vulgaris OX19 (O1) is built up of the following branched pentasaccharide repeating units connected via a phosphate group: where QuiNAc stands for 2‐acetamido‐2,6‐dideoxyglucose (N‐acetylquinovosamine). The basis of serospecificity of the Proteus group OX antigens and their cross‐reactivity with human anti‐rickettsial antibodies is discussed.

Two Distinct Antigenic Types of the Polysaccharide Chains of Helicobacter pylori Lipopolysaccharides Characterized by Reactivity with Sera from Humans with Natural Infection

ABSTRACT We have purified lipopolysaccharides (LPS) from 10Helicobacter 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 ofH. 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 α-l-fucosidases. The human epitopes appeared to be located on O-polysaccharide chains containing endo-β-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.

A phage in Bartonella bacilliformis.

Bacteriophage‐like particles were found in Bartonella bacilliformis culture. The particles consisted of head (icosahedral), 40 nm in diameter, and tail, 16 nm in length.