Several genes involved in the determination of Listeria monocytogenes pathogenesis have been identified. Among them, plcA gene encodes phosphatidylinositol-specific phospholipase C (PI-PLC), plcB gene encodes a broad-range phospholipase C (PC-PLC), and actA encodes a protein contributing to actin assembly in infected cells. The interaction of L. monocytogenes wild type (LO 28) strain and two derivative mutants, plcA^- (BUG 206) and actA^-/plcB^- (LUT 12), with macrophages and T lymphocytes was investigated in a mouse model of listeriosis. Both mutants showed evidence of attenuation. The plcA^- mutant, but not the plcB^- mutant, expressed an increase in susceptibility to the anti-listerial activity of macrophages. Both mutants showed a decreased ability to induce IL-12 production by bone marrow macrophages when co-stimulated with E. coli LPS or IFN-γ. In vivo, L. monocytogenes plcA^- mutant was found to be a more effective stimulator of T cells than the wild LO 28 strain.

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A negatively stained electron micrograph of regularly arranged porin proteins of Campylobacter jejuni on the isolated outer membrane of bacteria was analyzed in detail by the correlation averaging method using a computer-assisted program. The results showed that the porin of C. jejuni had a trimeric structure separated by about 10.4±0.15nm. In addition, the pores in the trimers were also separated by about 4.3±0.1nm.

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In July 1994, 6 cholera cases due to Vibrio cholerae O1 El Tor Ogawa sporadically appeared in Okinawa. All 6 patients had no history of traveling abroad. In the period of this cholera outbreak, a strain of V. cholerae O1 El Tor Ogawa was detected from an imported fish at the Naha port quarantine station. The isolates were characterized to clarify whether or not, they belonged to a common clone. Phenotypes were identical except that one strain revealed cured Celebes and the others were original Celebes in kappa phage typing. The restriction fragment patterns of DNA of the isolates hybridized with an enzyme-labeled oligonucleotide probe for cholera toxin gene (ctx) were identical. Randomly amplified polymorphic DNA of the isolates were identical when a primer was used, but 2 patterns were seen when another primer was used. Pulsed-field gel electrophoresis of the chromosomal DNA digested with NotI restriction enzyme showed 3 patterns. The DNA fragment pattern of the strain isolated from the imported fish was different from the clinical isolates. These results suggested that there was no epidemiological relation among the strains of V. cholerae O1 isolated during this period.

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To clarify the interactions of drugs for combination therapy of Helicobacter pylori infection, especially due to antibiotic-resistant strains, we have evaluated the in vitro effect of combining different drugs. Using a modified time-kill assay, we tested the effect of combining 2 drugs from 4 agents; amoxicillin (AMPC), clarithromycin (CAM), metronidazole (MTZ) and lansoprazole (a proton pump inhibitor). The H. pylori in the study consisted of 4 strains sensitive to the all drugs, 2 strains resistant only to CAM, 2 strains resistant only to MTZ, and 2 strains resistant to both CAM and MTZ. From the 6 different drug combinations, synergism was observed for 5 of the combinations, among which the combination of AMPC and CAM revealed such effects most frequently. However, all of the strains which showed synergism were sensitive to both of the drugs. In the case of the strains resistant to CAM and/or MTZ, no synergism was demonstrated in any of the combinations including CAM and/or MTZ. When a strain was resistant to one drug from a combination, no synergism was detected. Thus, the administration of a drug to which the strains are resistant may have no advantage in the eradication therapy of H. pylori. For a more effective and safer therapy, susceptibility testing should be performed before treatment.

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The gene (com1) encoding a 27-kDa outer membrane protein in 21 strains of Coxiella burnetii from a variety of clinical and geographical sources was sequenced for strain differentiation. The com1 gene was highly conserved among all the strains tested but there were several differences in nucleotide and deduced amino acid sequences. Based on the com1 gene-specific nucleotides and deduced amino acids, the 21 strains were divided into four groups. Group 1 contained 14 strains originating from ticks, cattle and human cases of acute Q fever. Groups 2 and 3 included 2 and 3 strains, respectively, originating from human cases of chronic Q fever. Group 4 contained 2 strains originating from a human case of acute Q fever and a goat with abortion. The results indicated that the strains originating from ticks, cattle and human cases of acute Q fever differed at the molecular level from those of human chronic Q fever. This study suggests that a sequence analysis of the com1 gene can be used for strain differentiation of C. burnetii.

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Alkaline phosphatase-conjugated oligonucleotide probes were developed to detect the gene coding for Vero toxin 1 (VT1) and Vero toxin 2 (VT2). Using these probes, 3hr was enough to detect VT genes when suspicious colonies of enterohaemorrhagic Escherichia coli (EHEC) were obtained on an agar plate. The results of a hybridization test with 144 isolates of EHEC O157 and one isolate of Shigella dysenteriae Type 1 agreed exactly with the immunological detection, reversed passive latex agglutination (RPLA) test, of VTs in their culture supernatants. The sensitivity levels of these probes for the detection of VT genes were 100%. The specificity of these probes were also tested with a total of 1, 002 strains of Escherichia coli other than EHEC and 8 strains of Shigella sp. other than Shigella dysenteriae Type 1; the results showed 100% specificity.

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We have previously reported that a nonapeptide thymic hormone, facteur thymique serique (FTS), is involved in the differentiation and activation of intestinal intraepithelial lymphocytes (i-IEL) in mice. In this study, we examined the effect of FTS treatment on enteropathy in a murine model for acute graft-vs.-host disease (GVHD) induced by injection of parental C57BL/6 splenocytes into unirradiated (C57BL/6× DBA/2) F₁ hybrids. FTS treatment significantly protected mice from developing acute GVHD as assessed by mortality rate, splenomegaly and enteropathy. The infiltration of donor-derived TCRαβ i-IEL bearing CD8αβ was significantly inhibited in the small intestine of FTS-treated mice, and the frequencies of apoptosis of crypt cells in the intestinal mucosa were decreased in these mice during acute GVHD. These results suggest that FTS treatment contributes to protection against enteropathy of acute GVHD. Thus, FTS may provide a useful approach to control acute GVHD after blood transfusion or bone marrow transplantation.

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Acute Plasmodium falciparum malaria in African children allows expansion of latent Epstein-Barr virus infection, leading to colonization of lymph nodes by virus-infected lymphoblasts in 60% of cases as demonstrated by in situ hybridization for the detection of EBER-1 and EBER-2 RNA. This probably arises against a background of malaria-induced immunosuppression to EBV and concurrent lymphoid activation. The relevance of the results to the pathogenesis of African endemic Burkitt's lymphoma is discussed.

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Kawasaki disease (KD) is an acute multisystem vasculitis of unknown etiology and is associated with marked activation of T cells and monocyte macrophages, leading to the assumption that superantigens are involved in its pathogenesis. To determine if an association exists between streptococcal superantigens and KD, we examined serum antibody responses to superantigens in sera from 50 paired acute and convalescent KD patients using purified recombinant streptococcal superantigens, such as SPEA, SPEC, SSA and MF. We found a very low frequency of detection of anti-superantigen antibodies by ELISA and no marked IgG seroconversion to each superantigen, indicating the absence of a serological relationship between toxin-producing streptococcal infection and the onset of KD.

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