Biomedical subjects

D E Berg

Publications and source records attributed to D E Berg.

At least 37 records · Page 2Linked to original sources

PubMed2000

Mouse-colonizing Helicobacter pylori SS1 is unusually susceptible to metronidazole due to two complementary reductase activities.

In most strains of Helicobacter pylori, mutational inactivation of the rdxA (HP0954) gene, which encodes a nitroreductase that converts metronidazole (MTZ) from a harmless prodrug to a mutagenic and bacteriocidal product, is sufficient to make this pathogen resistant to clinically significant levels of MTZ. Here we report that SS1, a strain with the special ability to colonize mice, is unusual in being susceptible to very low concentrations of MTZ (0.5 microgram/ml) and in being especially difficult to mutate to MTZ resistance (Mtz(r)). These phenotypic traits were traced to expression in this strain of the normally quiescent H. pylori frxA gene (HP0642, an rdxA paralog) along with rdxA. Transformation tests using rdxA::cam and frxA::kan insertion mutant DNAs, with selection solely for the chloramphenicol and kanamycin resistance markers, and sequence analyses of frxA in spontaneous Mtz(r) derivatives of rdxA null mutant strains each showed that the development of Mtz(r) in SS1 required inactivation of both rdxA and frxA. Inactivation of either gene alone left SS1 susceptible to MTZ, although it was readily mutable from an MTZ-susceptible to an Mtz(r) phenotype. Reverse transcriptase PCR tests showed that frxA mRNA was at least 10-fold more abundant in SS1 than in reference strain 26695. It is proposed that these reductases play primarily nutritional roles during bacterial growth.

Animals↗

PubMed2000

Cell vacuolation, a manifestation of the El tor hemolysin of Vibrio cholerae.

Culture supernatants of nontoxigenic nonepidemic clinical strains of Vibrio cholerae belonging to diverse serogroups were found to induce vacuolation of nonconfluent HeLa cells. The vacuoles became prominent 18 h after introduction of culture supernatant, and vacuolated cells survived for 48 h and then died. Only a fraction of the vacuolated cells took up neutral red dye, implying that there were differences in the vacuolar microenvironment. Further tests showed that the factor responsible for vacuolation was heat labile and proteinaceous. Vacuolating activity was completely neutralized by antibody to hemolysin of V. cholerae but not by antibody to vacuolating cytotoxin of Helicobacter pylori. Partial purification of the vacuolating factor led to elution of fractions, which showed both hemolytic and vacuolating activity. PCR amplification and cloning of the hemolysin structural gene (hlyA) into Escherichia coli DH5alpha led to isolation of clones producing cell vacuolating factor in a cell-associated form. Further, a null insertion mutation in the hlyA gene of a high-vacuolating-factor-producing strain led to complete abolition of both cell vacuolating and hemolytic activities. These analyses establish vacuolation as a potentially important but previously unrecognized property of V. cholerae El Tor hemolysin.

Animals↗

PubMed2000

Differences in genotypes of Helicobacter pylori from different human populations.

DNA motifs at several informative loci in more than 500 strains of Helicobacter pylori from five continents were studied by PCR and sequencing to gain insights into the evolution of this gastric pathogen. Five types of deletion, insertion, and substitution motifs were found at the right end of the H. pylori cag pathogenicity island. Of the three most common motifs, type I predominated in Spaniards, native Peruvians, and Guatemalan Ladinos (mixed Amerindian-European ancestry) and also in native Africans and U.S. residents; type II predominated among Japanese and Chinese; and type III predominated in Indians from Calcutta. Sequences in the cagA gene and in vacAm1 type alleles of the vacuolating cytotoxin gene (vacA) of strains from native Peruvians were also more like those from Spaniards than those from Asians. These indications of relatedness of Latin American and Spanish strains, despite the closer genetic relatedness of Amerindian and Asian people themselves, lead us to suggest that H. pylori may have been brought to the New World by European conquerors and colonists about 500 years ago. This thinking, in turn, suggests that H. pylori infection might have become widespread in people quite recently in human evolution.

Amino Acid Isomerases↗

PubMed2000

Distinctiveness of genotypes of Helicobacter pylori in Calcutta, India.

The genotypes of 78 strains of Helicobacter pylori from Calcutta, India (55 from ulcer patients and 23 from more-benign infections), were studied, with a focus on putative virulence genes and neutral DNA markers that were likely to be phylogenetically informative. PCR tests indicated that 80 to 90% of Calcutta strains carried the cag pathogenicity island (PAI) and potentially toxigenic vacAs1 alleles of the vacuolating cytotoxin gene (vacA), independent of disease status. This was higher than in the West (where cag PAI(+) vacAs1 genotypes are disease associated) but lower than in east Asia. The iceA2 gene was weakly disease associated in Calcutta, whereas in the West the alternative but unrelated iceA1 gene at the same locus is weakly disease associated. DNA sequence motifs of vacAm1 (middle region) alleles formed a cluster that was distinct from those of east Asia and the West, whereas the cagA sequences of Calcutta and Western strains were closely related. An internal deletion found in 20% of Calcutta iceA1 genes was not seen in any of approximately 200 strains studied from other geographic regions and thus seemed to be unique to this H. pylori population. Two mobile DNAs that were rare in east Asian strains were also common in Calcutta. About 90% of Calcutta strains were metronidazole resistant. These findings support the idea that H. pylori gene pools differ regionally and emphasize the potential importance of studies of Indian and other non-Western H. pylori populations in developing a global understanding of this gastric pathogen and associated disease.

Adult↗

PubMed2000

Sequential inactivation of rdxA (HP0954) and frxA (HP0642) nitroreductase genes causes moderate and high-level metronidazole resistance in Helicobacter pylori.

Helicobacter pylori is a human-pathogenic bacterial species that is subdivided geographically, with different genotypes predominating in different parts of the world. Here we test and extend an earlier conclusion that metronidazole (Mtz) resistance is due to mutation in rdxA (HP0954), which encodes a nitroreductase that converts Mtz from prodrug to bactericidal agent. We found that (i) rdxA genes PCR amplified from 50 representative Mtz(r) strains from previously unstudied populations in Asia, South Africa, Europe, and the Americas could, in each case, transform Mtz(s) H. pylori to Mtz(r); (ii) Mtz(r) mutant derivatives of a cultured Mtz(s) strain resulted from mutation in rdxA; and (iii) transformation of Mtz(s) strains with rdxA-null alleles usually resulted in moderate level Mtz resistance (16 microg/ml). However, resistance to higher Mtz levels was common among clinical isolates, a result that implicates at least one additional gene. Expression in Escherichia coli of frxA (HP0642; flavin oxidoreductase), an rdxA paralog, made this normally resistant species Mtz(s), and frxA inactivation enhanced Mtz resistance in rdxA-deficient cells but had little effect on the Mtz susceptibility of rdxA(+) cells. Strains carrying frxA-null and rdxA-null alleles could mutate to even higher resistance, a result implicating one or more additional genes in residual Mtz susceptibility and hyperresistance. We conclude that most Mtz resistance in H. pylori depends on rdxA inactivation, that mutations in frxA can enhance resistance, and that genes that confer Mtz resistance without rdxA inactivation are rare or nonexistent in H. pylori populations.

Amino Acid Substitution↗

PubMed2000

Metronidazole activation is mutagenic and causes DNA fragmentation in Helicobacter pylori and in Escherichia coli containing a cloned H. pylori RdxA(+) (Nitroreductase) gene.

Much of the normal high sensitivity of wild-type Helicobacter pylori to metronidazole (Mtz) depends on rdxA (HP0954), a gene encoding a novel nitroreductase that catalyzes the conversion of Mtz from a harmless prodrug to a bactericidal agent. Here we report that levels of Mtz that partially inhibit growth stimulate forward mutation to rifampin resistance in rdxA(+) (Mtz(s)) and also in rdxA (Mtz(r)) H. pylori strains, and that expression of rdxA in Escherichia coli results in equivalent Mtz-induced mutation. A reversion test using defined lac tester strains of E. coli carrying rdxA(+) indicated that CG-to-GC transversions and AT-to-GC transitions are induced more frequently than other base substitutions. Alkaline gel electrophoretic tests showed that Mtz concentrations near or higher than the MIC for growth also caused DNA breakage in H. pylori and in E. coli carrying rdxA(+), suggesting that this damage may account for most of the bactericidal action of Mtz. Coculture of Mtz(s) H. pylori with E. coli (highly resistant to Mtz) in the presence of Mtz did not stimulate forward mutation in E. coli, indicating that the mutagenic and bactericidal products of Mtz metabolism do not diffuse significantly to neighboring (bystander) cells. Our results suggest that the widespread use of Mtz against other pathogens in people chronically infected with H. pylori may stimulate mutation and recombination in H. pylori, thereby speeding host-specific adaptation, the evolution of virulence, and the emergence of resistance against Mtz and other clinically useful antimicrobials.

Amino Acid Substitution↗

PubMed2000

Functional organization and insertion specificity of IS607, a chimeric element of Helicobacter pylori.

A search by subtractive hybridization for sequences present in only certain strains of Helicobacter pylori led to the discovery of a 2-kb transposable element to be called IS607, which further PCR and hybridization tests indicated was present in about one-fifth of H. pylori strains worldwide. IS607 contained two open reading frames (ORFs) of possibly different phylogenetic origin. One ORF (orfB) exhibited protein-level homology to one of two putative transposase genes found in several other chimeric elements including IS605 (also of H. pylori) and IS1535 (of Mycobacterium tuberculosis). The second IS607 gene (orfA) was unrelated to the second gene of IS605 and might possibly be chimeric itself: it exhibited protein-level homology to merR bacterial regulatory genes in the first approximately 50 codons and homology to the second gene of IS1535 (annotated as "resolvase," apparently due to a weak short recombinase motif) in the remaining three-fourths of its length. IS607 was found to transpose in Escherichia coli, and analyses of sequences of IS607-target DNA junctions in H. pylori and E. coli indicated that it inserted either next to or between adjacent GG nucleotides, and generated either a 2-bp or a 0-bp target sequence duplication, respectively. Mutational tests showed that its transposition in E. coli required orfA but not orfB, suggesting that OrfA protein may represent a new, previously unrecognized, family of bacterial transposases.

Amino Acid Sequence↗

PubMed2000

Rapid, efficient detection and drug susceptibility testing of Mycobacterium tuberculosis in sputum by microscopic observation of broth cultures. The Tuberculosis Working Group in Peru.

Inexpensive, rapid, and reliable methods of detecting infection by and drug susceptibility of Mycobacterium tuberculosis (MTB) are crucial to the control of tuberculosis. The novel microscopic observation broth-drug susceptibility assay (MODS) detects early growth of MTB in liquid medium, allowing more timely diagnosis and drug susceptibility testing. Sputum samples from hospitalized patients in Peru were analyzed by using stains, culture, and PCR. Sensitivity of MODS (92%) compared favorably with the most sensitive of the other culture methods (93%). Sputum samples positive for tuberculosis were tested for susceptibility to isoniazid and rifampin with the microwell alamar blue assay (MABA) and MODS. In 89% of cases, there was concordance between MODS and MABA. Of the diagnostic and susceptibility testing methods used, MODS yielded results most rapidly (median, 9.0 and 9.5 days, respectively). MODS is a rapid, inexpensive, sensitive, and specific method for MTB detection and susceptibility testing; it is particularly appropriate for use in developing countries burdened by significant infection rates and increasing numbers of multiple-drug-resistant cases.

Antitubercular Agents↗

PubMed2000

Fate of Campylobacter jejuni in butter.

An outbreak of Campylobacter enteritis was associated with a restaurant in Louisiana during the summer of 1995. Thirty cases were identified, and four required hospitalization. Campylobacter jejuni was isolated from the patients, and epidemiologic studies revealed illness associated with eating garlic butter served at the restaurant. Three batches of garlic butter prepared by the restaurant associated with the outbreak and a C. jejuni isolate obtained from a patient involved in the outbreak were used for studies to determine the fate of C. jejuni in garlic butter. Studies also were done to determine the efficacy of the heat treatment used by the restaurant to prepare garlic bread to kill C. jejuni. Garlic butter was inoculated with approximately 10(4) and 10(6) CFU/g of C. jejuni and held at 5 or 21 degrees C. Results revealed that the survival of C. jejuni differed greatly, depending on the presence or absence of garlic. At 5 degrees C, C. jejuni populations decreased to an undetectable level (<10 CFU/g) within 3 h for two batches and within 24 h for another batch. In contrast, C. jejuni could survive at 5 degrees C for 13 days in butter with no garlic. At 21 degrees C, C. jejuni populations decreased to an undetectable level within 5 h for two batches and to 50 CFU/g in 5 h for another batch. In contrast, C. jejuni was detected at 500 CFU/g at 28 h after inoculation but was undetectable at 3 days in butter with no garlic held at 21 degrees C. The heating procedure (135 degrees C, 4 min) used to make garlic bread by the implicated restaurant was determined not to be sufficient for killing C. jejuni, with the internal temperature of the buttered bread after heating ranging from 19 to 22 degrees C. This study revealed that C. jejuni can survive for many days in refrigerated butter, but large populations (10(3) to 10(5) CFU/g) are killed within a few hours in butter that contains garlic. Furthermore, the heat treatment used by the restaurant to melt garlic butter in making garlic bread was not adequate to kill C. jejuni.

Animals↗

PubMed1999

Host specificity of Helicobacter pylori strains and host responses in experimentally challenged nonhuman primates.

BACKGROUND & AIMS: The specificity of colonization by Helicobacter pylori and complex host-bacterium interactions cannot be readily examined in humans. The aim of this study was to perform such analyses in rhesus monkeys. METHODS: Four animals that had been cured of natural H. pylori colonization were challenged with a mixture of 7 strains of human origin, and bacteria recovered during periodic videogastroscopy were DNA fingerprinted. RESULTS: Three animals carried mixtures of several strains for 4 months, after which strain J166 predominated. In the fourth animal, only strain J238 was isolated from the earliest phase of colonization through 7 months, but strain J166 again became predominant by 10 months after the challenge. Gastritis scores and plasma gastrin and anti-H. pylori immunoglobulin G titers reached levels observed in naturally colonized animals by 4 months after the challenge; however, no plasma immunoglobulin A response was observed up to 10 months. CONCLUSIONS: These results show that (1) natural colonization does not elicit protective immunity against subsequent H. pylori challenge; (2) individuals differ in susceptibility to different H. pylori strains during initial stages of colonization; and (3) certain strains are better suited than others for long-term survival in different hosts. These observations show the complexity of H. pylori-host interactions.

Animals↗

PubMed1999

Emergence of recombinant strains of Helicobacter pylori during human infection.

Genetic recombination can be important evolutionarily in speeding the adaptation of organisms to new environments and in purging deleterious mutations. Here, we describe polymerase chain reaction (PCR), hybridization and DNA sequence-based evidence of six such exchanges between two strains of Helicobacter pylori during natural mixed infection of a patient in Lithuania. One parent strain contained the 37 kb long, virulence-associated cag pathogenicity island (PAI), and the other strain lacked this PAI. Most H. pylori from the patient had descended from the cag+ parent, but had become cag- during infection. This had resulted from transfer of DNA containing the 'empty site' allele from the cag- strain and homologous recombination, not from excision of the cag PAI without DNA transfer. Other cases of recombination involved genes for an outer membrane protein (omp5 and omp29; also called HP0227 and HP1342) and a putative phosphoenolpyruvate synthase (ppsA; HP0121). Replacement of a short patch of DNA sequence (36-124 bp) was also seen. As the chance of forming any given recombinant is small, the abundance of recombinants in this patient suggests selection for particular recombinant genotypes during years of chronic infection. We suggest that genetic exchange among unrelated H. pylori strains, as documented here, is important because of the diversity of this gastric pathogen and its human hosts. Certain H. pylori recombinants may grow better in a given host than either parent. The vigour of growth, in turn, could impact on the severity of disease that infection can elicit.

Adolescent↗

PubMed1999

Helicobacter pylori with separate beta- and beta'-subunits of RNA polymerase is viable and can colonize conventional mice.

The genes encoding the beta- and beta'-subunits of RNA polymerase (rpoB and rpoC respectively) are fused as one continuous open reading frame in Helicobacter pylori and in other members of this genus, but are separate in other bacterial taxonomic groups, including the closely related genus Campylobacter. To test whether this beta-beta' tethering is essential, we used polymerase chain reaction-based cloning to separate the rpoB and rpoC moieties of the H. pylori rpoB-rpoC fusion gene with a non-polar chloramphenicol resistance cassette containing a new translational start, and introduced this construct into H. pylori by electro-transformation. H. pylori containing these separated rpoB and rpoC genes in place of the native fusion gene produced non-tethered beta and beta' RNAP subunits, grew well in culture and colonized and proliferated well in conventional C57BL/6 mice. Thus, the extraordinary beta-beta' tethering is not essential for H. pylori viability and gastric colonization.

Animals↗

PubMed1999

Recombination and clonal groupings within Helicobacter pylori from different geographical regions.

A collection of 20 strains of Helicobacter pylori from several regions of the world was studied to better understand the population genetic structure and diversity of this species. Sequences of fragments from seven housekeeping genes (atpA, efp, mutY, ppa, trpC, ureI, yphC ) and two virulence-associated genes (cagA, vacA) showed high levels of synonymous sequence variation (mean percentage Ks of 10-27%) and lower levels of non-synonymous variation (mean percentage Ka of 0.2-5.6%). Cluster analysis of pairwise differences between alleles revealed the existence of two weakly clonal groupings, which included half of the strains investigated. All six strains isolated from Japanese and coastal Chinese were assigned to the 'Asian' clonal grouping, probably reflecting descent from a distinct common ancestor. The clonal groupings were not totally uniform; recombination, as measured by the homoplasy test and compatibility matrices, was extremely common within all genes tested, except cagA. The fact that clonal descent could still be discerned despite such frequent recombination possibly reflects founder effects and geographical separation and/or selection for particular alleles of these genes.

Aldose-Ketose Isomerases↗

PubMed1999

PCR-based diagnosis of Helicobacter pylori infection in Polish children and adults.

Infection and associated disease caused by Helicobacter pylori are common in Poland, as in much of Eastern Europe, although the genotypes of strains have not been much studied, especially in terms of traits that might be important in disease. This study developed a sensitive and efficient polymerase chain reaction (PCR) test for the presence of H. pylori in gastric biopsy samples with ureA gene-specific primers and primers for the virulence-associated cag pathogenicity island (PAI). These tests were used with biopsy samples from 246 symptomatic children (age range 1-17 years) and 82 adults (age range 18-53 years) in Warsaw. An assessment was also made of the success of metronidazole-based therapy intended to eradicate infection. H. pylori was detected by ureA-specific PCR in 83 (76.9%) children and in 41 (87.2%) adults with histologically proven gastritis, and in 28.4% and 29.2%, respectively, of the 38 children and 7 adults with little or no evidence of gastritis. In general, H. pylori was detected more often by PCR than by culture (70.3% compared with 52.8% in children and 62.8% compared with 38.6% in adults), although in several cases a negative PCR was associated with a positive culture result. The rate of H. pylori infection increased with age from 5.4% in children up to 5 years old to 29.2% to age 10 and 65.4% to age 18. The tests detected the cagPAI in 97 (75%) and 44 (85%) of the H. pylori-infected children and adults, respectively. Some H. pylori-infected patients with a ureA+ PCR result contained the 'empty site' of the cagPAI and only four patients were infected with mixed cag+ cag- strains. PCR with cagPAI and 'empty site' of the cagPAI represents a novel tool for fast screening of mixed cag+ cag- infection. These results confirm and further illustrate that direct PCR of biopsy specimens can be useful for detection of infection and genotyping of resident strains, and that H. pylori infection is very common among children as well as adults in Poland. They also show that Polish strains vary with regard to the presence or absence of the cagPAI, and suggest that the proportion of strains that are cag+ is higher in Poland than in Western European countries, which may reflect the relatively higher risk of infection in this society.

Adolescent↗

PubMed1999

Insertion of mini-IS605 and deletion of adjacent sequences in the nitroreductase (rdxA) gene cause metronidazole resistance in Helicobacter pylori NCTC11637.

We found that NCTC11637, the type strain of Helicobacter pylori, the causative agent of peptic ulcer disease and an early risk factor for gastric cancer, is metronidazole resistant. DNA transformation, PCR-based restriction analysis, and DNA sequencing collectively showed that the metronidazole resistance of this strain was due to mutation in rdxA (gene HP0954 in the full genome sequence of H. pylori 26695) and that resistance did not depend on mutation in any of the other genes that had previously been suggested: catalase (katA), ferredoxin (fdx), flavodoxin (fldA), pyruvate:flavodoxin oxidoreductase (porgammadeltaalphabeta), RecA (recA), or superoxide dismutase (sodB). This is in accord with another recent study that attributed metronidazole resistance to point mutations in rdxA. However, the mechanism of rdxA inactivation that we found in NCTC11637 is itself also novel: insertion of mini-IS605, one of the endogenous transposable elements of H. pylori, and deletion of adjacent DNA sequences including 462 bp of the 851-bp-long rdxA gene.

Amino Acid Sequence↗

PubMed1999

Multiple genes in the left half of the cag pathogenicity island of Helicobacter pylori are required for tyrosine kinase-dependent transcription of interleukin-8 in gastric epithelial cells.

Helicobacter pylori strains that contain the cag pathogenicity island (PAI) elicit increased synthesis of gastric C-X-C chemokines, promote neutrophilic infiltration into the gastric epithelium, and stimulate the synthesis of interleukin-8 (IL-8) in cultured gastric epithelial cells. To investigate the effects of cag PAI genes on the transcription of the IL-8 gene, the Kato-3 gastric epithelial cell line was stably transfected with plasmid DNA containing the IL-8 gene promoter fused to a luciferase reporter gene. The resulting reporter cell line, L5F11, was used to monitor the effects of infection in cell culture by H. pylori 26695 and isogenic derivatives with null mutations in genes in the cag PAI on transcription of the IL-8 gene. We found that null mutations in eight open reading frames, including homologs of the Agrobacterium virB9, virB10, and virB11 genes, in the left half of the cag PAI abrogated the induction of IL-8 gene transcription. Further studies with the L5F11 cell line showed that IL-8 gene transcription induced by H. pylori was blocked by the protein tyrosine kinase inhibitor herbimycin A but not by the protein kinase C inhibitor calphostin C or by the protein kinase G inhibitor KT5823. IL-8 gene transcription in L5F11 cells could also be induced by the cytokine tumor necrosis factor alpha (TNF-alpha) without exposure to H. pylori. This TNF-alpha-induced IL-8 transcription was inhibited by the protein kinase A inhibitor H7, which had no significant effect on H. pylori-induced IL-8 transcription. These studies show that multiple genes in the left half of the cag PAI are essential for the transcription of the IL-8 gene in gastric epithelial cells and that this depends on protein tyrosine kinase activation.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗

PubMed1999

Fused and overlapping rpoB and rpoC genes in Helicobacters, Campylobacters, and related bacteria.

The genes coding for the beta (rpoB) and beta' (rpoC) subunits of RNA polymerase are fused in the gastric pathogen Helicobacter pylori but separate in other taxonomic groups. To better understand how the unique fused structure evolved, we determined DNA sequences at and around the rpoB-rpoC junction in 10 gastric and nongastric species of Helicobacter and in members of the related genera Wolinella, Arcobacter, Sulfurospirillum, and Campylobacter. We found the fusion to be specific to Helicobacter and Wolinella genera; rpoB and rpoC overlap in the other genera. The fusion may have arisen by a frameshift mutation at the site of rpoB and rpoC overlap. Loss of good Shine-Dalgarno sequences might then have fixed the fusion in the Helicobacteraceae, even if fusion itself did not confer a selective advantage.

Amino Acid Sequence↗

PubMed1999

Modulation of Helicobacter pylori induced interleukin-8 synthesis in gastric epithelial cells mediated by cag PAI encoded VirD4 homologue.

BACKGROUND: Strains of Helicobacter pylori carrying the virulence associated cag pathogenicity island (PAI) induce gastric epithelial synthesis of the chemokine interleukin-8 (IL-8), a neutrophil chemoattractant, and thereby a strong inflammatory response during chronic infection of the human gastric mucosa. Previous mutational analyses have shown that many genes in the cag PAI are needed to elicit IL-8 synthesis in gastric epithelial cells, and also that some genes are not involved. AIM: To test the possibility that certain genes in the cag PAI also downregulate (modulate) the inflammatory response elicited by cag+ H pylori infection. METHODS: Cells of L5F11, a derivative of the Kato-3 gastric epithelial cell line that carries an engineered IL-8 promoter-luciferase reporter gene fusion, were cocultured with H pylori strain 26695 or with an isogenic mutant in which most of the cag PAI ORF 10 gene, an Agrobacterium virD4 homologue, was deleted. Luciferase activity was measured to assess IL-8 gene transcription and secreted IL-8 was measured by enzyme linked immunosorbent assay to assess synthesis and release of IL-8 protein from gastric epithelial cells. RESULTS: Inactivation of ORF10 led to a 2.8-fold increase in IL-8 gene transcription and a 3.6-fold increase in IL-8 synthesis and secretion. CONCLUSIONS: The results suggest that this VirD4 homologue participates in the control of inflammation that H pylori infection elicits by downregulating (modulating) the strong induction of IL-8 synthesis mediated by other cag encoded proteins.

Bacterial Proteins↗