Margarita Camorlinga-Ponce

A Community-Based Seroepidemiologic Study of Helicobacter pylori Infection in Mexico

A nationwide community-based survey for Helicobacter pylori infection had not been done. This study sought to determine the seroprevalence of infection in Mexico, and the socioeconomic and demographic variables that are risk factors for infection. The survey assessed 11,605 sera from a sample population representing persons ages 1-90 years from all socioeconomic and demographic levels and from all regions of Mexico. Antibodies against H. pylori were studied by ELISA using whole cell antigen. Among the findings were that 66% of the population was infected and that age was the strongest risk factor for infection. By age 1 year, 20% were infected and by age 10 years, 50% were infected. Crowding (odds ratio [OR], 1.4), low educational level (OR, 2.42), and low socioeconomic level (OR, 1.43) were risk factors for infection. Prevalence was similar in urban and in rural communities (OR, 0.95). This study is the largest community-based seroepidemiologic study of H. pylori to date.

Increasing Multidrug Resistance in Helicobacter pylori Strains Isolated from Children and Adults in Mexico

ABSTRACT The susceptibilities to three antimicrobials of 195Helicobacter pylori strains isolated from Mexican patients is reported; 80% of the strains were resistant to metronidazole, 24% were resistant to clarithromycin, and 18% presented a transient resistance to amoxicillin. Resistance to two or more antimicrobials increased significantly from 1995 to 1997.

Validation of a Serologic Test for the Diagnosis of Helicobacter pylori Infection and the Immune Response to Urease and CagA in Children

Objective:Little is known about Helicobacter pylori infections and the immune response to urease and CagA in pediatric populations. Our aims were: 1) to validate serological assays for antibodies against whole cell extract, CagA, and urease of H. pylori; 2) to examine their role in diagnosis of infection in children with recurrent abdominal pain (RAP); and 3) to examine the antibody responses to CagA and urease in children.Methods:An enzyme-linked immunosorbent assay (ELISA) for diagnosis of H. pylori infection using whole cell extracts was validated in 50 children with biopsy-confirmed infection. The IgG and IgA antibody responses against recombinant CagA and urease were compared by ELISA in 82 children with RAP and in 246 age- and sex-matched healthy children.Results:The whole-cell extract ELISA had a sensitivity of 85% and specificity of 87%. Children with RAP were more infected with H. pylori than were healthy control subjects; however, IgG and IgA CagA seropositivity was lower among those with RAP than among asymptomatic children (34% and 23%vs 76% and 55%, respectively; p < 0.0001). In both groups of children, the immune response to urease was low.Conclusion:A serodiagnosis of H. pylori infection using native strains was developed. The difference in the immune response between children with RAP and control subjects suggests that RAP occurs during the acute phase of H. pylori infection. Our results also suggest that urease is a poor immunogen.

TLR4 single-nucleotide polymorphisms alter mucosal cytokine and chemokine patterns in Mexican patients with Helicobacter pylori-associated gastroduodenal diseases.

Helicobacter pylori is associated with peptic ulcer and gastric adenocarcinoma. Toll-like receptors (TLRs) participate in H. pylori recognition, and single-nucleotide polymorphisms (SNPs) in TLRs are associated with impaired immune response. We aimed to evaluate the association of TLR2/R753Q and TLR4/D299G/T399I SNPs with gastroduodenal diseases; and study the effect of SNPs on cytokine and chemokine expression in the gastric mucosa. Study included 450 Mexican patients with gastroduodenal diseases. SNPs in TLRs 2 and 4 genes were analyzed by allele-specific PCR. Cytokines and chemokines were assessed by qRT-PCR and immunoassay. TLR4/D299G/T399I polymorphisms were more frequent in duodenal ulcer and showed a trend in gastric cancer, when compared with non-atrophic gastritis. Patients with TLR4 polymorphisms expressed significantly lower levels of IL-1beta, IL-6, IL-8 and GRO-alpha; and higher levels of TNF-alpha, IL-10, MCP-1 and MIP-1alpha . SNPs in TLR4 gene had an association with severe H. pylori-associated disease and with modified pattern of inflammatory cytokines and chemokines in the gastric mucosa. These results suggest that TLR4 SNPs contributes importantly to the clinical outcome of H. pylori infection.

Age and Severity of Mucosal Lesions Influence the Performance of Serologic Markers in Helicobacter pylori–Associated Gastroduodenal Pathologies

Objective: The course of Helicobacter pylori infection and antibody response to CagA in patients with preneoplastic lesions and gastric cancer has not been thoroughly studied. We aimed to study H. pylori infection and antibody response to CagA in patients with non–atrophic gastritis, preneoplastic lesions, and gastric cancer. Methods: We studied patients attending one Oncology Hospital and one General Hospital in Mexico City. Diagnosis was based on endoscopy and histopathology in biopsies from six stomach regions. H. pylori infection was assessed by histology and serology, and antibodies against CagA were measured with immunoassay. Results: We included 618 patients, 368 with non–atrophic gastritis, 126 with precancerous lesions, and 65 with gastric cancer; in addition, 59 patients with duodenal ulcer were studied. Detection of infection and IgG against CagA had a significant increase from non–atrophic gastritis to mild and up to advanced stages of metaplasia (P < 0.05), followed by decreased infection and IgG to CagA in patients with gastric cancer (P < 0.05). However, infection and CagA antibodies were associated with young gastric cancer cases. Duodenal ulcer showed a significant association with infection detected by histology and serology, particularly among women, and a trend to associate with IgG to CagA. Conclusions: This study shows that H. pylori infection and CagA are risk markers for intestinal metaplasia. The prevalence of these risk markers decreases in gastric cancer, probably reflecting that infection decreases after advanced atrophy and metaplasia in the gastric mucosa. State of the disease, age, and sex influence the association of H. pylori infection and IgG response to CagA with gastroduodenal diseases. (Cancer Epidemiol Biomarkers Prev 2008;17(9):2498–504)

Differences in Genome Content among Helicobacter pylori Isolates from Patients with Gastritis, Duodenal Ulcer, or Gastric Cancer Reveal Novel Disease-Associated Genes†

ABSTRACT Helicobacter pylori establishes a chronic infection in the human stomach, causing gastritis, peptic ulcer, or gastric cancer, and more severe diseases are associated with virulence genes such as the cag pathogenicity island (PAI). The aim of this work was to study gene content differences among H. pylori strains isolated from patients with different gastroduodenal diseases in a Mexican-Mestizo patient population. H. pylori isolates from 10 patients with nonatrophic gastritis, 10 patients with duodenal ulcer, and 9 patients with gastric cancer were studied. Multiple isolates from the same patient were analyzed by randomly amplified polymorphic DNA analysis, and strains with unique patterns were tested using whole-genome microarray-based comparative genomic hybridization (aCGH). We studied 42 isolates and found 1,319 genes present in all isolates, while 341 (20.5%) were variable genes. Among the variable genes, 127 (37%) were distributed within plasticity zones (PZs). The overall number of variable genes present in a given isolate was significantly lower for gastric cancer isolates. Thirty genes were significantly associated with nonatrophic gastritis, duodenal ulcer, or gastric cancer, 14 (46.6%) of which were within PZs and the cag PAI. Two genes (HP0674 and JHP0940) were absent in all gastric cancer isolates. Many of the disease-associated genes outside the PZs formed clusters, and some of these genes are regulated in response to acid or other environmental conditions. Validation of candidate genes identified by aCGH in a second patient cohort allowed the identification of novel H. pylori genes associated with gastric cancer or duodenal ulcer. These disease-associated genes may serve as biomarkers of the risk for severe gastroduodenal diseases.

Variations in Helicobacter pylori Cytotoxin-Associated Genes and Their Influence in Progression to Gastric Cancer: Implications for Prevention

Helicobacter pylori (HP) is a bacterium that colonizes the human stomach and can establish a long-term infection of the gastric mucosa. Persistent Hp infection often induces gastritis and is associated with the development of peptic ulcer disease, atrophic gastritis, and gastric adenocarcinoma. Virulent HP isolates harbor the cag (cytotoxin-associated genes) pathogenicity island (cagPAI), a 40 kb stretch of DNA that encodes components of a type IV secretion system (T4SS). This T4SS forms a pilus for the injection of virulence factors into host target cells, such as the CagA oncoprotein. We analyzed the genetic variability in cagA and other selected genes of the HP cagPAI (cagC, cagE, cagL, cagT, cagV and cag Gamma) using DNA extracted from frozen gastric biopsies or from clinical isolates. Study subjects were 95 cagA+ patients that were histologically diagnosed with chronic gastritis or gastric cancer in Venezuela and Mexico, areas with high prevalence of Hp infection. Sequencing reactions were carried out by both Sanger and next-generation pyrosequencing (454 Roche) methods. We found a total of 381 variants with unambiguous calls observed in at least 10% of the originally tested samples and reference strains. We compared the frequencies of these genetic variants between gastric cancer and chronic gastritis cases. Twenty-six SNPs (11 non-synonymous and 14 synonymous) showed statistically significant differences (P<0.05), and two SNPs, in position 1039 and 1041 of cagE, showed a highly significant association with cancer (p-value = 2.07×10−6), and the variant codon was located in the VirB3 homology domain of Agrobacterium. The results of this study may provide preliminary information to target antibiotic treatment to high-risk individuals, if effects of these variants are confirmed in further investigations.

Intensity of Inflammation, Density of Colonization and Interleukin-8 Response in the Gastric Mucosa of Children Infected with Helicobacter pylori

Background.  Few reports exist on inflammation and interleukin (IL)‐8 response in H. pylori‐infected children. The aim of this study was to determine the intensity of inflammation, density of colonization and magnitude of IL‐8 response in children with and without H. pylori infection.

Sensitivity in culture of epithelial cells from rhesus monkey kidney and human colon carcinoma to toxins A and B from Clostridium difficile

The effect of toxins A and B from Clostridium difficile on human colon carcinoma cells (HT-29, epithelial), rhesus monkey kidney cells (MA-104, epithelial) and green monkey kidney cells (VERO, fibroblast) was studied. Both toxins caused rounding of HT-29 cells and rounding with projections remaining attached to the substrate in MA-104 and VERO cells; however, the sensitivity to each toxin varies considerably. Toxin A was detected in ng by VERO, pg by HT-29 and fractions of pg by MA-104 cells; for toxin B, pg were detected by VERO, ng by MA-104 and micrograms by HT-29 cells. HT-29 cells were grown with galactose to allow their differentiation to enterocytes, and their sensitivity to the toxins during the process was studied. At early stages, the sensitivity to both toxins was similar, and as the differentiation proceeded, the response to both toxins decreased continuously, and after 16 days no evident morphological effect was observed, even with micrograms amounts of either toxin. In contrast to all cell lines reported to date, HT-29 and MA-104 epithelial cells are exquisitely sensitive to toxin A and less responsive to toxin B. The rounding of HT-29 by these toxins depends on the degree of differentiation of the cell.

Serum Glycan Signatures of Gastric Cancer

Glycomics, a comprehensive study of glycans expressed in biologic systems, is emerging as a simple yet highly sensitive diagnostic tool for disease onset and progression. This study aimed to use glycomics to investigate glycan markers that would differentiate patients with gastric cancer from those with nonatrophic gastritis. Patients with duodenal ulcer were also included because they are thought to represent a biologically different response to infection with Helicobacter pylori, a bacterial infection that can cause either gastric cancer or duodenal ulcer. We collected 72 serum samples from patients in Mexico City that presented with nonatrophic gastritis, duodenal ulcer, or gastric cancer. N-glycans were released from serum samples using the generic method with PNGase F and were analyzed by matrix-assisted laser desorption/ionization Fourier transform-ion cyclotron resonance mass spectrometry. The corresponding glycan compositions were calculated based on accurate mass. ANOVA-based statistical analysis was performed to identify potential markers for each subgroup. Nineteen glycans were significantly different among the diagnostic groups. Generally, decreased levels of high-mannose–type glycans, glycans with one complex type antenna, bigalactosylated biantennary glycans, and increased levels of nongalactosylated biantennary glycans were observed in gastric cancer cases. Altered levels of serum glycans were also observed in duodenal ulcer, but differences were generally in the same direction as gastric cancer. Serum glycan profiles may provide biomarkers to differentiate gastric cancer cases from controls with nonatrophic gastritis. Further studies will be needed to validate these findings as biomarkers and identify the role of protein glycosylation in gastric cancer pathology. Cancer Prev Res; 7(2); 226–35. ©2013 AACR.