Browsing by Author "Riera, F."

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    CagA antibodies as a marker of virulence in Chilean patients with Helicobacter pylori infection
    (2003) Harris, Paul R.; Godoy, A.; Arenillas, S.; Riera, F.; Garcia, D.; Einisman, H.; Pena, A.; Rollan, T.; Duarte, I.; Guiraldes, E.; Perez-Perez, G.
    Background: The bacterial and host factors that influence the clinical outcomes of the Helicobacter pylori infection have not been fully identified. Cytotoxin-associated gene product (CagA), one of the virulence factors, has been associated with a more aggressive form of infection. The authors studied the relationship between CagA status and clinical outcome in Chilean children and adults with H. pylori infection. Methods: One hundred eighty consecutive patients undergoing upper gastrointestinal endoscopic analysis were enrolled after informed consent was obtained. Rapid urease test and histologic analysis were used to detect H. pylori infection. IgA and IgG antibodies to H. pylori whole cell antigen preparation and IgG antibodies to CagA were measured by enzyme-linked immunosorbent assay (ELISA). Results: H. pylori infection was detected in 42% of the patients by biopsy or urease test and in 38% and 20% of patients by IgG and IgA antibodies, respectively. The prevalence of H. Pylori either by the invasive or the serologic tests was directly related to patient age. Among patients with H. pylori, there was no significant association between age and prevalence of CagA. Nearly 70% of the patients with H. pylori and peptic ulcer disease had CagA-positive strains. In contrast, only 49% of the patients with chronic gastritis alone had CagA-positive strains (P < 0.05). Conclusions: In Chile, patients infected with H. pylori have a proportion of CagA-positive strains similar to that reported in developed countries. CagA prevalence was not significantly different in adults and children infected with H. pylori, suggesting that variations in clinical outcome may be related to host immune or environmental factors.
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    Helicobacter pylori Gastritis in Children Is Associated With a Regulatory T-Cell Response
    (2008) Harris, P.R.; Wright, S.W.; Serrano, C.; Riera, F.; Duarte, I.; Torres, J.; Peña, A.; Rollán, A.; Viviani, P.; Guiraldes, E.; Schmitz, J.M.; Lorenz, R.G.; Novak, L.; Smythies, L.E.; Smith, P.D.
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    Relevance of adjusted cut-off values in commercial serological immunoassays for Helicobacter pylori infection in children
    (2005) Harris, Paul R.; Perez-Perez, G.; Zylberberg, A.; Rollán, A.; Serrano, C.; Riera, F.; Einisman, H.; García, D.; Viviani, P.
    We assessed the sensitivity and specificity of H. pylori IgG and IgA with a commercial immunoassay performed in Chile and a second non-commercial immunoassay performed in a reference laboratory in the United States, in serum of 80 children and adults referred for gastrointestinal endoscopies in a developing country. Overall, 56% of the patients were infected with H. pylori based on rapid urease test and staining techniques on gastric biopsies. When Receiver Operator Curves (ROC) were developed, the sensitivity and specificity were similar for IgG and IgA. Both immunoassays exhibited better specificity, positive and negative predictive value (NPV) in children than in adults when cut-off values were corrected according to the local population than when they were assessed using the cut-off values pre-defined in other populations. These results underline the need to establish more precise cut-off values corrected in the local populations where assessments of antibodies as diagnostic markers of H. pylori infection are planning. © 2005 Springer Science+Business Media, Inc.