Fatores de risco associados à infecção pelo Helicobacter pylori e ao desfecho clínico

Abstract

Helicobacter pylori is a bacterium that infects the gastric mucosa of approximately 50% of the world´s human population. H. pylori infection has been associated with a variety of diseases such as gastritis, peptic ulcer disease and gastric carcinoma. It is believed that the combination of environmental/behavioral variables, host genetic factors and bacterial pathogenicity genes can interfere in the severity of gastric damage and in the clinical outcome of H. pylori infection. In this sense, the present study aimed to determine the frequency and potential risk factors of the H. pylori infection, even as identify polymorphisms in the interleukin (IL)-1, IL-6, IL-8 and IL-10 genes and their associations with H. pylori infection, with cagA gene of H. pylori, and with gastric pathologies. For this, it was conducted a cross-sectional study, including gastric biopsy samples from 227 patients, submitted to upper gastrointestinal endoscopy. A questionnaire was applied to the patients before endoscopy. The diagnosis of H. pylori was based in histology and in polymerase chain reaction (PCR). The cagA gene was identified by PCR. The polymorphisms in the genes of IL-1B (at positions -511, -31 and +3954), IL-6 (at position -174), IL-8 (at position -251) and IL-10 (at positions -819 and -592) were detected by PCR-restriction fragment length polymorphism (PCR-RFLP). The analysis of the variable number of tandem repeat (VNTR) polymorphism in the IL-1RN gene was performed by PCR followed by electrophoresis agarose gel. Of the 227 patients included in this study, 151 were positive for H. pylori and 76 negative. Based on the questionnaires applied to the patients, it was found a significant association between the presence of H. pylori and the household crowding, the age, and the diagnoses histological and endoscopic. As for host genetic factors was observed that polymorphisms in the promoter region of the IL-1B and IL-8 genes were significantly related with H. pylori infection. The strains from patients H. pylori positive carrying the cagA gene were significantly associated with the polymorphism of IL-1B at position -511. Additionally, in the presence of H. pylori infection, it was demonstrated that polymorphisms in the promoter region of the IL-1B gene were correlated with an enhanced risk of gastritis, while those in the IL-8 and IL-10 genes were associated with higher risk of peptic ulcer disease. We conclude that probably, the host genetic polymorphisms exert influence in the course and gravity of gastric diseases. It is hoped that the results of this work may contribute soon, to the prevention of these diseases and for a more appropriate and effective therapy, this because the knowledge of the molecular basis of the host and the microorganism enables the development of molecular tests that may to be applied toward a correct prognosis of gastric pathologies.