RESUMO
The cytotoxin-associated antigen A (CagA) of Helicobacter pylori prevalent in East Asian countries, where the mortality rate due to gastric cancer is high, has been reported to be structurally different from that in Western countries, where the gastric cancer mortality rate is relatively low. Based on the structural features of the EPIYA motifs located at the carboxyl terminal of the protein, CagA was subdivided into two types: East Asian CagA and Western CagA. A recent study suggested that immunohistochemistry with anti-East Asian-specific antibody (alpha-EAS Ab), which was specifically immunoreactive with East Asian CagA but not with Western CagA, may be useful for diagnosis of the cagA genotype. To further evaluate the value of this diagnostic method in terms of sensitivity, specificity, and accuracy, 143 gastric biopsy specimens with alpha-EAS Ab were analyzed on immunohistochemistry and compared with the sequencing of the cagA gene. It was found that diagnosis of the cagA genotype of H. pylori on immunohistochemistry using the alpha-EAS Ab was highly sensitive (sensitivity 93.2%) and specific (specificity 72.7%), suggesting that immunohistochemical diagnosis of the cagA genotype is useful for diagnosis of the cagA genotype.
Assuntos
Antígenos de Bactérias/genética , Proteínas de Bactérias/genética , Genes Bacterianos , Helicobacter pylori/genética , Motivos de Aminoácidos/genética , Sequência de Aminoácidos , Especificidade de Anticorpos , Antígenos de Bactérias/química , Antígenos de Bactérias/imunologia , Proteínas de Bactérias/química , Proteínas de Bactérias/imunologia , Biomarcadores/metabolismo , Mucosa Gástrica/metabolismo , Mucosa Gástrica/microbiologia , Mucosa Gástrica/patologia , Genótipo , Infecções por Helicobacter/diagnóstico , Infecções por Helicobacter/metabolismo , Infecções por Helicobacter/microbiologia , Helicobacter pylori/imunologia , Helicobacter pylori/isolamento & purificação , Humanos , Imuno-Histoquímica , Dados de Sequência Molecular , Polimorfismo Genético , Análise de Sequência de DNARESUMO
Cytotoxin-associated antigen A (CagA) protein produced by Helicobacter pylori is proposed to be associated with the pathogenesis of gastric cancer as well as gastritis and gastroduodenal ulcer. It has been reported that the CagA of H. pylori widespread in East Asian countries, where the mortality rate due to gastric cancer is high, is structurally different from that in Western countries, where the gastric cancer mortality rate is relatively low. In this study, we generated an antibody, East Asian CagA-specific antibody (alpha-EAS Ab), which is specifically immunoreactive with East Asian CagA but not with Western CagA. The CagA was immunohistochemically detected at the surface of the gastric mucosa. Interestingly, positive immunoreactivity was also detected in the nucleus and cytoplasm of the infected gastric epithelium, suggesting that CagA may play some pathogenic role in both the nucleus and cytoplasm. Immunohistochemistry of 47 gastric biopsy specimens detected East Asian CagA-positive H. pylori in 43 cases. In 46 of the 47 cases examined, the data obtained by immunohistochemistry were completely consistent with those obtained by sequencing of the cagA gene of the isolated strain, suggesting that our immunohistochemical method is reliable and useful for diagnosis of the cagA genotype.
