Immunohistochemical Differentiation between Western and East Asian Types of CagA-Positive in Gastric Biopsy Samples.

Background: Cag A-positive isolated from human gastric mucosa is categorized as a Western or East Asian allele-type based on whether the gene encodes an EPIYA-C or EPIYA-D motif. We aimed to differentiate between the 2 types of by immunohistochemistry (IHC) using formalin-fixed paraffin-embedded (FFPE) gastric biopsy samples.

Materials And Methods: We developed 2 monoclonal antibodies (mAbs) that detect either the EPIYA-C or EPIYA-D motif of the CagA protein by IHC using FFPE tissues. FFPE tissue sections from 30 Japanese and 39 Brazilian gastric biopsy samples with infection confirmed by Giemsa staining (moderate/severe in the Sydney classification system) were examined by IHC with the novel mAbs followed by polymerase chain reaction (PCR) for EPIYA-C or EPIYA-D using DNA extracted from adjacent tissue sections.

Results: Differentiation among Western and East Asian types and CagA-negative was successful in most (97%) samples by IHC with the novel mAbs and commercially available mAbs that react with a species-specific lipopolysaccharide or a common CagA motif of . The detection status of EPIYA-C/D motifs by IHC with the novel mAbs was consistent with the PCR results in 61 (88%) of 69 samples: EPIYA-C(+)/D(-) in zero Japanese and 26 Brazilian samples, EPIYA-C(-)/D(+) in 26 Japanese and 1 Brazilian sample, and EPIYA-C(-)/D(-) in 1 Japanese and 7 Brazilian samples. The detection sensitivity and specificity of IHC with each novel mAb compared with the PCR results were, respectively, 84% and 97% for EPIYA-C, and 97% and 95% for EPIYA-D.

Conclusions: The novel mAbs specific to each EPIYA-C or EPIYA-D motif differentiated between Western and East Asian types of CagA-positive by IHC using FFPE tissues. Applying these novel mAbs to large numbers of archived pathology samples will contribute to elucidating the association of these allele types with gastric cancer.