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Published on: March 24, 2017
Proteomic characterization of Helicobacter pylori CagA antigen recognized by child serum antibodies and its epitope
Junko Akada1, Masumi Okuda2, Narumi Hiramoto1
1Department of Biochemistry and Functional Proteomics, Yamaguchi University Graduate School of Medicine, Ube, Yamaguchi, Japan.
Insights
This study identified key Helicobacter pylori antigens, particularly CagA, in Japanese children. These findings improve serological diagnosis of H. pylori infection in pediatric populations.
Area of Science:
- Immunology
- Microbiology
- Pediatrics
Background:
- Serum antibodies are crucial for fighting infections and diagnosing diseases.
- Helicobacter pylori (H. pylori) is a gastric bacterium linked to gastric cancer, with established adult serodiagnosis needing pediatric refinement.
Purpose of the Study:
- To identify antigenic proteins in Japanese children's serum against H. pylori.
- To improve serological diagnosis of H. pylori infection in pediatric patients.
Main Methods:
- Two-dimensional electrophoresis, immunoblot, and LC-MS/MS analysis were used to identify H. pylori antigens in pediatric serum samples.
- A novel peptide/protein-combined array chip method was employed to pinpoint CagA epitopes.
Main Results:
- Twenty-four candidate antigen proteins were identified from a Japanese H. pylori strain.
- The cytotoxin-associated gene A protein (CagA) was the most reactive antigen in all H. pylori-positive children, including those under three.
- Specific CagA epitopes, unique to East Asian strains, were identified, highlighting their diagnostic significance.
Conclusions:
- The study identified CagA as a highly reactive antigen for H. pylori serodiagnosis in children.
- Regional CagA epitopes are important for accurate H. pylori diagnosis in pediatric populations.
- These findings contribute to improved diagnostic tools for H. pylori infection in children.
Abstract:
Serum antibodies against pathogenic bacteria play immunologically protective roles, and can be utilized as diagnostic markers of infection. This study focused on Japanese child serum antibodies against Helicobacter pylori, a chronically-infected gastric bacterium which causes gastric cancer in adults. Serological diagnosis for H. pylori infection is well established for adults, but it needs to be improved for children. Serum samples from 24 children, 22 H. pylori (Hp)-positive and 2 Hp-negative children, were used to catalogue antigenic proteins of a Japanese strain CPY2052 by two-dimensional electrophoresis followed by immunoblot and LC-MS/MS analysis. In total, 24 proteins were identified as candidate antigen proteins. Among these, the major virulence factor, cytotoxin-associated gene A protein (CagA) was the most reactive antigen recognized by all the Hp-positive sera even from children under the age of 3 years. The major antigenic part of CagA was identified in the middle region, and two peptides containing CagA epitopes were identified using a newly developed peptide/protein-combined array chip method, modified from our previous protein chip method. Each of the epitopes was found to contain amino acid residue(s) unique to East Asian CagA. Epitope analysis of CagA indicated importance of the regional CagA antigens for serodiagnosis of H. pylori infection in children.
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