Characterization of a novel Helicobacter pylori East Asian‑type CagA ELISA for detecting patients infected with various cagA genotypes

Currently, Western-type CagA is used in most commercial Helicobacter pylori CagA ELISA kits for CagA detection rather
than East Asian-type CagA. We evaluated the ability of the East Asian-type CagA ELISA developed by our group to detect
anti-CagA antibody in patients infected with different cagA genotypes of H. pylori from four different countries in South
Asia and Southeast Asia. The recombinant CagA protein was expressed and later purified using GST-tag affinity chromatog-
raphy. The East Asian-type CagA-immobilized ELISA was used to measure the levels of anti-CagA antibody in 750 serum
samples from Bhutan, Indonesia, Myanmar, and Bangladesh. The cutoff value of the serum antibody in each country was
determined via Receiver-Operating Characteristic (ROC) analysis. The cutoff values were different among the four countries
studied (Bhutan, 18.16 U/mL; Indonesia, 6.01 U/mL; Myanmar, 10.57 U/mL; and Bangladesh, 6.19 U/mL). Our ELISA had
better sensitivity, specificity, and accuracy of anti-CagA antibody detection in subjects predominantly infected with East
Asian-type CagA H. pylori (Bhutan and Indonesia) than in those infected with Western-type CagA H. pylori predominant
(Myanmar and Bangladesh). We found positive correlations between the anti-CagA antibody and antral monocyte infiltra-
tion in subjects from all four countries. There was no significant association between bacterial density and the anti-CagA
antibody in the antrum or the corpus. The East Asian-type CagA ELISA had improved detection of the anti-CagA antibody
in subjects infected with East Asian-type CagA H. pylori. The East Asian-type CagA ELISA should, therefore, be used in
populations predominantly infected with East Asian-type CagA.