A strain-specific antigen in Japanese Helicobacter pylori recognized in sera of Japanese children

Abstract

An enzyme immuno assay (EIA) test based on Japanese strain-derived high-molecular-weight cell-associated proteins (JHM-CAP) was evaluated by comparing with a previously developed EIA test based on a U.S. strain-derived high-molecular-weight cell-associated proteins (HM-CAP). Serum samples of 131 Japanese asymptomatic children (mean age, 5.5 years; range, 0 to 21 years) were tested that include 43 positive and 88 negative children as judged by Helicobacter pylori stool antigen test (HpSA test). Both tests showed comparable and reliable specificities, but the sensitivity of JHM-CAP EIA, at 93.0%, was much higher than that of HM-CAP EIA, at 67.4%. More false-negative results of HM-CAP were obtained in children under 10 years of age. Immunoblot analysis revealed that the JHM-CAP but not the HM-CAP preparation had a 100-kDa antigen recognized by JHM-CAP positive sera. It was concluded that JHM-CAP EIA is highly accurate for the serodiagnosis of H. pylori infection in Japanese young children and that the high sensitivity of JHM-CAP EIA in contrast to HM-CAP EIA is due to the presence of a 100-kDa antigen in Japanese strains that may be recognized by the host immune system at an early stage of infection.

FIG. 1.

Relationship of EVs between JHM-CAP and HM-CAP EIA of HpSA-positive (○) and -negative children (•). Dotted areas represent equivocal EVs, and the horizontal and vertical dotted lines represent the mean EVs of JHM-CAP and HM-CAP EIA, respectively, of 43 HpSA-positive children.

FIG. 2.

(A) Immunoblotting of JHM-CAP-positive/HM-CAP-negative sera (cases 8 and 1), positive control (case 23), and negative control sera (case 26) with JHM-CAP antigen (JHM) and HM-CAP antigen preparations (HM). JHM-CAP (0.36 μg) and HM-CAP (0.56 μg) antigens were separated by SDS-PAGE, followed by immunoblotting. EVs of JHM-CAP and HM-CAP EIA of sample sera: case 8, 3.0 and 1.7; case 1, 5.9 and 1.0; case 23, 7.4 and 5.3; case 26, 0.6 and 0.3, respectively. M, molecular size markers (in kilodaltons). (B) SDS-PAGE of JHM-CAP (2.9 μg) and HM-CAP (2.24 μg) antigen preparations. M, molecular size markers (in kilodaltons).