IMMUNOBLOT ASSAY FOR SERODIAGNOSIS OF HELICOBACTER-PYLORI INFECTIONS

An immunoblot assay for the serological diagnosis of Helicobacter pylo ri infection was evaluated, Serum samples from patients whose gastric biopsy specimens were known to be positive or negative for H. pylori o n culture were used to establish interpretive criteria for the immunob lot assay, A panel of sera from patients with diseases other than H. p ylori infection and sera from healthy blood donors were included to va lidate these criteria, All sera were initially assessed in an enzyme i mmunoassay (Ge-ELA), based on acid glycine-extracted cell surface prot eins of H. pylori NCTC 11637, The same antigen extract was used in the immunoblot assay, In addition, the Ge-EIA and the immunoblot assay we re compared with a commercially available EIA (Seradyn, Color Vue Pylo ri), Bands of 110/120 kDa and/or two of five low-molecular-mass protei ns (26, 29, 30, 31, and 33 kDa, in any combination) showed a strong co rrelation with the H. pylori culture-positive patients (97.5%) compare d to the correlation obtained with the EIA results (Ge-EIA, 87.5%; Ser adyn EIA, 92.5%), and the antibody responses to these proteins were co nsidered specific reactions, In 37 of 40 serum samples from culture-ne gative patients and also in sera from patients with other disorders, a moderate antibody reactivity to the medium-size proteins (43 to 66 kD a) was observed, and these were considered not valuable for a specific immunoblot assay, Among sera from culture-positive patients, 39 of 40 serum samples were defined to be immunoblot positive, and from among sera from culture-negative patients, 3 of 40 serum samples were define d to be immunoblot positive, The use of sera from patients with negati ve cultures for H. pylori as negative controls may decrease the sensit ivity due to sampling error and false-negative culture results, Immuno blot assay-positive results were detected among 10% of sera from patie nts with other diseases, whereas they were detected among 42.5% of ser a by the Ge-EIA and 47.5% of sera by the Seradyn-EIA, The higher numbe r of EIA-positive sera in this group reflects a possible cross-reactiv ity (false-positive EIA result), Of the blood donors, representing asy mptomatic but possibly colonized subjects, 24% were immunoblot positiv e, In conclusion, our data indicate that immunoblotting is more sensit ive as well as more specific than ELA, Moreover, it permits detection of antibody responses to specific antigens, e.g., the cytotoxin-associ ated CagA protein, which may have pathological implications.