Immune response to natural and recombinant antigens of Helicobacter pyloriin patients with dyspeptic complaints

Sera of 223 dyspeptic patients with endoscopic findings of nonulcer dyspeps ia (72%), gastric ulcer (15%) and duodenal ulcer (13%) were tested for anti bodies against Helicobacter pylori with an enzyme immunoassay and an immuno blot technique using lysates of Helicobacter pylori cells as antigen source . One hundred and fifty-one (68%) sera were found to be positive for Helico bacter pylori IgG with both methods: 5% of the positive results in the enzy me immunoassay were false-positive due to cross-reactions mainly of protein s with a molecular mass of 43-66 kDa, Since cross-reactivity not only reduc es the diagnostic value of the immunoassay but also complicates evaluation of the immunoblot results, an attempt was made to overcome these problems b y using specific purified recombinant proteins instead of the crude cell pr eparations as antigens, Of the commonly recognised immunogens of Helicobact er pylori, antibodies against a cell surface protein of 26 kDa, the small u rease subunit (29 kDa) and the cytotoxin-associated protein (130 kDa) were identified as highly sensitive serological markers for inclusion in a recom binant antigen mixture for Helicobacter pylori screening, Only the cytotoxi n-associated protein was confirmed to be an indicator immunogen for ulcerog enic strains. To assess the reliability of recombinant fragments of this pr otein in serological screening, the reactivity of antibody to purified frag ments of the cytotoxin-associated protein was compared with that to the nat ural protein. A C-terminal recombinant fragment of 58 kDa showed results id entical to those obtained with the natural protein and was thus considered to be an appropriate component of an antigen mixture for serological detect ion of Helicobacter pylori.