A novel Helicobacter pylori blood group antigen binding (BAB) adhesin protein was isolated and purified, whereby said protein or fractions thereof bind specifically to fucosylated blood group antigens. The protein sequence of said adhesin is disclosed in this application. Simultaneously the DNA sequences for two genes, babA and babB, producing highly similar proteins, are disclosed. Said adhesin and/or DNA is useful for diagnose and therapy and/or prophylaxis directed against H. pylori induced infections, e.g. gastritis and acid peptic disease, i.e. active vaccination.A new immunoglobulin composition, which exhibits specific activity to a Lewis.sup.b antigen binding Helicobacter pylori adhesin, or preferably, monoclonal and/or polyclonal antibodies to said adhesin offer a new and more efficient method of treatment and/or prevention of gastrointestinal diseases, caused by Helicobacter pylori or other Helicobacter species, i.e. passive vaccination.