Studies of immune responses to cell surface proteins of Helicobacter pylori and Borrelia burgdorferi by enzyme immunoassay and immunoblotting

Sammanfattning: Helicobacter pylori and Borrelia burgdorferi s.l. can cause chronic infections by evading the immune system. These two human pathogens express a number of immunogenic cell surface proteins. The aims of this study were to gain further knowledge about these antigens and to analyse the serum antibody response in infected individuals. Both invasive and non-invasive diagnostic methods are available for the diagnosis of the infections. Diagnostic techniques based on non-invasive sampling have been evaluated in this study. H. pylori infected patients can harbour more than one strain in the stomach. The specificity and sensitivity of serological methods varies with the antigens chosen. An immunoblot assay for detection of IgG antibodies to acid glycine extracted cell surface proteins of a H. pylori type strain was evaluated. Serum antibodies from culture positive patients specifically reacted with high and low molecular weight surface proteins and cross-reactivity was found with the medium- sized proteins. An optimised assay can now be defined by removing these cross-reacting proteins. There is much evidence today that H. pylori are involved in the development of gastric cancer. Antibodies to the cytotoxin-associated CagA protein were significantly higher in gastric cancer cases than in a random adult population. The immunoblot was more sensitive than the recombinant CagA-EIA. Variations in the antigenic and genetic profile of different Lyme Borrelia species occur. Antibody reactivity to a Borrelia-antigen preparation, lacking heat shock proteins and flagellin was compared with results obtained with a whole cell extract. An increase in test specificity was revealed with the purified Borrelia-fraction. EIA and immunoblots with antigens of B.afzelii were found to detect a higher number of seropositive individuals suggesting that the reliability of serological assays could be increased when serum antibodies against antigens of Borrelia spp. predominant in the local geographical region are measured.