Assessment of Helicobacter pylori vacA and cagA genotypes and host serological response

Helicobacter pylori strains can be distinguished by genotyping of virulence -associated genes, such as vacA and cagA. Because serological discriminatio n between strain types would reduce the need for endoscopy, 61 patients car rying H. pylori were studied by vacA and cagA genotyping of H. pylori in ga stric biopsy specimens and by detection of specific serum antibodies. Serol ogical responses to H. pylori were determined by Helicoblot (versions 2.0 a nd 2.1). Antibodies to CagA also were determined by a rapid anti-CagA assay (Pyloriset screen CagA) as well as by two noncommercially developed enzyme immunoassays, each using a recombinant CagA protein. Assessment of perform ance of the Helicoblot assays indicated substantial interobserver variation , with kappa values between 0.20 and 0,93. There was no relationship betwee n the serological profiles on the Helicoblot and the genotypes from the sam e patients, except for strong associations between the presence of anti-Cag A and the cagA-positive and racA s1 H. pylori genotypes, Detection of anti- CagA by the five different assays varied considerably, with kappa values ra nging from 0.21 to 0.78, Using the cagA genotype as the "gold standard," th e sensitivity and specificity of the anti-CagA assays varied from 71.4 to 8 5.7% and from 54.2 to 100%, respectively. Thus, serological profiles of ant ibodies to H. pylori are heterogeneous and, with the exception of anti-CagA antibodies, show no relation to the H. pylori vacA and cagA genotypes, Det ection of anti-CagA antibodies is strongly dependent on the test used.