Isocitrate dehydrogenase ofHelicobacter pyloripotentially induces humoral immune response in subjects with peptic ulcer disease and gastritis

Background.H. pyloricauses gastritis and peptic ulcers and is a risk factor for the development of gastric carcinoma. Many of the proteins such as urease, porins, flagellins and toxins such as lipo-polysaccharides have been identified as potential virulence factors which induce proinflammatory reaction. We report immunogenic potentials of isocitrate dehydrogenase (ICD), an important house keeping protein ofH. pylori.Methodology/Principal Findings. Amino acid sequences ofH. pyloriICD were subjected to in silico analysis for regions with predictably high antigenic indexes. Also, computational modelling of theH. pyloriICD as juxtaposed to theE. coliICD was carried out to determine levels of structure similarity and the availability of surface exposed motifs, if any. Theicdgene was cloned, expressed and purified to a very high homogeneity. Humoral response directed againstH. pyloriICD was detected through an enzyme linked immunosorbent assay (ELISA) in 82 human subjects comprising of 58 patients withH. pyloriassociated gastritis or ulcer disease and 24 asymptomatic healthy controls. TheH. pyloriICD elicited potentially high humoral immune response and revealed high antibody titers in sera corresponding to endoscopically-confirmed gastritis and ulcer disease subjects. However, urea-breath-test negative healthy control samples and asymptomatic control samples did not reveal any detectable immune responses. The ELISA for proinflammatory cytokine IL-8 did not exhibit any significant proinflammatory activity of ICD.Conclusions/Significance. ICD ofH. pyloriis an immunogen which interacts with the host immune system subsequent to a possible autolytic-release and thereby significantly elicits humoral responses in individuals with invasiveH. pyloriinfection. However, ICD could not significantly stimulate IL8 induction in a cultured macrophage cell line (THP1) and therefore, may not be a notable proinflammatory agent.