Roles of virD4 and cagG genes in the cag pathogenicity island of Helicobacter pylori using a Mongolian gerbil model

Abstract

Background and Aims: The roles of the virD4 and the cagG genes in the cag pathogenicity island of Helicobacter pylori for gastroduodenal pathogenesis are unclear and their roles in vivo have not been examined. Methods: Seven week old male Mongolian gerbils were inoculated with the wild type H pylori TN2GF4, its isogenic virD4, or cagG mutants. Animals were sacrificed at 4, 12, and 24 weeks after inoculation. Gastric inflammation and H pylori density were evaluated by histology, inflammatory response (as measured by interleukin (IL)-1b mRNA levels), proliferative activity (as assessed by 59-bromo29deoxyuridine labelling indices), and host systemic reaction (as measured by anti-H pylori IgG antibody). Results: Degree of gastric inflammation, proliferative activity, and mucosal IL-1b mRNA levels remained low throughout the first 12 weeks in gerbils infected with the virD4 mutants. Degree of gastric inflammation and proliferative activity increased at 24 weeks with the virD4 mutants reaching levels comparative with those seen at four weeks with the wild-type strains. Mucosal IL-1b mRNA levels were also increased at 24 weeks with the virD4 mutants and levels at 24 weeks were similar between the wild-type and virD4 mutants. In contrast, gerbils infected with the cagG mutants had reduced ability to colonise gerbils, and no or little gastric inflammation or proliferative activity was observed. Conclusions: Loss of the virD4 gene temporally retarded but did not abrogate gastric inflammation. Loss of the cagG gene abolished gastric inflammation partially via reduced ability to colonise gerbils. Unknown factors related to the type IV secretion system other than CagA may influence gastric inflammation.

Structural and functional aspects of unique type IV secretory components in the Helicobacter pylori cag‐pathogenicity island

“…Analogous to cagI, cagG deletion mutants are incapable of delivering CagA into gastric epithelial cells, although they retain the capacity to induce IL-8 production, pointing toward a potential effector role for the protein. Other studies provided different evidence, showing a marked reduction of IL-8 production from gastric epithelial cells, as well as a reduced capacity to adhere to epithelial cells in vitro and to colonize Mongolian gerbils in vivo [33]. Similar results were found in an experiment with cagG-deleted strains tested on cultivated KATOIII cells [34].…”

Pattern of Transcription Factor Activation in Helicobacter pylori–Infected Mongolian Gerbils

“…Specific primers and TaqMan probes for KC, IL-6, IFN-γ, and GAPDH were described previously. 23,24 Real-time PCR was performed as previously described. 24 Cytokine messenger RNA (mRNA) levels were expressed as the ratio of cytokine mRNA to GAPDH mRNA (100,000 × cytokine mRNA [unit/µL]/ GAPDH mRNA [unit/µL]).…”

Identification of Helicobacter pylori Strain cagPAI+ and cagPAI− Antigens by IgG Antibodies from Sera of Experimentally Colonized Meriones unguiculatus (Mongolian gerbils)

“…Four infected gerbils from each group were later sacrificed at 4,8,12,16,20, and 24 weeks. The stomach was extracted, sectioned, and homogenized (Cole-Parmer, Vernon Hills, IL, USA).…”

“…Group D was initially inoculated with J99 ⁄ CG3 and was then inoculated with 251F ⁄ CG3 4 weeks later, while Group E was initially inoculated with 251F ⁄ CG3 and was then inoculated with J99 ⁄ CG3 4 weeks later ( Table 1). Four gerbils from each group were sacrificed at 6,8,12,16,20,24, and 40 weeks postinoculation after an intramuscular injection of anesthesia. For Groups D and E, prior to the inoculation of the second strain, two animals were sacrificed to verify the presence and identity of the first H. pylori strain.…”