Synergistic effects of cagA+ Helicobacter pylori co-infected with Opisthorchis viverrini on hepatobiliary pathology in hamsters.

Human liver fluke infection caused by Opisthorchis viverrini is associated with several biliary diseases including cholangiocarcinoma (CCA). Recently, it was discovered that the liver fluke is a reservoir of Helicobacter pylori, particularly the cagA-positive strain (cytotoxin-associated gene A) in its gut. Given that two carcinogenic pathogens are associated with CCA development, however, the role of cagA-positive H. pylori in opisthorchiasis has not been clarified. The present study was therefore aimed to investigate histopathological changes of the biliary system in hamsters co-infected with O. viverrini and cagA-positive H. pylori or O. viverrini and cagA-negative H. pylori, with controls of O. viverrini, cagA-positive H. pylori, or cagA-negative H. pylori alone, over time. Major histopathological changes were systematically investigated. All pathological features were quantified/semi-quantified and compared among the experimental groups. The results showed that O. viverrini infection groups (O. viverrini, cagA-positive H. pylori and cagA-negative H. pylori) showed a high degree of eosinophil and mononuclear cell infiltration, lymphoid aggregation and granuloma. Specifically, O. viverrini co-infected with cagA-positive H. pylori presented significantly higher inflammatory scores than O. viverrini and O. viverrini with cagA-positive H. pylori. Proliferation and adaptive lesions such as hyperplasia, goblet cell metaplasia and dysplasia were detected only in O. viverrini infection groups. Dysplasia, the precancerous lesion of CCA, was observed in the first-order bile ducts, especially where the inflammation existed and was found earlier and more severely in O. viverrini with cagA-positive H. pylori than other groups. Similarly, the BrdU (bromodeoxyuridine) proliferation index was significantly higher in O. viverrini co-infected with cagA-positive H. pylori than O. viverrini and O. viverrini with cagA-negative H. pylori groups. Periductal fibrosis was a prominent histopathologic feature in chronic infection in O. viverrini infection groups. Multiple logistic regression showed that O. viverrini co-infected with cagA-positive H. pylori and the duration of infection were the most important factors associated with periductal fibrosis (OR 3.02, 95% CI 1.02-9.29, p = 0.04 and OR 3.82, 95% CI 2.61-5.97, p<0.001). This study demonstrates that the liver fluke co-infected with cagA-positive H. pylori induces severe biliary pathology that may predispose to cholangiocarcinogenesis.