Infectivity and pathological changes in murine clonorchiasis: Comparison in immunocompetent and immunodeficient mice

The main complications of clonorchiasis are periportal inflammation, biliar y hyperplasia, periductal fibrosis, and subsequently the development of bil iary tumors in the liver. This study was undertaken to compare the infectiv ity and histopathologic changes between in immunocompetent FVB/NJ and BALB/ cA strains, and immunodeficient severe combined immunodeficient (SCID) and athymic nude mice after the metacercariae of Clonorchis (C). sinensis were infected. The experiment showed that C. sinensis was very infective in all strains studies, but the status of worm development. infectivity, recovery rate, and morphological changes of livers were very different in each strai n. FVB/NJ mice showed more worm recovery than any other strain. Histopathol ogically the liver of FVB/NJ mice at 4 weeks postinfection showed marked cy stic and fibrotic changes, in which C. sinensis was fully developed with ov um production, severe infiltration of inflammatory cells, mostly eosinophil s, and birth degrees of biliary hyperplasia. In SCID and nude mice, there w ere few foci of inflammatory cells even at 8 weeks postinfection in peripor tal areas of the liver, associated with no development into adult worm with ovum production. Fibrosis occurring at 4 weeks postinfection was highly co rrelated with inflammatory infiltration when each strain was compared. We s uggest that massive infiltration of eosinophil and plasma cells caused by t he infection might initiate cystic formation and fibrosis. These data demon strate that the infection of C. sinensis might be related to pathologic con sequences of inflammatory cell infiltration, cystic formation and fibrosis which might play a role in the defense mechanism against the parasitism in the liver of each strain. The FVB/NJ mouse model might be very helpful in e lucidating the mechanism for human clonorchiasis.