OBJECTIVETo examine the expression profile and immunofluorescence localization of the major egg antigen p40 of Schistosoma japonicum (Sjp40) during granuloma formation in the liver of infected New Zealand white rabbits.

METHODSNew Zealand white rabbits were infected with S. japonicum cercariae, and the livers were harvested at 29 and 45 days post-infection (dpi). The total RNA of the liver tissues was extracted for expression profiling of Sjp40 by quantitative reverse transcription-PCR (qRT-PCR) with GAPDH of S. japonicum as the endogenous reference gene. The expression of Sjp40 in the liver were detected by Western blotting using anti-Sjp40 monoclonal antibody (mAb) 9G7 or anti-Toxoplasma gondii tSAG1 mAb Y3A8 (control) as the primary antibody. Paraffin sections of the liver were prepared for observing egg granuloma formation using HE staining and for indirect immunofluorescence assay of Sjp40 location in the trapped eggs and egg granulomas.

RESULTSThe level of Sjp40 mRNA in the eggs trapped in rabbit livers was significantly higher at 45 dpi than that at 29 dpi (P<0.05), and Western blotting confirmed the presence of Sjp40 protein in the rabbit livers at both 29 and 45 dpi. Immunofluorescence assay demonstrated localized expression of Sjp40 in the immature eggs in the rabbit liver at 29 dpi, but at 45 dpi fluorescence was detected in clusters of mature eggs containing miracidium and in the surrounding egg granulomas.

CONCLUSIONSThe transcriptional levels of Sjp40 significantly increased with the maturation of eggs trapped in the rabbit livers. Sjp40 protein spread from the eggs to the surrounding egg granuloma at 45 dpi when acute liver granulomatous lesions occur, suggesting that Sjp40 plays a key role in egg granulomas formation in the livers of infected New Zealand white rabbits.