Abstract: Objective To investigate whether exogenous green fluorescence protein(GFP) could be expressed in Schistosoma japonicum and generate green fluorescence. Methods The fusion protein-expressing plasmid pEGFP-LacZ-C1 was constructed and used to transfect 293T cells and S. japonicum schistosomula at 14 days after infection, respectively, using PEI as the transfection reagent. The GFP fluorescent signal was then observed under a fluorescence microscope at 48 h after transfection; β-galactosidase staining was performed in these cells to observe the presence of blue products under an optical microscope. Meanwhile, the schistosomula were added to 12-well plates of 293T cells and observed by optical microscopy and fluorescence microscopy. Finally, a high concentration of lentivirus(titer: 3 × 10⁸ colony-forming units/ml) was used to infect schistosomula and 293T cells, respectively, and GFP fluorescent signal was observed at 96 h after infection. Results Both GFP fluorescent signal and blue spots were seen in 293T cells transfected with pEGFP-LacZ-C1. However, neither was observed in schistosomula. In addition, the GFP fluorescence luminance in 293T cells was higher than that of spontaneous fluorescence of S. japonicum, and differential colors were seen: the color of the former was bright green, while the later was yellow-green. In the experiment of lentivirus infection, the fluorescent spots were clearly seen around the intestine of schistosomula under the fluorescent microscope. Besides, the movements of fluorescent spots were consistent with muscle movement. Conclusion The spontaneous fluorescence of S. japonicum does not influence the detection of GFP fluorescent signal under sufficient expression of exogenous GFP. Lentivirus infection at a high concentration can improve the transfection efficiency and increase GFP expression at 96 h after infection. In this way, the fluorescent signal of GFP transfected into schistosomula has been observed.

Key words: Schistosoma japonicum, Green fluorescence protein, Lentiviral vector