Abstract: Objective To investigate on the effect of Plasmodium yoelii（BY265 strain）circumsporozoite protein （CSP）on the activation of nuclear transcription factor κB（NF-κB）in hepatoma cells（HepG2）stimulated by TNF-α. Methods Entire coding sequence of CSP was reverse transcribed and amplified by RT-PCR with sporozoite total RNA as template，then cloned into pFLAG-CMV8 for construction of the recombinant plasmid pFLAG-CMV8-CSP. Indirect immunofluorenscence staining with rabbit anti-csp was applied to verify the expression and distribution of FLAG-CSP fusion protein in HepG2. Three groups were established for the experiment: group A with HepG2 transfected by pFLAG-CMV8 as negative control, group B with HepG2 transfected by pFLAG-CMV8 and stimulated by 100 ng/ml TNF-α, and group C with HepG2 transfected by pFLAG-CMV8-CSP and stimulated by 100 ng/ml TNF-α. Dual-luciferase assay and EMSA were performed to detect the nuclear translocation and activation of NF-κB, to observe if pFLAG-CMV8-CSP suppressed the activation of NF-κB in HepG2 stimulated by TNF-α. Result The expression of pFLAG-CMV8-CSP was localized on cytoplasm of HepG2. The activity ratio of firefly luciferase to Renilla luciferase in group C（0.228±0.029） was significantly lower than both groups A（0.438±0.085）and B（0.571±0.030） （P<0.05）. EMSA showed that the band in group C was significantly weaker than group B. Conclusion Plasmodium yoelii CSP localizes in the cytoplasm of HepG2 and inhibits the activation and nuclear translocation of NF-κB in HepG2 stimulated by TNF-α.

Key words: Plasmodium yoelii, Circumsporozoite protein, Nuclear transcription factor κB, Hepatoma cell