Hepatitis B surface antigen with N-terminal addition of mCherry can assemble into functional subviral particles

Aim: To label HBsAg with the mCherry protein without impairing its functionality. Materials & methods: A vector expressing mCherry-HBsAg fusion protein was constructed and transfected into Huh7 cell lines. The expression, secretion and subcellular localization of HBsAg was detected by western blotting, ELISA and immunofluorescence staining, respectively. Then the assembly of subviral particles was evaluated by sucrose density gradient centrifugation, dot blotting and electron microscopic assay. Results: mCherry-HBsAg fusion protein can be expressed and secreted in a similar manner to HBsAg. More importantly, mCherry-HBsAg fusion protein can self-assemble into spherical subviral-like particles. Conclusion: mCherry could be introduced into HBsAg without affecting its biological characters including expression, secretion and assembly.