Abstract: Objective To construct an eukaryotic expression plasmid containing gp120 gene of HIV-1 subtype B and obtain gp120 gene expression in HepG2 cells.Methods According to the published gp120 gene sequence in Genbank,a pair of primers was designed and synthesized.The PCR amplification product of gp120 gene was cloned into pMD-18T vector using TA cloning followed by BamHⅠ and XhoⅠ digestion and sequence analysis.The target gene was then subcloned into a highly efficient eukaryotic expression vector pcDNA3.1(+).The recombinant plasmid was sequenced and identified by restrictive endonuclease digestion,and transfected into HepG2 cells via liposome.The expression of gp120 gene was analyzed by RT-PCR and Western blotting,respectively.Results Restriction endonuclease digestion and sequence analysis verified successful construction of the recombinant vector pcDNA3.1(+)/gp120.The target fragment gp120 was identical with U26942 in Genbank,and the expression of gp120 gene was detected in the lysate of the transfected HepG2 cells by RT-PCR and Western blotting.Conclusion The eukaryotic expression plasmid for gp120 has been constructed successfully,which is capable of stable expression in HepG2 cells.