Construction of a hexon-chimeric human adenovirus type 3 vector expressing two neutralizing epitopes of hepatitis B surface antigen preS1 and analysis of antigenicity of the chimeric epitopes

Objective To construct a hexon-chimeric human adenovirus type 3 （ HAd3 ） vector expressing two neutralizing epitopes of hepatitis B surface antigen preS 1 （HBsAg-preS1） and to analyze the antigenicity of the chimeric epitopes .Methods Two neutralizing epitopes of HBsAg-preS1 including KR359 and KR127 were inserted into hypervariable region 1 （ HVR1） and hypervariable region 2 （ HVR2） of HAd3 hexon .Chimeric hexon gene encoding the two epitopes was amplified by overlap PCR and then subcloned into shuttle plasmid pBR322-L/R containing the homologous recombination regions .The digested shuttle plasmid containing chimeric hexon gene was co-transfected into Escherichia coli BJ5183 cells together with backbone plasmid pBRAdΔE3GFP to construct pBRAdΔE3GFP-preS1 vector.Then pBRAdΔE3GFP-preS1 vector was digested with AsiSⅠand transfected into AD293 cells to construct recombinant virus （rAD3E-preS1）. CsCl gradient centrifugation was used for purification .Glutathione S-transferase （ GST ） fusion protein KR359KR127 （ GST-KR359KR127 ） was expressed in Escherichia coli BL21 by using expression vector pGEX-4T3.Female BALB/c mice at age 6-8 weeks were intraperitoneally injected with 10^10 virus particles or 80 μg GST fusion protein .Serum samples were collected to analyze the antigenicity of two epitopes by ELISA and Western blot .Results ELISA showed that KR 359 and KR127 were successfully exposed on viral surfaces by using hexon-chimeric HAd3 vector .The induced polyclonal antibodies in serum samples could recognize GST fusion protein and native HBsAg from patients infected with hepatitis B virus .Conclusion The antigen capsid-incorporation strategy could be used to display epitopes on viral surface .Enhanced antigenspecific responses could be achieved through inserting multiple foreign epitopes into hexon HVRs .This study provided evidence for further application of hexon -chimeric human adenovirus type 3 vector in the developmentof vaccine, especially for the development of multivalent hepatitis B vaccine . Key words: Human adenovirus type 3 ;  Hexon ;  Hepatitis B surface antigen ;  Neutralizing epitope