Cloning and expression of hepatitis B surface gene in E. coli

Background: Hepatitis B virus (HBV) is among the smallest DNA viruses resulting in ~800,000 deaths each year. Pakistan is considered a country affected by HBV. In Pakistan, the most dominant genotype is D. HBV is an enveloped virus of 3.2 kb. The study's goal was to express hepatitis B surface antigen in a bacterial host to produce a recombinant protein.Method: Blood samples were collected in EDTA coated vacutainer from patients after their consent. DNA was extracted from serum through the phenol-chloroform method; Hepatitis B surface gene was cloned in TA cloning vector, subclone in pET 28a expression vector. An expression vector containing the Surface gene was then transformed into a competent bacterial host BL21 and inducted with IPTG at 0.1-0.2mM concentration for expression. The expressed proteins (soluble and pellet form) were analyzed on SDS PAGE.Results: Hepatitis B Surface gene of 681bp after PCR were detected under UV light then successfully cloned and subcloned in pET 28 expression vector. The restricted fragment indicating the gene of interest was 681bp when analyzed on 1.2% Agarose gel under UV light. The required protein of 25kDa was obtained in soluble form when detected on 12% SDS PAGE after staining with Coomassie Blue dye.Conclusion: Hepatitis B surface gene was successfully expressed in both insoluble and pellet forms using E.coli. The expression of surface protein needs to maximize through optimizing conditions to be used as potent candidate for vaccine production to prevent hepatitis B infection.Keywords: Hepatitis B virus; Surface gene; Cloning vector; pET expression vector