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Volume 47, Number 4, August 2014

Immunoreactivity assessment of hepatitis C virus NS3 protease and NS5A proteins expressed in TOPO cloning system 

Mahsa Alaee, Peyman Rajabi, Zohreh Sharifi, Mohammad Morad Farajollahi

Received: April 30, 2012    Revised: June 30, 2012    Accepted: August 9, 2012   


Corresponding author:

Mohammad Morad Farajollahi, Department of Medical Biotechnology, Faculty of Allied Medical Sciences, Tehran University of Medical Sciences, Tehran, Iran
Corresponding Author InformationCorresponding author. Department of Medical Biotechnology, Faculty of Allied Medical Sciences & Cellular and Molecular Research Center, Tehran University of Medical Sciences, Hemmat Highway, Tehran, Iran. 


Background and purpose: 

Hepatitis C virus (HCV) is a major cause of acute and chronic liver disease. Numerous screening assays based on the detection of immunoresponses to HCV structural and nonstructural proteins have been designed. Various studies have demonstrated genotype-specific differences in anti-HCV antibody responses to different HCV proteins. 



Full-length NS3 protease and N-terminally truncated NS5A were expressed using pET TOPO 102/D system. Antigenicity of the purified recombinant proteins was assessed by immunoblotting and indirect enzyme-linked immunosorbent assay (ELISA). Furthermore, anti-HCV antibody responses to the recombinant proteins were evaluated in three prevalent genotypes in Iran. 



We were able to express and purify NS5A and NS3 protease using TOPO cloning system. The HCV NS3 protease and NS5A produced in BL21 Star (DE3) was immunoreactive. Our results demonstrate that NS3 protease and NS5A have good immunoreactivity, but they are not sufficient for detecting all HCV-positive sera. No significant genotype-specific differences were detected in immunoresponses to the recombinant proteins. 



In conclusion, we successfully isolated, expressed, and purified substantial amount of HCV NS3 protease and N-terminally truncated NS5A, and used them as capturing antigens in a screening ELISA assay with high sensitivity, reproducibility, and specificity. Accordingly, it is well confirmed that TOPO cloning system can be used as a dynamic system in order to express higher amount of immunoreactive viral proteins. 


Key words:

Hepatitis C virus, Indirect enzyme-linked immunosorbent assay, NS3 protease, NS5A, TOPO cloning