Antigenic heterogeneity of the NS3 proteins in hepatitis C virus genotypes 1 and 6.

OBJECTIVE To investigate the effect of sequence variability between different genotypes of hepatitis C virus (HCV) on the antigenic properties of the NS3 proteins, and to evaluate the significance of the proteins in the serological diagnosis. METHODS The recombinant expression plasmids of pET/NS3-1 and pET/NS3-6 were constructed with the NS3 region fragments from HCV genotypes 1 and 6, respectively. The antigenic reactivity of the recombinant NS3 proteins was determined. The NS3 nucleotide sequences were aligned with 6 HCV full-length strains representing different genotypes. RESULTS The two recombinant NS3 proteins were generated and enzyme immunoassay tests were developed. The positive rates of anti-NS3 were 61.2 and 58.8% by using the NS3 antigens from HCV genotypes 1 and 6, respectively. This difference had no statistical significance (p > 0.05). However, it was interesting that 16 samples gave a discordant result for different genotype NS3 antigens.The two partial NS3 sequences shared approximately 63.9-79.9% identity with the different genotype strains. CONCLUSION The primary structure of the HCV NS3 region is highly variable. Thus, sequence variability has a profound effect on the antigenic properties of the NS3 regions, and the antigenic differences should be taken into account for the development of more effective diagnostic tests.