The relationship between virological characteristics of hepatitis C virus (HCV) and reactivity to the regional specific proteins of HCV

Abstract

Background: Although the polyproteins of hepatitis C virus(HCV) are processed and formed in nearly equimolar amounts, individual functional proteins have a discrepancy in their time of appearance following HCV infection and eliciting immune response. This study was conducted to compare the reactivity toward regional specific HCV protein in relation to virological characteristics, including HCV genotype and HCV replication.

Methods: Sera from forty-five patients with chronic HCV infection were analyzed through the experiments of the recombinant immunoblot assay(RIBA-2), HCV genotyping and HCV RNA quantitation.

Results: The frequencies of seropositivity to C22-3, C33C, C100-3 and 5-1-1 proteins were 91.1%, 91.1%, 64.4% and 53.3%, respectively, of all the patients, and thus the antibodies to C22-3 and C33C proteins were found more frequently (p < 0.05). The antibody responses between core or NS3 proteins and NS4 proteins showed more discrepancy in the HCC group than that in the CH group, implying a possibility of oncogenic potential of core or NS3 gene in hepatocarcinogenesis. The detection rate of antibodies to C22-3 and C33C, in accordance with serum HCV RNA levels, was significantly higher in highly viremic patients than that in low viremic patients (p < 0.05). Antibodies to C22-3, C33C, C100-3 and 5-1-1 were also found more frequently in patients with HCV genotype 1b, compared to those with HCV genotype 2a (p < 0.05).

Conclusion: These results suggest that antibody detection of HCV may depend on the virological characteristics of HCV, the levels of HCV replication and HCV genotype and, therefore, HCV RNA detection using RT-PCR technique is essential for confirmatory diagnosis for HCV infection. Furthermore, the HCV core or NS3 Protein may play important role in hepatocarcinogenesis.

Figure 1.

Determination of HCV genotype and HCV RNA quantitation by RT-PCR. The lane 1, 2, 3 and N in the panel A shows genotype 1a, -1b, -2a and negative control, respectively. The band on the lane 3 shows 241 bp in fragment size corresponding genotype 2a. In the panel B, the upper bands depicting 268 bp in fragment size indicate amplified DNA fragments derived from serially diluted target HCV RNA, and the lower bands showing 188 bp indicate those from the internal template as competitor. At the equivalent point of signal intensities between the two bands, the amounts of target HCV RNA are the same as the copy numbers of the internal templates which are serially diluted. The arrows indicate the point of HCV RNA titer, 4 × 10⁴ copies/μL serum.

Figure 2.

The frequency of HCV antibodies relative to serum HCV RNA levels. The seropositivity of antibody to C22-3 and C33C shows a significant difference between patients with high HCV titers and with low HCV titers (p<0.05). However, no significant difference in each seropositivity of antibody to C100-3 and 5-1-1 was seen between both groups.

Figure 3.

The relationship between serum HCV RNA levels and the reactivity of antibodies to HCV core(C22-3), NS3(C33C), NS4(C100-3 and 5-1-1) protein in chronic liver diseases with HCV infection. Positive correlations between the antibody responses to HCV core and NS3 protein are shown in panel A and B, respectively.

Figure 4.

The relationship between HCV genotypes and antibody responses to each regional specific protein. The significant correlations between HCV genotypes and the frequency of HCV antibodies to C22-3, C33C, C100-3 and 5-1-1 proteins are seen.