A study based on four immunoassays: Hepatitis C virus antibody against different antigens may have unequal contributions to detection

Abstract

Background: All commercial Hepatitis C virus antibody (anti-HCV) assays use a combination of recombinant antigens to detect antibody response. Antibody responses to individual antigenic regions (core, NS3/4 and NS5) used in assays have not been investigated.

Methods: In this study, we quantified HCV viral load, tested anti-HCV with four commercial assays (Ortho-ELISA, Murex-ELISA, Architect-CMIA and Elecsys-ECLIA) in 682 plasma specimens. In antigenic region ELISA platform, microwells were coated with three antigens: core (c22-3), NS3/4 (c200) and NS5 individually. The signal-to-cutoff (S/Co) values of different assays, and antibody responses to individual antigens were compared. The specimens were divided into HCV RNA positive group, anti-HCV consistent group, and anti-HCV discrepant group.

Results: Anti-core and anti-NS3/4 were simultaneously detected in 99.2% of HCV RNA positive specimens and showed great consistency with total anti-HCV signals. Responses to the core region were more robust than those to the NS3/4 region in anti-HCV consistent group (p < 0.001). Anti-NS5 only occurred in companying with responses to the core and NS3/4 antigens, and failed to affect the final anti-HCV positive signals. In anti-HCV discrepant group, 39.0% of positive signals could not be traced back to any single antigenic region.

Conclusion: Antibody responses to the core and NS3/4 antigens were stronger, whereas responses to the NS5 antigen were the weakest, indicating that individual antigenic regions played different roles in total anti-HCV signals. This study provides an impetus for optimizing commercial anti-HCV assays.

Keywords: Anti-HCV immunoassays; Blood donor screening strategy; HCV antigens; Hepatitis C virus.

Fig.1

Schematic illustration of the analytical steps on anti-HCV assays. 682 anti-HCV positive samples were collected. The samples were retested anti-HCV with four assays independently. With the results of anti-HCV and HCV viral load, the samples were divided into three groups: (1) HCV RNA positive group (n = 264); (2) HCV RNA negative, anti-HCV consistent group (n = 223); (3) HCV RNA negative, anti-HCV discrepant group (n = 195). NCCL National Center for Clinical Laboratories, ELISA enzyme linked immunosorbent assay, ECLIA electro chemiluminescent immunoassay, CMIA chemiluminescent microparticle immunoassay

Fig.2

S/Co value distribution in four anti-HCV assays. Distribution of the Signal-to-Cutoff (S/Co) values in Ortho-ELISA (a), Murex-ELISA (b), Elecsys-ECLIA (c) and Architect-CMIA (d) assays were shown. The default cutoff value is 1.0 and S/Co ≥ 1 is regarded as positive. S/Co values were higher in chemiluminescent assays (Elecsys-ECLIA and Architect-CMIA) than in enzyme immunoassays (Ortho-ELISA and Murex-ELISA) due to colorimeter high-end reading limitations

Fig.3

Individual and combination of antibody response to different regions. Five antibody response patterns, indicated by percentage, were compiled in column format for each of the three HCV serological groups (a); the compiled antibody response patterns in serological discrepant group were displayed for each of the four assays (b); Antibody response to individual core, NS3/4 and NS5 antigenic regions were showed in percentage in three serological groups (c), as well as in the serological discrepant group by each of the four assays (d)

Fig.4

Analysis of antibody response to core, NS3/4 and NS5 antigenic regions. Antibody response to the HCV core, NS3/4 and NS5 antigenic regions were analyzed in HCV RNA positive group (a), HCV RNA negative group (b), HCV RNA negative, anti-HCV consistent group (c) and HCV RNA negative, anti-HCV discrepant group (d). The default cutoff value is 1.0 and S/Co ≥ 1 is considered as positive. ns not significant