Influence of viraemia and genotype upon serological reactivity in screening assays for antibody to hepatitis C virus

Abstract

Detection of antibody to recombinant proteins derived from hepatitis C virus (HCV) genotype 1 represents the principal method for diagnosis of HCV infection. A method was developed for quantifying antibody reactivity in two third-generation enzyme immunoassays (Ortho EIA 3.0 and Murex VK48), and the influence of viraemia, HCV genotype, and host factors such as age, gender, and risk group upon antibody levels were investigated in a consecutive series of 117 anti-HCV-positive volunteer blood donors. Viraemic donors (as assessed by the polymerase chain reaction; PCR) showed significantly higher levels of anti-HCV by the Ortho EIA than those who were nonviraemic (adjusted mean difference of 10.1 fold after multiple regression analysis). The only other factor to influence significantly antibody level was genotype, where it was found that donors infected with type 1 showed 4 to 4.5 times greater serological reactivity by the Ortho assay than those infected with type 2 or 3. Antibody levels by the Ortho assay correlated closely to those detected by the Murex VK48 assay, and similar differences between PCR-positive and negative donors and between those infected with different genotypes were found. Differences in serological reactivity between genotypes indicate that a large proportion of epitopes of the type 1a or 1b recombinant proteins used in current assays are genotype specific. Variation in sensitivity of screening assays for different genotypes is of potential concern when used in countries where non-type 1 genotypes predominate in the blood donor or patient population.

New hepatitis viruses: Contenders and pretenders

“…As diagnostic tests for the detection of HCV antibodies are based on recombinant antigens of HCV genotype 1, there has been speculation that such screening assays may lack sensitivity for detection of non‐genotype 1 infections. Consistent with this, a reduced reactivity to HCV genotype 2 and 3 has been reported in the third generation antibody screening assays 10 . In addition to virus variation influencing detection, infections may not be detected because of an inadequate serological response in patients who are immunocompromised or immunosuppressed.…”

Differential reactivity of putative genotype 2 hepatitis C virus F protein between chronic and recovered infections

“…4b) in this study confirmed the data reported by Nikolaeva et al (2002), who showed a range of 1 : 800-1 : 40 000 of anti-core IgG titres in chronic HCV and an antibody titre value of 1 : 5-1 : 200 in a recovered group. Because of the lack of variation of high anti-HCV reactivity in donors chronically infected with different genotypes using the HCV 3.0 ELISA, it was unlikely that a reliable correlation between anti-F and anti-HCV could be found in terms of the S : CO ratio, even though a 4-4.5-fold greater seroreactivity of genotype 1 samples compared with genotype 2 or 3 was reported using a commercial assay (Dhaliwal et al, 1996). However, the higher correlation between anti-F and anti-core antibody levels in genotypes 1 and 2 than in genotype 3 suggest that the F protein produced along with core protein during natural HCV infection is cross-reactive but potentially genotype-specific.…”

Relevance of Reactivity in Commercially Available Hepatitis C Virus Antibody Assays

“…To achieve a more reliable diagnosis, sera with positive results in an EIA should always be retested by a confirmatory assay based on immunodominant antigens clearly different from those used in screening assays to exclude both assays from detecting the same false reactivity (11). Second, HCV diagnosis is hampered by the restriction of antigens used in commercially available tests to genotype 1a, which is predominantly found in the United States; these antigens do not necessarily represent viral genotypes found in other parts of the world (3,5,8). Thus, our confirmatory assay based on local isolates proved to be superior to commercial assays (6) and led to a very low number of patients for whom a final diagnosis was not possible (1.7%).…”