Enzyme immunoassays for anti-hepatitis C virus antibodies improved specificity and analytical sensitivity by combination of three different recombinant viral proteins in second generation tests.

The detection of hepatitis C virus infection currently relies on a "virology without a virus" approach. So far, only viral nucleic acid has been isolated and sequenced by the methods of genetic engineering. The resulting viral sequence was then used to "design" proteins for diagnostic use as antigens in enzyme immunoassays (EIA). A first-generation EIA (EIA I), which uses a non-structural hepatitis C virus protein as antigen, detected 26 (0.6%) reactive sera out of a total of 4350 blood donors. An inhibition test using recombinant hepatitis C virus antigen, and EIAs using other, both synthetic and recombinant hepatitis C virus peptides were used as a specificity enhancing measure and as confirmatory tests, respectively. Only 7 of these reactives (0.16%, inhibition test) and 5 (0.11%, peptide EIA) were confirmed positive. Of the 26 initially reactive donor sera, 5 sera (0.11%) reacted positive in a second-generation anti-hepatitis C virus antibody EIA (EIA II), which uses two different recombinant non-structural hepatitis C virus proteins and one recombinant core protein. Seventeen (77%) of 22 haemophiliacs reacted positive in EIA I, and 19 (86%) did so in EIA II. There were no false positives in this cohort. Twenty-eight (19%) out of 148 liver disease patients showed a positive reaction in EIA I, and 31 (21%) were reactive in EIA II. Based on the results of the peptide enzyme immunoassay, 1 serum of this group was false positive in EIA I, while none of the sera of this group were false positive in EIA II.(ABSTRACT TRUNCATED AT 250 WORDS)