Diverse patterns of recognition of hepatitis C virus core and nonstructural antigens by antibodies present in Egyptian cancer patients and blood donors.

Serum samples from 429 cancer patients, 82 unpaid blood donors, and 74 paid blood donors were tested for hepatitis C virus (HCV) markers in two commercially available enzyme immunoassays (EIAs). A total of 229 of 429 (53.4%) cancer patients were positive by the two EIAs. A total of 34 of 156 (21.8%) of the blood donors were positive by the EIAs, with a higher prevalence among paid blood donors (20/74; 27%) compared with that among the unpaid blood donors (14 of 82; 17%). EIA-positive sera were tested for confirmation of the results in an immunoblot assay (LiaTek) in which reactivities to four synthetic peptides representing the HCV core protein and two synthetic peptides representing nonstructural proteins 4 and 5 were measured. Of 243 first and/or second EIA-positive samples from cancer patients, 188 (77.2%) were confirmed to be positive in the synthetic peptide immunoblot. A total of 33 of 35 (94.3%) blood donor samples were confirmed to be positive. A great diversity in reactivity patterns was seen. However, all sera from the group of paid blood donors were exclusively reactive to core peptides 1 and 2. A subset of LiaTek assay-positive samples were tested by the four-antigen RIBA-2 assay. The sera from the paid blood donors were all nonreactive. A subset of the LiaTek-positive sera was analyzed for the presence of the HCV genome by reverse transcriptase-PCR. Eleven of the 20 serum samples with reactivity to LiaTek core peptides 1 and 2 only were HCV reverse transcriptase-PCR positive, as were the majority of the sera with other reactivity patterns by the LiaTek assay. The results confirm the very high prevalence of HCV infection in Egypt. Furthermore, the results indicate that there is circulating in Egypt, particularly in the group of blood donors paid for their donation, an HCV variant which elicits an immune response that is not detected by the RIBA-2 assay.