Analysis of hepatitis C virus isolates by serotyping and genotyping

Hepatitis C virus (HCV)-positive sera from 106 chronically infected patients which had previously been genotyped were characterized by serotyping. Genotypes were determined by a first-generation line probe assay (INNO-LiPA HCV) and by sequence analyses of the core, core-E1, and NS5B regions. HCV serotypes were determined by measuring type-specific antibodies to NS4-derived peptide antigens (Murex HCV serotyping 1-6 assay). Of 106 serum samples, serotype-specific antibodies were detected in 88 (sensitivity, 83.0%), and 77 (specificity, 87.5%) of these serotypeable samples revealed a corresponding serotype (total concordance, 72.6%). Eleven samples revealed discrepant results as follows. (i) Five serum samples in which only a single genotype was detected contained an additional serotype. (ii) In one sample with two genotypes only one serotype was detected. (iii) In five isolates the serotype (all serotype 1) was completely different from the genotype. Double infections, as determined by genotyping, were confirmed by serotyping in two of four cases. Of 11 serum samples from chronically infected hemodialysis patients, 7 (64%) were reactive in the serotyping assay. In conclusion, genotyping allows discrimination between (sub)types but requires the relatively complex reverse transcriptase PCR. The novel serotyping assay offers an alternative method to distinguish the major types of HCV, although the sensitivity of the assay may be limited by the immunocompetence of the infected host.