Transmission of hepatitis C virus quasispecies between human adults.

To elucidate how hepatitis C virus (HCV) with multiple variants (quasispecies) is transmitted and adapts to the host during infection, we compared nucleotide and deduced amino acid sequences from hypervariable region1 (HVR1) of the E2 gene of HCV between a donor and a recipient who developed hepatitis after a needlestick accident. Thirty clones from each subject were sequenced after PCR amplification, cloning, and purification of plasmid DNA from single colonies of transformed bacteria. Genetic analysis revealed that the recipient's viral sequences were much less diverse than the donor's. We found a single predominant HCV HVR1 clone of the recipient in 22/30 isolates with the same amino acid sequence, and mimic clones in 8/30 isolates with only one amino acid substitution. These were all absent in the donor, who had 21 highly diverse sequences. Phylogenetic analysis of virus E1/E2 gene sequences showed that the recipient's unique sequences were related to the population of variants from the donor, in whom one isolate had 96% similarity to the recipient's predominant amino acid sequence. These results suggest that a minor subset of the donor's HCV variants is selectively transmitted to the recipient, and that the selection determines the predominant variant in the new host.