Hepatitis C virus genomic variability in untreated and immunosuppressed patients.

To investigate whether immune pressure enhances the genetic diversity of the hepatitis C virus (HCV) hypervariable region 1, nucleotide sequences were compared in multiple sera, collected longitudinally, from three untreated patients and four patients undergoing liver transplantation for HCV-related cirrhosis. A minor variant became dominant in three of three patients following transplantation and persisted unchanged for months. Compared with untreated HCV carriers, transplant recipients had fewer quasispecies, fewer nucleotide changes (1.61 and 2.58/month), fewer amino acid sequence changes (0.40 and 1.94/month), as well as higher ratio of transitional to transversional mutations (2.57 and 0.98, P < 0.02) and lower replacement to silent mutations (1.33 and 8.21, P < 0.01). The two patients with the least genomic variation died of HCV graft infection. The data suggest that HCV variants which infect the graft are selected by recipient immune pressure at the time of transplant and that preferential replication in the graft is enhanced by routine immunosuppression.