Exposure of hepatitis C virus (HCV) RNA-positive recipients to HCV RNA-positive blood donors results in rapid predominance of a single donor strain and exclusion and/or suppression of the recipient strain

We have analyzed three cases of hepatitis C virus (HCV)-infected recipients who received blood from HCV-infected donors. Two recipients were exposed t o two different HCV RNA-positive donors, and one was exposed to a single do nor. All parental genomes from the actual infecting units of blood and the recipients were defined, and their presence in the follow-up serum samples was determined using sensitive strain-specific assays. The strain from one of the donors was found to predominate in all recipients' serum samples col lected throughout the follow-up period of 10 to 30 months. In two recipient s exposed to two infected donors, the strain from the second donor was occa sionally found at very low level. However, the original recipients' strains were not detected. Our observations show that HCV-infected individuals can be superinfected with different strains, and this event may lead to eradic ation or suppression of the original infecting strain. Furthermore, our fin dings demonstrate that simultaneous exposure to multiple HCV strains may re sult in concomitant infection by more than one strain, although a single st rain could rapidly establish its dominance. The results of the present stud y suggest the existence of competition among infecting HCV strains which de termines the ultimate outcome of multiple HCV exposure.