• HCV genotyping;
  • HIV/HCV co-infection;
  • mixed-HCV infection;
  • occult genotype;
  • PBMC culture;
  • PBMC reservoir

Summary.  Individuals with haemophilia who received non heat-treated factor concentrates were likely to undergo multiple exposures to the hepatitis C virus (HCV). Therefore, HCV mixed-genotype infections might be more frequent in these patients than in the general population. Their prevalence is extremely variable in similar groups of patients tested by different assays due to the fact that currently available genotyping techniques are not suitable to detect multiple HCV genotypes in a viral population. As an HCV viral reservoir, the peripheral blood mononuclear cell (PBMC) might harbor viral variants distinct from the genotypes detected in plasma. We investigated the presence of HCV genotypes in a group of chronically infected haemophilic patients in the PBMC compartment using a non-stimulated cell culture system that allows the detection of the HCV genome in culture supernatants. We compared them to the HCV genotypes found in plasma samples. Cell culture experiments performed with PBMC demonstrated the presence of additional HCV genotypes that were undetected in the corresponding plasma samples with the same genotyping technique. Although mixed infections at HCV genotype level became evident in 5.6% of the patients (16/288), the culture methodology increased the number of HCV infections with multiple genotypes to 62.5% (10/16) (P < 0.0001). Once more, the role of mononuclear cells as HCV viral reservoirs is emphasized. Considering minor strains could influence the outcome of treatment, detection of covert HCV mixed-genotype infections might be essential for choosing the adequate therapeutic regimen.