Codon variability at HCV NS3 positions associated with major drug resistance to PIs and its impact on the genetic barrier to drug resistance development in HCV-genotypes 1–6.

aThe wild-type amino-acid of HCV genotype 1b at each position associated with drug resistance is shown.
bPredominant wild-type codon for each genotype is reported in bold.
cCodon for drug-resistance mutation requiring the lowest number of transitions/transversions starting from the wild-type or polymorphic codon detected in drug-naïve patients.
dMinimal numerical score obtained by summing the number of nucleotide transitions and/or transversions (scored as 1 and 2.5, respectively, see methods) required to generate the specific drug-resistance mutation.
WT, wild-type.