Evolution of genotypic resistance to nucleoside analogues in patients receiving protease inhibitor-containing regimens.

: The prevalence of genotypic resistance to nucleoside analogues (NA) was examined using a line probe assay (LiPA, Innogenetics, Spain) and a point mutation assay to test for codon 151 polymorphism in plasma from 34 individuals who had been exposed to NA for longer than 1 year. The testing was repeated in the same population after 6 months of being on a new potent protease inhibitor (PI)-containing antiretroviral combination. Only nine (47%) of the 19 patients initially carrying the codon 41 mutation restored zidovudine wild-type (WT) virus population. Similarly, eight (33%) out of 24 carrying the codon 215 mutation restored the wild-type variant. Two subjects carrying codon 74 didanosine mutation reverted to wild-type genotype, as well as two (18%) out of 11 harbouring the codon 184 lamivudine-resistant variant. To conclude, the extent to which drug recycling might be of benefit in subjects showing a restoration of genotypic sensitivity to former drugs needs to be explored.