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J Clin Virol. 2008 Aug;42(4):405-8. doi: 10.1016/j.jcv.2008.03.023. Epub 2008 May 12.

The HIV-1 protease resistance mutation I50L is associated with resistance to atazanavir and susceptibility to other protease inhibitors in multiple mutational contexts.

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VircoLab Inc., Durham, NC 27713, USA.



The HIV-1 protease mutation I50 L causes atazanavir resistance but increases susceptibility to other PIs. Predicted phenotypic FC values were obtained from viral genotypes, using the virtual Phenotype-LM bioinformatics tool (powering vircoTYPE).


To evaluate I50 L's effect on susceptibility to 8 PIs, in a large genotype database.


I50 L containing routine clinical isolate samples in Virco's genotype database were paired with samples having like patterns (or profiles) of IAS-USA-defined primary PI mutations, but lacking I50 L. Using vircoTYPE (version 4.1), the median predicted FC for each mutational profile was determined. I50 L-associated shifts in FC were evaluated using drug-specific CCOs.


We selected 307 and 37098 samples with and without I50 L. These corresponded to 31 mutation patterns of > or =3 samples each. I50 L caused resistance to atazanavir in all 31 mutation contexts, but was associated with higher susceptibility for other PIs. The largest I50 L-associated shifts in median predicted FC were: 1.2 to 42.4 (atazanavir), 10.2 to 3.2 (amprenavir), 3.3 to 0.5 (darunavir), 13 to 0.5 (indinavir), 34.9 to 1.3 (lopinavir), 22.3 to 1.3 (nelfinavir), 5.2 to 0.3 (saquinavir) and 29.9 to 5.2 (tipranavir).


The PI mutation I50 L causes clinically relevant resistance and increased susceptibility to atazanavir and other PIs respectively.

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