Human immunodeficiency virus type 1 (HIV-1) Gag protease cleavage sites (CS) undergo sequence changes during the development of resistance to several protease inhibitors (PIs). We have analyzed the association of sequence variation at the p7/p1 and p1/p6 CS in conjunction with amprenavir (APV)-specific protease mutations following PI combination therapy with APV. Querying a central resistance data repository resulted in the detection of significant associations (P < 0.001) between the presence of APV protease signature mutations and Gag L449F (p1/p6 LP1F) and P453L (p1/p6 PP5L) CS changes. In population-based sequence analyses the I50V mutant was invariably linked to either L449F or P453L. Clonal analysis revealed that both CS mutations were never present in the same genome. Sequential plasma samples from one patient revealed a transition from I50V M46L P453L viruses at early time points to I50V M46I L449F viruses in later samples. Various combinations of the protease and Gag mutations were introduced into the HXB2 laboratory strain of HIV-1. In both single-and multiple-cycle assay systems and in the context of I50V, the L449F and P453L changes consistently increased the 50% inhibitory concentration of APV, while the CS changes alone had no measurable effect on inhibitor sensitivity. The decreased in vitro fitness of the I50V mutant was only partially improved by addition of either CS change (I50V M46I L449F mutant replicative capacity Ϸ 16% of that of wild-type virus). Western blot analysis of Pr55 Gag precursor cleavage products from infected-cell cultures indicated accumulation of uncleaved Gag p1-p6 in all I50V viruses without coexisting CS changes. Purified I50V protease catalyzed cleavage of decapeptides incorporating the L449F or P453L change 10-fold and 22-fold more efficiently than cleavage of the wild-type substrate, respectively. HIV-1 protease CS changes are selected during PI therapy and can have effects on both viral fitness and phenotypic resistance to PIs.

Chronic pain has a significant prevalence and impact on patients' lives for several years after thoracic surgery. Nerve dysfunction is associated with more severe pain, a greater impact and tends to persist. The reason for the individual consultant being an important factor in post-thoracotomy pain needs further investigation.

Previous data have indicated that the development of resistance to amprenavir, an inhibitor of the human immunodeficiency virus type 1 protease, is associated with the substitution of valine for isoleucine at residue 50 (I50V) in the viral protease. We present further findings from retrospective genotypic and phenotypic analyses of plasma samples from protease inhibitor-naïve and nucleoside reverse transcriptase inhibitor (NRTI)-experienced patients who experienced virological failure while participating in a clinical trial where they had been randomized to receive either amprenavir or indinavir in combination with NRTIs. Paired baseline and on-therapy isolates from 31 of 48 (65%) amprenavir-treated patients analyzed demonstrated the selection of protease mutations. These mutations fell into four distinct categories, characterized by the presence of either I50V, I54L/I54M, I84V, or V32I؉I47V and often included accessory mutations, commonly M46I/L. The I50V and I84V genotypes displayed the greatest reductions in susceptibility to amprenavir, although each of the amprenavir-selected genotypes conferred little or no cross-resistance to other protease inhibitors. There was a significant association, for both amprenavir and indinavir, between preexisting baseline resistance to NRTIs subsequently received during the study and development of protease mutations (P ‫؍‬ 0.014 and P ‫؍‬ 0.031, respectively). Our data provide a comprehensive analysis of the mechanisms by which amprenavir resistance develops during clinical use and present evidence that resistance to concomitant agents in the treatment regimen predisposes to the development of mutations associated with protease inhibitor resistance and treatment failure.

The study findings suggest that either the amount of intra-operative intercostal nerve damage is not indicative of long-term nerve damage or that there is a more significant cause for chronic pain other than intercostal nerve injury.

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