Prevalence of C-terminal gag cleavage site mutations in HIV from therapy-naïve patients.

OBJECTIVES: HIV protease - as well as gag cleavage site (CS) - mutations occur in HIV with PI resistance but little is known about the prevalence of CS mutations in drug-naïve patients. PATIENTS AND METHODS: HIV samples (collected before 1997: n=94, after 1997: n=1617) from drug-naïve patients were analysed in the C-terminal gag and pol gene. Additionally, sequences from HIV Stanford database were included according to the collection date of the blood sample (before 1997: n=200, after 1997: n=375). RESULTS: Only CS mutations 431V and 452S were correlated with primary PI resistance in drug-naïve HIV. Previously described therapy-associated CS mutations (431V/449F/449H/451T/452S/453A) were found in less than 0.5% of therapy-naïve HIV without primary drug resistance and were totally absent in HIV isolates collected before 1997. The detection of 431V in the absence of PR mutations was significantly correlated with the presence of 429K. The treatment-associated CS mutations (436R/437V/453L) were generally found in more than 1% of drug-naïve HIV with differences between HIV subtypes. Natural polymorphisms were frequently found and also differed between HIV subtype B and non-B subtypes. CONCLUSIONS: The majority of therapy-associated CS mutations were rarely detected in drug-naïve HIV, but can be found in the absence of protease mutations. Moreover, the prevalence of these CS mutations seemed to have increased in recent years. The presence of treatment-associated CS mutations in drug-naïve patients might lower the genetic barrier of first-line therapies with protease inhibitors.

Compensatory mutations at the HIV cleavage sites p7/p1 and p1/p6-gag in therapy-naive and therapy-experienced patients.

BACKGROUND: Mutations in the genome of HIV conferring drug resistance are a major reason for the failure of antiretroviral therapy, but they often compromise viral fitness. Protease (PR) cleavage site (CS) mutations could compensate for impaired replication capacity of drug-resistant viruses. PATIENTS AND METHODS: We analysed the cleavage sites p1/p7 and p1/p6-gag of 500 HIV-1 subtype B infected patients. The collective consists of 275 therapy-naive and 225 therapy-experienced patients with at least one primary PR mutation, from whom eight underwent therapy-interruption in different clinical settings. RESULTS: Multiple mutations within the CS p7/p1 and p1/p6-gag accumulated in therapy-experienced isolates (p7/p1: A431V-K436R-I437V and p1/p6-gag: L449F/V-P452S-P453L/A). Further rare CS mutations were totally absent in therapy-naive viruses. Sixty percent of all therapy-experienced viruses exhibited at least one therapy-associated CS mutation, but so did 10% of therapy-naive viruses. The analysis of CS and PR mutations in therapy-experienced viruses revealed several positive correlations--A431V with L24I-M46I/L-I54V-V82A; I437V with I54V-V82F/T/S; L449V with I54M/L/S/T/A; and L449F/R452S/P453L: with D30N-I84V--whereas P453L and V82A were negatively correlated. Mutagenetic trees constructed form this cross-sectional data showed an ordered accumulation of the most prominent CS mutations along two pathways L90M-I84V-P453L and I54-V82-A431V followed by either M46L or L24I. Furthermore, eight viruses with at least one therapy-associated mutation at each CS displayed an outstanding maintenance of major PR mutations during therapy interruption. CONCLUSIONS: These findings emphasize the relevance of CS mutations in the evolution of HIV resistance to PR inhibitors. Therefore, therapy-associated CS mutations should be considered in HIV resistance tests to estimate viral fitness in different clinical settings.