Detection of drug resistance mutations in HIV-1 patients with early viral rebound during ongoing combination therapy program

K Soderbarg, with the Professional Genetics Lab in Uppsala, reported on this study whose objective was to determine whether drug resistance mutations in the RT and protease genes could be found in 7 patients which, during ongoing drug therapy, show minor increases in viral load.

Viral RNA was isolated from samples with as few as 50 copies/ml, after which PCR amplification was performed. Mutations that are likely to cause drug resistance were detected in all patients. These mutations were detected early in the rebound process. Viral loads were as low as between 50 to 500 copies/ml. But in samples with as few as 50 copies/ml, it was possible to detect mutant viruses. The authors concluded mutations causing drug resistance are possible to detect in samples with very low viral load. Therefore, ongoing replication may result in further development of resistance. Some researchers question the reliability of mutations observed in individuals with low viral load <50 copies/ml.