Prevalence, genotypic associations and phenotypic characterization of K65R, L74V and other HIV-1 RT resistance mutations in a commercial database.

BACKGROUND: Nucleoside reverse transcriptase inhibitor (NRTI)-associated mutations (NAMs) can affect response to treatment with NRTIs and might also result in HIV-1 with reduced replication capacity.
METHODS: A large commercial HIV-1 database (n=60,487) was analysed for the prevalence of NAMs, antiviral drug susceptibilities and viral replication capacity.
RESULTS: Thymidine analogue mutations (TAMs) and M184V were the most commonly observed NAMs (>25%). L74V/I was detected in 11% of isolates. K65R was detected in 3.3% of isolates and its frequency remained stable from 2003 to 2006, similar to trends observed for other NAMs. TAMs were rarely observed in combination with K65R, but frequently associated with L74V/I. HIV-1 with K65R or L74V/I alone were fully susceptible to zidovudine and stavudine. K65R was associated with reduced susceptibility to tenofovir, didanosine, abacavir and lamivudine; L74V/I was associated with reduced susceptibility to abacavir and didanosine. The addition of M184V to either K65R or L74V/I improved susceptibility to tenofovir, zidovudine and stavudine, but reduced susceptibility to abacavir, didanosine and lamivudine. Other NAMs commonly associated with K65R were A62V, S68G and Y115F; their NRTI susceptibilities were similar to those of viruses containing K65R alone. The replication capacity for HIV-1 with M184V/I or K65R was significantly reduced compared with wild-type (median 68%/ and 72%, respectively; P<0.0001), whereas replication capacity for HIV-1 with L74V or TAMs was not significantly reduced (88% and 97%, respectively).
CONCLUSIONS: These results demonstrate a relative stability in the prevalence of HIV-1 clinical isolates with NAMs from 2003 to 2006. Differences between the genotypic patterns, phenotype and replication capacity associated with common NAMs are described.