Parikh U, Koontz D, Sluis-Cremer N, Hammond J, Bacheler L, Schinazi R, Mellors J; Conference on Retroviruses and Opportunistic Infections (11th : 2004 : San Francisco, Calif.).

Program Abstr Conf Retrovir Oppor Infect 11th 2004 San Franc Calif. 2004 Feb 8-11; 11: abstract no. 54.

Univ. of Pittsburgh, PA, USA

BACKGROUND: The 65R mutation in HIV-1 RT is selected in vitro by many D-nucleosides but has been paradoxically rare in vivo until recently. In the GS903 and ES30009 trials, 65R emerged in 24 to 54% of patients experiencing virologic failure on regimens containing tenofovir (without AZT). The reason for this change and the impact of 65R on susceptibility to approved and investigational NRTIs is uncertain. To gain further insight, we examined trends in the prevalence of 65R and its association with other NRTI mutations, determined the resistance profile of 65R alone and in combination with thymidine analog mutations (TAM), and analyzed the effect of 65R on the primer unblocking activity of RT.METHODS: We searched the Virco databases for the frequency of 65R and its association with other NRTI mutations. We examined the effect of 65R alone and with TAM on HIV-1 susceptibility to a large panel (n = 31) of D- , L-, and acyclic NRTI using a single cycle or multiple cycle replication assay. The primer unblocking activity of RT was assessed by measuring ATP-catalyzed removal of AZTMP from AZTMP-terminated primers.RESULTS: Of the >60,000 samples submitted to Virco for testing that contained any NRTI mutation, the frequency of 65R increased from 0.8% in 1998 to 3.8% in 2003. HIV-1 encoding 65R showed 2.5-fold to >>10-fold reduced susceptibility to all D-, L- , and acyclic NRTI tested except those with a 3'azido moiety (AZT, AZA, AZG), which had wildtype sensitivity. In examining the frequency of other NRTI mutations that occurred with 65R, a strong negative relation was noted with 41L, 67N, 210W, and 215Y/F. This suggested that 65R is antagonistic to TAM. Indeed, the addition of 65R to 2 different clones (41L/210W/215Y or 67N/70R/215F/219Q) reduced AZT resistance >10-fold (>30-fold to ~3-fold) and reduced primer unblocking activity ~10-fold to wildtype levels. In addition, TAM altered the phenotypic effect of 65R, reducing resistance to ddC, ddI, d4T, abacavir, and tenofovir.CONCLUSIONS: 65R is a multi-NRTI resistance mutation, reducing susceptibility to all D-, L-, and acyclic NRTI tested except those containing a 3'-azido moiety. 65R and TAM exhibit bidirectional phenotypic antagonism. Combining AZT with NRTIs that can select 65R is likely to prevent 65R from emerging.

Publication Types:

• Meeting Abstracts

Keywords:

• 3'-azido-3'-deoxythymidine 5'phosphate
• Adenine
• Didanosine
• Dideoxynucleosides
• HIV-1
• Humans
• In Vitro
• Mutation
• Nucleosides
• Phosphonic Acids
• Prevalence
• Stavudine
• Tamoxifen
• Thymidine
• Zalcitabine
• Zidovudine
• abacavir
• epidemiology
• genetics
• reverse transcriptase, Human immunodeficiency virus 1
• tenofovir

Other ID:

• GWAIDS0031145

UI: 102270782

From Meeting Abstracts