To the Editor:
A combination of 2 or more nucleoside reverse transcriptase inhibitors (NRTIs) is generally part of each antiretroviral regimen for the treatment of HIV-1-infected patients.1 The emergence of NRTI-resistant HIV-1 mutants can be a major cause of antiretroviral treatment failure.2 The mechanisms of resistance to NRTIs can result from a cluster of base-pair substitutions leading to amino-acid replacements in the reverse transcriptase coding region and can also result from isolated mutations responsible for interference with the binding and incorporation of NRTIs.2 This is the case with the reverse transcriptase K65R mutation, which confers major in vivo resistance to tenofovir as well reduced susceptibility to abacavir, didanosine, and lamivudine.3,4 Recently, several studies have reported that the prevalence of this mutation has significantly increased over the last 4 years, which corresponds to the widespread use of tenofovir.5 The aim of the present study was to assess the overall prevalence of the K65R mutation in a cohort of HIV-1-infected patients failing an antiretroviral regimen. For each subject infected with a K65R-mutated variant, we determined the dynamics of selection and reversion of the K65R mutation during standard longitudinal virologic, immunologic, and therapeutic follow-up.
The study patients were part of a cohort that included HIV-1-infected subjects seen at the University Medical Center of Reims (France) between May 2001 and May 2004. They were failing an antiretroviral regimen, and they underwent genotype resistance testing (GRT) on a peripheral blood sample after the therapeutic failure. For each of the patients harboring a K65R mutation, a genotype resistance assay was retrospectively performed on sequential plasma samples taken since the initiation of the antiretroviral regimen suspected to have selected for this mutation (Table 1). A reverse transcriptase genotypic resistance study was performed on viral plasma RNA using the Agence Nationale de Recherches sur le SIDA (ANRS) consensus technique as described previously.6,7
Among 268 HIV-1-infected patients who underwent GRT after the failure of therapy, 6 (2.2%) harbored the K65R mutation. In these 6 patients, the K65R mutation seemed to be selected within 2 to 11 months (median = 5.5 months) after the initiation of a treatment susceptible to selection for this mutation (see Table 1). This regimen included an association of tenofovir and didanosine in 2 cases; a combination of tenofovir, didanosine, and abacavir in 1 case; and didanosine or tenofovir alone in 3 cases (see Table 1). The K65R mutation was associated with other nucleoside analogs mutations (NAMs) as M184V (patients 1-3, 5, and 6), Q151M (patient 4), L74V (patient 3), and M41L (patient 6) (see Table 1). In patient 3, the L74V mutation was selected within 4 months after beginning therapeutic regimen containing a combination of didanosine and abacavir, and its reversion occurred at the time of selection of the K65R mutation. In patient 6, the M41L mutation was selected within 7 months after the initiation of a new drug regimen containing didanosine, and its selection was concomitant with the reversion of the K65R mutation (see Table 1). Interestingly, 4 of the 6 patients harboring the K65R mutation underwent a programed treatment interruption. In 1 of them (patient 5), this mutation remained selected in sequential plasma virus samples, whereas a reversion was observed in the plasma virus of the other 3 (patients 1, 2, and 4). This reversion occurred within 2 to 3 months after beginning this strategy and was followed by a response to a new therapy including NRTIs in only 1 individual (patient 1) (see Table 1).
In the present study, we report the presence of the K65R mutation in plasma virus of 6 of 268 HIV-1-infected NRTI-experienced patients, demonstrating a global prevalence of 2.2% during a 3-year period corresponding to the widespread used of tenofovir in this cohort. The low prevalence level of this mutation confirmed the findings of previously published studies that reported the presence of the K65R mutation in only 3% to 4% of plasma virus samples of HIV-1-infected NRTI-experienced patients.5,8 Interestingly we report here, for the first time, that this mutation could be rapidly selected in less than 5.5 months after the initiation of a new drug regimen that included tenofovir, didanosine, or abacavir alone or a dual or triple combination of these drugs in NRTI-experienced patients (see Table 1). Moreover, the longitudinal GRT on plasma virus samples of patients harboring the K65R mutation demonstrated the presence of other NAMs (see Table 1). In patient 3, the L74V mutation selected by abacavir or didanosine therapy reverted at the time of selection of the K65R mutation. This phenomenon could explain the low prevalence of the L74V mutation in tenofovir-containing regimens as reported in several studies.2 In patient 6, the selection of the M41L mutation was clearly concomitant with reversion of the K65R mutation, suggesting that the coselection of these 2 NAMS may be responsible for strong functional constraints of the reverse transcriptase, resulting in failing virus replication.2 This observation supports the hypothesis that zidovudine, which is known to select for the M41L mutation and other NAMs, could be used in association with tenofovir-, didanosine-, or abacavir-containing regimens to prevent the selection of the K65R mutation.9-11 The second interesting finding from the present study is that the use of a programmed treatment interruption strategy could be sufficient to obtain a reversion of the K65R mutation (see Table 1; patients 1, 2, and 4). These data indicate that recycling of antiretroviral drugs whose antiviral activity is affected by the K65R mutation could be successful after a programmed drug wash-out, even in NRTI-pretreated patients.
In conclusion, this study confirms the low prevalence level of the K65R mutation in HIV-1-infected NRTI-experienced patients failing an antiretroviral regimen. Moreover, our data show a rapid dynamic selection of the K65R mutation after failure of antiretroviral regimens containing tenofovir, abacavir, or didanosine and indicate that a reversion of the K65R mutation could be induced not only by selection of the M41L mutation but by the use of programmed treatment interruption strategies.
Véronique Brodard, MD*
Hélène Moret, PhD*
Isabelle Béguinot, MD†
Lydie Morcrette, MB*
Lysiane Bourdaire, MB*
Jérôme Jacques, MSc*
Christine Rouger, MD†
Christophe Strady, MD†
Jean-Luc Berger, MD†
Laurent Andréoletti, MD, PhD*
*Laboratoire de Virologie Centre Hospitalier Universitaire et IFR 53/EA-3798 (DAT/PPCIDH) Faculté de Médecine Reims, France †Service des Maladies Infectieuses Centre Hospitalier Universitaire Faculté de Médecine Reims, France
1. Yeni PG, Hammer SM, Hirsch MS, et al. Treatment for adult HIV infection: recommendations of the International AIDS Society-USA Panel. JAMA
2. Miller MD, Margot N, Lu B, et al. Genotypic and phenotypic predictors of the magnitude of response to tenofovir disoproxil fumarate treatment in antiretroviral-experienced patients. J Infect Dis
3. Gu Z, Gao Q, Fang H, et al. Identification of a mutation at codon 65 in the IKKK motif of reverse transcriptase that encodes human immunodeficiency virus resistance to 2′,3′-dideoxy-3′-thiacytidine. Antimicrob Agents Chemother
4. Roge BT, Katzenstein TL, Obel N, et al. K65R with and without S68: a new resistance profile in vivo detected in most patients failing abacavir, didanosine and stavudine. Antiviral Ther
5. Winston A, Pozniak A, Mandalia S, et al. Which nucleoside and nucleotide backbone combinations select for the K65R mutation in HIV-1 reverse transcriptase. AIDS
6. Jung M, Agut H, Candotti D, et al. Susceptibility of HIV-1 isolates to zidovudine: correlation between widely applicable culture test and PCR analysis. J Acquir Immune Defic Syndr Hum Retrovirol
7. Larder BA, Kellam P, Kemp SD. Zidovudine resistance predicted by direct detection of mutations in DNA from HIV-infected lymphocytes. AIDS
8. MacArthur RD, Crane LR, Alvarez D, et al. Factors associated with selection of the K65R mutation: a retrospective chart review [abstract 835]. In: Program and Abstracts of the Second International AIDS Society Conference on Pathogenesis and Treatment
. Paris; 2003.
9. Jemsek J, Hutcherson P, Harper E. Poor virologic responses and early emergence of resistance in treatment naive, HIV-infected patients receiving a once daily triple nucleoside regimen of didanosine, lamivudine, and tenofovir DF [abstract 51]. In: Program and Abstracts of the 11th Conference on Retroviruses and Opportunistic Infections
. San Francisco; 2004.
10. Elion R, Cohen C, DeJesus E, et al. COL40263: resistance and efficacy of once-daily trizivir and tenofovir DF in antiretroviral naïve subjects [abstract 53]. In: Program and Abstracts of the 11th Conference on Retroviruses and Opportunistic Infections
. San Francisco; 2004.
11. Wainberg MA, Turner D. Resistance issues with new nucleoside/nucleotide backbone options. J Acquir Immune Defic Syndr
. 2004;37(Suppl 1):S36-S43.