Reduced susceptibility to lamivudine and emtricitabine associated with the novel K66N mutation in HIV-1 reverse transcriptase.
Gen De Wittelaan L11 B42800 Mechelen, Belgium
Y. Verlinden, G. Muyldermans, M. Van Houtte, K. Van Der Borght, L. Rimsky* and T. Pattery
Virco BVBA, Mechelen, Belgium; *Tibotec BVBA, Mechelen, Belgium
epancies between results obtained in phenotypic drug resistance tests and genotype or phenotype • F
ollow-up of genotypic/phenotypic data for 3TC and FTC for a
interpretation algorithms often lead to the recognition of important resistance-associated mutations.
patient failing his antiretroviral treatment.
xplained therapy failures can lead to the discovery of new mutations that are associated to HIV resistance.
Virco Geno database was searched for isolates harbouring
e we describe the identification of the drug resistance profile of K66N, a novel mutation in HIV-1 reverse
transcriptase (RT) conferring reduced susceptibility to the nucleoside RT inhibitors (NRTI) lamivudine (3TC) and • A
HIV-1 HXB2 site-directed mutant (SDM) harbouring K66N in the
emtricitabine (FTC), that was identified as a result of discrepant phenotype/genotype results.
RT was tested in the phenotypic assay (Antivirogram®, Virco). A. Genotypic/phenotypic data follow-up of a patient failing his antiretroviral treatment • The
genotypic/phenotypic data of different plasma samples taken during therapy from a • Genoty
pic analysis of the different plasma samples showed the introduction of a 66N
patient failing his antiretroviral treatment are shown in table 1 and table 2.
and 67G(1) mutation in RT, which can lead to reduced susceptibility for 3TC and FTC.
therapy, reduced susceptibility for 3TC and FTC was observed in the phenotypic • One
visit (visit 3) showed reduced susceptibility for 3TC and FTC although the 67G
assay (Antivirogram®) from visit 3 onwards, while the genotype interpretation algorithms
mutation was not present in the tested virus population.
(Virco®TYPE-HIV-1, Virco; Stanford; ANRS) showed a susceptible profile for 3TC and FTC
Table 2: Genotypic data follow-up of different samples from a HIV-1 infected patient Table 1: Phenotypic data follow-up of different samples from a HIV-1 infected patient 335D 356K 357T 370D
377M 386I 335D 356K 357T 370D
377M 386I
294P/T 329L 335D/G
357M/T 376A 379G 386I
294P/T 329L 335D/G
357M/T 376A 379G 386I
20R 35L 66N 101E 104R 115F 122K 181C/Y 214F
20R 35L 66N 101E 104R
297K 322T 335D 356K 115F 122K 181C/Y 214F
297K 322T 335D 356K
20R 35L 66N 67D/G 101E
104R 106I/V 115F 122K 181C 214F 272A 277K
20R 35L 66N 67D/G 101E
104R 106I/V 115F 122K 335D 356K/R 357T 370D 181C 214F 272A 277K 335D 356K/R 357T 370D
20R 35L 66N 67G 101E
104R 115F 122K 179F 181C 214F 272A 277K
20R 35L 66N 67G 101E
104R 115F 122K 179F 335D 357T 370D 377M 181C 214F 272A 277K 335D 357T 370D 377M
20R 35L 66N 67G 101E
104R 115F 122K 179F 181C 214F 272A 277K
20R 35L 66N 67G 101E
104R 115F 122K 179F 335D 356K/R 357T 370D 181C 214F 272A 277K 335D 356K/R 357T 370D Table 3: Antivirogram® Fold-Change values of Site-Directed Mutant 66N in RT
Green background: FC values ≤ Biological Cutoff (BCO); Red background: FC values ≥ BCO;
B. Occurrence of K66N
was a very rare mutation occurring in 0.026% of queried sequences of isolates
present in the Virco Geno database (77/292,910).
of all K66N isolates found in the database harboured the mutation as a mixture
with the wild-type amino acid (34/77).
% of all isolates with K66N had a pure K66N mutation (40/77).
16% of all K66N isolates (12/77), the K66N mutation was found in combination with
the M184V, indicating that the emergence of this mutation may be associated with exposure Green background: FC value ≤ BCO; Red background: FC value ≥ BCOto 3TC or FTC. C. In vitro phenotyping of a HIV-1 HXB2 SDM harbouring K66N in RT
old-change (FC) values obtained in the phenotypic assay (Antivirogram®) of a SDM
drug resistance profile of K66N, a novel mutation in HIV-1 reverse transcriptase
harbouring K66N are shown in Table 3.
(RT), is identified as a result of discrepant phenotype/genotype results.
FC values of SDM K66N in the phenotypic assay are above the BCO for 3TC and FTC.
e rare mutation K66N in HIV-1 RT is associated with reduced phenotypic
The mean of 4 measurements was 5.3 and 4.9 for 3TC and FTC, respectively.
susceptibility to 3TC and FTC and not to the other NRTIs.
research is required to investigate the clinical impact of this finding, how the
mutation evolves and whether it is selected during a specific therapy. REFERENCE: (1)Richard N. et al., AAC 2000; 44: 1127.
HIV9, 9th International Congress on Drug Therapy in HIV Infection, 9-13 November 2008, Glasgow, UK
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