Rare mutations at codon 103 of HIV-1 reverse transcriptase can confer resistance to non-nucleoside reverse transcriptase inhibitors.
BACKGROUND
The K103N mutation in HIV-1 reverse transcriptase (RT) confers high-level resistance to current non-nucleoside reverse transcriptase inhibitors (NNRTI). The prevalence and resistance profile of HIV-1 with other substitutions at RT codon 103 is less well documented.


METHODS
K103 substitutions among over 70,000 clinical samples submitted for routine antiretroviral resistance testing at two independent centres were examined. Phenotypic resistance profiles of isolates harboring rare K103 variants in the absence of known NNRTI-associated resistance mutations were retrieved from Virco's correlative genotype/phenotype database. Genotyped samples with known treatment histories were retrieved from the British Columbia Centre for Excellence in HIV/AIDS database. Site-directed mutants containing K103 variants were constructed and phenotyped.


RESULTS
K103N, R and S were observed in 29, 1.8, and 0.9% of Virco isolates and in 16, 1.5 and 0.4% of British Columbia isolates. K103T/Q/H substitutions were observed only rarely (<0.2%). The prevalence of unusual codon 103 substitutions remained stable over 5 years, except K103S, which increased over fourfold in both datasets. K103R/Q-containing clinical isolates remained phenotypically susceptible to NNRTI, whereas K103S/T/H-containing isolates showed over 10-fold decreased NNRTI susceptibility. Among patients with a known treatment history, K103S/T/H were observed primarily in individuals failing NNRTI-containing regimens. Site-directed mutants confirmed decreased susceptibility to NNRTI in K103S/T/H-containing recombinants.


CONCLUSIONS
Variants at HIV RT codon 103 other than K103N are observed relatively rarely in clinical isolates, but K103 S, T and H confer decreased susceptibility to NNRTI. These data are relevant for interpretive genotype algorithms and in the design of assays specific to RT codon 103 mutations.
Harrigan
P Richard
PR
BC Centre for Excellence in HIV/AIDS, Vancouver, BC, Canada.
Mo
Theresa
T
Wynhoven
Brian
B
Hirsch
Jennifer
J
Brumme
Zabrina
Z
McKenna
Paula
P
Pattery
Theresa
T
Vingerhoets
Johan
J
Bacheler
Lee T
LT
D019943:Amino Acid Substitution / Q000235:genetics*; D003062:Codon / Q000235:genetics; D024882:Drug Resistance, Viral / Q000235:genetics*; D015658:HIV Infections / Q000188:drug therapy / Q000235:genetics*; D054303:HIV Reverse Transcriptase / Q000235:genetics*; D006801:Humans; D009154:Mutation / Q000235:genetics*; D010641:Phenotype; D011110:Polymorphism, Genetic; D018894:Reverse Transcriptase Inhibitors / Q000627:therapeutic use
D003062:Codon; D018894:Reverse Transcriptase Inhibitors; D054303:HIV Reverse Transcriptase