Poster Presentation 8th Australasian Virology Society Meeting and 11th Annual Meeting of the Australian Centre for Hepatitis & HIV Virology Meeting 2015

Increasing Prevalence of Silent Mutations K65K and K66K in HIV-1 Subtype B RT That Confer a Fitness Advantage to a Multi-Drug Resistant Clinical Isolate     (#202)

Sushama Telwatte 1 , Chanson J Brumme 2 3 , Anna Hearps 1 4 , Cath F Latham 1 , Con Sonza 5 , Richard P Harrigan 2 , Gilda Tachedjian 1 4 5 6
  1. Burnet Institute, Melbourne, VIC, Australia
  2. BC Centre for Excellence, Vancouver, British Columbia, Canada
  3. University of British Columbia, British Columbia, Canada
  4. Department of Infectious Diseases, Monash University, Melbourne, VIC, Australia
  5. Department of Immunology and Microbiology, Melbourne University, Melbourne, VIC, Australia
  6. Department of Microbiology, Monash University, Melbourne, VIC, Australia

Resistance to combination antiretroviral therapy (cART) in HIV-1 infected individuals is typically due to non-synonymous mutations that change the protein sequence; yet, the selection of synonymous or ‘silent’ mutations in HIV-1 has been reported. Silent K65K and K66K mutations in HIV-1 reverse transcriptase (RT) are associated with thymidine analog mutations (TAMs) D67N and K70R, which confer decreased susceptibility to most HIV-1 nucleoside RT inhibitors. We previously demonstrated that D67N/K70R in HIV-1 RT increase indel frequency by 100-fold, contributing to impaired viral fitness, and that K65K or K66K substitutions reversed these defects1 . However, the impact of the silent mutations in clinically-relevant virus backbones and their prevalence over time are unknown.

Growth competition assays between multidrug resistant HIV-1 variants ±K65K or K66K derived from a patient isolate revealed that these silent mutations confer a 2.01 ± 0.11% and 2.41 ± 0.41% fitness advantage respectively relative to virus lacking these mutations in the absence of drug pressure (n=3 for each). A retrospective analysis of all treatment-naïve HIV-infected individuals enrolled in the British Columbia Centre for Excellence in HIV/AIDS Drug Treatment Program between 1997 and 2014 determined that K65K and K66K increased in prevalence in drug-naïve individuals from 11% in 1997 to 25% in 2012 (p<0.0001, n=5221). Additionally, a longitudinal analysis of RT sequences from 2,131 patients from the same cohort showed K65K and K66K emerged in drug treated patients in the absence of TAMs in over 13% (p= 3.0x10-36) of the cohort suggesting there may be a role for these silent mutations independent of TAMs.

These data provide new insights into the role of silent mutations K65K and K66K selected during cART, suggesting potential transmission of these mutations to drug-naïve individuals and subsequent persistence in a population, which further alludes to the relevance of silent mutations in RNA viruses more broadly. 

  1. Telwatte, S., Hearps, A. C., Johnson, A., Latham, C. F., Moore, K., Agius, P., Tachedjian, M., Sonza, S., Sluis-Cremer, N., Harrigan, P. R. and Tachedjian, G. (2015) 'Silent mutations at codons 65 and 66 in reverse transcriptase alleviate indel formation and restore fitness in subtype B HIV-1 containing D67N and K70R drug resistance mutations', Nucleic Acids Res, 43(6), pp. 3256-71.