The A62V and S68G mutations in HIV-1 reverse transcriptase partially restore the replication defect associated with the K65R mutation.
BACKGROUND
The K65R mutation in human immunodeficiency virus type 1 reverse transcriptase can be selected by abacavir, didanosine, tenofovir, and stavudine in vivo resulting in reduced susceptibility to these drugs and decreased viral replication capacity. In clinical isolates, K65R is frequently accompanied by the A62V and S68G reverse transcriptase mutations.


METHODS
The role of A62V and S68G in combination with K65R was investigated using phenotypic, viral growth competition, pre-steady-state kinetic, and excision analyses.


RESULTS
Addition of A62V and S68G to K65R caused no significant change in human immunodeficiency virus type 1 resistance to abacavir, didanosine, tenofovir, or stavudine but partially restored the replication defect of virus containing K65R. The triple mutant K65R+A62V+S68G still showed some replication defect compared with wild-type virus. Pre-steady-state kinetic analysis demonstrated that K65R resulted in a decreased rate of incorporation (kpol) for all natural dNTPs, which were partially restored to wild-type levels by addition of A62V and S68G. When added to K65R and S68G, the A62V mutation seemed to restore adenosine triphosphate-mediated excision of tenofovir to wild-type levels.


CONCLUSIONS
A62V and S68G serve as partial compensatory mutations for the K65R mutation in reverse transcriptase by improving the viral replication capacity, which is likely due to increased incorporation efficiency of the natural substrates.
Svarovskaia
Evguenia S
ES
Gilead Sciences, Inc, 4 University Place, 4611 University Drive, Durham, NC 27707, USA. jenny.svarovskaia@gilead.com
Feng
Joy Y
JY
Margot
Nicolas A
NA
Myrick
Florence
F
Goodman
Derrick
D
Ly
John K
JK
White
Kirsten L
KL
Kutty
Nilima
N
Wang
Ruth
R
Borroto-Esoda
Katyna
K
Miller
Michael D
MD
D000225:Adenine / Q000031:analogs & derivatives* / Q000494:pharmacology; D023241:Antiretroviral Therapy, Highly Active; D016049:Didanosine / Q000494:pharmacology*; D015224:Dideoxynucleosides / Q000494:pharmacology*; D024921:Drug Resistance, Multiple, Viral / Q000235:genetics; D015658:HIV Infections / Q000821:virology*; D054303:HIV Reverse Transcriptase / Q000187:drug effects*; D015497:HIV-1 / Q000187:drug effects* / Q000502:physiology*; D063065:Organophosphonates / Q000494:pharmacology*; D017354:Point Mutation; D018894:Reverse Transcriptase Inhibitors / Q000494:pharmacology*; D018119:Stavudine / Q000494:pharmacology*; D000068698:Tenofovir; D014779:Virus Replication; D000099227:Abacavir
D000225:Adenine; D016049:Didanosine; D015224:Dideoxynucleosides; D054303:HIV Reverse Transcriptase; D063065:Organophosphonates; D018894:Reverse Transcriptase Inhibitors; D018119:Stavudine; D000068698:Tenofovir; D000099227:Abacavir; C514824:reverse transcriptase, Human immunodeficiency virus 1