title: Attenuated replication of human immunodeficiency virus type 1 with a didanosine-selected reverse transcriptase mutation.
abstract: The Leu-74 to Val (Leu74Val) mutation in human immunodeficiency virus type 1 reverse transcriptase (RT) develops as a consequence of didanosine (ddI) therapy and is associated with a decreased susceptibility to ddI. In this report, we provide evidence that the ddI-associated Leu74Val mutation confers a replication disadvantage to the virus. In a series of experiments, we have shown that (i) a cloned virus with an engineered Leu74Val mutation in RT was attenuated for replication; (ii) a Val-to-Leu revertant of Leu74Val in the pNL4-3 background replicated with an efficiency similar to that of the wild-type virus; (iii) when two isolates from the same patient were compared, a clinical isolate containing mutations Leu74Val and Thr215Tyr was attenuated for replication compared to one in which the Thr215Tyr mutation alone was present; and (iv) the viruses with the Leu74Val mutation showed an 11% loss of fitness in a single passage compared to the wild-type and a mutant virus containing a Lys70Arg mutation. The loss of fitness for viruses grown in drug-free medium could result in an inability to detect a Leu74Val mutant in clinical isolates obtained post-ddI therapy. The decreased replication ability of the Leu74Val mutant virus selected by ddI therapy provides a strong rationale for the lower viral RNA levels observed with ddI therapy compared to zidovudine therapy in clinical trials.
authors.affiliation: Division of Infectious Disease, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts 02215, USA. psharma@bidmc.harvard.edu
authors.forename: P L
authors.initials: PL
authors.lastname: Sharma
authors.forename: C S
authors.initials: CS
authors.lastname: Crumpacker
mesh_terms: D019943:Amino Acid Substitution; D002478:Cells, Cultured; D016049:Didanosine / Q000494:pharmacology*; D004352:Drug Resistance, Microbial; D054303:HIV Reverse Transcriptase / Q000235:genetics*; D015497:HIV-1 / Q000201:enzymology / Q000254:growth & development*; D006801:Humans; D007930:Leucine; D017354:Point Mutation; D012641:Selection, Genetic; D014633:Valine; D014779:Virus Replication
chemical_list: D054303:HIV Reverse Transcriptase; D007930:Leucine; D014633:Valine; D016049:Didanosine