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Title: Impact on replicative fitness of the G48E substitution in the protease of HIV-1: an in vitro and in silico evaluation
Authors: Zimmer, Jean-Marie ×
Roman, François
Lambert, Christine
Jonckheer, Abel
Vazquez, Ana
Plesséria, Jean-Marc
Servais, Jean-Yves
Covens, Kris
Weber, Jan
Van Laethem, Kristel
Schmit, Jean-Claude
Vandamme, Anne-Mieke
Quinones-Mateu, Miguel E
De Maeyer, Marc #
Issue Date: Jul-2008
Publisher: Lippincott Williams & Wilkins
Series Title: Journal of Acquired Immune Deficiency Syndromes vol:48 issue:3 pages:255-62
Abstract: We observed an unusual glycine-to-glutamate substitution at protease (PR) residue position 48 (G48E) in an African patient infected with a subtype A1 HIV-1 strain failing a saquinavir-containing regimen. Phenotypic analysis of protease inhibitor (PI) susceptibility showed that the G48E site-directed mutant, when introduced into an NL4-3 HIV-1 PR backbone, was slightly resistant to SQV (2-fold when compared with the wild-type virus). In addition, the G48E and G48E/V82A site-directed mutants were associated with a decrease in fitness, whereas a reversion to the wild type at position 48 was observed in vitro. Growth competition experiments using a novel growth competition assay based on enhanced green fluorescent protein- or Discosoma spp. red fluorescent protein-expressing viruses showed that the replicative fitness of the G48E virus was reduced to 55% compared with the parental NL4-3 virus. Synthesizing all possible site-directed mutants found in the patient strain is too time-consuming; therefore, a molecular dynamics (MD) simulation approach was used to understand why this mutation survived despite its fitness cost. These simulations documented that the G48E mutant interacted with PI resistance mutations (M46I, I54V, Q58E, and L63P) and with natural polymorphisms specific to subtype A1 (E35D, M36I, and R57K) that were present in the patient's virus. We hypothesize that the polymorphisms contained in the PR flap regions of the patient's virus may compensate for the presence of G48E, possibly by restoring the flexibility of the PR flaps. In summary, our results demonstrate that the G48E substitution, when introduced in the context of an HIV-1 subtype B strain, is highly unstable and gives rise to viruses with a poor replicative fitness in vitro. We also showed that when confronted with too many mutations to evaluate in vitro, MD simulations are helpful to draft hypotheses on how polymorphisms can interact with resistance mutations to stabilize their potential fitness cost.
URI: 
ISSN: 1525-4135
Publication status: published
KU Leuven publication type: IT
Appears in Collections:Laboratory of Clinical and Epidemiological Virology (Rega Institute)
Biochemistry, Molecular and Structural Biology Section
Research Group Neurophysiology
Laboratory for Auditive Neurophysiology
Molecular and Vascular Biology
× corresponding author
# (joint) last author

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