Low accumulation of L90M in protease from subtype F HIV-1 with resistance to protease inhibitors is caused by the L89M polymorphism

Abstract

Background. This work evaluates the role of subtype F human immunodeficiency virus type 1 (HIV-1) protease (PR) substitutions L89M and L90M in viral replication and resistance to PR inhibitors (PIs). Methods. Subtype B and F PR genes were subjected to site-directed mutagenesis, to create and reverse the methionine at positions 89 and 90. Viruses were re-created in cell culture, and their replicative capacity was assessed by fitness assay. Generated viruses were also phenotyped for PI resistance. Results. The subtype F clone (89M90L) showed a replicative capacity comparable to that of the PI-susceptible subtype B clone (89L90L) and was more fit than the L89M mutated subtype B clone (89M90L). Both 89M90M subtype B and F clones presented the lowest fitness 5 values. The L89M mutation impacted phenotypic resistance to all PIs in half of the subtype F isolates but not in the subtype B isolates. Subtype F isolates presented a phenotypic profile similar to that of subtype B isolates when the M89L mutation was introduced. Conclusion. The L89M mutation in subtype F viruses is a high genetic barrier to the accumulation of the L90M resistance mutation and can function as a resistance mutation, depending on the presence of other polymorphisms in the subtype F PR backbone. © 2005 by the Infectious Diseases Society of America. All rights reserved.