HIV-1 dual/mixed tropic isolates show different genetic and phenotypic characteristics and response to maraviroc in vitro

Valentina Svicher, Emanuela Balestra, Valeria Cento, Loredana Sarmati, Luca Dori, Ina Vandenbroucke, Roberta D'Arrigo, Anna Rita Buonomini, Herwig Van Marck, Matteo Surdo, Patrizia Saccomandi, Wendy Mostmans, Jeroen Aerssens, Stefano Aquaro, Lieven J. Stuyver, Massimo Andreoni, Francesca Ceccherini-Silberstein, Carlo Federico Perno

Research output: Contribution to journalArticlepeer-review


Dual/mixed-tropic HIV-1 strains are predominant in a significative proportion of patients, though few information is available regarding the genetic characteristics, quasispecies composition, and susceptibility against CCR5-antagonists of the primary-isolates. For this reason, we investigated in deep details, both phenotypically and genotypically, the characteristics of 54 HIV-1 primary-isolates obtained from HIV-infected patients. Tropism was assessed by multiple-cycles phenotypic-assay on U87MG-CD4+-CCR5+-/CXCR4+-expressing cells. In vitro selection in PBMCs of X4-tropic viral strains following maraviroc-treatment was also performed.Phenotypic-assay reported pure R5-tropic viruses in 31 (57.4%) isolates, dual/mixed-tropic viruses in 22 (40.7%), and pure X4-tropic virus in only 1 (1.8%). Among dual/mixed-tropic isolates, 12 showed a remarkably higher replication-efficacy in CCR5-expressing cells (R5+/X4), and 2 in CXCR4-expressing cells (R5/X4+). Genotypic-tropism testing showed a correlation between PSSM-scores, geno2pheno false-positive-rate, and V3-net-charge with both CCR5-usage and syncytium-inducing ability. Moreover, specific gp120- and gp41-mutations were significantly associated with tropism and/or syncytium-inducing ability.Ultra-deep V3-pyrosequencing showed the presence of a swarm of genetically distinct species with a preference for CCR5-coreceptor not only in all pure R5-isolates, but also in 6/7 R5+/X4-tropic isolates. In both pure-X4 and R5/X4+-isolates, we observed extensive prevalence of X4-using species. In vitro selection-experiments with CCR5-inhibitor maraviroc (up to 2months) showed no-emergence of X4-tropic variants for all R5- and R5+/X4-isolates tested (while X4-virus remained fully-resistant).In conclusion, our study shows that dual/mixed-tropic viruses are constituted by different species, whereby those with characteristics R5+/X4 are genotypically and phenotypically similar to the pure-R5 isolates; thus the use of CCR5-antagonists in patients with R5+/X4-tropic viruses may be a therapeutic-option that deserves further investigations.

Original languageEnglish
Pages (from-to)42-53
Number of pages12
JournalAntiviral Research
Issue number1
Publication statusPublished - Apr 2011


  • Env mutations
  • HIV-1 tropism
  • Maraviroc
  • Phenotyping
  • Pyrosequencing

ASJC Scopus subject areas

  • Virology
  • Pharmacology


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