Poster Presentation Melbourne Protein Group Student Symposium 2013

A common mechanism of clinical HIV-1 resistance to the CCR5 antagonist maraviroc despite divergent resistance level and lack of common gp120 resistance mutations (#70)

Hamid Salimi 1 2 , Michael Roche 1 , Lachlan Gray 1 2 , Renee Duncan 1 , Brendan Wilkin 3 , Jasminka Sterjovski 1 , Anne Ellett 1 , Miranda Moore 1 , Kelechi Chikere 4 , Benhur Lee 4 , Becky Jubb 5 , Mike Westby 5 , Melissa Churchill 1 2 , Paul Gorry 1 2 6
  1. Burnet institute, Melbourne
  2. Monash University, Melbourne
  3. University of Sydney, Sydney
  4. David Geffen School of Medicine, UCLA, USA
  5. Pfizer Global Research and Development, UK
  6. University of Melbourne, Australia

Background: Maraviroc (MVC) binds to a hydrophobic cavity within the trans-membrane helices of CCR5, and induces conformational alterations in the extra-cellular loops (ECLs) rendering CCR5 unrecognizable by HIV-1. HIV-1 can develop resistance to MVC by acquiring the ability to utilize the MVC-bound conformation of CCR5. Here, we compared the functional properties of two patient-derived MVC-resistant HIV-1 envelopes (Envs) with their parental sensitive Envs in order to elucidate the molecular mechanisms involved in development of resistance.

Materials and methods: Four HIV-1 Envs were isolated from patients 17 and 24 before the initiation of MVC (17-Sens and 24-Sens) and after virological failure (17-Res and 24-Res). The resistance phenotypes were determined in NP2-CD4/CCR5 cells and PBMCs by measuring the maximum percent inhibition (MPI). The 293-Affinofile assay was used to determine the ability of the resistant Envs to utilize MVC-bound CCR5. The mechanism of CCR5 engagement by resistant Envs was determined using entry assays in cells expressing alternative CCR5 mutants, and neutralization/inhibition assays.

Results: The resistant Envs displayed broad and divergent levels of resistance to MVC, with MPIs as high as 90% for 17-Res Env and as low as 0-12% for 24-Res Env. The magnitude of resistance was associated with the ability of the Envs to utilize the inhibitor-bound CCR5. Despite having highly divergent resistant phenotypes, and lack of common Env resistance mutations, both the resistant Envs acquired a critical dependence on the CCR5 N-terminus and charged histidine residues in the CCR5 ECLs to escape MVC. Increased dependence on the CCR5 N-terminus rendered the resistant Envs susceptible to inhibition by a sulfated peptide mimic of the CCR5 N-terminus.

Conclusion: A common molecular pathway of altered CCR5 engagement appears to be a common mechanism of HIV-1 escape from MVC, regardless of the level of resistance and the underlying resistance mutations. This altered pathway suggests a new avenue for blocking HIV-1 entry by CCR5 N-terminus sulfopeptidomimetic drugs.