title: Processivity and drug-dependence of HIV-1 protease: determinants of viral fitness in variants resistant to protease inhibitors.
abstract: OBJECTIVE
  To investigate the role of processivity and drug-dependence of HIV-1 protease as fitness determinants in variants resistant to protease inhibitors (PI).
  
  
  METHODS
  HIV-1 protease sequences from 32 infected subjects (27 patients who failed PI-treatments and five PI-naive controls) were evaluated using a recombinant method. The HIV-1 phenotype to seven PI was analysed together with the replication capacity of recombinants and the processivity and drug-dependence of the HIV-1 proteases. Protease mutants (positions 10, 46, 54, 82, 84, 90, and combinations thereof) were generated in vitro and studied under identical experimental conditions.
  
  
  RESULTS
  In the absence of PI, 24 of 27 (89%) resistant proteases from treated subjects showed decreased processivity compared with the wild type. Processivity was lower in sequences bearing fewer mutations, than in more mutated ones. Twelve sequences (44%) conferred slower replication kinetics to the recombinant viruses. Seven sequences (26%) showed higher processivity levels in the presence of PI than in their absence, suggesting that drug-dependence influences PI-resistant variants. Among the mutants generated in vitro, mutations 82A and 90M determined broad cross-resistance to PI in association with 10I. A drop of processivity was observed for the 82A+90M variants; 10I allowed partial recovery for 82A and 84V, and marked recovery for 90M mutants.
  
  
  CONCLUSIONS
  A decrease in HIV-1 protease processivity parallels early selection of primary mutations, whereas its recovery is driven by compensatory mutations. Furthermore, a PI may select drug-dependent, besides resistant, HIV-1 protease variants. Changes in processivity and drug-dependence of HIV-1 proteases have implications in the replication capacity of PI-resistant viruses.
authors.affiliation: Istituto di Microbiologia, Universitá di Ancona, Italy.
authors.forename: Stefano
authors.initials: S
authors.lastname: Menzo
authors.forename: Alessia
authors.initials: A
authors.lastname: Monachetti
authors.forename: Claudia
authors.initials: C
authors.lastname: Balotta
authors.forename: Stefano
authors.initials: S
authors.lastname: Corvasce
authors.forename: Stefano
authors.initials: S
authors.lastname: Rusconi
authors.forename: Stefania
authors.initials: S
authors.lastname: Paolucci
authors.forename: Fausto
authors.initials: F
authors.lastname: Baldanti
authors.forename: Patrizia
authors.initials: P
authors.lastname: Bagnarelli
authors.forename: Massimo
authors.initials: M
authors.lastname: Clementi
mesh_terms: D003001:Cloning, Molecular; D024882:Drug Resistance, Viral; D016333:HIV Protease / Q000187:drug effects* / Q000235:genetics; D017320:HIV Protease Inhibitors / Q000494:pharmacology*; D015497:HIV-1 / Q000187:drug effects* / Q000235:genetics / Q000472:pathogenicity; D006801:Humans; D016297:Mutagenesis, Site-Directed; D010641:Phenotype; D017354:Point Mutation; D014779:Virus Replication
chemical_list: D017320:HIV Protease Inhibitors; D016333:HIV Protease