title: Duration and predictors of CD4 T-cell gains in patients who continue combination therapy despite detectable plasma viremia.
abstract: BACKGROUND
  Sustained elevations in CD4 cell counts commonly occur despite incomplete viral suppression with protease inhibitor-based antiretroviral therapy.
  
  
  OBJECTIVE
  To determine the incidence and risk factors associated with return of CD4 cell count to pre-therapy levels in patients experiencing virologic failure of protease inhibitor therapy.
  
  
  METHODS
  This is a clinic-based cohort study of HIV-infected adults who failed to maintain durable viral suppression on a protease inhibitor-based regimen.
  
  
  METHODS
  Virologic failure was defined as persistent plasma HIV RNA level > 500 copies/ml. Immunologic failure was defined as return of CD4 cell count to pre-therapy levels.
  
  
  RESULTS
  A total of 291 patients experienced virologic failure on a protease inhibitor-based regimen and had a treatment-mediated CD4 cell increase above pre-therapy levels at the time of virologic failure. If patient data were censored at the time a successful salvage regimen was initiated, then the median time to immunologic failure after the onset of virologic failure was 3 years. If patient data were also censored at the time therapy was discontinued, then 36.8% of the cohort experienced immunologic failure after 3 years of continuous virologic failure. The change in viral load from a pre-treatment baseline, and not the absolute level of viremia achieved, was a strong and independent predictor of immunologic failure. Discontinuing therapy was associated with immunologic failure independent of viral load changes.
  
  
  CONCLUSIONS
  Reduction in T CD4+ cell numbers may eventually occur during prolonged virologic failure of a protease inhibitor-based regimen and is predicted by the degree of virologic suppression below a pre-therapy 'set-point'.
authors.affiliation: UCSF AIDS Program, University of California and San Francisco General Hospital, San Francisco, California 94110, USA. sdeeks@php.ucsf.edu
authors.forename: Steven G
authors.initials: SG
authors.lastname: Deeks
authors.forename: Jason D
authors.initials: JD
authors.lastname: Barbour
authors.forename: Robert M
authors.initials: RM
authors.lastname: Grant
authors.forename: Jeffrey N
authors.initials: JN
authors.lastname: Martin
mesh_terms: D000328:Adult; D023241:Antiretroviral Therapy, Highly Active; D018791:CD4 Lymphocyte Count; D015496:CD4-Positive T-Lymphocytes / Q000166:cytology / Q000187:drug effects*; D018450:Disease Progression; D015658:HIV Infections / Q000097:blood / Q000188:drug therapy* / Q000276:immunology / Q000821:virology; D017320:HIV Protease Inhibitors / Q000627:therapeutic use*; D015497:HIV-1 / Q000187:drug effects* / Q000235:genetics; D006801:Humans; D019469:Indinavir / Q000627:therapeutic use; D019888:Nelfinavir / Q000627:therapeutic use; D012367:RNA, Viral / Q000097:blood; D019438:Ritonavir / Q000627:therapeutic use; D019258:Saquinavir / Q000627:therapeutic use; D013997:Time Factors; D017211:Treatment Failure; D014766:Viremia / Q000097:blood / Q000188:drug therapy* / Q000276:immunology / Q000821:virology
chemical_list: D017320:HIV Protease Inhibitors; D012367:RNA, Viral; D019469:Indinavir; D019888:Nelfinavir; D019258:Saquinavir; D019438:Ritonavir