title: HIV phenotype switching during antiretroviral therapy: emergence of saquinavir-resistant strains with less cytopathogenicity.
abstract: OBJECTIVE
  The aim of the study was to investigate changes in virological characteristics of HIV strains isolated from 38 HIV-seropositive subjects during antiretroviral therapy.
  
  
  METHODS
  Patients with a CD4+ cell count < or = 300 x 10(6)/l were treated with zidovudine (12 individuals) and saquinavir (10 individuals) alone or in combination (16 individuals). CD4+ cell count, viral load, HIV biological phenotype and drug resistance were evaluated during the study period.
  
  
  RESULTS
  After 52 weeks, 28 subjects (74%) harboured drug-resistant strains. In patients with a syncytium-inducing (SI) strain, a decline of CD4+ cell count and an increase of viral load were observed aside from the emergence of drug resistance. Conversely, at the emergence of antiretroviral resistance, an immunological and virological deterioration was observed only in patients who had a non-syncytium-inducing (NSI) strain. During the study, a phenotype switching of HIV isolates was detected in eight (21%) patients and a temporal correspondence between the appearance of phenotype switching and the emergence of drug resistance was found in seven cases. Three patients harbouring saquinavir-resistant strains showed a switch from SI to NSI variants associated with a moderate increase in CD4+ cell count.
  
  
  CONCLUSIONS
  The emergence of resistant strains during antiretroviral therapy may be associated with the selection of viral strains with less cytopathogenicity, while it could become a poor prognostic sign in patients with NSI isolates.
authors.affiliation: Department of Public Health and Cellular Biology, University of Rome Tor Vergata, Italy.
authors.forename: L
authors.initials: L
authors.lastname: Ercoli
authors.forename: L
authors.initials: L
authors.lastname: Sarmati
authors.forename: E
authors.initials: E
authors.lastname: Nicastri
authors.forename: G
authors.initials: G
authors.lastname: Giannini
authors.forename: C
authors.initials: C
authors.lastname: Galluzzo
authors.forename: S
authors.initials: S
authors.lastname: Vella
authors.forename: M
authors.initials: M
authors.lastname: Andreoni
mesh_terms: D019380:Anti-HIV Agents / Q000494:pharmacology*; D018791:CD4 Lymphocyte Count; D018450:Disease Progression; D004352:Drug Resistance, Microbial; D005260:Female; D014644:Genetic Variation; D015658:HIV Infections / Q000188:drug therapy* / Q000821:virology*; D015497:HIV-1 / Q000235:genetics*; D006801:Humans; D008297:Male; D010641:Phenotype; D012367:RNA, Viral / Q000145:classification / Q000235:genetics; D019258:Saquinavir / Q000494:pharmacology*; D013997:Time Factors; D015215:Zidovudine / Q000494:pharmacology
chemical_list: D019380:Anti-HIV Agents; D012367:RNA, Viral; D015215:Zidovudine; D019258:Saquinavir