title: X4 tropic viruses are on the rise in recent HIV-1 seroconverters in Spain.
abstract: BACKGROUND
  Transmission of HIV-1 with drug resistance mutations (DRMs) in Spain remains stable around 13%. However, the profile of recent HIV-1 seroconverters has experienced significant changes.
  
  
  METHODS
  Retrospective analyses of all individuals with HIV-1 infection acquired within the past 12 months recruited at a national registry since year 1997.
  
  
  RESULTS
  A total of 1032 recent HIV-1 seroconverters were examined (92.2% men; median age 31 years; 84% homosexual men). At the moment of diagnosis, median plasma HIV-RNA and CD4 cell counts were 4.5  log copies/ml and 558 cells/μl, respectively. A total of 136 individuals (13.8%) carried non-B subtypes. Major primary DRMs were found in 13.4%, being 7.7% for nucleoside reverse transcriptase inhibitor (NRTI), 5.8% for nonnucleoside reverse transcriptase inhibitor (NNRTI) and 2.9% for protease inhibitor. NRTI DRM significantly declined from 23.7% in 1997-2000 to 5.7% in 2010-2012 (P<0.01). Overall, X4 viruses were found in 19.7% of HIV-1 seroconverters, increasing from 11.5% before 2001 to 23.3% since year 2010 (P=0.04). Interestingly, median CD4 cell counts were significantly lower in seroconverters diagnosed during the last period after adjusting for potential confounders. In multivariate analyses, X4 tropism, high HIV-RNA, foreigners and non-B subtypes were independent predictors of lower CD4 cell counts.
  
  
  CONCLUSIONS
  Transmission of NRTI DRM has declined significantly in recent HIV-1 seroconverters in Spain. Conversely, X4 tropic viruses are on the rise and currently account for 23.3% of new HIV-1 infections. These individuals present with lower CD4 cell counts suggesting that circulating HIV-1 strains might have gained virulence.
authors.affiliation: aHospital Carlos III bCentro Sanitario Sandoval, Madrid cHospital Conxo-CHUS, Santiago dHospital General, Elche & Universidad Miguel Hernández, Alicante eHospital Rio Hortega, Valladolid fHospital Vall d'Hebron, Barcelona gHospital Universitario Puerta de Hierro & Puerta de Hierro Research Institute, Madrid, Spain.
authors.forename: Rocío
authors.initials: R
authors.lastname: Sierra-Enguita
authors.forename: Carmen
authors.initials: C
authors.lastname: Rodriguez
authors.forename: Antonio
authors.initials: A
authors.lastname: Aguilera
authors.forename: Felix
authors.initials: F
authors.lastname: Gutierrez
authors.forename: Jose M
authors.initials: JM
authors.lastname: Eiros
authors.forename: Estrella
authors.initials: E
authors.lastname: Caballero
authors.forename: Mariana
authors.initials: M
authors.lastname: Lapaz
authors.forename: Vicente
authors.initials: V
authors.lastname: Soriano
authors.forename: Jorge
authors.initials: J
authors.lastname: del Romero
authors.forename: Carmen
authors.initials: C
authors.lastname: de Mendoza
mesh_terms: D000328:Adult; D018791:CD4 Lymphocyte Count; D005260:Female; D015658:HIV Infections / Q000453:epidemiology* / Q000635:transmission / Q000821:virology*; D015497:HIV-1 / Q000502:physiology*; D006801:Humans; D008297:Male; D019718:Receptors, CXCR4 / Q000378:metabolism*; D015728:Receptors, HIV / Q000378:metabolism*; D012189:Retrospective Studies; D013030:Spain / Q000453:epidemiology; D056189:Viral Tropism
chemical_list: C527276:CXCR4 protein, human; D019718:Receptors, CXCR4; D015728:Receptors, HIV