title: Analysis of infectious virus clones from two HIV-1 superinfection cases suggests that the primary strains have lower fitness.
abstract: BACKGROUND
  Two HIV-1 positive patients, L and P, participating in the Amsterdam Cohort studies acquired an HIV-1 superinfection within half a year from their primary HIV-1 infection (Jurriaans et al., JAIDS 2008, 47:69-73). The aim of this study was to compare the replicative fitness of the primary and superinfecting HIV-1 strains of both patients. The use of isolate-specific primer sets indicated that the primary and secondary strains co-exist in plasma at all time points after the moment of superinfection.
  
  
  RESULTS
  Biological HIV-1 clones were derived from peripheral blood CD4 + T cells at different time point, and identified as the primary or secondary virus through sequence analysis. Replication competition assays were performed with selected virus pairs in PHA/IL-2 activated peripheral blood mononuclear cells (PBMC's) and analyzed with the Heteroduplex Tracking Assay (HTA) and isolate-specific PCR amplification. In both cases, we found a replicative advantage of the secondary HIV-1 strain over the primary virus. Full-length HIV-1 genomes were sequenced to find possible explanations for the difference in replication capacity. Mutations that could negatively affect viral replication were identified in the primary infecting strains. In patient L, the primary strain has two insertions in the LTR promoter, combined with a mutation in the tat gene that has been associated with decreased replication capacity. The primary HIV-1 strain isolated from patient P has two mutations in the LTR that have been associated with a reduced replication rate. In a luciferase assay, only the LTR from the primary virus of patient P had lower transcriptional activity compared with the superinfecting virus.
  
  
  CONCLUSIONS
  These preliminary findings suggest the interesting scenario that superinfection occurs preferentially in patients infected with a relatively attenuated HIV-1 isolate.
authors.affiliation: Laboratory of Experimental Virology, Department of Medical Microbiology, Centre for Infection and Immunity Amsterdam (CINIMA), Academic Medical Centre, University of Amsterdam, Amsterdam, The Netherlands. a.c.vanderkuyl@amc.uva.nl
authors.forename: Antoinette C
authors.initials: AC
authors.lastname: van der Kuyl
authors.forename: Karolina
authors.initials: K
authors.lastname: Kozaczynska
authors.forename: Kevin K
authors.initials: KK
authors.lastname: Ariën
authors.forename: Youssef
authors.initials: Y
authors.lastname: Gali
authors.forename: Victoria R
authors.initials: VR
authors.lastname: Balázs
authors.forename: Stefan J
authors.initials: SJ
authors.lastname: Dekker
authors.forename: Fokla
authors.initials: F
authors.lastname: Zorgdrager
authors.forename: Guido
authors.initials: G
authors.lastname: Vanham
authors.forename: Ben
authors.initials: B
authors.lastname: Berkhout
authors.forename: Marion
authors.initials: M
authors.lastname: Cornelissen
mesh_terms: D002478:Cells, Cultured; D004252:DNA Mutational Analysis; D015658:HIV Infections / Q000821:virology*; D015497:HIV-1 / Q000235:genetics / Q000254:growth & development / Q000302:isolation & purification* / Q000472:pathogenicity*; D006801:Humans; D007963:Leukocytes, Mononuclear / Q000821:virology; D008297:Male; D016254:Mutagenesis, Insertional; D020125:Mutation, Missense; D010949:Plasma / Q000821:virology; D017422:Sequence Analysis, DNA; D015163:Superinfection / Q000821:virology*; D019562:Viral Load; D014774:Virulence; D014779:Virus Replication