title: Low incidence of HIV-1 superinfection even after episodes of unsafe sexual behavior of homosexual men in the Amsterdam Cohort Studies on HIV Infection and AIDS.
abstract: BACKGROUND
  Human immunodeficiency virus type 1 (HIV-1) superinfection is infection of an HIV-1 seropositive individual with another HIV-1 strain. The rate at which HIV-1 superinfection occurs might be influenced by sexual behavior. Superinfection might be detected more often by analyzing longitudinal samples collected from time periods of unsafe sexual behavior.
  
  
  METHODS
  Envelope C2-C4 and gag sequences were generated from HIV-1 RNA from longitudinal serum samples that were obtained around self-reported sexual risk periods from 15 homosexual therapy-naïve men who participated in the Amsterdam Cohort Studies on HIV Infection and AIDS. Maximum likelihood phylogenetic analysis was used to determine whether HIV-1 superinfection had occurred.
  
  
  RESULTS
  We studied a total of 124 serum samples from 15 patients with a median of 8 samples and of 5.8 person-years of follow-up per patient. Phylogenetic analysis on 907 C2-C4 env and 672 gag sequences revealed no case of HIV-1 superinfection, resulting in a superinfection incidence rate of 0 per 100 person-years [95%CI: 0 - -4.2].
  
  
  CONCLUSIONS
  We conclude that HIV-1 superinfection incidence is low in this subgroup of homosexual men who reported unsafe sexual behavior. Additional studies are required to estimate the impact of also other factors, which may determine the risk to acquire HIV-1 superinfection.
authors: Department of Experimental Immunology, Sanquin Research, Landsteiner Laboratory, and Center for Infection and Immunity Amsterdam, Academic Medical Center of the University of Amsterdam, Amsterdam, The Netherlands
authors: Andrea
authors: A
authors: Rachinger
authors: Precious
authors: P
authors: Manyenga
authors: Judith A
authors: JA
authors: Burger
authors: Tom L P
authors: TL
authors: Derks van de Ven
authors: Ineke G
authors: IG
authors: Stolte
authors: Maria
authors: M
authors: Prins
authors: Angélique B
authors: AB
authors: van 't Wout
authors: Hanneke
authors: H
authors: Schuitemaker