1. Laboratory of Retrovirology, Department of Infection and Immunity, Luxembourg Institute of Health, Luxembourg, Luxembourg.
2. Laboratoire de Virologie, Hôpital Adultes, Centre Hospitalier Universitaire de Nancy-Brabois, Vandoeuvre les Nancy, France.
3. Université Catholique de Louvain, AIDS Reference Laboratory, Brussels, Belgium.
4. Laboratory of Virology, Department of Medical Microbiology, University Medical Center Utrecht, Utrecht, the Netherlands.
5. Service National des Maladies Infectieuses, Centre Hospitalier Luxembourg, Luxembourg, Luxembourg.