[1] MCGILL UNIV,DEPT MED,MONTREAL,PQ H3A 1A1,CANADA
[2] ROYAL VICTORIA HOSP,MONTREAL,PQ H3A 1A1,CANADA
[3] DUKE UNIV,MED CTR,DEPT MED,DURHAM,NC 27710
[4] DUKE UNIV,MED CTR,DEPT MICROBIOL,DURHAM,NC 27710
[5] UNIV LIBRE BRUXELLES,DEPT BIOL MOLEC,B-1050 BRUSSELS,BELGIUM