[1] MCGILL UNIV,DEPT BIOCHEM,MONTREAL H3G 1Y6,QUEBEC,CANADA
[2] MCGILL UNIV,MCGILL CANC CTR,MONTREAL H3G 1Y6,QUEBEC,CANADA
[3] HARVARD UNIV,SCH MED,DEPT MICROBIOL & MOLEC GENET,BOSTON,MA 02115
[4] BRIGHAM & WOMENS HOSP,DEPT MED,DIV INFECT DIS,BOSTON,MA 02115
[5] SHIPLEY INST MED,BOSTON,MA 02115