[1] CHILDRENS HOSP PHILADELPHIA, DEPT PATHOL & LAB MED, PHILADELPHIA, PA 19104 USA
[2] UNIV PENN, SCH DENT MED, DEPT MICROBIOL, PHILADELPHIA, PA 19104 USA
[3] UNIV PENN, SCH DENT MED, CTR ORAL HLTH RES, PHILADELPHIA, PA 19104 USA
[4] UNIV PENN, SCH VET MED, DEPT PATHOBIOL, PHILADELPHIA, PA 19104 USA
[5] SWISS INST EXPTL CANC RES, DEPT MOLEC BIOL, CH-1066 EPALINGES, SWITZERLAND