[1] UNIV VIRGINIA,DEPT MICROBIOL,CHARLOTTESVL,VA 22901
[2] MCMASTER UNIV,DEPT BIOL,HAMILTON,ONTARIO,CANADA
[3] ANIM VIRUS RES INST,PIRBRIGHT,SURREY,ENGLAND
[4] ALBERT EINSTEIN COLL MED,DEPT MICROBIOL & IMMUNOL,BRONX,NY 10461
[5] WISTAR INST,PHILADELPHIA,PA 19104
[6] UNIV ILLINOIS,DEPT BOT,URBANA,IL 61801