[1] ROY PRINCE ALFRED HOSP, AW MORROW DEPT GASTROENTEROL, SYDNEY, AUSTRALIA
[2] UNIV QUEENSLAND, ROY BRISBANE HOSP, DEPT MED, BRISBANE 4029, Qld, AUSTRALIA
[3] FDA, BUR BIOL, DIV VIROL, ROCKVILLE, MD USA
[4] ROY MELBOURNE HOSP, WALTER & ELIZA INST, CLIN RES UNIT, MELBOURNE, AUSTRALIA