1. Institute of Blood Transfusion, Chinese Academy of Medical Sciences & Peking Union Medical College, Chengdu, Sichuan 610052, PR China
2. Department of Infectious Diseases, The Third Affiliated Hospital of Sun Yat-Sen Univekrsity, Guangzhou 510000, PR China
3. Toronto General Research Institute, University of Toronto, Toronto, M5G1L6, Ontario, Canada