1 Department of Microbiology, HKU Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong.
2 AIDS Institute, HKU Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong.
3 The State Key Laboratory of Emerging Infectious Diseases and the Research Centre of Infection and Immunology, HKU Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong.