1. Department of Pathogen Biology, Hainan Medical University, Haikou 571199, P. R. China
2. University of Maryland, Maryland 20850, USA
3. Key Laboratory of Translation Medicine Tropical Diseases, Hainan Medical University, Haikou 571199, P. R. China
4. Hainan Medical University-The University of Hong Kong Joint Laboratory of Tropical Infectious Diseases, Hainan Medical University, Haikou 571199, P. R. China