1. Department of Pathology, College of Medicine, University of Arkansas for Medical Sciences, 4301 West Markham Street, Slot 502, Little Rock, AR 72205, USA
2. Department of Pediatrics, College of Medicine, University of California, San Francisco, 3333 California Street, San Francisco, CA 94143, USA
3. Department of Microbiology and Parasitology, College of Basic Medical Sciences, China Medical University, Shenyang 110001, China