1. Department of Pathogenic Biology, College of Basic Medical Science, China Medical University, Shenyang, Liaoning 110122, P.R. China
2. College of Animal Science and Veterinary Medicine, Shenyang Agricultural University, Shenyang, Liaoning 110866, P.R. China
3. Department of Microbiology and Cell Biology, College of Life Science and Pharmaceuticals, Shenyang Pharmaceutical University, Shenyang, Liaoning 110016, P.R. China