1. Department of Pathology, Okayama University Medical School, Ibaraki, Japan
2. Department of Virology, Okayama University Medical School, Ibaraki, Japan
3. School of Health Sciences, Okayama University, Okayana City, Ibaraki, Japan
4. Tsukuba Primate Center for Medical Science, NIH, Tsukuba City, Ibaraki, Japan