1. Department of Life Science, Hanyang University, Seoul 133-791, Korea.
2. Research Institute for Natural Sciences, Hanyang University, Seoul 133-791, Korea.
3. Department of Anatomy & Cell Biology, College of Medicine, Hanyang University, Seoul 133-791, Korea.
4. Division of Vaccine Discovery, La Jolla Institute for Allergy and Immunology, La Jolla, CA 92037, USA.