1. Department of Pediatrics/Developmental Pediatrics; Nagoya University Graduate School of Medicine; Aichi Nagoya 466-8550 Japan
2. Department of Pediatrics; Showa Hospital; Aichi Kohnan 483-8703 Japan
3. Laboratory of Virology, Research Institute for Disease Mechanism and Control; Nagoya University School of Medicine; Aichi Nagoya 466-8550 Japan
4. Department of Health Science; Nagoya University School of Medicine; Aichi Nagoya 461-8673 Japan