1. Vaccine Research and Development Group, AIDS Research Center, National Institute of Infectious Diseases, Tokyo, 162-8640 Japan
2. Department of Pediatrics, Tokyo Metropolitan Komagome Hospital, Tokyo, 113-8560 Japan
3. Infectious Disease Division, Tokyo Metropolitan Komagome Hospital, Tokyo, 113-8560 Japan
4. Department of Communicable Diseases and Pediatrics, Kyoto City Hospital, Kyoto, 604-8602 Japan
5. Department of Pediatrics, Juntendo University, Juntendo Urayasu Hospital, Chiba, 279-0021 Japan
6. Department of Obstetrics and Gynecology, National Hospital of Narashino, Chiba, 275-8522 Japan
7. Department of Obstetrics and Gynecology, National Defense Medical College, Saitama, 359-8522 Japan
8. Obstetrics and Gynecology Department, National Hospital of Nagoya, Nagoya, Aichi 460, Japan