<qa>  What was the long-term treatment period of 101-MS-322?Study 101-MS-322 NCT00306592 was conducted to evaluate the safety of natalizumab monotherapy following re-exposure to natalizumab in former clinical trial participants in Studies C-1801 NCT00027300, C-1802 NCT00030966, and C-1803 NCT00097760 and included subjects in North America. In parallel with the conduct of that study, this study 101-MS-321 NCT00297232 was initiated for participants in Europe and the rest of the world. In addition, after 48 weeks, participants from 101-MS-322 NCT00306592 could enter study 101-MS-321 NCT 00297232, which was considered the Long-Term Treatment Period of 101-MS-322 NCT00306592. 