Patient description: The patient is a 20 year old Caucasian female presents to the clinic with one-sided vision lost and facial weakness, dysarthria and numbness lasting for 1 day. She visited her PCP and underwent brain MRI which revealed a single plaque in the brainstem. After few months, she experienced lower extremities weakness led to balance problem. The second MRI revealed another lesion in the left cerebral hemisphere. The diagnosis of Relapsing Remitting Multiple Sclerosis (RRMS) is confirmed after the second MRI. Her past surgical history is significant for a C-section 2 years ago and she has a one child. She is divorced and is not currently in any sexual relationship. She smokes 10 cigarettes per day and drinks alcohol occasionally. She is working as an editor in a publisher company and she is happy that she can keep working from home most of the time. She is under the treatment of RRMS from 7 months ago.

Clinical trial eligibility criteria: eligible ages (years): 18.0-60.0,  Multiple Sclerosis Multiple Sclerosis, Relapsing-Remitting The study population will consist of 2 cohorts of patients with an accrual ceiling of 40 subjects: A. Long-term daclizumab therapy cohort: Up to 16 patients with HI-MS (both RR-MS and SP-MS) who have been successfully treated with IV daclizumab for a minimum of 1 year. B. New treatment cohort: Up to 15 patients with HI-MS (both RR-MS and SP-MS) who have not been successfully treated with or have not tolerated standard FDA-approved immunomodulatory therapies, or who, for whatever reason, choose not to be treated with standard FDA approved immunomodulatory therapies MS as defined by the modified McDonald (Polman, Reingold et al. 2005) HI-MS (RR-MS or SP-MS) before initiation of daclizumab therapy, defined as greater than or equal to 3 CEL on a single pre-daclizumab MRI or greater than or equal to 1 MS exacerbation per year before initiation of daclizumab therapy or progression of sustained disability by greater than or equal to 1.0 point on the expanded disability status scale (EDSS) in the year preceding daclizumab therapy Age 18-60, inclusive EDSS 0 to 6.0, inclusive Able to provide informed consent Willing to participate in all aspects of trial design and follow-up  (FOR BOTH PP-MS or low-inflammatory SP-MS Alternative diagnoses that can explain neurological disability and MRI findings (e.g., ischemia/gliosis, CNS lyme disease, SLE, sarcoidosis, etc.) History of malignancy, with the following exceptions: excised or treated basal cell carcinoma or fewer than 3 squamous cell carcinomas, grade 1 endometrial carcinomas treated with total hysterectomy and without evidence for recurrence for greater than or equal to 3 years Clinically significant medical disorders that, in the judgment of the investigators, could cause CNS tissue damage or limit its repair, expose the patient to undue risk of harm or prevent the patient from completing the study (e.g., immunodeficiency disorders, other autoimmune or immune-mediated disorders or chronic infections). Specific exclusions (based on baseline laboratory evaluation) are positive HIV or HTLV-1 serology positive hepatitis B or C serology pregnant or breastfeeding female known history of severe allergic or anaphylactic reactions known hypersensitivity to study drug or its excipients