The Effects of Tysabri Treatment on Vaccination Response and Lymphocyte Subsets in Subjects With Relapsing Forms of Multiple Sclerosis

Inclusion Criteria:

able to give written informed consent
diagnosis of a relapsing form of MS and must fall within the therapeutic indication stated in the approved label for Tysabri
aged 18-60 years, inclusive at the time of consent
free of signs and symptoms suggestive of any serious opportunistic infection, based on medical history, physical examination, or laboratory testing
must have a known history of tetanus toxoid immunization

Major Exclusion Criteria:

tetanus toxoid vaccination less than 2 years prior to Screening
known hypersensitivity to tetanus-diphtheria vaccine or KLH or any other administered vaccinations or their components (such as thimerosal)
known allergy to shellfish
history of active tuberculosis or undergoing treatment for tuberculosis
previous exposure to KLH or vaccines containing KLH components (e.g., cancer vaccines)
known history of human immunodeficiency virus (HIV), hepatitis C, or hepatitis B infection
history of, or available abnormal laboratory results indicative of any significant disease
history of malignancy
history of organ transplantation (including anti-rejection therapy)
history of severe allergic or anaphylactic reactions or known drug hypersensitivity
a clinically significant infectious illness within 30 days prior to the Screening visit
prior exposure to Tysabri, rituximab, any murine protein, or any therapeutic monoclonal antibody at any time
receipt of intravenous (IV) or intramuscular (IM) immunoglobulin within 6 months of screening
live virus, bacterial vaccines, or any other vaccines within 3 months of screening
treatment with immunosuppressant medications within 6 months prior to screening
treatment with cyclophosphamide within 1 year prior to screening
treatment with immunomodulatory medications (interferon beta and glatiramer acetate) within 2 weeks prior to screening
treatment with systemic corticosteroids within 4 weeks prior to screening
treatment with any investigational product or approved therapy or vaccination for investigational use within 6 months prior to Screening
women who are breastfeeding, pregnant, or planning to become pregnant during the study
female subjects who are not postmenopausal for at least 1 year, surgically sterile (does not include tubal ligation), or willing to practice effective contraception during the study