Volunteers will be admitted to an inpatient unit during the Treatment Period. Blood samples will be collected periodically to assess the effect of CDX-301. Volunteers will be followed for safety for 28 days following the last dose. Any volunteer who develops anti-CDX-301 antibodies will be followed monthly until the antibody response is below the limit of detection. In general, the total duration of the study will be between approximately 33-38 days.