Inclusion Criteria:

• Age 3 to 45 years (later on the study plans to enroll younger teens and children)
• Insulin dependent type 1-diabetes mellitus diagnosed within the previous 3 months
• Stimulated C-peptide levels greater than or equal to 0.2 pmol/ml measured during a mixed meal tolerance test (MMTT) conducted within 3 weeks from diagnosis of diabetes
• Presence of GAD65 antibodies
• At least one month from last immunization
• Willing to comply with intensive diabetes management
• If participant is a woman with reproductive potential, she must be willing to avoid pregnancy and have a negative pregnancy test
• Must weigh at least 25 kg at study entry
• Willing to forgo routine clinical immunizations during the first 100 days after initial study drug administration

Exclusion Criteria:

• Immunodeficiency or clinically significant chronic lymphopenia
• Active infection
• Positive PPD test result
• Pregnant or lactating or anticipating becoming pregnant for 24 months following first injection
• Ongoing use of medications known to influence glucose tolerance
• Require use of systemic immunosuppressant(s)
• Serologic evidence of current or past HIV, Hep B, or Hep C infection
• History of malignancies
• Ongoing use of non-insulin pharmaceuticals to affect glycemic control
• Participation in another clinical trial with a new chemical entity within the past 3 months
• Complicating medical issues or abnormal clinical laboratory results that interfere with study conduct or cause increased risk including neurological, or clinically significant blood count abnormalities (such as lymphopenia, leukopenia, or thrombocytopenia)
• History of epilepsy, head trauma or cerebrovascular accident or clinical
• History of alcohol or drug abuse