Discloses the use of a fusion protein composition in the manufacture of a medicament for treating or preventing type 1 diabetes mellitus in a subject, wherein the composition comprises a fusion protein and an oil-based carrier, wherein the fusion protein comprises the extracellular domain of CTLA4, an effective fragment or immunologically active variant of the extracellular domain of CTLA4 and a portion of an immunoglobulin molecule, and wherein the oil-based carrier is a water-in-oil emulsion which includes an immune stimulator.
