Solution behavior of a novel type 1 interferon, interferon-τ

Interferon-tau (IFN-tau) is a novel cytokine that appears during fetal development of mammals. It is currently being investigated for treatment of viral infections and autoimmune diseases. In order to develop a commercial product, a stable formulation will need to be identified. In this study, the solution behavior of IFN-tau was studied using a variety of biophysical methods. The overall structure of IFN-tau is well defined, with the polypeptide chain folding into a four-helix bundle structure, much like other type 1 interferons. However, its solution behavior has not been characterized. The globular structure has a free energy of unfolding of ∼4 kcal/mole at room temperature. IFN-tau was found to remain monomeric upon increasing the protein concentration, even up to 60 mg/mL. The overall structure of IFN-tau is maintained across a pH range of 2-8, but is significantly altered in the presence of nonaqueous solvents. However, IFN-tau appears to refold efficiently when diluted into an aqueous medium from a nonaqueous solution. This behavior allows the protein to be formulated in low water content formulations suitable for use in capsules. © 2005 Wiley-Liss, Inc. and the American Pharmacists Association.