Crystallization and preliminary X-ray diffraction analysis of the complex between a human anti-interferon antibody fragment and human interferon α-2A

Crystals of the complex between the Fab fragment of a human anti-interferon α therapeutic antibody and human interferon α-2A have been obtained and diffracted to 3.0 Å resolution. Recombinant human interferon α-2A (rhIFN-α-2A) has been crystallized in complex with the recombinantly produced Fab fragment of a therapeutic monoclonal antibody (MEDI545; IgG1/κ) which targets several human interferon α subtypes. This constitutes the first reported crystals of a human type I interferon bound to an antibody. The orthorhombic crystals belonged to either space group I222 or I2₁2₁2₁, with unit-cell parameters a = 134.82, b = 153.26, c = 163.49 Å. The diffraction of the crystals extended to 3.0 Å resolution. The asymmetric unit contained two Fab–rhIFN-α-2A complexes. This corresponded to a crystal volume per protein weight (V_M) of 3.02 ų Da⁻¹ and a solvent content of 59.3%. The corresponding three-dimensional structure is expected to shed light on the mechanism of action of MEDI545 and the molecular basis of its specificity