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We use atomistic modeling to investigate the shear resistance and interaction with point defects of a Cu-Nb interface found in nanocomposites synthesized by severe plastic deformation. The shear resistance of this interface is highly anisotropic: in one direction shearing occurs at stresses below 1200MPa while in the other it does not occur at all. The binding energy of vacancies, interstitials, and He impurities to this interface depends sensitively on the binding location, but there is no point defect delocalization nor does this interface contain any constitutional defects. These behaviors are markedly dissimilar from a different Cu-Nb interface found in magnetron sputtered composites. The dissimilarities may, however, be explained by quantitative differences in the detailed structure of these two interfaces.* Corresponding author: demkowicz@mit.edu 617-324-6563 MIT, room 4-142 77 Massachusetts Ave.