From the Molecular Genetics and Microbiology Department (D.A. McDonald, D.A. Marchuk), Duke University Medical Center, Durham, NC; the University of Chicago Medical Center (C.S., R.S., F.L., I.A.A.), Biological Sciences Division, University of Chicago, Chicago, IL; and the Department of Medicine (R.A.S., M.H.G.), University of California, San Diego, San Diego, CA. (At 2012-02)