1. Axis Genetics plc, Babraham, Cambridge CB2 4AZ, UK
2. Department of Microbiology and Immunology, Louisiana State University Medical Center, School of Medicine in Shreveport, Shreveport, LA 71130-3932, USA
3. Department of Molecular Biology, The Scripps Research Institute, 10666 North Torrey Pines Road, La Jolla, CA 92037, USA