1. Cancer Immunology, Genentech, Inc., 1 DNA Way, South San Francisco, CA 94080, USA.
2. Howard Hughes Medical Institute, University of California, San Francisco, CA 94158, USA.
3. Department of Biochemistry and Biophysics, University of California, San Francisco, CA 94158, USA.
4. Research Centre for Infectious Diseases, School of Molecular and Biomedical Science, University of Adelaide, South Australia, 5005, Australia.