1. Ferrier Research Institute, Victoria University of Wellington, 69 Gracefield Road, Lower Hutt 5040, New Zealand
2. The Maurice Wilkins Centre for Molecular Biodiscovery, The University of Auckland, Auckland 1142, New Zealand
3. Institute for Antiviral Research, Utah State University, Logan, Utah 84322-5600, United States
4. Department of Microbiology & Immunology, University of Otago, PO Box 56, Dunedin 9054, New Zealand