1. Department of Biomedical Sciences and Veterinary Public Health Swedish University of Agricultural Sciences Box 7036 750 07 Uppsala Sweden
2. Nanotechnology and Functional Materials Department of Engineering Sciences Box 534, Uppsala University 75121 Uppsala Sweden
3. Unit of Virology Immunobiology and Parasitology The National Veterinary Institute (SVA) 751 89 Uppsala Sweden
4. Division of Materials Science Luleå University of Technology 971 87 Luleå Sweden