1. August Kirchenstein Institute of Microbiology and Virology, Riga Stradins University, Ratsupites 5, LV-1067 Riga, Latvia
2. Latvian Biomedical Research & Study Centre, Ratsupites 1, Riga LV-1067, Latvia
3. Faculty Institute for Cancer Sciences, University of Manchester, Manchester, M13 9WL, UK