2 Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, 171 77 Stockholm, Sweden.
3 Department of Research, Riga Stradins University, LV-1007 Riga, Latvia.
4 N.F. Gamaleya Research Center for Epidemiology and Microbiology, 123098 Moscow, Russia.
5 M.P. Chumakov Federal Scientific Center for Research and Development of Immune-and-Biological Products of Russian Academy of Sciences, 108819 Moscow, Russia.