[1] Karolinska Inst, Dept Med, Ctr Infect Med, S-14186 Stockholm, Sweden
[2] Karolinska Inst, Dept Biosci & Nutr, Ctr Biosci, S-14186 Stockholm, Sweden
[3] Univ York, Hull York Med Sch, Ctr Immunol & Infect, York YO10 5DD, N Yorkshire, England
[4] Univ York, Dept Biol, York YO10 5DD, N Yorkshire, England