[1] Univ Med Ctr Rotterdam, Erasmus MC, Dept Neurol, Rotterdam, Netherlands
[2] Univ Med Ctr Rotterdam, Erasmus MC, Dept Viroscie, Rotterdam, Netherlands
[3] Univ Med Ctr Rotterdam, Erasmus MC, Dept Immunol, Rotterdam, Netherlands
[4] Royal Cornwall Hosp Trust, Cornwall Gastrointestinal Unit, Truro, Cornwall, England
[5] Univ Exeter, Sch Med, European Ctr Environm & Human Hlth, Truro, England