Ruth Herbst1, Maartje G. Huijbers2,3, Julien Oury4 and Steven J. Burden5 1Center for Pathophysiology, Infectiology and Immunology, Medical University of Vienna, 1090 Vienna, Austria 2Department of Human Genetics, Leiden University Medical Centre LUMC, 2300 RC Leiden, the Netherlands 3Department of Neurology, Leiden University Medical Centre LUMC, 2333 ZA Leiden, the Netherlands 4Helen L. and Martin S. Kimmel Center for Biology and Medicine at the Skirball Institute of Biomolecular Medicine, NYU School of Medicine, New York, New York 10016, USA 5Neurology Department, Massachusetts General Hospital, Charlestown, Massachusetts 02129, USA Correspondence: sburden{at}mgh.harvard.edu