1. Department of Virology, Aggeu Magalhães Institute (IAM), Oswaldo Cruz Foundation (Fiocruz), 50670-420, Recife, Pernambuco, Brazil
2. Leslie Dan Faculty of Pharmacy, University of Toronto, Toronto, ON M5S 3M2, Canada
3. MRC-University of Glasgow Centre for Virus Research, Glasgow, Scotland G61 1QH, U.K.