1. Complex Carbohydrate Research Center, The University of Georgia, Athens, GA 30602, USA
2. Department of Medicine/Infectious Diseases, University of Virginia, Charlottesville, VA 22903, USA
3. International Centre for Diarrhoeal Disease Research, Bangladesh (icddr,b), Dhaka 1212, Bangladesh
4. Department of Medicine, University of Vermont, Burlington, VT 05401, USA