1 Section of Gastroenterology, Hepatology & Nutrition, Department of Pediatrics, Baylor College of Medicine and Texas Children's Hospital, Houston, Texas, United States of America.
2 National School of Tropical Medicine, Department of Pediatrics and Molecular Virology & Microbiology, Baylor College of Medicine, Houston, Texas, United States of America; Sabin Vaccine Institute and Texas Children's Hospital Center for Vaccine Development, Houston, Texas, United States of America; James A. Baker III Institute for Public Policy, Rice University, Houston, Texas, United States of America; Department of Biology, Baylor University, Waco, Texas, United States of America.