Center for Cell and Gene Therapy, Baylor College of Medicine, Texas Children's Hospital and Houston Methodist Hospital, Houston, TX, USA. Department of Pediatric Hematology/Oncology, Texas Children's Cancer Center, Baylor College of Medicine, Houston, TX, USA. Biostatistics Core of the Dan L. Duncan Cancer Center, Baylor College of Medicine, Houston, TX, USA. Department of Pediatrics, Division of Pediatric Gastroenterology and Nutrition, Texas Children's Hospital, Houston, TX, USA. Departments of Pediatrics, Infectious Diseases Section, and Molecular Virology and Microbiology, Baylor College of Medicine, Houston, TX, USA.