Animal Model Division and Divisions of Basic Science, Vaccine Research, and Epidemiology and Prevention, Institute of Human Virology, University of Maryland, Baltimore, MD 21201; Division of Comparative Medicine and Department of Microbiology and Immunology, University of Maryland, Baltimore, MD 21201; Division of Thoracic and Cardiovascular Surgery, School of Medicine, University of Maryland, Baltimore, MD 21201; Children's Research Institute, Children's National Medical Center, Washington, DC... (At 2001-07-31)