1. Department of Biological and Environmental Engineering, Cornell University, Ithaca, New York 14853, Departments of Nuclear Medicine, of Microbiology and Immunology, and of Medicine, Albert Einstein College of Medicine, Bronx, New York 10461, Medical Fellows Program, Howard Hughes Medical Institute, Chevy Chase, Maryland 20815, The Mount Sinai School of Medicine, New York, New York 10029, and Mycology Unit, National Center for Microbiology, Instituto de Salud Carlos III, Madrid, Spain