1. Center for Pulmonary and Infectious Disease Control, University of Texas Health Center, Tyler, Texas 75708
2. Tulane Regional Primate Research Center, Covington, Louisiana 70433
3. Center for Pulmonary and Infectious Disease Control, and Departments of Microbiology and Immunology and Medicine University of Texas Health Center, Tyler, Texas 75708
4. University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261