1. Department of Pathology and Center for Tropical Diseases, University of Texas Medical Branch, Galveston, Texas 77555-06091;
2. Department of Human Biological Chemistry and Genetics and Sealy Center for Structural Biology, University of Texas Medical Branch, Galveston, Texas 77555-06452; and
3. Division of Vector-Borne Infectious Diseases, Centers for Disease Control and Prevention, Fort Collins, Colorado 805223