1. Trudeau Institute Inc., Saranac Lake, NY 12983, USA.
2. Viral Diseases Branch, Center of Infectious Disease Research, Walter Reed Army Institute of Research, Silver Spring, MD 20910, USA.
3. Southwest National Primate Center, Texas Biomedical Research Institute, San Antonio, TX 78227, USA.
4. Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, TX 77555, USA.