1. Laboratory of Infectious Diseases, (NIAID), National Institutes of Health (NIH), Bethesda, Maryland.
2. University of Virginia, Charlottesville, Virginia; JMW: Laboratory of Immunopathology, NIH, Bethesda, Maryland.
3. GlaxoSmithKline Biologicals, Rixensart, Belgium.
4. Comparative Medicine Branch, (NIAID), National Institutes of Health (NIH), Bethesda, Maryland.