1. Department of Medical Microbiology, Stanford University, Stanford, CA 94305.
2. Laboratory of Pathobiology, NIAID Rocky Mountain Laboratories, Hamilton, MT 59840.
3. Department of Bacteriology, Praxis Biologics, Inc., Rochester, NY 14623.
4. Burroughs Wellcome Company, Research Triangle Park, NC 27514.
5. Department of Pediatrics, Stanford University, Stanford, CA 94305.