1. Department of Infectious Diseases and Microbiology, Graduate School of Public Health, University of Pittsburgh, Pittsburgh, Pennsylvania 15260
2. Department of Molecular Genetics and Biochemistry, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15260
3. Children's Memorial Hospital, Northwestern University, Evanston, Illinois 60201
4. Hospital Universitario Clementino Fraga Filho, Faculdade de Medicina, Universidade Federal do Rio de Janeiro, Brazil
5. Division of Infectious Diseases, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania 15260