1. Department of Molecular Microbiology and Immunology and Malaria Research Institute, Johns Hopkins Bloomberg School of Public Health, 615 North Wolfe Street, Baltimore, Maryland 21205, Programas de Biologia Molecular e Biotecnologia e Bioquímica e Biofísica Celular, Instituto de Bioquímica Médica, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, 21941-590, Brasil, Departments of Genetics and Pathology, Case Western Reserve University, Cleveland, Ohio 44106