Affiliation: | From the *Unite d''Immunologie Virale, Institut Pasteur, 75724 Paris, France; the ‡Department of Molecular Biology, Infectious Disease Section, Wyeth-Ayerst Research, Pearl River, New York 10965; and the §Département d''Ingénierie et d''Etudes des Protéines, CEA Saclay, 91190 Gif-sur-Yvette, France |