1. M. A. Wainberg, H. Salomon, M. Hsu, G. Borkow, M. A. Parniak, Z. Gu, McGill AIDS Centre, Jewish General Hospital, Montreal, Canada H3T 1E2.
2. W. C. Drosopoulos, Q. Song, J. Manne, S. Islam, G. Castriota, V. R. Prasad, Department of Microbiology and Immunology, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461, USA.