[1] Univ Alabama Birmingham, Dept Med & Microbiol, Birmingham, AL 35294 USA
[2] Univ Alabama Birmingham, Howard Hughes Med Inst, Birmingham, AL 35294 USA
[3] Inst Pasteur, Unite Biol Retrovirus, F-75724 Paris, France
[4] Inst Pasteur, Mol Virol Lab, F-75015 Paris, France
[5] Thomas Jefferson Univ, Jefferson Canc Inst, Dept Microbiol & Immunol, Philadelphia, PA 19107 USA
[6] Inst Human Virol, Baltimore, MD 21201 USA
[7] Univ Nottingham, Queens Med Ctr, Div Genet, Nottingham NG7 2RD, England