[1] Emory Univ, Yerkes Natl Primate Res Ctr, Atlanta, GA 30322 USA
[2] Univ Ulm, Med Ctr, Insititute Mol Virol, D-89069 Ulm, Germany
[3] Univ Cologne, Dept Internal Med, D-50931 Cologne, Germany
[4] Univ Cologne, Ctr Mol Med Cologne, D-50931 Cologne, Germany