[1] Tulane Univ, Sch Med, Dept Microbiol & Immunol, New Orleans, LA 70112 USA
[2] Univ Texas Austin, Inst Cell & Mol Biol, Austin, TX 78712 USA
[3] Univ Texas Austin, Dept Chem & Biochem, Austin, TX 78712 USA
[4] Univ Nevada, Dept Microbiol, Sch Med, Reno, NV 89557 USA
[5] Tulane Natl Primate Res Ctr, Div Microbiol, Covington, LA USA