[1] NIAID, Infect Dis Lab, NIH, Bethesda, MD 20892 USA
[2] Baylor Coll Med, Dept Mol Virol & Microbiol, Houston, TX 77030 USA
[3] Macrae Grp, Rockville, MD USA
[4] Univ Virginia, Sch Med, Charlottesville, VA 22908 USA
[5] Macfarlane Burnet Ctr Med Res, Melbourne, Vic, Australia