[1] Johns Hopkins Univ, Sch Med, Ctr Oncol, Baltimore, MD 21231 USA
[2] Johns Hopkins Univ, Sch Med, Dept Genet & Mol Biol, Baltimore, MD 21231 USA
[3] McGill Univ, Dept Microbiol & Immunol, Montreal, PQ H3T 1E2, Canada
[4] Human Genome Sci Inc, Rockville, MD 20850 USA