[1] Brown Univ, Miriam Isl Hosp, Lab Retrovirol, Dept Med,Div Infect Dis, Providence, RI 02903 USA
[2] Texas Tech Univ, Hlth Sci Ctr, Paul L Foster Sch Med, Div Biostat, El Paso, TX USA
[3] Brown Univ, Warren Alpert Med Sch, Dept Med, Div Hematol & Oncol, Providence, RI 02903 USA
[4] Thomas Jefferson Univ, Jefferson Med Coll, Kimmel Canc Ctr, Philadelphia, PA 19107 USA