[1] Wistar Inst Anat & Biol, HIV 1 Immunopathogenesis Lab, Philadelphia, PA 19104 USA
[2] Univ Massachusetts, Sch Publ Hlth & Hlth Sci, Amherst, MA 01003 USA
[3] Univ Witwatersrand, Clin HIV Res Unit, Johannesburg, South Africa
[4] Natl Hlth Lab Serv, Dept Chem Pathol, Johannesburg, South Africa
[5] Natl Hlth Lab Serv, Dept Hematol & Mol Med, Johannesburg, South Africa