[1] Int Ctr Genet Engn & Biotechnol, Cape Town, South Africa
[2] Univ Cape Town, Div Med Biochem & Struct Biol, Dept Integrat Biomed Sci, Cape Town, South Africa
[3] Univ Cape Town, Inst Infect Dis & Mol Med, Cape Town, South Africa
[4] Frederick Natl Lab Canc Res, Leidos Biomed Res, AIDS & Canc Virus Program, Viral Oncol Sect, Frederick, MD USA