1. Division of Medical Virology, Institute of Infectious Disease and Molecular Medicine (IDM), University of Cape Town, Cape Town, South Africa.
2. Desmond Tutu HIV Foundation, Cape Town, South Africa.
3. Division of Immunology, Institute of Infectious Disease and Molecular Medicine (IDM), University of Cape Town, Cape Town, South Africa.
4. Centre for the AIDS Programme of Research in South Africa (CAPRISA), Durban, South Africa.
5. National Health Laboratory Services, Cape Town, South Africa.