1 The Desmond Tutu HIV Centre, University of Cape Town, Cape Town, South Africa; The Department of Medicine, University of Cape Town and Groote Schuur Hospital, Cape Town 7925, South Africa. Electronic address: linda-gail.bekker@hiv-research.org.za.
2 The Department of Medicine, University of Cape Town and Groote Schuur Hospital, Cape Town 7925, South Africa.