1. Department of Immunology, Faculty of Health Sciences, University of Pretoria, Pretoria, South Africa
2. Department of Internal Medicine, Faculty of Health Sciences, Steve Biko Academic Hospital, University of Pretoria, Pretoria, South Africa
3. Department of Immunology, Tshwane Academic Division of the National Health Laboratory Service of South Africa, Pretoria, South Africa
4. Department of Haematology, Faculty of Health Sciences, University of Pretoria, and Tshwane Academic Division of the National Health Laboratory Service of South Africa, Pretoria, South Africa
5. Department of Internal Medicine, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa