1. AIDS Virus Research Unit, National Institute for Communicable Diseases (NHLS), Private Bag X4, Sandringham 2131, Johannesburg, South Africa
2. School of Molecular and Cell Biology, University of the Witwatersrand, Johannesburg 2050, South Africa
3. Electron Microscope Unit, National Institute for Communicable Diseases (NHLS), Private Bag X4, Sandringham 2131, Johannesburg, South Africa
4. Department of Internal Medicine, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg 2050, South Africa
5. Sexually Transmitted Infections Reference Centre, National Institute for Communicable Diseases (NHLS), Private Bag X4, Sandringham 2131, Johannesburg, South Africa