1. Ethio-Netherlands AIDS Research Project (ENARP), Ethiopian Health and Nutrition Research Institute, Addis Ababa, Ethiopia.
2. Department of Biology, Addis Ababa University, Addis Ababa, Ethiopia.
3. Department of Human Retrovirology, Academic Medical Centre, University of Amsterdam, 1105 AZ Amsterdam, The Netherlands.
4. AIDS Centre, Hadassah, University Hospital, Hebrew University, Jerusalem, Israel.