1. National Institute of Infectious Diseases, AIDS Research Center, Tokyo 162-8640, Japan; Noguchi Memorial Institute for Medical Research, Ghana University, Accra, Ghana
2. Institute of Tropical Medicine, 2000 Antwerp, Belgium
3. Noguchi Memorial Institute for Medical Research, Ghana University, Accra, Ghana
4. National Institute of Infectious Diseases, AIDS Research Center, Tokyo 162-8640, Japan
5. Unidade de Virologia, Instituto de Higiene e Medicina Tropical (UNL), Lisbon P-1349-008, Portugal
6. Tokyo Medical and Dental University, Tokyo 113-8519, Japan
7. School of Medical Sciences, Kumasi, Ghana