1. Ashworth Laboratories, Institute for Immunology and Infection Research, School of Biological Sciences, The University of Edinburgh, King's Buildings, Edinburgh EH9 3JT, UK
2. Institute of Tropical Medicine Antwerp, Nationalestraat 155, 2000 Antwerp, Belgium
3. Schistosomiasis Section, National Institute of Health Research, Box CY 570, Causeway, Harare, Zimbabwe
4. Biochemistry Department, University of Zimbabwe, P.O. Box MP 167, Mount Pleasant, Harare, Zimbabwe
5. Harvard School of Public Health, Botswana Havard Aids Institute, P. Bag 320, Gaborone, Botswana