[1] Uganda Virus Res Inst, MRC, Porgramme AIDS, Entebbe, Uganda
[2] Univ Liverpool, Liverpool Sch Trop Med, Liverpool L3 5QA, Merseyside, England
[3] Univ Edinburgh, Ctr HIV Res, Edinburgh, Midlothian, Scotland
[4] Univ London Imperial Coll Sci Technol & Med, Jefferiss Res Trust Lab St Marys, London, England