[1] Univ Oxford, Wellcome Trust Ctr Human Genet, Oxford OX3 7BN, England
[2] MRC Labs, Fajara, Gambia
[3] Univ London Imperial Coll Sci Technol & Med, Sch Med, St Marys Hosp, London W2 1PG, England
[4] Roche Discovery Welwyn, Welwyn Garden City AL7 3AY, Herts, England
[5] Univ Aquila, I-67100 Laquila, Italy