[1] Univ Manchester, Sch Biol Sci, Manchester M13 9PT, Lancs, England
[2] European Bioinformat Inst, Cambridge CB10 1SD, England
[3] Edward Jenner Inst Vaccine Res, Newbury RG20 7NN, Berks, England
[4] Glaxo Wellcome Res & Dev Ltd, Med Res Ctr, Stevenage SG1 2NY, Herts, England