Edward Jenner Institute for Vaccine Research, Compton, RG20 7NN, UK. irini.doytchinova@jenner.ac.uk|Edward Jenner Institute for Vaccine Research, Compton, RG20 7NN, UK. irini.doytchinova@jenner.ac.uk|Edward Jenner Institute for Vaccine Research, Compton, RG20 7NN, UK. irini.doytchinova@jenner.ac.uk