Key virulence factors of Streptococcus pneumoniae and non-typeable Haemophilus influenzae: roles in host defence and immunisation

Identification and prioritisation of candidate antigens on which novel vaccines can be based, or the efficacy of existing vaccines improved, are critically dependent on characterising the strategies utilised by microbial pathogens to evade host defences, and, in particular, the key virulence factors involved. In this review, we have focused on the immune evasion strategies utilised by two important bacterial respiratory pathogens, viz Streptococcus pneumoniae and non-typeable Haemophilus influenzae, with particular emphasis on key virulence factors and their potential to serve as candidate immunogens.