haemophilus influenzae (hi) is a gram-negative bacterium capable of causing severe invasive infection such as meningitis and is classified by the presence or absence of polysaccharide capsule. the polysaccharide capsule is the most important virulence factor for encapsulated strains. hi serotype a (hia) is an encapsulated form of hi that is recognized as an important emerging pathogen with incidence of invasive disease similar to hi serotype b (hib) prior to the introduction of the hib vaccination. despite this, not much is known about how hia interacts with the innate immune system and how it induces an inflammatory response. non-typeable hi (nthi) (the unencapsulated form of hi) has recently been shown to activate the innate immune system through a multiprotein complex known as inflammasome. as such, this study aimed to investigate if hia activates this innate immune complex and how this differs in encapsulated versus unencapsulated strains and invasive versus non-invasive strains.