Immunostimulatory activity of the heat shock protein DnaK from Francisella tularensis (45.18)

Abstract

Abstract Francisella tularensis is the causative agent of tularemia, a severe debilitating disease of humans and other mammals. Since this microorganism is also considered as a ‘category A pathogen’ and a potential biowarfare agent, there is a need for an effective vaccine. Several antigens of F. tularensis including the heat shock protein DnaK have been proposed for use in a potential subunit vaccine. In this study we investigated the immunostimulatory properties of F. tularensis DnaK on murine bone marrow derived dendritic cells (DC). Recombinant DnaK was produced using a bacterial expression system and purified using a three-step purification procedure, i.e., affinity, ion exchange and size exclusion chromatography. DnaK induced DC to produce the proinflammatory cytokines IL-6, TNF-α and IL-12p40 in a dose dependant manner. DnaK did not induce IL-23p19 production. IL-10 production was low compared to IL-12p40. DnaK also induced DC maturation as demonstrated by an up-regulation of CD40 and CD86 expression. The responses were not mediated by endotoxin contamination, since the immunostimulatory activity of DnaK was resistant to polymixin B treatment, but sensitive to boiling or proteinase K digestion. An understanding of the interactions between virulence antigens of F. tularensis and immune cells is crucial for the development of a safe and efficacious vaccine against F. tularensis.