Adjuvant Effects for Oral Immunization Provided by Recombinant Lactobacillus casei Secreting Biologically Active Murine Interleukin-1β

Vaccine delivery systems using lactic acid bacteria are under development, but their efficiency is insufficient. Autologous cytokines, such as interleukin-1 beta (IL-1 beta), are potential adjuvants for mucosal vaccines and can be provided by recombinant lactic acid bacteria. The aim of this study was the construction and evaluation of recombinant Lactobacillus casei producing IL-1 beta as an adjuvant delivery agent. The recombinant strain was constructed using an expression/secretion vector plasmid, including a mature IL-1 beta gene from mouse. The biological activity of the cytokine was confirmed by IL-8 production from Caco-2 cells. In response to the recombinant L. casei secreting IL-1 beta, expression of IL-6 was detected in vivo using a ligated-intestinal-loop assay. The release of IL-6 from Peyer's patch cells was also detected in vitro. Intragastric immunization with heat-killed Salmonella enterica serovar Enteritidis (SE) in combination with IL-1 beta-secreting lactobacilli resulted in relatively high SE-specific antibody production. In this study, it was demonstrated that recombinant L. casei secreting bioactive murine IL-1 beta provided adjuvant effects for intragastric immunization.