Innate inflammatory responses to the Gram-positive bacterium Lactococcus lactis

SummaryLactococcus lactis is a non-pathogenic and non-colonizing Gram-positive bacterium commonly used in the dairy industry. To support the potential applications of this bacterium, such as use as an oral live vaccine, it is of interest to investigate the adjuvant properties of L. lactis. We compared the proinflammatory effects of L. lactis with two non-pathogenic Gram-negative bacteria: Escherichia coli and Salmonella typhi, a widely studied live vaccine. The gene expression profiles of chemokines induced by the three bacteria were examined in macrophages in vitro and in cells recruited into murine air-pouches in vivo. In addition, we studied the effect of co-incubating bacteria with dendritic cells (DCs) generated from mice bone marrow. We demonstrate that L. lactis exhibits proinflammatory effects, which indicates a capacity for adjuvanticity by this bacterium.