Leptospira interrogans is recognized through DC-SIGN and induces maturation and cytokine production by human dendritic cells.

Leptospirosis is a global zoonotic disease, caused by pathogenic Leptospira species including Leptospira interrogans, that causes public health and livestock problems. Pathogenesis, immune response and cellular receptors for Leptospira are not well understood. Interaction of dendritic cells (DCs) with L. interrogans serovar Autumnalis L-643 and BL-6 isolated from leptospirosis patients, and both virulent and avirulent serovar Pyrogenes 2317 strains isolated from animal were investigated. Carbohydrate analysis using lectins showed that all of these leptospires contained high mannose components as a common backbone and DC-SIGN was involved in leptospires' attachment. Interaction of the L. interrogans strains with DCs induced maturation, but had different effects on IL-10, IL-12p70 and tumor necrosis factor (TNF)-alpha production. Both virulent and avirulent Pyrogenes 2317 and Autumnalis BL-6 but not L-643 strains induced IL-12p70 and TNF-alpha production, but minimal IL-10 secretion. These data demonstrated that L. interrogans binds DC-SIGN and induces DCs maturation and cytokine production, which should provide new insights into cellular immune processes during leptospirosis.