Interaction between Leptospiral Lipopolysaccharide and Toll-like Receptor 2 in Pig Fibroblast Cell Line, and Inhibitory Effect of Antibody against Leptospiral Lipopolysaccharide on Interaction.

Leptospiral lipopolysaccharide (L-LPS) has shown potency in activating toll-like receptor 2 (TLR2) in pig fibroblasts (PEFs_NCC1), and causes the expression of proinflammatory cytokines. However, the stimulation by L-LPS was weak eliciting the function of TLR2 sufficiently in pig innate immunity responses during Leptospira infection. In this study, the immune response of pig embryonic fibroblast cell line (PEFs_SV40) was investigated and was found to be the high immune response, thus TLR2 is the predominate receptor of L-LPS in pig cells. Further, we found a strategy using the antibody against L-LPS, to prevent L-LPS interaction with TLR2 in pig cells which could impact on immune activation.

Mannose-Binding Lectin Inhibits the Motility of Pathogenic Salmonella by Affecting the Driving Forces of Motility and the Chemotactic Response.

Mannose-binding lectin (MBL) is a key pattern recognition molecule in the lectin pathway of the complement system, an important component of innate immunity. MBL functions as an opsonin which enhances the sequential immune process such as phagocytosis. We here report an inhibitory effect of MBL on the motility of pathogenic bacteria, which occurs by affecting the energy source required for motility and the signaling pathway of chemotaxis. When Salmonella cells were treated with a physiological concentration of MBL, their motile fraction and free-swimming speed decreased. Rotation assays of a single flagellum showed that the flagellar rotation rate was significantly reduced by the addition of MBL. Measurements of the intracellular pH and membrane potential revealed that MBL affected a driving force for the Salmonella flagellum, the electrochemical potential difference of protons. We also found that MBL treatment increased the reversal frequency of Salmonella flagellar rotation, which interfered with the relative positive chemotaxis toward an attractive substrate. We thus propose that the motility inhibition effect of MBL may be secondarily involved in the attack against pathogens, potentially facilitating the primary role of MBL in the complement system.

Mannose-binding lectin impairs Leptospira activity through the inhibitory effect on the motility of cell.

Mannose-binding lectin (MBL) plays key role in lectin pathway of innate immunity, and shows the ability of triggering opsonization intermediately. Substantial increase in the serum level of MBL has been confirmed during leptospirosis, which caused by a pathogenic spirochete, Leptospira. Leptospira has a fascinating locomotion pattern, which simultaneously gyrating and swimming forward, such motility enables that Leptospira is difficult to be captured by immune cells if without any assistance. In this study, the effect of mannose-binding lectin to Leptospira was quantitatively investigated by measuring some kinematic parameters, to discover the mechanism behind MBL-mediated immune responses during leptospiral infection. The results showed that mannose-binding lectin is capable of inhibiting the motility of Leptospira by transforming free swimming cells to tumbled rotating cells, resulted in the increase number of rotating cells. Otherwise, decrease in rotation rate of rotating cell has been observed. However, the swimming speed of swimming Leptospira cells showed no observable change under the effect of MBL. The inhibitory effect were only valid in a relatively short period, Leptospira cells regained their original motility after 2 h. This raises an interesting topic that Leptospira is somehow able to escape from the inhibitory effect of MBL by dragging such unfavorable molecules toward to the cell end and eventually throwing it out. The inhibitory effect of MBL on the motility of Leptospira is expected to provide a new insight into lectin pathway.