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

Abstract

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.

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

“…The swimming speeds of Salmonella recovered to the control level within several hours. This indicates that motility inhibition by MBL is temporary in agreement with the previous report showing the inhibitory effect of MBL on spirochete motility [ 24 ],.…”

“…MBL may also cooperate with phagocytic cells to enhance the opsonization of pathogens [ 8 ]. It was recently reported that the binding of MBL to spirochetes inhibits their motility [ 24 ]. Because bacterial motility is known to strongly correlate with virulence, this finding suggests a novel contribution of MBL to host immunity against infections of microorganisms; namely, MBL is proposed to be responsible for not only triggering innate immunity but also indirectly attacking pathogens by impairing their motility.…”

“…For example, the motility of Leptospira , a pathogenic spirochete causing worldwide zoonosis leptospirosis outbreaks, is also known as a critical factor for establishing infection [ 22 ]. Mannose is a sugar component of the LPS in some Leptospira strains [ 23 ], and our recent study showed that MBL impairs the motility of Leptospira [ 24 ]. Thus, MBL is considered to contribute to preventing infection of microorganisms through not only opsonization but also by inhibiting the motility of pathogens.…”