Interaction of human mannose-binding lectin (MBL) with Yersinia enterocolitica lipopolysaccharide

The lipopolysaccharide (LPS) is involved in the interaction between Gram-negative pathogenic bacteria and host. Mannose-binding lectin (MBL), complement-activating soluble pattern-recognition receptor targets microbial glycoconjugates, including LPS. We studied its interactions with a set of Yersinia enterocolitica O:3 LPS mutants. The wild-type strain LPS consists of lipid A (LA) substituted with an inner core oligosaccharide (IC) which in turn is substituted either with the O-specific polysaccharide (OPS) or the outer core hexasaccharide (OC), and sometimes also with the enterobacterial common antigen (ECA). The LPS mutants produced truncated LPS, missing OPS, OC or both, or, in addition, different IC constituents or ECA. MBL bound to LA-IC, LA-IC-OPS and LA-IC-ECA but not LA-IC-OC structures. Moreover, LA-IC substitution with both OPS and ECA prevented the lectin binding. Sequential truncation of the IC heptoses demonstrated that the MBL targets the IC heptose region. Furthermore, microbial growth temperature influenced MBL binding; binding was stronger to bacteria grown at room temperature (22°C) than to bacteria grown at 37°C. In conclusion, our results demonstrate that MBL can interact with Y. enterocolitica LPS, however, the in vivo significance of that interaction remains to be elucidated.