Serial Changes in Mannose-Binding Lectin in Patients with Sepsis

Levels of mannose-binding lectin (MBL) associates with sepsis-related in-hospital mortality in women

Background

Mannose-binding lectin (MBL) mediates the innate immune response either through direct opsonisation of microorganisms or through activation of the complement system. There are conflicting data whether MBL deficiency leads to increased susceptibility to infections or not. The aim of this study was to determine if low levels of mannose-binding lectin (MBL) predict sepsis development, sepsis severity and outcome from severe sepsis or septic shock.

Method

Patients aged 18 years or more with documented sepsis within 24 h after admission to the intensive care unit were included if they had participated in a health survey and donated blood samples prior to the sepsis event. A subset of these patients had stored plasma also from the acute phase. Two matched referents free of known sepsis were selected for each case. Plasma levels MBL were determined in stored samples from health surveys (baseline) and from ICU admission (acute phase). The association between MBL and sepsis, sepsis severity and in-hospital mortality were determined with 1300 ng/mL as cut-off for low levels.

Results

We identified 148 patients (61.5% women) with a first-time sepsis event 6.5 years (median with IQR 7.7) after participation in a health survey, of which 122 also had samples from the acute septic phase. Both high MBL levels in the acute phase (odds ratio [95% confidence interval]) (2.84 [1.20-6.26]), and an increase in MBL levels from baseline to the acute phase (3.76 [1.21-11.72]) were associated with increased risk for in-hospital death in women, but not in men (0.47 [0.11-2.06]). Baseline MBL levels did not predict future sepsis, sepsis severity or in-hospital mortality.

Conclusions

An increase from baseline to the acute phase as well as high levels in the acute phase associated with an unfavourable outcome in women.

Molecular and functional characterisation of a mannose-binding lectin-like gene from Japanese sea bass (Lateolabrax japonicus)

Mannose-binding lectin (MBL) plays an important role in host immune responses against pathogens. LjMBL-like-1 was identified from Japanese sea bass (Lateolabrax japonicas), which has selectivity for galactose. Herein, this lectin might be better designated as galactose-binding lectin (LjGalBL-1). LjGalBL-1 transcripts were detected in all tested tissues, with highest expression in liver. Upon Vibrio harveyi infection, LjGalBL-1 mRNA expression was increased in major immune-related tissues, and protein levels in serum were also upregulated. Recombinant LjGalBL-1 (rLjGalBL-1) bound to monosaccharides and polysaccharides, and both rLjGalBL-1 and native LjGalBL-1 (nLjGalBL-1) agglutinated three Gram-positive bacteria (Staphylococcus aureus, Streptococcus iniae and Micrococcus luteus) and four Gram-negative bacteria (Aeromonas hydrophila, Edwardsiella tarda, Vibrio anguillarum and V. harveyi) in a Ca²⁺-dependent manner in vitro. Moreover, rLjGalBL-1 increased the survival rate of V. harveyi-infected fish and decreased bacterial load in liver, spleen, kidney and blood. Thus, LjGalBL-1 protects L. japonicas against V. harveyi infection.

Role of mannose-binding lectin in regulating monocytes/macrophages functions during Aeromonas hydrophila infection in grass carp, Ctenopharyngodon idella

Mannose-binding lectin (MBL) is a vital component in host's innate immune system and the initiator of the lectin pathway of complement cascade. However, its opsonic role has rarely been reported. In this study, we revealed the biological function of Ctenopharyngodon idella MBL (CiMBL) in regulating monocytes/macrophages (MO/MФ) in the grass carp (C. idella). Flow cytometry results indicated that recombinant CiMBL (rCiMBL) significantly enhanced the phagocytotic activity of MO/MФ. Recombinant CiMBL also enhanced bactericidal activity and respiratory burst capacity in Aeromonas hydrophila-infected MO/MФ, regulated A. hydrophila-induced polarization of MO/MФ including down- and up-regulated pro- and anti-inflammatory cytokines, respectively, suppressed the inducible nitric oxide synthase activity, and enhanced the arginase activity. In addition, rCiMBL suppressed the bacteria burden in tissues and blood in vivo and enhanced the survival rate of juvenile A. hydrophila-infected grass carp. We provide evidence that CiMBL was synthesized by MO/MФ, regulating the biological function of MO/MФ against A. hydrophila infection.