Chicken mannose-binding lectin function in relation to antibacterial activity towards Salmonella enterica

Analysis of Mannose-Binding Lectin Protein and mRNA Levels on Selected Chicken Breeds in South Africa

BACKGROUND

Mannose-binding lectin (MBL) is a key component of the innate immune system that plays a crucial role in binding to the microbial sugar surface to recognize and eliminate pathogens by activating the complement system.

OBJECTIVE

To detect and quantify the MBL protein concentration and chicken MBL expression in selected chicken breeds in South Africa.

METHODS

Forty-five blood samples from three indigenous chicken breeds, Ovambo (OV = 9), Venda (VD = 9) and Potchefstroom Koekoek (PK = 9), and two exotic chicken breeds, Rhode Island Red (RIR = 9) and Lohmann Brown (LB = 9), were used for MBL protein concentration using enzyme-linked immunosorbent assay (ELISA) techniques. Also 20 liver samples from symptomatic two indigenous chicken breeds, OV (5) and PK (5), and two exotic chicken breeds, RIR (5) and LB (5), were used for MBL expression using quantitative polymerase chain reaction (qPCR) techniques. A general linear model was done using Tukey's multiple comparison post hoc test.

RESULTS

The findings revealed MBL protein concentration from 5.26 to 18.56 µg/mL. The LB breed had the lowest mean 6.40 ± 0.80 µg/mL, whereas the PK breed had the highest mean MBL concentration of 17.70 ± 0.24 µg/mL of MBL protein concentration. At 12, 25 and 35 weeks, the MBL proteins of OV, VD, PK, RIR and LB varied significantly at p ≤ 0.05. The mRNA MBL expression of OV and LB breeds showed a 1-fold decrease in MBL expression, while RIR showed a 2-fold increase in MBL expression, and the PK showed more than a 3-fold increase in MBL expression relative to the control. The least-squares means for OV, LB, PK and RIR mRNA MBL expression were 0.54 ± 0.19, 0.68 ± 0.30, 4.46 ± 2.76 and 2.89 ± 0.19 µg/mL, respectively.

CONCLUSION

MBL protein was detected and quantified with distinct differences in concentration and expression levels  at the presence of mycoplasma gallisepticum among the sampled South African chicken breeds. This highlights the genetic diversity of MBL as a tool for disease prevention in South African chicken breeds.

Differential role of M cells in enteroid infection by Mycobacterium avium subsp. paratuberculosis and Salmonella enterica serovar Typhimurium

Infection of ruminants such as cattle with Mycobacterium avium subsp. paratuberculosis (MAP) causes Johne's disease, a disease characterized by chronic inflammation of the small intestine and diarrhoea. Infection with MAP is acquired via the faecal-to-oral route and the pathogen initially invades the epithelial lining of the small intestine. In this study we used an in vitro 3D mouse enteroid model to determine the influence of M cells in infection of the gut epithelia by MAP, in comparison with another bacterial intestinal pathogen of veterinary importance, Salmonella enterica serovar Typhimurium. The differentiation of M cells in the enteroid cultures was induced by stimulation with the cytokine receptor activator of nuclear factor-κB ligand (RANKL), and the effects on MAP and Salmonella uptake and intracellular survival were determined. The presence of M cells in the cultures correlated with increased uptake and intracellular survival of Salmonella, but had no effect on MAP. Interestingly neither pathogen was observed to preferentially accumulate within GP2-positive M cells.

Quantitative Proteomic Analysis Reveals Yeast Cell Wall Products Influence the Serum Proteome Composition of Broiler Chickens

With an ever-growing market and continual financial pressures associated with the prohibition of antibiotic growth promoters, the poultry industry has had to rapidly develop non-antibiotic alternatives to increase production yields. A possible alternative is yeast and its derivatives, such as the yeast cell wall (YCW), which have been proposed to confer selected beneficial effects on the host animal. Here, the effect of YCW supplementation on the broiler chicken was investigated using a quantitative proteomic strategy, whereby serum was obtained from three groups of broilers fed with distinct YCW-based Gut Health Products (GHP) or a control basal diet. Development of a novel reagent enabled application of ProteoMiner™ technology for sample preparation and subsequent comparative quantitative proteomic analysis revealed proteins which showed a significant change in abundance (n = 167 individual proteins; p < 0.05); as well as proteins which were uniquely identified (n = 52) in, or absent (n = 37) from, GHP-fed treatment groups versus controls. An average of 7.1% of proteins showed changes in abundance with GHP supplementation. Several effects of these GHPs including immunostimulation (via elevated complement protein detection), potential alterations in the oxidative status of the animal (e.g., glutathione peroxidase and catalase), stimulation of metabolic processes (e.g., differential abundance of glyceraldehyde-3-phosphate dehydrogenase), as well as evidence of a possible hepatoprotective effect (attenuated levels of serum α-glutathione s-transferase) by one GHP feed supplement, were observed. It is proposed that specific protein detection may be indicative of GHP efficacy to stimulate broiler immune status, i.e., may be biomarkers of GHP efficacy. In summary, this work has developed a novel technology for the preparation of high dynamic range proteomic samples for LC-MS/MS analysis, is part of the growing area of livestock proteomics and, importantly, provides evidential support for beneficial effects that GHP supplementation has on the broiler chicken.

Activity of Mannose-Binding Lectin on Bacterial-Infected Chickens-A Review

Simple Summary

In the quest to combat bacterial-related diseases in chickens, different methods, of which some are less economical and less effective on the long-term, have been adapted. However, chickens possess mannose-binding lectin (MBL) which could be vital in managing pathogenic bacteria in chickens. MBL is one of the soluble proteins secreted by the chicken’s innate immune system which can be activated when chickens are exposed to chicken-related diseases. This review explains how mannose-binding lectin activation can help in fighting bacterial pathogens in chickens. This knowledge is believed to reduce incessant use of antibiotics and to assist in developing a profitable breeding program with less or no adverse effect on the chicken, human and the environment.

Abstract

In recent years, diseases caused by pathogenic bacteria have profoundly impacted chicken production by causing economic loss in chicken products and by-product revenues. MBL (mannose-binding lectin) is part of the innate immune system (IIS), which is the host’s first line defense against pathogens. The IIS functions centrally by identifying pathogen-specific microorganism-associated molecular patterns (MAMPs) with the help of pattern recognition receptors (PRRs). Studies have classified mannose-binding lectin (MBL) as one of the PRR molecules which belong to the C-type lectin family. The protective role of MBL lies in its ability to activate the complement system via the lectin pathway and there seems to be a direct link between the chicken’s health status and the MBL concentration in the serum. Several methods have been used to detect the presence, the level and the structure of MBL in chickens such as Enzyme-linked immunosorbent assay (ELISA), Polymerase Chain Reaction (PCR) among others. The concentration of MBL in the chicken ranges from 0.4 to 35 µg/mL and can be at peak levels at three to nine days at entry of pathogens. The variations observed are known to depend on the bacterial strains, breed and age of the chicken and possibly the feed manipulation strategies. However, when chicken MBL (cMBL) becomes deficient, it can result in malfunctioning of the innate immune system, which can predispose chickens to diseases. This article aimed to discuss the importance and components of mannose-binding lectin (MBL) in chickens, its mode of actions, and the different methods used to detect MBL. Therefore, more studies are recommended to explore the causes for low and high cMBL production in chicken breeds and the possible effect of feed manipulation strategies in enhancing cMBL production.

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.

Avian coronavirus infection induces mannose-binding lectin production in dendritic cell precursors of chicken lymphoid organs

The aim of this immunocytochemical study was to compare mannose-binding lectin (MBL) production induced by avian coronavirus in the spleen and caecal tonsil (CT). One-day-old specific-pathogen-free (SPF) chickens were experimentally infected with six QX field isolates and the H120 vaccine strain. In the negative control birds, the spleen was MBL negative, while the CT showed scattered MBL-positive cells in close proximity and within the surface epithelium and germinal centre (GC)-like cell clusters. MBL was detectable in the ellipsoid-associated cells (EACs) and cell clusters in the periarterial lymphoid sheath (PALS) by 7 days post infection (dpi). In both organs, the MBL-positive cells occupy antigen-exposed areas, indicating that GC formation depends on resident precursors of dendritic cells. The majority of MBL-positive EACs express the CD83 antigen, providing evidence that coronavirus infection facilitated the maturation of dendritic cell precursors. Surprisingly, co-localisation of MBL and CD83 was not detectable in the CT. In the spleen (associated with circulation), the EACs producing MBL and expressing CD83 are a common precursor of both follicular (FDC) and interdigitating dendritic cells (IDC). In the CT (gut-associated lymphoid tissue, GALT) the precursors of FDC and IDC are MBL-producing cells and CD83-positive cells, respectively. In the CT the two separate precursors of lymphoid dendritic cells provide some 'autonomy' for the GALT.

In vitro phagocytosis of opsonized latex beads by HD11 cells as a method to assess the general opsonization potential of chicken serum

Opsonins, an important arm of the innate immune system, are various soluble proteins, which play a critical role in destruction of invading pathogens directly or via engulfment of pathogens through the intermediate of phagocytosis. The diversity of opsonin profiles is under genetic influence and may be associated with variation in disease resistance. The aim of this study was to set up an assay to determine serum opsonophagocytic potential (OPp) for chicken sera by flow cytometry and to evaluate the assay using samples from different chicken lines. Two chicken lines selected for high and low concentrations of mannose-binding lectin, a known opsonin, in serum were used to establish the method. Furthermore, the presumed "robust" Hellevad chickens and two other commercial chicken lines (Hisex and Bovans) were tested to evaluate OPp as a parameter reflecting general immune competence. The results showed that Hellevad and Bovans chickens had higher OPp than Hisex chickens. There were no correlations between concentrations of total IgY or mannose-binding lectin and OPp. However, a strong positive correlation was observed between vaccine-induced infectious bronchitis virus titres and OPp. Moreover, inverse relationships were observed between concentrations of total serum IgM as well as natural antibody levels, and OPp. In conclusion, in vitro opsonophagocytosis assessment and determination of OPp may be of relevance when addressing general innate immunocompetence. RESEARCH HIGHLIGHTS A flow cytometry method was developed to assess poultry serum opsonophagocytosis potential. This method is based on serum-opsonin-coated polystyrene beads and HD11 cell phagocytosis. Serum samples from different commercial chicken lines were compared. Opsonophagocytic potential may be included in assay panels for general immune competence of poultry.

Chicken mannose binding lectin has antiviral activity towards infectious bronchitis virus

Mannose binding lectin (MBL) is a collagenous C-type lectin, which plays an important role in innate immunity. It can bind to carbohydrates on the surface of a wide range of pathogens, including viruses. Here we studied the antiviral effect of recombinant chicken (rc)MBL against Infectious Bronchitis Virus (IBV), a highly contagious coronavirus of chicken. rcMBL inhibited in a dose-dependent manner the infection of BHK-21 cells by IBV-Beaudette, as detected by immunofluorescence staining of viral proteins and qPCR. ELISA and negative staining electron microscopy showed that rcMBL bound directly to IBV, resulting in the aggregation of viral particles. Furthermore, we demonstrated that MBL bound specifically to the spike S1 protein of IBV which mediates viral attachment. This subsequently blocked the attachment of S1 to IBV-susceptible cells in chicken tracheal tissues as shown in protein histochemistry. Taken together, rcMBL exhibits antiviral activity against IBV, based on a direct interaction with IBV virions.

Expression and characterization of recombinant chicken mannose binding lectin

Mannose binding lectin (MBL) is a serum collagenous C-type lectin that plays an important role in the innate immune protection against pathogens. Previously, human and mouse studies have demonstrated that MBL binds a broad range of pathogens that results in their neutralization through agglutination, enhanced phagocytosis, and/or complement activation via the lectin pathway. The role of MBL in chicken is not well understood although the MBL concentration in serum seems to correlate with protection against infections. To investigate the role of MBL in chicken further, recombinant chicken MBL (RcMBL) was produced in HeLa R19 cells and purified using mannan affinity chromatography followed by gel filtration. RcMBL was shown to be structurally and functionally similar to native chicken MBL (NcMBL) isolated from serum. RcMBL is expressed as an oligomeric protein (mixture of trimers and oligomerized trimers) with a monomeric mass of 26kDa as determined by mass spectrometry, corresponding to the predicted mass. Glycan array analysis indicated that RcMBL bound most strongly to high-mannose glycans but also glycans with terminal fucose and GlcNac residues. The biological activity of RcMBL was demonstrated via its capacity to agglutinate Salmonella Typhimurium and to inhibit the hemagglutination activity of influenza A virus. The production of a structurally well-characterized and functionally active RcMBL will facilitate detailed studies into the protective role of MBL in innate defense against pathogens in chicken and other avian species.