Serum levels of chicken mannan-binding lectin (MBL) during virus infections; indication that chicken MBL is an acute phase reactant

Differing Expression and Potential Immunological Role of C-Type Lectin Receptors of Two Different Chicken Breeds against Low Pathogenic H9N2 Avian Influenza Virus

Diverse immune responses in different chicken lines can result in varying clinical consequences following avian influenza virus (AIV) infection. We compared two widely used layer breeds, Lohmann Brown (LB) and Lohmann White (LW), to examine virus replication and immune responses against H9N2 AIV infection. The transcription profile in the spleen of H9N2-infected chickens was compared using a microarray. Confirmatory real-time RT-PCR was used to measure the expression of C-type lectin, OASL, and MX1 genes. Additionally, to investigate the role of chicken lectin receptors in vitro, two C-type lectin receptors (CLRs) were expressed in DF-1 cells, and the early growth of the H9N2 virus was evaluated. The LB chickens shed a lower amount of virus from the cloaca compared with the LW chickens. Different expression levels of C-type lectin-like genes were observed in the transcription profile, with no significant differences in OASL or MX gene expression. Real-time RT-PCR indicated a sharp decrease in C-type lectin levels in the spleen of H9N2-infected LW chickens. In vitro studies demonstrated that cells overexpressing CLR exhibited lower virus replication, while silencing of homeostatic CLR had no effect on AIV replication. This study demonstrated distinct immune responses to H9N2 avian influenza in LB and LW chickens, particularly with differences in C-type lectin expression, potentially leading to lower virus shedding in LB chickens.

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.

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.

Rapid whole blood assay using flow cytometry for measuring phagocytic activity of chicken leukocytes

Phagocytic activity of leukocytes in whole blood was assessed as a potential immune competence trait in chickens. A flow cytometry based whole blood phagocytosis (WBP) assay was set up and evaluated using blood from chickens homozygous for four different MHC haplotypes, B12, B15, B19 and B21. Fluorescent latex beads and two serotypes of fluorescently labelled heat-killed bacteria (Salmonella Infantis and Salmonella. Typhimurium) were evaluated as phagocytic targets. In addition, the opsonophagocytic potential (OPp) of individual sera from the birds was included in a phagocytosis assay using the HD11 chicken macrophage cell line. Results showed that both serotypes of bacteria but not the latex beads were effectively phagocytosed by leukocytes in the whole blood cultures. Differences were observed in the phagocytic capacity of monocytes and thrombocyte/lymphocytes, respectively between the different MHC lines. No significant differences on the OPp of serum was identified between MHC lines. In addition, for both phagocytic activity of leukocytes and OPp of serum large variations between individuals were observed within MHC haplotypes. No significant relationships were observed between the phagocytic activity of leukocytes and serum OPp or Salmonella-specific IgY levels. In conclusion, our results suggest that the WBP assay, using a no-lyse no-wash single staining method, is a rapid and convenient method to assess phagocytic functions of different leukocyte populations.

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.

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

Mannose-binding lectin (MBL) is a C-type serum lectin of importance in innate immunity. Low serum concentrations of MBL have been associated with greater susceptibility to infections. In this study, binding of purified chicken MBL (cMBL) to Salmonella enterica subsp. enterica (S. enterica) serotypes B, C1 and D was investigated by flow cytometry, and Staphylococcus aureus (S. aureus) was used for comparison. For S. enterica the C1 serotypes were the only group to exhibit binding to cMBL. Furthermore, functional studies of the role of cMBL in phagocytosis and complement activation were performed. Spiking with cMBL had a dose-dependent effect on the HD11 phagocytic activity of S. enterica subsp. enterica serovar Montevideo, and a more pronounced effect in a carbohydrate competitive assay. This cMBL dose dependency of opsonophagocytic activity by HD11 cells was not observed for S. aureus. No difference in complement-dependent bactericidal activity in serum with high or low cMBL concentrations was found for S. Montevideo. On the other hand, serum with high concentrations of cMBL exhibited a greater bactericidal activity to S. aureus than serum with low concentrations of cMBL. The results presented here emphasise that chicken cMBL exhibits functional similarities with its mammalian counterparts, i.e. playing a role in opsonophagocytosis and complement activation.

Characterization of cellular and humoral immune responses after IBV infection in chicken lines differing in MBL serum concentration

Chickens from two inbred lines selected for high (L10H) or low (L10L) mannose-binding lectin (MBL) serum concentrations were infected with infectious bronchitis virus (IBV), and innate as well as adaptive immunological parameters were measured throughout the experimental period. Chickens with high MBL serum concentrations were found to have less viral load in the trachea than chickens with low MBL serum concentrations indicating that these chickens were less severely affected by the infection. This study is the first to show that MBL expression is present in the lungs of healthy chickens and that the expression is upregulated at days 3 postinfection (p.i.) in L10H chickens. Furthermore, in the liver of infected chickens, the MBL expression was upregulated at day 7 p.i., despite the fact that the MBL serum concentrations were decreased below baseline at that time point. The number of TCRγδ+CD8α+ cells in the blood of noninfected chickens increased from week 0 to 3 p.i. However, the number of cells was higher in L10H chickens than in L10L chickens throughout the experiment. No increase was observed in the number of TCRγδ+CD8α+ cells in the blood of the infected L10H and L10L chickens. The numbers of B cells at week 3 p.i. were higher for noninfected L10L chickens than for the other chickens. No differences were observed between the infected and noninfected L10H chickens or between the infected L10H and L10L chickens. Furthermore, at week 3 p.i., the number of monocytes was higher in infected and noninfected L10H chickens than in the infected and noninfected L10L chickens. Thus, these results indicate that MBL is produced locally and may be involved in the regulation of the cellular immune response after an IBV infection. However, MBL did not appear to influence the humoral immune response after IBV infection in this study.

Mannan binding lectin attenuates double-stranded RNA-mediated TLR3 activation and innate immunity

Mannan binding lectin (MBL) functions as a pattern recognition molecule (PRM) which is able to initiate complement activation. Here, we characterize a previously unrecognized attribute of MBL as a double-stranded RNA (dsRNA) binding protein capable of modifying Toll like receptor 3 (TLR3) activation. MBL interacts with poly(I:C) and suppresses poly(I:C)-induced activation of TLR3 pathways and subsequent cytokine production. In addition, MBL binds to TLR3 directly. Surprisingly, disrupting the interaction between MBL and complement receptor 1 (CR1) or restraining the traffic of MBL to phagosome reversed the MBL limited TLR3 activation. We demonstrate the importance of MBL guided ligands intracellular localization, emphasizing the significance of understanding the dynamics of TLR agonists complexed with MBL or other PRMs inside the cell in immune defense.

Changes of several acute phase factors in broiler chickens in response to infectious bronchitis virus infection

This study was performed to clarify the acute phase response following infectious bronchitis virus inoculation. Ninety clinically healthy 1-d-old Ross chicks were randomly assigned into 2 groups: control (n = 20) and infected group (n = 70). At the age of 20 d, all birds in the infected group were challenged intranasally with allantoic fluid containing 10⁵ embryo lethal dose (ELD₅₀)/0.1 mL of the infectious bronchitis virus. Blood samples were collected from 20 clinically healthy and 70 infected chicks at prior and 1, 2, 3, 5, 7, 11, 13, 15, and 20 d postinoculation. On d 1, 7, and 11 postinoculation 4 chickens from the experimental group and 2 chickens from the control group were randomly selected. Their trachea, lungs, and cecal tonsil were collected for virus detection and quantitation by real-time reverse-transcription PCR assay. In the serum the acute phase proteins (haptoglobin and serum amyloid A), pro-inflammatory cytokines (interferon-γ and tumor necrosis factor-α), and serum sialic acid (total, TSA; lipid-bound, LBSA; and protein-bound, PBSA) concentrations were measured using validated standard procedures. All variables were significantly higher in the infected birds after virus inoculation compared with the healthy group (P < 0.05). There were positive correlations between all variables in the infected group. Correlation coefficients were significantly positive between haptoglobin and interferon-γ, LBSA and TSA, and TSA and LBSA (P < 0.05). There were positive correlations among viral RNA and all studied variables; however, these correlations were not statistically significant (P > 0.05).

Effect of mild heat stress and mild infection pressure on immune responses to an E. coli infection in chickens

Outdoor or organic farming demands robust chickens that are able to combat common infections before they spread to the flock. Priming the immune system of the chickens early in life with micro-organisms that they will encounter later in life prepares chickens to a life in environments where they are subjected to a more natural level of infection pressure. Also, exposure to non-infectious stressful situations may prepare the immune system to combat infectious challenges. The present study investigated whether the immune system could be primed by applying small doses of infective material to the chicken flock or by exposure to short-term non-infectious stimulation, and whether the effect of those stimuli would depend on the genetic material chosen. The effect of the stimulations was examined on selected immunological variables in two chicken strains, using small amounts of manure and litter from other chickens or short-term heat stress, respectively. After 6 weeks of treatment, all chickens were subjected to an Escherichia coli infection and followed for another 3 weeks. Measures of body weight gain, chicken mannan-binding lectin (cMBL), percentage of CD4+ and MHCII+ lymphocytes, mean fluorescence intensity (m.f.i.) of CD4 on CD4+ cells and MHCII on MHCII+ cells and antibody titres to E. coli were taken. In conclusion, the chickens redistribute lymphocyte populations in peripheral blood in response to potentially infectious agents as well as to stressful non-infectious treatments. Responses to stress situations were dependent on the frequencies of stress exposures and on the chicken breed. This may reflect the superiority of one breed over another in adapting to treatments or in discriminating whether a treatment is harmless or dangerous. However, the differences did not influence the disease resistance to infection with a mixture of E. coli O2, O11 and O78 in the present study.

Mannan Oligosaccharides in Nursery Pig Nutrition and Their Potential Mode of Action

Simple Summary

The aim of the paper is to provide a review of mannan oligosaccharide products in relation to their growth promoting effect and mode of action. Mannan oligosaccharide products maintain intestinal integrity and the digestive and absorptive function of the gut in the post-weaning period in pigs and enhance disease resistance by promoting antigen presentation. We find that dietary supplementation has growth promoting effects in pigs kept in a poor hygienic environment, while the positive effect of MOS is not observed in healthy pig herds with high hygienic standards.

Abstract

Mannan oligosaccharides (MOSs) are often referred to as one of the potential alternatives for antimicrobial growth promoters. The aim of the paper is to provide a review of mannan oligosaccharide products in relation to their growth promoting effect and mode of action based on the latest publications. We discuss the dietary impact of MOSs on (1) microbial changes, (2) morphological changes of gut tissue and digestibility of nutrients, and (3) immune response of pigs after weaning. Dietary MOSs maintain the intestinal integrity and the digestive and absorptive function of the gut in the post-weaning period. Recent results suggest that MOS enhances the disease resistance in swine by promoting antigen presentation facilitating thereby the shift from an innate to an adaptive immune response. Accordingly, dietary MOS supplementation has a potential growth promoting effect in pigs kept in a poor hygienic environment, while the positive effect of MOS is not observed in healthy pig herds with high hygienic standards that are able to maintain a high growth rate after weaning.

Effect of different levels of mannan-oligosaccharide supplementation on some immunological variables in weaned piglets

The effect of different doses of mannan-oligosaccharide (MOS) on specific and non-specific immune responses was studied in piglets, weaned at 28 days. A total of 58 piglets were used in six groups. Five groups were fed 0, 1, 2, 4 g MOS product per kg diet or with growth promoting antibiotics and immunized by inactivated Aujeszky’s disease virus (AyV) vaccine at week 1 and 3 of the experiment (35 and 49 days). A sixth group, receiving the same non-supplemented diets was not immunized. Blood samples for lymphocyte stimulation (LST) and AyV neutralization (VN) tests were taken from all pigs on the first day of the experiment and at weekly intervals for 5 weeks. At week 8, the immunized piglets were infected orally with transmissible gastroenteritis virus. All piglets were weighed and slaughtered at week 10, digesta from small intestine were collected and tested for the presence of secretory (s)IgA. Feeding MOS supplementation resulted in enhanced specific and non-specific immune responses, however, a regressive dose-response of MOS was observed. Both the specific cellular (LST) and humoral responses (VN) were enhanced after 2 weeks of feeding 1 g/kg MOS and significantly differed from the antibiotic positive control. The same tendency was detected in case of the non-specific LSTs, although these started some weeks later showing significant differences by the fifth week. Higher doses of MOS had no further beneficial effect on systemic immunity. In addition, 1 g/kg MOS supplementation group also showed some advantage in local immune responsiveness. Therefore, based on the studied immune variables, 1 g/kg MOS product is suggested in the diet of weaned piglets.

Plasma ladderlectin concentration following sterile inflammation and Aeromonas salmonicida subsp. salmonicida infection

Plasma samples obtained from rainbow trout either experimentally infected with Aeromonas salmonicida or injected with either A. salmonicida lipopolysaccharide (LPS) or a commercial A. salmonicida vaccine (Lipogen) were analysed by enzyme immunoassay to evaluate changes in rainbow trout ladderlectin (RTLL) concentrations during the acute phase response (APR). Plasma RTLL concentrations in fish injected with A. salmonicida LPS, vaccine or live A. salmonicida varied over a 10 day period, but did not significantly increase. In contrast, fish experimentally infected with A. salmonicida exhibited a modest, but statistically significant (P < 0.05), decrease in RTLL concentration. These studies demonstrate that RTLL is not detectably induced during the trout APR to sterile inflammation or A. salmonicida infection, but plasma concentration of this protein may be reduced during bacterial infection.

Influence of chicken serum mannose-binding lectin levels on the immune response towards Escherichia coli

This study aimed to investigate the effect of mannose-binding lectin (MBL) on infections with Escherichia coli in chickens. Initially, the basic levels of MBL in 4 different lines of layer chickens, namely ISA Brown, Lohmann Selected Leghorn, Lohmann Braun, and Hellevad, were investigated. This investigation revealed a 2-to 3-fold difference in the basic levels of MBL in serum between some of these commercial lines. Furthermore, the ontogeny of the basic level of MBL in serum of an experimental chicken line was investigated. The level of MBL was very stabile for long periods, with an elevation at 5 to 7 wk of age. Another elevation in MBL level started around 18 to 19 wk of age and stayed elevated at least until 38 wk of age. In this study, it was hypothesized that chickens with high levels of MBL (H-type) may be less prone to disease caused by E. coli infection than chickens with low levels of MBL (L-type) after attempts were made to immunosuppress the chickens by immunization with a live attenuated infectious bursal disease virus (IBDV) vaccine strain. The H-type and L-type chickens were divided into 4 groups receiving either no treatment (I-E-), E. coli alone (I-E+), IBDV alone (I+E-), or IBDV and E. coli (I+E+). Body weight gain was depressed by IBDV immunization as well as E. coli inoculation. The depression of BW gain was significantly larger in L-type chickens compared with H-type chickens. The antibody response to E. coli was significantly depressed by IBDV vaccination and antibody titers to E. coli were elevated by experimental E. coli inoculation, but only in the group not given IBDV (I-E- vs. I-E+). On d 28, T-cell responses in L-type chickens showed a lower percentage of proliferating CD4+ and CD8+ T cells compared with the H-type, regardless of treatment. In conclusion, immune reactions toward infections with E. coli differed between chickens having different basal serum MBL levels, and as such, MBL may be of importance for future selection of more robust chickens for outdoor or organic farming.

Mannan-binding lectin (MBL) in two chicken breeds and the correlation with experimental Pasteurella multocida infection

The present study is the first demonstration of an association of the genetic serum Mannan-binding lectin (MBL) concentration with bacterial infections in chickens. The genetic serum MBL concentration was determined in two chicken breeds, and the association with the specific Pasteurella multocida humoral immune response during an experimental infection was examined. Furthermore, we examined the association of the genetic serum MBL concentration with systemic infection. The chickens with systemic infection had a statistically significant lower mean serum MBL concentration than the rest of the chickens, suggesting that MBL plays an important role against P. multocida. A statistically significant negative correlation was found between the specific antibody response and the genetic serum MBL concentration for both breeds. This indicates that MBL in chickens is capable of acting as the first line of defence against P. multocida by diminishing the infection before the adaptive immune response takes over.

Mannan-binding lectin (MBL) serum concentration in relation to propagation of infectious bronchitis virus (IBV) in chickens

Mannan-binding lectin (MBL) is a collectin that mediates activation of the complement system and is of importance for host defenses. In humans low concentrations of MBL in serum have been associated with susceptibility to several viral diseases. To understand the function of MBL in relation to infectious viral diseases two chicken lines were selected for high and low concentrations of MBL in serum for several generations. Offspring from the two sub-lines were subjected to infection with infectious bronchitis virus (IBV) in order to determine their genetic susceptibility to the virus. Results suggested that MBL plays a role in the innate immunity against IBV in the way that it performs an acute phase response, is able to activate complement, and inhibits the propagation of the virus in the trachea.

An assay for measuring the mannan-binding lectin pathway of complement activation in chickens

To investigate the ability of chicken mannan-binding lectin (cMBL) to work as a complement activator, a heterogeneous ELISA test was developed, in which the deposition of human complement factor 4 (C4) was used as a measure of complement activation ability. Serum from different experimental chicken lines was tested. The correlation between serum cMBL concentrations and human C4 deposition was high (correlation = 0.8549, P < 0.0001). There was no difference in C4 deposition among sera from the chicken lines when calculated as C4 deposition relative to the cMBL concentration.

Single-nucleotide polymorphisms in porcine mannan-binding lectin A

The MBL1 and MBL2 genes encode mannan-binding lectins (MBL) A and C, respectively, that are collagenous lectins (collectins) produced mainly by the liver. Several single-nucleotide polymorphisms (SNPs) in the human MBL2 gene are responsible for various innate immune dysfunctions due to abnormal structure or expression of human MBL-C. The MBL1 gene encodes MBL-A, which has bacteria-binding properties in pigs and rodents but is mutated to a pseudogene in humans and chimpanzees. In these studies, we surveyed both porcine MBL genes for SNPs that might impair disease resistance. Single-strand conformational polymorphism (SSCP) analysis of MBL cDNAs from porcine liver revealed three SNPs within the coding region of MBL1 in various breeds of pigs. One nonsynonymous SNP that substituted cysteine for glycine in the collagen-like domain of pig MBL-A was found by a multiplex PCR test in all European pig breeds examined, with allele frequencies ranging from 1.4 to 46.4%. No SNPs were identified in the coding region of porcine MBL2 but the expression of MBL-C in the liver was widely variable in comparison to the expression of MBL-A, GAPDH, PigMAP, and haptoglobin. These results indicate that some pigs have a miscoding defect in MBL-A and a possible expression defect in MBL-C, which are analogous to coding and promoter polymorphisms that affect human MBL-C.

Reciprocal Antibody and Complement Responses of Two Chicken Breeds to Vaccine Strains of Newcastle Disease Virus, Infectious Bursal Disease Virus and Infectious Bronchitis Virus

Serum antibody responses and haemolytic complement activity were evaluated in White Leghorn (WLH) and Rhode Island Red (RIR) chickens that were vaccinated with live-attenuated vaccines of Newcastle disease virus, or infectious bronchitis virus, or infectious bursal disease virus by means of ocular challenge at 10 times the normal vaccination dose. Complement titres in non-vaccinated birds were significantly higher in WLH birds compared to RIR birds. The lentogenic viral infection resulted in an immediate stimulation of complement activity, followed by a decrease to initial complement levels within 2 weeks post vaccination, when the antibody response took over immune defence. As compared to WLH chickens, RIR birds mounted a faster and significantly higher antibody response to the vaccine viruses used. In WLH hens, significantly higher haemolytic complement activity post vaccination was found as compared to RIR hens. Possible consequences of the observed differences in immune responsiveness of the two breeds to viral vaccines are discussed.

Immune parameters of dry cows fed mannan oligosaccharide and subsequent transfer of immunity to calves

The objective of this study was to evaluate the benefits of supplementation of mannan oligosaccharide (MOS) to cows during the last 3 wk of the dry period on immune function of the cows and subsequent transfer of passive immunity to their calves. Indicators of nonspecific and specific immunity were evaluated. Cows were vaccinated against rotavirus at 4 and 2 wk before expected parturition. Blood samples were obtained from cows before vaccination and at weekly intervals until calving and from calves at birth and 24 h for analysis of serum protein concentrations, packed cell volume, white blood cell counts, white blood cell differentials, and serum rotavirus neutralization titers. Colostrum quantity and quality were measured at calving, and immunoglobulin isotype concentrations in colostrum were determined. Specific immunity was enhanced by MOS supplementation as evidenced by greater serum rotavirus neutralization titers at calving in cows supplemented with MOS compared with control cows. Colostral rotavirus neutralization titers were not affected by treatment. Although numerical differences appeared large, there was a high degree of variability in the colostral rotavirus neutralization titers. Calves from cows fed MOS tended to have greater serum rotavirus neutralization titers compared with calves from cows fed the control diet. There was a tendency for greater increases in serum protein concentrations from birth to 24 h in calves from cows fed MOS compared with calves from cows fed the control diet. Results indicate that supplementation of MOS to cows during the dry period enhanced their immune response to rotavirus and tended to enhance the subsequent transfer of rotavirus antibodies to calves.

Current research on acute phase proteins in veterinary diagnosis: an overview

The acute phase proteins (APP) are a group of blood proteins that contribute to restoring homeostasis and limiting microbial growth in an antibody-independent manner in animals subjected to infection, inflammation, surgical trauma or stress. In the last two decades, many advances have been made in monitoring APP in both farm and companion animals for clinical and experimental purposes. Also, the mechanism of the APP response is receiving attention in veterinary science in connection with the innate immune systems of animals. This review describes the results of recent research on animal APP, with special reference to their induction and regulatory mechanisms, their biological functions, and their current and future applications to veterinary diagnosis and animal production.

Serum levels of mannan-binding lectin in chickens prior to and during experimental infection with avian infectious bronchitis virus

Mannan-binding lectin (MBL) is a glycoprotein and a member of the C-type lectin super family, the collectin family, and the acute phase protein family. The MBL exerts its function by directly binding to microbial surfaces through its carbohydrate recognition domains, followed by direct opsonization or complement activation via MBL-associated serine proteases (MASP)-1 and -2. Thus, MBL plays a major role in the first-line innate defense against pathogens. We investigated the MBL concentrations in serum during experimental infectious bronchitis virus (IBV) infections in chickens. The results showed that the acute phase MBL response to infection with IBV was, to a degree (P < 0.0068), dependent on whether the chickens were inoculated after 12 h of rest (dark) or after 12 h of activity (light). The acute phase response in chickens challenged after 12 h of activity peaked after 4.6 d with an increase of 24%, whereas the acute phase response in chickens challenged after 12 h of rest peaked after 3.1 d with an increase of 51%. The specific antibody titer against IBV was also tested, and a difference (P < 0.0091) between the two experimental groups was found with peak titer values of 6,816 and 4,349. However, the highest value was found in chickens inoculated after 12 h of activity. Thus, an inverse relation exists between the MBL response and the IBV specific antibody response. The ability of MBL to activate the complement cascade was tested in a heterologous system by deposition of human C4 on the chicken MBL/MASP complex. The complement activation was directly associated with the concentration of MBL in serum, indicating neutralization of the virus before the humoral antibody response took over.

Identification of ovotransferrin as an acute phase protein in chickens

Inflammation is homeostatic process associated with a variety of cellular injuries resulting from infections, toxicosis, and physical trauma. The studies on inflammation in avian species are limited. To understand the inflammation-induced changes, 4-wk-old male broiler chickens were subjected to experimental inflammation by a subcutaneous injection of croton oil (inflammatory) with changes in serum measured over time and were compared with birds treated similarly with olive oil (injected control). Croton oil treatment significantly elevated serum interleukin (IL)-6 concentrations and heterophil counts by 6 and 16 h postinjection, respectively, which returned to the basal levels of controls at 16 and 24 h, respectively. Croton oil treatment affected the serum protein profiles of chickens as assessed by SDS-PAGE and densitometric analyses. Compared with olive oil-injected or noninjected chicken sera, there were increases in the density of protein bands corresponding to molecular weights (MW) of 42, 65, 200, and 219 kDa and decreases in bands corresponding to 49 kDa (serum albumin) and a 56-kDa protein in chickens treated with croton oil. Most of these changes were evident at 24 h and lasted through 48 h. The protein band corresponding to 65 kDa was further characterized using two-dimensional gel electrophoresis and N-terminal sequence analyses. A sequence similarity search in the Genbank database using the first 22 amino acids yielded a complete homology with chicken ovotransferrin. Western blot analysis using antichicken serum transferrin or antichicken ovotransferrin antibodies also confirmed the 65-kDa protein band to be ovotransferrin. Under nonreducing conditions, the ovotransferrin standard also showed an apparent MW corresponding to 65 kDa, like the serum transferrin. The serum ovotransferrin was found to be glycosylated using a glycoprotein stain. Although the significance of ovotransferrin in avian inflammation is not clear, these results show that it is a major acute phase protein (APP) in chickens.

Mannan-binding lectin (MBL) in chickens: molecular and functional aspects

Mannan-binding lectin (MBL) is a serum collectin (i.e. mosaic protein with collagenous and lectin domains) involved in the innate immune defence against various microbes. In vitro studies indicate that MBL exerts its function by binding to the microbial surface through its carbohydrate recognition domains followed by direct opsonization or complement activation via the MBL associated serine proteases MASP-1 and MASP-2. In Aves (i.e. chickens), as in man, only one MBL form has been found, while traditional laboratory animals (i.e. mouse and rat) have two MBL forms in serum. MBL has been extensively studied in mammals but recently also in Aves. This review summarizes the present knowledge of MBL in chickens and compares it to the situation in mammals.