Poul Sørensen

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.

MHC haplotype and susceptibility to experimental infections (Salmonella Enteritidis, Pasteurella multocida or Ascaridia galli) in a commercial and an indigenous chicken breed.

In three independent experimental infection studies, the susceptibility and course of infection of three pathogens considered of importance in most poultry production systems, Ascaridia galli, Salmonella Enteritidis and Pasteurella multocida were compared in two chicken breeds, the indigenous Vietnamese Ri and the commercial Luong Phuong. Furthermore, the association of the Major Histocompatibility Complex (MHC) with disease-related parameters was evaluated, using alleles of the LEI0258 microsatellite as markers for MHC haplotypes. The Ri chickens were found to be more resistant to A. galli and S. Enteritidis than commercial Luong Phuong chickens. In contrast, the Ri chickens were more susceptible to P. multocida, although production parameters were more affected in the Luong Phuong chickens. Furthermore, it was shown that the individual variations observed in response to the infections were influenced by the MHC. Using marker alleles of the microsatellite LEI0258, which is located within the MHC region, several MHC haplotypes were identified as being associated with infection intensity of A. galli. An association of the MHC with the specific antibody response to S. Enteritidis was also found where four MHC haplotypes were shown to be associated with high specific antibody response. Finally, one MHC haplotype was identified as being associated with pathological lesions and mortality in the P. multocida experiment. Although not statistically significant, our analysis suggested that this haplotype might be associated with resistance. These results demonstrate the presence of local genetic resources in Vietnamese chickens, which could be utilized in breeding programmes aiming at improving disease resistance.

Ascaridia galli infection influences the development of both humoral and cell-mediated immunity after Newcastle Disease vaccination in chickens.

Potent vaccine efficiency is crucial for disease control in both human and livestock vaccination programmes. Free range chickens and chickens with access to outdoor areas have a high risk of infection with parasites including Ascaridia galli, a gastrointestinal nematode with a potential influence on the immunological response to vaccination against other infectious diseases. The purpose of this study was to investigate whether A. galli infection influences vaccine-induced immunity to Newcastle Disease (ND) in chickens from an MHC-characterized inbred line. Chickens were experimentally infected with A. galli at 4 weeks of age or left as non-parasitized controls. At 10 and 13 weeks of age half of the chickens were ND-vaccinated and at 16 weeks of age, all chickens were challenged with a lentogenic strain of Newcastle disease virus (NDV). A. galli infection influenced both humoral and cell-mediated immune responses after ND vaccination. Thus, significantly lower NDV serum titres were found in the A. galli-infected group as compared to the non-parasitized group early after vaccination. In addition, the A. galli-infected chickens showed significantly lower frequencies of NDV-specific T cells in peripheral blood three weeks after the first ND vaccination as compared to non-parasitized chickens. Finally, A. galli significantly increased local mRNA expression of IL-4 and IL-13 and significantly decreased TGF-ß4 expression in the jejunum two weeks after infection with A. galli. At the time of vaccination (six and nine weeks after A. galli infection) the local expression in the jejunum of both IFN-? and IL-10 was significantly decreased in A. galli-infected chickens. Upon challenge with the NDV LaSota strain, viral genomes persisted in the oral cavity for a slightly longer period of time in A. galli-infected vaccinees as compared to non-parasitized vaccinees. However, more work is needed in order to determine if vaccine-induced protective immunity is impaired in A. galli-infected chickens.

Adjuvant effects of mannose-binding lectin ligands on the immune response to infectious bronchitis vaccine in chickens with high or low serum mannose-binding lectin concentrations.

Abstract Mannose-binding lectin (MBL) plays a major role in the immune response as a soluble pattern-recognition receptor. MBL deficiency and susceptibility to different types of infections have been subject to extensive studies over the last decades. In humans and chickens, several studies have shown that MBL participates in the protection of hosts against virus infections. Infectious bronchitis (IB) is a highly contagious disease of economic importance in the poultry industry caused by the coronavirus infectious bronchitis virus (IBV). MBL has earlier been described to play a potential role in the pathogenesis of IBV infection and the production of IBV-specific antibodies, which may be exploited in optimising IBV vaccine strategies. The present study shows that MBL has the capability to bind to IBV in vitro. Chickens from two inbred lines (L10H and L10L) selected for high or low MBL serum concentrations, respectively, were vaccinated against IBV with or without the addition of the MBL ligands mannan, chitosan and fructooligosaccharide (FOS). The addition of MBL ligands to the IBV vaccine, especially FOS, enhanced the production of IBV-specific IgG antibody production in L10H chickens, but not L10L chickens after the second vaccination. The addition of FOS to the vaccine also increased the number of circulating CD4+ cells in L10H chickens compared to L10L chickens. The L10H chickens as well as the L10L chickens also showed an increased number of CD4−CD8α−γδ T-cells when an MBL ligand was added to the vaccine, most pronouncedly after the first vaccination. As MBL ligands co-administered with IBV vaccine induced differences between the two chicken lines, these results indirectly suggest that MBL is involved in the immune response to IBV vaccination. Furthermore, the higher antibody response in L10H chickens receiving vaccine and FOS makes FOS a potential adjuvant candidate in an IBV vaccine.

The influence of vitamin c on the antioxidative status of chickens in vivo at slaughter and on the oxidative stability of broiler meat products

Broiler chickens were fed diets containing 0, 210, 420 or 840 mg vitamin C kg−1 feed from 10 to 42 days of age. The diets contained 13.6% fat and 87.7% unsaturated fatty acids. Activity of creatine‐kinase (CK) and glutathione peroxidase (GSH‐Px) decreased with increasing levels of dietary vitamin C. No statistical difference between groups was found with respect to the concentration of vitamin E or lutein in plasma, but chickens fed diets containing 420 or 840 mg vitamin C kg−1 feed had a significantly higher plasma concentration of retinol and s‐carotene compared with chickens fed diets containing 0 to 210 mg vitamin C kg−1 feed. A considerable erythrocyte haemolysis in vitro was demonstrated in all groups and increased with increasing dietary level of vitamin C. The unsupplemented group had a lower concentration of fatty acids expressed as a percentage in extracted fat compared with the vitamin C supplemented group. No influence of dietary vitamin C on the concentration of antioxidative vitamins in the ...

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.

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.

Feeding activity in groups of newly hatched broiler chicks: effects of strain and hatching time.

The feeding activity of 2 strains of broiler chickens was investigated during their first week of life in relation to their hatching time. Fast (Ross 308) and slow-growing (LB) strains were allocated to 1 of 3 (early, middle, or late hatch) single-strain groups of 80 to 100 as-hatched birds in 4 replicates divided into 2 time-separated blocks. Behavioral observations differed between blocks and were carried out at intervals on d 1 to 6, and the percentage of birds feeding (from trough or paper), drinking, or being otherwise active (block 2 only) were registered. A higher mortality caused by flip-over was seen among the late-hatching birds from the slow-growing strain. The percentage of birds engaged in feeding activity was similar for the 2 strains, but LB birds began to eat from the paper later and were observed eating from the trough less than Ross 308 birds, which in turn were less active than LB, especially in the early and middle hatch groups. Early hatch groups were observed feeding from the paper more than the middle and late hatch groups. Drinking behavior mirrored feeding from the trough, indicating that drinking was prandial. Within strain, no effect of hatch time was found on live weight at hatch, but the feeding behavior of early hatched birds led to a small, transient weight advantage on d 3 after hatch. The transition from feeding on paper to feeding only from the trough may have less effect on birds that feed from the trough sooner, such as the fast-growing strain.

No protection in chickens immunized by the oral or intra-muscular immunization route with Ascaridia galli soluble antigen

In chickens, the nematode Ascaridia galli is found with prevalences of up to 100% causing economic losses to farmers. No avian nematode vaccines have yet been developed and detailed knowledge about the chicken immune response towards A. galli is therefore of great importance. The objective of this study was to evaluate the induction of protective immune responses to A. galli soluble antigen by different immunization routes. Chickens were immunized with a crude extract of A. galli via an oral or intra-muscular route using cholera toxin B subunit as adjuvant and subsequently challenged with A. galli. Only chickens immunized via the intra-muscular route developed a specific A. galli antibody response. Frequencies of γδ T cells in spleen were higher 7 days after the first immunization in both groups but only significantly so in the intra-muscularly immunized group. In addition, systemic immunization had an effect on both Th1 and Th2 cytokines in caecal tonsils and Meckels diverticulum. Thus both humoral and cellular immune responses are inducible by soluble A. galli antigen, but in this study no protection against the parasite was achieved.

The consequence of low mannose-binding lectin plasma concentration in relation to susceptibility to Salmonella Infantis in chickens

Mannose-binding lectin (MBL) is a key protein in innate immunity. MBL binds to carbohydrates on the surface of pathogens, where it initiates complement activation via the lectin-dependent pathway or facilitates opsonophagocytosis. In vitro studies have shown that human MBL is able to bind to Salmonella, but knowledge in relation to chicken MBL and Salmonella is lacking. In order to study this relation day-old chickens from two selected lines L10H and L10L, differing in MBL serum concentration, were either orally infected with S. Infantis (S.123443) or kept as non-infected controls. The differences between healthy L10H and L10L chicken sublines were more profound than differences caused by the S. Infantis infection. The average daily body weight was higher for L10H than for L10L, regardless of infection, indicating beneficial effects of MBL selection on growth. Salmonella was detected in cloacal swabs and the number of Salmonella positive chickens during the experiment was significantly higher in L10L than L10H, indicating that MBL may affect the magnitude of Salmonella colonisation in day-old chickens. MBL expression was determined in ceca tissue by real-time RT-PCR. L10H chickens showed a significantly higher relative expression than L10L at days 1 and 41 pi, regardless of infection. Finally, flow cytometric analysis of whole blood from infected chickens showed that L10H had a significantly higher count of all assessed leucocyte subsets on day 5 pi, and also a higher count of monocytes on day 12 pi than L10L. No difference was observed between infected and non-infected L10L chicken.