Haemolytic complement activity, C3 and Factor B consumption in serum from chickens divergently selected for antibody responses to sheep red blood cells

Exonic SNP in MHC-DMB2 is associated with gene expression and humoral immunity in Japanese quails

The DMB2 gene is widely expressed at high levels in avian. This gene plays an important role in humoral immunity. The aim of this study was to investigate the effects of 361 G > C Single nucleotide polymorphism (SNP) on DMB2 protein structure and gene expression to determine how the 361 G > C SNP affects humoral immune response in Japanese quails. 0.2 mL of 5% sheep red blood cell (SRBC) was injected into breast muscle of 130 Japanese quails on 28 days. After DNA extraction, PCR was carried out to amplify a 333-base pair DNA fragment from the exon 2 of DMB2 gene. The pattern of all samples was determined through RFLP technique. PCR-RFLP results identified two alleles segregating (C, G) as three genotypes (CC, CG and GG) in Japanese Quails. The antibody response to SRBC with CC genotype was significantly higher than the CG and GG genotypes (P < 0.01). In silico analysis showed that the 361 G > C SNP has no effect on the physicochemical properties and 3D structure. The results of RT-qPCR indicated that the effect of genotype on gene expression is significant, so that the expression of CC genotype is more than CG and GG genotype. It can be inferred that the 361 G > C SNP in the exon 2 of MHC-DMB2 gene is not desirable. This mutation decreases humoral immune response by reducing DMB2 gene expression.

Innate immunity in vertebrates: an overview

Innate immunity is a semi-specific and widely distributed form of immunity, which represents the first line of defence against pathogens. This type of immunity is critical to maintain homeostasis and prevent microbe invasion, eliminating a great variety of pathogens and contributing with the activation of the adaptive immune response. The components of innate immunity include physical and chemical barriers, humoral and cell-mediated components, which are present in all jawed vertebrates. The understanding of innate defence mechanisms in non-mammalian vertebrates is the key to comprehend the general picture of vertebrate innate immunity and its evolutionary history. This is also essential for the identification of new molecules with applications in immunopharmacology and immunotherapy. In this review, we describe and discuss the main elements of vertebrate innate immunity, presenting core findings in this field and identifying areas that need further investigation.

Effects of feed access after hatch and inclusion of fish oil and medium chain fatty acids in a pre-starter diet on broiler chicken growth performance and humoral immunity

Delayed feed and water access is known to impair growth performance of day old broiler chickens. Although effects of feed access on growth performance and immune function of broilers have been examined before, effects of dietary composition and its potential interaction with feed access are hardly investigated. This experiment aimed to determine whether moment of first feed and water access after hatch and pre-starter composition (0 to 7 days) affect growth rate and humoral immune function in broiler chickens. Direct fed chickens received feed and water directly after placement in the grow-out facility, whilst delayed fed chickens only after 48 h. Direct and delayed fed chickens received a control pre-starter diet, or a diet containing medium chain fatty acids (MCFA) or fish oil. At 21 days, chickens were immunized by injection of sheep red blood cells. The mortality rate depended on an interaction between feed access and pre-starter composition (P=0.014). Chickens with direct feed access fed the control pre-starter diet had a higher risk for mortality than chickens with delayed feed access fed the control pre-starter diet (16.4% v. 4.2%) whereas the other treatment groups were in-between. BW gain and feed intake till 25 days in direct fed chickens were higher compared with delayed fed chickens, whilst gain to feed ratio was lower. Within the direct fed chickens, the control pre-starter diet resulted in the highest BW at 28 days and the MCFA pre-starter diet the lowest (Δ=2.4%), whereas this was opposite for delayed fed chickens (Δ=3.0%; P=0.033). Provision of MCFA resulted in a 4.6% higher BW gain and a higher gain to feed ratio compared with other pre-starter diets, but only during the period it was provided (2 to 7 days). Minor treatment effects were found for humoral immune response by measuring immunoglobulins, agglutination titers, interferon gamma (IFN- γ ), and complement activity. Concluding, current inclusion levels of fish oil (5 g/kg) and MCFA (30 g/kg) in the pre-starter diet appear to have limited (carryover) effects on growth and development, as well as on humoral immune function.

A specific assay for quantification of human C4c by use of an anti-C4c monoclonal antibody

The increasing evidence of the implication of the complement system in the pathogenesis of several diseases has emphasized the need for the development of specific and valid assays, optimized for quantitative detection of complement activation in vivo. In the present study, we have developed a mouse monoclonal antibody (mAb) that is able to detect fluid phase C4c without interference from other products generated from the complement component C4. The C4c specific mAb was tested in different enzyme-linked immunosorbent assay (ELISA) combinations with various types of in vitro activated sera and samples from factor I deficient patients. The specificity of the mAb was further evaluated by immunoprecipitation techniques and by analysis of eluted fragments of C4 after immunoaffinity chromatography. The anti-C4c mAb was confirmed to be C4c specific, as it showed no cross-reactivity with native (un-cleaved) C4, C4b, iC4b, or C4d. Also, no reaction was observed with C4 fragments in factor I deficient plasma or serum samples. We established and validated a sandwich ELISA based on this C4c specific antibody. The normal range of C4c in EDTA/futhan plasma collected from 100 Danish blood donors was measured, with a mean of 0.85mg/L and a range of 0.19-2.21mg/L. We believe that the C4c specific antibody and the ELISA might be important tools in the future assessment of in vivo activation in situations where the classical or the lectin complement pathways are involved in the pathogenesis.

Breeding for high specific immune reactivity affects sensitivity to the environment

Lipopolysaccharides (LPS) are present in high levels in the air of chicken houses and likely have immune-modulating effects. In this study, layers from the 30th generation of a divergent selection experiment for humoral immune reactivity to subcutaneously administered sheep red blood cells were concurrently intratracheally challenged with human serum albumin (HuSA) and LPS at 7 and 12 wk of age following a crossing over design. Chickens selected for high humoral immune reactivity (H line) showed higher specific antibody responses to intratracheally administered HuSA and a higher level of natural antibody binding keyhole limpet hemocyanin compared with chickens genetically selected for low humoral immune reactivity (L line), and were also more sensitive to immune modulation by LPS at 7 wk of age. Body weight gain was negatively affected by LPS at 7 wk of age in the L line, but after 12 wk of age in the H line. Egg production was lower and delayed in the H line. We conclude that these chicken selection lines differ in sensitivity to the environment (LPS), and consequently may therefore also react differently to infection, vaccinations, and other immune responses. In addition, selection for immune responsiveness affected growth and egg lay.

When conservation management becomes contraindicated: impact of food supplementation on health of endangered wildlife

Understanding the conditions that force the implementation of management actions and their efficiency is crucial for conservation of endangered species. Wildlife managers are widely and increasingly using food supplementation for such species because the potentially immediate benefits may translate into rapid conservation improvements. Supplementary feeding can also pose risks eventually promoting undesired, unexpected, subtle, or indirect, and often unnoticed, effects that are generally poorly understood. For two decades, intensive food supplementation has been used in attempting to improve the breeding productivity of the Spanish Imperial Eagle, Aquila adalberti, one of the most endangered birds of prey in the world. Here, we examined the impact of this intensive management action on nestling health, including contamination, immunodepression, and acquisition of disease agents derived from supplementation techniques and provisioned food. Contrary to management expectations, we found that fed individuals were often inadvertently "medicated" with pharmaceuticals (antibiotics and antiparasitics) contained in supplementary food (domestic rabbits). Individuals fed with medicated rabbits showed a depressed immune system and a high prevalence and richness of pathogens compared with those with no or safe supplementary feeding using non-medicated wild rabbits. A higher presence of antibiotics (fluoroquinolones) was found in sick as opposed to healthy individuals among eaglets with supplementary feeding, which points directly toward a causal effect of these drugs in disease and other health impairments. This study represents a telling example of well-meaning management strategies not based on sound scientific evidence becoming a "contraindicated" action with detrimental repercussions undermining possible beneficial effects by increasing the impact of stochastic factors on extinction risk of endangered wildlife.

Chicken lines divergently selected for antibody responses to sheep red blood cells show line-specific differences in sensitivity to immunomodulation by diet. Part I: Humoral parameters

Individual differences in nutrient sensitivity have been suggested to be related with differences in stress sensitivity. Here we used layer hens divergently selected for high and low specific antibody responses to SRBC (i.e., low line hens and high line hens), reflecting a genetically based differential immune competence. The parental line of these hens was randomly bred as the control line and was used as well. Recently, we showed that these selection lines differ in their stress reactivity; the low line birds show a higher hypothalamic-pituitary-adrenal (HPA) axis reactivity. To examine maternal effects and neonatal nutritional exposure on nutrient sensitivity, we studied 2 subsequent generations. This also created the opportunity to examine egg production in these birds. The 3 lines were fed 2 different nutritionally complete layer feeds for a period of 22 wk in the first generation. The second generation was fed from hatch with the experimental diets. At several time intervals, parameters reflecting humoral immunity were determined such as specific antibody to Newcastle disease and infectious bursal disease vaccines; levels of natural antibodies binding lipopolysaccharide, lipoteichoic acid, and keyhole limpet hemocyanin; and classical and alternative complement activity. The most pronounced dietary-induced effects were found in the low line birds of the first generation: specific antibody titers to Newcastle disease vaccine were significantly elevated by 1 of the 2 diets. In the second generation, significant differences were found in lipoteichoic acid natural antibodies of the control and low line hens. At the end of the observation period of egg parameters, a significant difference in egg weight was found in birds of the high line. Our results suggest that nutritional differences have immunomodulatory effects on innate and adaptive humoral immune parameters in birds with high HPA axis reactivity and affect egg production in birds with low HPA axis reactivity.

Chicken lines selected for their primary antibody response to sheep red blood cells show differential hypothalamic-pituitary-adrenal axis responsiveness to mild stressors

The interaction between the neuroendocrine system and the immune system is well established and supports their mutually affecting relationship. Many animal selection lines have been created according to individual behavioral or neuroendocrine responses to stress. Here we present 2 chicken lines selected for 25 generations for their primary antibody response to immunization with SRBC, as well as the control line from the same parental strain. In the first experiment, the blood-sampling procedure caused a mild stress response, with the expected increase in plasma corticosterone levels. In a second experiment, group housing caused the expected increase in corticosterone levels. In both experiments, the hens of the low line showed the greatest increase in corticosterone levels to our 2 mild stressors. Our results show that birds selected throughout 25 generations for an immune parameter show different HPA axis responsiveness.

Cellular and humoral immunodepression in vultures feeding upon medicated livestock carrion

Veterinary pharmaceuticals contained in dead livestock may be ingested by avian scavengers and negatively affect their health and consequently their population dynamics and conservation. We evaluated the potential role of antibiotics as immunodepressors using multiple parameters measuring the condition of the cellular and humoral immune system in griffon (Gyps fulvus), cinereous (Aegypius monachus) and Egyptian vultures (Neophron percnopterus). We confirmed the presence of circulating antimicrobial residues, especially quinolones, in nestlings of the three vulture species breeding in central Spain. Individuals ingesting antibiotics showed clearly depressed cellular and humoral immune systems compared with nestlings from the control areas, which did not ingest antibiotics. Within central Spain, we found that individuals with circulating antibiotics showed depressed cellular (especially CD4(+)and CD8(+)T-lymphocyte subsets) and humoral (especially acellular APV complement and IL8-like) immune systems compared with nestlings without circulating antibiotics. This suggests that ingestion of antibiotics together with food may depress the immune system of developing nestlings, temporarily reducing their resistance to opportunistic pathogens, which require experimental confirmation. Medicated livestock carrion should be considered inadequate food for vultures due to their detrimental consequences on health derived from the ingestion and potential effects of the veterinary drugs contained in them and for this reason rejected as a management tool in conservation programmes.

Natural Humoral Immune Competence and Survival in Layers

The relation between survival and levels of humoral components of innate (and specific) immune competence of laying hens was investigated in a population of 1,063 laying hens from 12 purebred layer lines. Natural immune competence of the chickens was studied by measuring levels of natural antibodies (NAb) binding to keyhole limpet hemocyanin (KLH) or lipopolysaccharide (LPS), respectively, and hemolytic (classical and alternative) complement activity at 20, 40, and 65 wk of age. In addition, levels of antibodies binding a Newcastle disease vaccine strain as a measure of specific immunity were investigated at 20 wk of age. A distinction could be made between lines showing high or low immune competence with respect to NAb, complement activity, and specific antibodies. Within lines, significant correlations were found for each of the innate parameters among the 3 ages. The innate and specific parameters were, however, not correlated with each other. Based on the limited data set, it was not possible to draw conclusions on line differences for innate or specific immune competence in relation to survival. However, regardless of line, low levels of NAb binding to KLH or high levels of NAb binding to LPS were detected in chickens that did not survive the laying period. The major difference between the responses of NAb binding to KLH or LPS was that the chickens probably did not encounter KLH, which suggests a reflection of the capacity to respond, whereas the chickens most probably did encounter LPS, which suggests a reflection of the active status of the innate humoral immune system. In conclusion, we propose that levels (KLH) and activation (LPS) of components of natural antibodies are indicative for the probability that chickens survive a laying period.

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.

A hemolysis-hemagglutination assay for characterizing constitutive innate humoral immunity in wild and domestic birds

Methods to assess immunocompetence requiring only a single sample are useful in comparative studies where practical considerations prevent holding or recapturing individuals. The assay for natural antibody-mediated complement activation and red blood cell agglutination described here, requiring approximately 100 microl of blood, is highly repeatable. The effects of complement deactivation, 2-mercaptoethanol (2-ME), age, and lipopolysaccharide (LPS)-induced sickness response were examined to validate comparisons among diverse avian species. Complement deactivation by heating significantly reduces lysis and treatment with 2-ME reduces both lysis and agglutination. Lysis and agglutination both increase with age in chickens; LPS treatment does not influence these variables in 11-week-old chickens. In a comparison of 11 species, both lysis (0.0-5.3 titers) and agglutination (1.8-8.0 titers) vary significantly among species. Accordingly, this assay can be used to compare constitutive innate humoral immunity among species and with respect to age, sex, and experimental treatments within populations.

Differential Effects of Lipopolysaccharide and Lipoteichoic Acid on the Primary Antibody Response to Keyhole Limpet Hemocyanin of Chickens Selected for High or Low Antibody Responses to Sheep Red Blood Cells

Various bacterial components are potent activators of the innate immune system and probably (in)directly determine subsequent specific immune responses. Therefore, effects of i.v. administered Salmonella enteriditis-derived lipopolysaccharide (LPS) and Staphylococcus aureus-derived lipoteichoic acid (LTA), respectively, on the primary antibody (Ab) response to keyhole limpet hemocyanin (KLH) were studied in cocks from 2 lines divergently selected for high (H line) and low (L line) Ab responses to SRBC. The Ab responses to KLH were significantly affected by a line-by-treatment-by-time interaction. Significantly higher Ab titers to KLH, S. aureus LTA, and S. enteriditis LPS were found in H line birds than in the L line birds. Ab titers to KLH were enhanced if the chickens were intravenously pretreated 24 h earlier with LTA but decreased if the chickens were intravenously pretreated 24 h earlier with LPS. Ab responses to S. enteriditis LPS were significantly enhanced when birds were immunized with KLH or pretreated with S. aureus LTA. Ab responses to S. aureus LTA were also significantly enhanced when birds were immunized with KLH or pretreated with LTA and subsequently immunized with KLH. Our findings suggest that LTA and LPS have immunomodulatory features in chickens, albeit in opposite directions. In addition, KLH acted in an immunomodulatory role too. Possible mechanisms underlying our observations and the role of LTA and LPS in polarization of the specific immune response in chickens are discussed.

Serum haemolytic complement activities in 11 different MHC (B) typed chicken lines

To study the relation between serum complement levels and the chicken MHC (B) complex, complement haemolytic activity was measured in sera from hens from seven pure-bred B-typed White and one Brown Leghorn lines, and three ISA-Warren lines that had been divergently selected for antibody responses to sheep red blood cells (SRBC). Significant differences occurred in the serum haemolytic complement activities, both belonging to the classic (CPW) and the alternative (APW) pathways, among the 11 different haplotyped chicken lines. Hens with high CPW and high APW titres predominantly displayed the B2 or B21 haplotypes. Chickens with low CPW and APW were found in B14 and B15 haplotypes. Haplotype B14 appears to be different in complement levels when present into the pure-bred lines or into the ISA-Warren line selected for low antibody responses to SRBC. Otherwise, the presence of B21 in ISA-Warren line selected for high antibody responses to SRBC does not differ with the B21 in the inbred lines (except in the NL-line for CPW values). In general the haplotypes B2 and B21 are found in chicken lines with enhanced disease resistance, and the B15 haplotype has been connected with enhanced disease susceptibility. Our results suggest that levels of haemolytic complement activity, either from the classical or from the alternative pathways, may underlie part of the immunocompetence ascribed to the MHC (B) complex in chickens.