Jackdaw nestlings rapidly increase innate immune function during the nestling phase but no evidence for a trade-off with growth.

Although animals are born with a protective immune system, even the innate immune system is under development from birth to adulthood and this development may be affected by sex and growth. However, most knowledge comes from captive animals or long-lived slow growing species. Moreover, little is known about how innate immune function, the important first line of defence, develops during early life in fast-growing animals such as free-living passerines. We studied development of innate baseline immune function in nestlings of free-living jackdaws Corvus monedula. We measured four immune parameters (hemolysis, hemagglutination, bacterial-killing capacity, haptoglobin concentration) and structural body size (body mass, wing length, tarsus length) at day 12 and day 29 post-hatching. We found that three out of four immune parameters (hemolysis, hemagglutination, bacterial-killing capacity) substantially increased with nestling age and had roughly reached adult levels shortly prior to fledging. We found little differences in immune development between males and females despite them differing in structural development. We also found no evidence that the nestlings traded off immune development with growth. That nestlings rapidly increase innate baseline immune function during early life and similarly in males and females indicates the importance of a well-functioning immune system already during the nestling phase.

Characterization of Chicken Tumor Necrosis Factor-α, a Long Missed Cytokine in Birds.

Tumor necrosis factor-α (TNF-α) is a pleiotropic cytokine playing critical roles in host defense and acute and chronic inflammation. It has been described in fish, amphibians, and mammals but was considered to be absent in the avian genomes. Here, we report on the identification and functional characterization of the avian ortholog. The chicken TNF-α (chTNF-α) is encoded by a highly GC-rich gene, whose product shares with its mammalian counterpart 45% homology in the extracellular part displaying the characteristic TNF homology domain. Orthologs of chTNF-α were identified in the genomes of 12 additional avian species including Palaeognathae and Neognathae, and the synteny of the closely adjacent loci with mammalian TNF-α orthologs was demonstrated in the crow (Corvus cornix) genome. In addition to chTNF-α, we obtained full sequences for homologs of TNF-α receptors 1 and 2 (TNFR1, TNFR2). chTNF-α mRNA is strongly induced by lipopolysaccharide (LPS) stimulation of monocyte derived, splenic and bone marrow macrophages, and significantly upregulated in splenic tissue in response to i.v. LPS treatment. Activation of T-lymphocytes by TCR crosslinking induces chTNF-α expression in CD4+ but not in CD8+ cells. To gain insights into its biological activity, we generated recombinant chTNF-α in eukaryotic and prokaryotic expression systems. Both, the full-length cytokine and the extracellular domain rapidly induced an NFκB-luciferase reporter in stably transfected CEC-32 reporter cells. Collectively, these data provide strong evidence for the existence of a fully functional TNF-α/TNF-α receptor system in birds thus filling a gap in our understanding of the evolution of cytokine systems.

Susceptibility of Carrion Crows to Experimental Infection with Lineage 1 and 2 West Nile Viruses.

West Nile virus (WNV) outbreaks in North America have been characterized by substantial die-offs of American crows (Corvus brachyrhynchos). In contrast, a low incidence of bird deaths has been observed during WNV epidemic activity in Europe. To examine the susceptibility of the western European counterpart of American crows, we inoculated carrion crows (Corvus corone) with WNV strains isolated in Greece (Gr-10), Italy (FIN and Ita09), and Hungary (578/10) and with the highly virulent North American genotype strain (NY99). We also inoculated American crows with a selection of these strains to examine the strains' virulence in a highly susceptible bird species. Infection with all strains, except WNV FIN, resulted in high rates of death and high-level viremia in both bird species and virus dissemination to several organs. These results suggest that carrion crows are highly susceptible to WNV and may potentially be useful as part of dead bird surveillance for early warning of WNV activity in Europe.

Identification of antibodies against hydropericardium syndrome in wild birds.

1. Domestic fowl and free-living birds were examined for the presence or absence of antibodies against hydropericardium syndrome (HPS) using an indirect haemagglutination assay. 2. Two-hundred and eighty serum samples of commercial (45 broilers, 20 adult layers and 15 Fayoumi fowl) and wild birds, including 65 peafowl, 45 pigeons, 10 crows, 30 house sparrows, 10 doves, 15 ducks, 10 parrots and 15 guinea fowl, were collected and examined. 3. The percentage of HPS-positive serum samples was 80% in house crows, 78% in pigeons, 7% in house sparrows and 6% in peafowl. 4. The sera obtained from parrots, doves, ducks and guinea fowl were all negative. 5. This study suggests that crows and pigeons could be carriers of the HPS agent.

Yolk androgens and the development of avian immunity: an experiment in jackdaws (Corvus monedula).

Maternally derived androgens have been shown to influence offspring phenotype in various ways. In birds, the benefits of prenatal androgen exposure, such as increased competitiveness and accelerated growth in nestlings, have been suggested to be balanced by costs, such as reduced immune function. In this study, we used an integrative approach to examine the influence of yolk androgens on the development of immune function in jackdaw (Corvus monedula) nestlings. Specifically, we tested whether the effects of yolk androgens on offspring immunity may extend over the first few days of life and be detectable even after several weeks. We manipulated yolk androgen concentrations in jackdaw eggs and estimated immune responsiveness by challenging the young with different pathogens at different stages of the nestling period. Six-day-old chicks hatched from eggs with elevated yolk androgen levels had lower pre-challenge antibody titres against lipopolysaccharide (LPS) than control chicks. However, antibody titres against LPS did not differ between treatment groups eight days after a challenge with LPS. During the late nestling phase, both humoral (towards diphtheria/tetanus antigens) and cell-mediated (towards phytohaemagglutinin) immune responsiveness were lower in chicks from yolk androgen-treated eggs compared with control chicks. Our experimental study on jackdaw chicks shows that elevated yolk androgen levels result in a general immunosuppression in offspring; this conclusion was based on results for several immunological tests of both humoral and cell-mediated immunity conducted at 1-2 and 3-4 weeks of age.

West Nile virus antibody prevalence in American crows (Corvus brachyrhynchos) and fish crows (Corvus ossifragus) in Georgia, USA.

Crows have been the centerpiece of avian West Nile virus (WNV) surveillance and research in North America. This work has demonstrated variation in susceptibility to WNV infection between American (Cor vus brachyrhynchos) andFish Crows (Corvus ossifragus). The higher WNV-associated mortality rate in American Crows compared with Fish Crows suggests that WNV antibody prevalence would be greater in the Fish Crow population. The objectives of this study were to 1) determine whether Fish Crows had higher WNV antibody prevalencethan American Crows, 2 ) determine th e persistence o f antibodies to WNV in naturally infected Fish Crows, and 3) develop a technique to distinguish Fish Crows from American Crows on the basis of sequence analysis and restriction enzyme digestion of a mitochondrial DNA fragment. West Nile virus antibody prevalence was 16.5% (n = 97) in Fish Crows and 5.7% in American Crows (n = 53) collected from Georgia between 2004 and 2006. Antibodies persisted at high titers for 12 mo in Fish Crows. This is the first report of WNV antibody persistence in a crow species. A polymerase chain reaction technique paired with restriction enzyme digestion easily distinguished American Crows from Fish Crows on the basis of a mitochondrial DNA fragment.

[Immune response of jackdaw (Corvus monedula) to antigens of Capillaria resecta (Nematoda)-western blotting analysis]. / Odpowiedz immunologiczna kawki (Corvus monedula) przeciwko antygenom nicienia Capillaria resecta--technika western blotting.

Biotinylated surface and somatic protein extracts of the nematode Capillaria resecta were analysed by SDS-PAGE followed by Western blotting in order to examine their antigenic character. The antigens were probing with serum of C. resecta naturally infected birds (jackdaws). Surface and somatic antigens were recognised by serum IgG, IgA and IgM antibodies. The most intense reactivity of sera was evident with TBS-soluble surface proteins. The present paper has shown that surface proteins of C. resecta are more immunogenic than somatic and they are able to elicit stronger immune response in the bird's body.