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T-cell immune responses were shown to play an important role in the regulation of infectious bursal disease virus (IBDV) replication and development of lesions in the bursa of Fabricius (BF) (bursal lesions) but also in the recovery from the infection. Studies suggested that the host-genotype influences T-cell responses during the acute phase of infection. Genotype-related differences in the recovery phase were not investigated so far. The present study used commercial broiler- (BT), layer- (LT), dual-purpose type (DT) chicken lines as well as a specific pathogen free (SPF) LT chicken as a reference for comparison of T-cell related differences in IBDV-immunopathogenesis not only in the early phase post inoculation (pi) but also in the recovery phase. The Deventer formula was used to determine the optimal time point of inoculation with an intermediate plus IBDV strain when maternally derived antibody (MDA) titers were below the calculated breakthrough level of the virus for all genotypes. Differences in the bursal lesion development, intrabursal CD4+ and CD8+ T-cell accumulation and numbers of IBDV-positive cells were determined. In addition, anti-IBDV antibody development and the relative amount of anti-inflammatory cytokine mRNA were recorded until 28 days post IBDV inoculation. Differences between the genotypes were observed in the duration and magnitude of bursal lesions, CD4+ and CD8+ T-cell infiltration as well as the presence of anti-inflammatory Interleukin (IL)-10 and Transforming growth factor (TGF) β4 cytokine mRNA (P < 0.05). While the investigated immune parameters were comparable between the genotypes at seven days pi, during 14, 21 and 28 days pi a delayed recovery process in LT and DT chickens compared to BT chickens was observed (P < 0.05). Furthermore, the age and residual MDA levels had a genotype-dependent influence on the onset of the anti-IBDV specific humoral and T-cell mediated immune responses. This study suggests, that the impact of T-cell immunity on the recovery process after IBDV infection may need to be considered further for the development of new breeding programs for disease resistant chicken lines., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Despite the importance of Bordetella avium (BA) as a respiratory pathogen of young turkeys, no infection model for the evaluation of BA-vaccine efficacy is available. The objective of this study was to evaluate the influence of route and dose of infection on the establishment of a BA-challenge model. In our first experiment, 28-day-old turkeys were either inoculated oculonasally with 10 5 , 10 7 or 10 9 colony forming units (CFU) of BA per bird or exposed to BA by aerosol with 10 5 -10 8  CFU/m 3 . The respiratory tract of all inoculated birds was BA-colonized, which was confirmed by choanal swabs and samples of trachea and lung, showing the highest prevalence in the aerosol-inoculated group. BA-specific humoral immune response was detected in the form of IgG in serum from five days post infection (dpi) and IgA in lacrimal fluid from seven dpi. In the second experiment, the model was tested in a vaccination trial. Twenty-one-day-old turkeys were vaccinated with a formalin-inactivated BA vaccine intramuscularly and challenged 21 days post vaccination with 10 7  CFU per bird oculonasally. BA-specific IgG antibodies were detected in serum and in lacrimal fluid 14 days post vaccination. As in the first experiment, secretory BA-specific antibodies of the IgA isotype were only detected in the inoculated groups from seven dpi. Despite the lack of clinical signs or pathological alterations in both experiments, vaccine efficacy was demonstrated by significant reduction in BA colonization of the trachea (P ≤ 0.05). In our study, a reliable model for BA infection has been established and has been demonstrated to be suitable for evaluation of vaccine efficacy.

Infectious bursal disease (IBD) is an economically important disease affecting poultry production worldwide. Previous experimental studies indicated that IBD live vaccination may induce transient immunosuppression, leading to suboptimal vaccine responses and therefore insufficient protection against other pathogens. Layer pullets are commonly not only vaccinated against IBD within their rearing period, but also against a variety of other pathogens. Therefore, it is of interest to investigate the effects of different IBD vaccination regimes on conventionally applied vaccines against other pathogens, and possible protection against widely spread very virulent IBD-virus (vvIBDV). A commercially available Herpesvirus of turkey vector vaccine (vHVT-IBD) expressing viral protein 2 of IBDV, and two IBD live vaccines were compared in commercial pullets for their effects on circulating B cell numbers, the ability of vaccinated birds to mount a humoral immune response against different antigens as well as their ability to induce protection against vvIBDV challenge. The results of this study demonstrate a clear immunosuppressive effect of the intermediate plus IBD live vaccine on the humoral branch of the immune system. On the other hand, no detectable effects of vHVT-IBD vaccination on these parameters were observed. All tested IBD vaccines protected against clinical IBD, although none induced sterile immunity in commercial layer pullets. vHVT-IBD-vaccinated birds showed significantly less lesions after vvIBDV challenge than IBD live-vaccinated or non-vaccinated birds (P < 0.05). Therefore, vHVT-IBD may be a suitable alternative to conventional IBD live vaccines, and may be applied even in the presence of maternally derived IBD antibodies without induction of detectable humoral immunosuppression.

While B cell development in the birds' primary B cell organ, the bursa Fabricius, is relatively well understood, very little is known about post bursal B cell differentiation into plasma and memory cells though these cells are essential for a protecting antibody response and so far, no specific markers for these cells were available. Since immunoglobulin class switch is one part of the B cell differentiation process, our objective was to conduct a first detailed investigation of class-switched chicken B cells. As only very few IgY and IgA expressing cells were detected in lymphoid organs of young chickens, we used CD40L and IL-10 to establish a prolonged in vitro culture system, which induces B cell proliferation, class switch to IgY and IgA and enhanced antibody secretion. This enabled a phenotypic analysis of differentiating B cells. Importantly, these cells lost surface expression of the B cell markers chB6 and BAFF-R. B cell receptor surface expression remained unchanged, showing that while differentiating toward plasma cells, B cells can be addressed by L chain staining. Newly generated potential plasma cell markers CD138 and TACI showed only a transient expression on cultured cells and rather act as markers for B cell activation than plasma/memory cells in general. CD57 upregulation was connected to activation and blast formation but not to class switch. We also examined potential changes in class-switched cells in different age groups and post vaccination. Surprisingly, bursa involution, laying and age had no distinct effects on the presence of class-switched cells, but we detected significantly more class-switched B cells post vaccination. Hence, we are now able to generate class-switched plasmablasts in vitro for a more detailed characterization and can address them under different conditions in chickens for further analysis of their B cell response. [ABSTRACT FROM AUTHOR]

Vaccination is crucial for health protection of poultry and therefore important to maintaining high production standards. Proper vaccination requires knowledge of the key players of the well-orchestrated immune system of birds, their interdependence and delicate regulation, and, subsequently, possible modes of stimulation through vaccine antigens and adjuvants. The knowledge about the innate and acquired immune systems of birds has increased significantly during the recent years but open questions remain and have to be elucidated further. Despite similarities between avian and mammalian species in their composition of immune cells and modes of activation, important differences exist, including differences in the innate, but also humoral and cell-mediated immunity with respect to, for example, signaling transduction pathways, antigen presentation, and cell repertoires. For a successful vaccination strategy in birds it always has to be considered that genotype and age of the birds at the time point of immunization as well as their microbiota composition may have an impact and may drive the immune reactions into different directions. Recent achievements in the understanding of the concept of trained immunity will contribute to the advancement of current vaccine types helping to improve protection beyond the specificity of an antigen-driven immune response. The fast developments in new omics technologies will provide insights into protective B- and T-cell epitopes involved in cross-protection, which subsequently will lead to the improvement of vaccine efficacy in poultry. Estudio recapitulativo- Bases inmunológicas de la vacunación. La vacunación es crucial para la protección de la salud de las aves comerciales y por lo tanto, importante para mantener altos estándares de producción. Una vacunación adecuada requiere el conocimiento de los factores clave del sistema inmunológico bien orquestado de las aves, su interdependencia y su delicada regulación y posteriormente, los posibles modos de estimulación a través de antígenos y adyuvantes de las vacunas. El conocimiento sobre los sistemas inmunológicos innato y adquirido de las aves ha aumentado significativamente durante los últimos años, pero quedan preguntas abiertas que deben dilucidarse con profundidad. A pesar de las similitudes entre las especies de aves y mamíferos en la composición de células inmunes y modos de activación, existen diferencias importantes, incluidas las diferencias en la inmunidad innata, pero también en la inmunidad humoral y en la mediada por células, con respecto a las vías de transducción de señales, la presentación de antígenos. y repertorios celulares. Para una estrategia de vacunación exitosa en las aves, siempre se debe considerar que el genotipo y la edad de las aves en el momento de la inmunización, así como la composición de su microbiota pueden tener un impacto y pueden impulsar las reacciones inmunes en diferentes direcciones. Los logros recientes en la comprensión del concepto de inmunidad entrenada contribuirán al avance de los tipos de vacunas actuales que ayudarán a mejorar la protección más allá de la especificidad de una respuesta inmune impulsada por antígenos. Los rápidos avances en las nuevas tecnologías ómicas proporcionarán información sobre los epítopes protectores de las células B y T implicados en la protección cruzada, lo que posteriormente conducirá a la mejora de la eficacia de las vacunas en la avicultura. [ABSTRACT FROM AUTHOR]

Aims: Our aim was to analyse the survival of Enterococcus cecorum (EC) at various temperatures, relative air humidities and on different substrates commonly existing in broiler houses. Methods and Results: A pathogenic EC isolate (EC14) was used to inoculate sterile litter, polyvinyl chloride (PVC) and dust samples. Incubation at 37, 25 or 15°C with either 32% relative humidity (RH) or 78% RH followed. At defined time points (0–4272 h post‐inoculation), samples were examined in triplicate for the total viable count. Selected combinations were repeated for a non‐pathogenic and two additional pathogenic EC strains. For EC14, the measured survival time ranged from 48 to 4272 h (178 days) depending on the substrate–humidity–temperature combination. The longevity was the highest on litter, followed by dust and then PVC. Lower temperatures facilitated its survival, lower relative air humidity favoured the survival only in combination with 25 or 15°C. All three pathogenic strains showed longer survival times (up to 432 h, 18 days) compared to the non‐pathogenic EC strain (168 h, 7 days) under the same conditions. Conclusions: Enterococcus cecorum demonstrates a high persistence in the environment especially at 15°C and 32% RH. Significance and Impact of the Study: Hygiene management plans should consider the durability of EC and the risk of a carry‐over to control consecutive EC outbreaks. [ABSTRACT FROM AUTHOR]

Despite the importance of Bordetella avium (BA) as a respiratory pathogen of young turkeys, no infection model for the evaluation of BA-vaccine efficacy is available. The objective of this study was to evaluate the influence of route and dose of infection on the establishment of a BA-challenge model. In our first experiment, 28-day-old turkeys were either inoculated oculonasally with 105, 107 or 109 colony forming units (CFU) of BA per bird or exposed to BA by aerosol with 105-108 CFU/m3. The respiratory tract of all inoculated birds was BA-colonized, which was confirmed by choanal swabs and samples of trachea and lung, showing the highest prevalence in the aerosol-inoculated group. BA-specific humoral immune response was detected in the form of IgG in serum from five days post infection (dpi) and IgA in lacrimal fluid from seven dpi. In the second experiment, the model was tested in a vaccination trial. Twenty-one-day-old turkeys were vaccinated with a formalin-inactivated BA vaccine intramuscularly and challenged 21 days post vaccination with 107 CFU per bird oculonasally. BA-specific IgG antibodies were detected in serum and in lacrimal fluid 14 days post vaccination. As in the first experiment, secretory BA-specific antibodies of the IgA isotype were only detected in the inoculated groups from seven dpi. Despite the lack of clinical signs or pathological alterations in both experiments, vaccine efficacy was demonstrated by significant reduction in BA colonization of the trachea (P ≤ 0.05). In our study, a reliable model for BA infection has been established and has been demonstrated to be suitable for evaluation of vaccine efficacy. [ABSTRACT FROM AUTHOR]

Riemerella anatipestifer (RA) is the causative agent of septicaemic and exudative diseases in a variety of bird species. Despite numerous outbreaks, little is known about the pathogenicity of RA for turkeys. We investigated the development of RA-induced disease in commercial turkey poults following RA inoculation via different respiratory routes. Inoculation by aerosol or injection into the abdominal air sac led to systemic infection and mild gross lesions, including pericarditis, epicarditis and airsacculitis, which were less pronounced compared with field outbreaks. It was speculated, that viral pathogens, such as the avian metapneumovirus (aMPV), may exacerbate RA pathogenesis under field conditions. We inoculated turkey poults with virulent aMPV. Subsequently, aMPV-infected and virus-free birds were exposed 3 to 5 days later to a high dose of RA by aerosol (>1010 colony-forming units/ml in 8 ml aerosol per 11 or 12 birds) or were inoculated 4 days later with a low RA dose (104.9 colony-forming units per bird) via the intranasal route. Intranasal RA inoculation with the low bacterial dose led to a respiratory and systemic RA infection in aMPV-infected birds, while virus-free birds remained RA-negative. Following exposure to a high RA dose by aerosol, aMPV-infected groups showed slightly enhanced incidences of gross lesions and RA re-isolation. The present study clearly confirms that RA is pathogenic for turkeys after experimental inoculation via respiratory routes, which are speculated to be the natural route of infection. However, experimental models in this study did not reproduce the severity of RA-related disease as observed under field conditions, which emphasizes the importance of other contributing factors. aMPV-induced respiratory lesions may serve as a predisposing factor for the establishment of RA infection, since they favour colonization of the bacterium. [ABSTRACT FROM AUTHOR]

Abstract: Not much is known about IBDV-pathogenesis and immune mechanisms following in ovo vaccination. In this study, we compared the immunopathogenesis of an intermediate IBDV-vaccine in post-hatch- and in ovo-inoculated chickens. In ovo-vaccinated birds recovered significantly faster from lesions of the bursa of Fabricius than post-hatch vaccinated (P &#60;0.05). A significant accumulation of intrabursal CD8+ T cells was observed in post-hatch but not in in ovo-vaccinated chickens (P &#60;0.05). The innate immunity was comparable between in ovo- and post-hatch-vaccinated groups as indicated by comparable intrabursal macrophage accumulation and intrabursal IBDV-clearance. Overall, our observations indicate that IBDV in ovo vaccination may be advantageous over post-hatch. In ovo-vaccinated birds recover faster from bursa lesions and exhibit similar protection against challenge in comparison to post-hatch vaccinated. [Copyright &y& Elsevier]

Abstract: Highly pathogenic avian influenza viruses (HPAIV) of subtypes H5 and H7 cause fatal disease in poultry (fowl plague) but also have zoonotic potential. Currently commercially available vaccines often do not provide sufficient protection and do not allow easy discrimination between vaccinated and infected birds. Therefore, vaccination of domestic poultry against H5 and H7 HPAIV is not allowed in many countries, or is only possible after special permission has been provided. We generated a recombinant marker vaccine based on non-transmissible vesicular stomatitis virus (VSV) expressing the HA antigen of HPAIV A/FPV/Rostock/34 (H7N1) in place of the VSV G gene. This virus, VSV*ΔG(HA), was propagated on a helper cell line providing VSV G in trans. Since no progeny virus was produced after infection of non-complementing cells, the vector was classified as biosafety level 1 organism (“safe”). Chickens were immunized via the intramuscular route. Following booster vaccination with the same replicons high titers of serum antibodies were induced, which neutralized avian influenza viruses of subtypes H7N1 and H7N7 but not H5N2. Vaccinated chickens were protected against a lethal dose of heterologous HPAIV A/chicken/Italy/445/99 (H7N1). Secretion of challenge virus was short-term and significantly reduced. Finally, it was possible to discriminate vaccinated chickens from infected ones by a simple ELISA assay. We propose that VSV replicons have the potential to be developed to high-quality vaccines for protection of poultry against different subtypes of avian influenza viruses. [Copyright &y& Elsevier]

The genotype of chickens is assumed to be associated with variable immune responses. In this study a modern, moderate performing dual-purpose chicken line (DT) was compared with a high-performing layer-type (LT) as well as a broiler-type (BT) chicken line. One group of each genotype was vaccinated in ovo with a recombinant herpesvirus of turkeys expressing the virus protein VP2 of the infectious bursal disease virus (HVT-IBD) while one group of each genotype was left HVT-IBD unvaccinated (control group). Genotype associated differences in innate and adapted immune responses between the groups were determined over five weeks post hatch. HVT-IBD vaccination significantly enhanced humoral immune responses against subsequently applied live vaccines compared to non-HVT-IBD vaccinated groups at some of the investigated time points (P < 0.05). In addition HVT-IBD vaccination had depending on the genotype a significant impact on splenic macrophage as well as bursal CD4+ T-cell numbers (P < 0.05). On the other hand, the detectable genotype influence on Interferon (IFN) γ and nitric oxide (NO) release of ex vivo stimulated spleen cells was independent of HVT-IBD vaccination. The results of our study suggest considering a genotype specific vaccination regime in the field. • HVT-IBD vaccination influences humoral immune responses against other vaccines. • The number of germinal centers in the spleen differs between chicken genotypes and increases after HVT-IBD vaccination. • BT chickens show more vigorous immune responses during the first 35 dph compared to LT and DT chickens. [ABSTRACT FROM AUTHOR]