Protective efficacy of classical vaccines and vaccination protocols against an exotic Newcastle disease virus genotype VII.2 in Belgian layer and broiler chickens.

Vaccination against Newcastle disease (ND) has been routinely implemented in the Belgian professional poultry sector since 1993, using genotype I and II vaccines. Despite this, an outbreak of genotype VII.2 avian paramyx-ovirus 1 (APMV-1) occurred in 2018, with 20 reported cases over the course of 3 months.

Immunogenicity and protective efficacy of a multivalent herpesvirus vectored vaccine against H9N2 low pathogenic avian influenza in chicken.

The application of recombinant herpesvirus of turkey, expressing the H9 hemagglutinin gene from low pathogenic avian influenza virus (LPAIV) H9N2 and the avian orthoavulavirus-1 (AOAV-1) (commonly known as Newcastle Disease virus (NDV)) fusion protein (F) as an rHVT-H9-F vaccine, is an alternative to currently used classical vaccines. This study investigated H9- and ND-specific humoral and mucosal responses, H9-specific cell-mediated immunity, and protection conferred by the rHVT-H9-F vaccine in specific pathogen-free (SPF) chickens. Vaccination elicited systemic NDV F- and AIV H9-specific antibody response but also local antibodies in eye wash fluid and oropharyngeal swabs.

Protection conferred by an H5 DNA vaccine against highly pathogenic avian influenza in chickens: The effect of vaccination schedules.

H5 highly pathogenic avian influenza (HPAI) viruses of the Asian lineage (A/goose/Guangdong/1/96) belonging to clade 2.3.4.

Molecular and virological characterization of the first poultry outbreaks of Genotype VII.2 velogenic avian orthoavulavirus type 1 (NDV) in North-West Europe, BeNeLux, 2018.

After two decades free of Newcastle disease, Belgium encountered a velogenic avian orthoavulavirus type 1 epizootic in 2018. In Belgium, 20 cases were diagnosed, of which 15 occurred in hobby flocks, 2 in professional poultry flocks and 3 in poultry retailers. The disease also disseminated from Belgium towards the Grand Duchy of Luxembourg by trade.

Effectiveness of a Simultaneous rHVT-F(ND) and rHVT-H5(AI) Vaccination of Day-Old Chickens and the Influence of NDV- and AIV-Specific MDA on Immune Response and Conferred Protection.

The recombinant herpesvirus of turkey (rHVT) vaccines targeting Newcastle disease (ND) and H5Nx avian influenza (AI) have been demonstrated efficient in chickens when used individually at day-old. Given the practical field constraints associated with administering two vaccines separately and in the absence of a currently available bivalent rHVT vector vaccine expressing both F(ND) and H5(AI) antigens, the aim of this study was to investigate whether interference occurs between the two vaccines when simultaneously administered in a single shot. The studies have been designed to determine (i) the ND and AI-specific protection and antibody response conferred by these vaccines inoculated alone or in combination at day-old, (ii) the influence of maternally-derived antibodies (MDA), and (iii) the potential interference between the two vaccine.

Atypical Pathogenicity of Avian Influenza (H3N1) Virus Involved in Outbreak, Belgium, 2019.

In 2019, an outbreak of avian influenza (H3N1) virus infection occurred among commercial poultry in Belgium. Full-genome phylogenetic analysis indicated a wild bird origin rather than recent circulation among poultry. Although classified as a nonnotifiable avian influenza virus, it was associated with reproductive tropism and substantial mortality in the field.

Cytokine production and phenotype of Histomonas meleagridis-specific T cells in the chicken.

The protozoan parasite Histomonas meleagridis is the causative agent of the re-emerging disease histomonosis of chickens and turkeys. Due to the parasite's extracellular occurrence, a type-2 differentiation of H. meleagridis-specific T cells has been hypothesized.

Study of the underlying mechanisms and consequences of pathogenicity differences between two in vitro selected G1-H9N2 clones originating from a single isolate.

The G1-H9N2 avian influenza virus (AIV) has caused significant economic losses in the commercial poultry industry due to reduced egg production and increased mortality. The field observations have shown that H9N2 viruses circulate and naturally mix with other pathogens and these simultaneous infections can exacerbate disease. To avoid an incorrect virus characterization, due to co-infection, isolates were purified by in vitro plaque assays.

Early immune responses and profiling of cell-mediated immunity-associated gene expression in response to rHVT-IBD vaccination.

Infectious bursal disease (IBD) remains a major threat to the poultry industry. Recombinant herpesvirus of turkey (rHVT)-IBD vaccines have been successfully used to induce a protective immune response against IBD. However, the capacity for rHVT-IBD vaccines to induce early protection without detectable antibodies, and the underlying mechanisms mediating specific cell-mediated responses in the early stages following vaccination, have been poorly investigated.

Characterization of two recombinant HVT-IBD vaccines by VP2 insert detection and cell-mediated immunity after vaccination of specific pathogen-free chickens.

Infectious bursal disease (IBD) is an avian viral disease that causes severe economic losses in the poultry industry worldwide. The live IBD virus (IBDV) has a potential immunosuppressive effect. Currently available IBDV vaccines have shortcomings, prompting the development of safer and more effective vaccination approaches, including the use of the recombinant turkey herpesvirus vaccine expressing the immunogenic structural VP2 protein of IBDV (recombinant HVT (rHVT)-IBD).

Experimental and Field Results Regarding Immunity Induced by a Recombinant Turkey Herpesvirus H5 Vector Vaccine Against H5N1 and Other H5 Highly Pathogenic Avian Influenza Virus Challenges.

Vaccination against H5N1 highly pathogenic avian influenza (AI) virus (HPAIV) is one of the possible complementary means available for affected countries to control AI when the disease has become, or with a high risk of becoming, endemic. Efficacy of the vaccination against AI relies essentially, but not exclusively, on the capacity of the vaccine to induce immunity against the targeted virus (which is prone to undergo antigenic variations), as well as its capacity to overcome interference with maternal immunity transmitted by immunized breeding hens to their progeny. This property of the vaccine is a prerequisite for its administration at the hatchery, which assures higher and more reliable vaccine coverage of the populations than vaccination at the farm.

Comparison of single 1-day-old chick vaccination using a Newcastle disease virus vector with a prime/boost vaccination scheme against a highly pathogenic avian influenza H5N1 challenge.

Avian influenza (AI) vaccines should be used as part of a whole comprehensive AI control programme. Vectored vaccines based on Newcastle disease virus (NDV) are very promising, but are so far licensed in only a few countries. In the present study, the immunogenicity and protection against a highly pathogenic H5N1 influenza challenge were evaluated after vaccination with an enterotropic NDV vector expressing an H5 haemagglutinin (rNDV-H5) in 1-day-old specific pathogen free chickens inoculated once, twice or once followed by a heterologous boost with an inactivated H5N9 vaccine (iH5N9).

Infectious Bursal Disease: a complex host-pathogen interaction.

Infectious Bursal Disease (IBD) is caused by a small, non-enveloped virus, highly resistant in the outside environment. Infectious Bursal Disease Virus (IBDV) targets the chicken's immune system in a very comprehensive and complex manner by destroying B lymphocytes, attracting T cells and activating macrophages. As an RNA virus, IBDV has a high mutation rate and may thus give rise to viruses with a modified antigenicity or increased virulence, as emphasized during the last decades.

Measurement of systemic and local respiratory cell-mediated immunity after influenza infection in chickens.

The detection of ChIFN production after ex vivo antigenic-stimulation of T-lymphocytes has been evaluated for the first time, as a tool to assess cell-mediated immunity (CMI) after avian influenza (AI) infection in 10-day-old SPF chickens. Preliminarily, recall antigens have been produced either by concentrating and inactivating the whole virus or by dissociating the viral proteins. Biologically and structurally intact forms of the viral proteins were isolated by non-ionic detergents while heating, chemical agents and ionic detergent used for virus inactivation altered the antigenic viral components.

The positive adjuvant effect of chitosan on antigen-specific cell-mediated immunity after chickens vaccination with live Newcastle disease vaccine.

The development of safe, novel strong adjuvants is necessary to maximize the efficacy of and the immune response induced by new and/or available vaccines administered through the mucosal route to chickens. Chitosan is a non-toxic, biocompatible, biodegradable and natural polysaccharide derived from the exoskeleton of crustaceans and insects. It has been demonstrated to be an effective absorption enhancer to improve mucosal delivery of peptide and protein drugs in human and mice.

Improved vaccination against Newcastle disease by an in ovo recombinant HVT-ND combined with an adjuvanted live vaccine at day-old.

The continuous outbreaks of fatal Newcastle disease (ND) in commercial poultry flocks demonstrate that current vaccination strategies are not fully efficacious and should be improved by new generation of vaccines. In this context, maternally immune conventional layer chickens were vaccinated in ovo with a turkey herpesvirus recombinant expressing the fusion (F) gene of NDV (rHVT-ND) and/or at day-old with an apathogenic enterotropic live ND vaccine co-administrated or not with chitosan by oculo-nasal route. The induced vaccinal immune responses and conferred protection against a challenge with a circulating NDV velogenic viscerotropic strain were evaluated.

Humoral, cell-mediated and mucosal immunity induced by oculo-nasal vaccination of one-day-old SPF and conventional layer chicks with two different live Newcastle disease vaccines.

To further characterize the immune response elicited by two live Newcastle disease vaccines, humoral, cellular and mucosal immunity was evaluated after oculo-nasal vaccination of day-old chickens. The preferential replication sites for each vaccine strain were investigated by screening different tissues using quantitative real-time reverse transcription-polymerase chain reaction (QRRT-PCR). The interference of maternally derived antibody with vaccination was also considered in conventional layer chickens.

Pivotal role of ChIFNgamma in the pathogenesis and immunosuppression of infectious bursal disease.

This study investigates the pivotal role of chicken interferon-gamma (ChIFNgamma) in the pathogenesis and immunosuppression of infectious bursal disease virus (IBDV) infection and is divided into in vivo, ex vivo and in vitro experiments. Two-week-old specific pathogen free chickens were inoculated with the 849VB very virulent strain of IBDV. The levels of systemic ChIFNgamma and chicken interleukin-6 in the serum were followed for 2 weeks during in vivo experiments.

Kinetic and biologic properties of recombinant ChIFN-gamma expressed via CELO-virus vector.

In this study, a replicative fowl adenovirus serotype 1 (CELO) recombinant expressing chicken interferon-gamma (ChIFN-gamma) was constructed. In the engineered recombinant, the ChIFN-gamma gene was placed under the control of cytomegalovirus (CMV) promoter. The ChIFN-gamma expression cassette was inserted in the right end of the CELO genome (D fragment), which was able to carry the largest insertion of foreign DNA without affecting the replication functions of the vector.