Efficacy of a Salmonella live vaccine for turkeys in different age groups and antibody response of vaccinated and non-vaccinated turkeys.

OBJECTIVE: Human Salmonellosis continues to be one of the most important foodborne zoonoses worldwide, although a decrease in case numbers has been noted in recent years. It is a foodborne zoonotic infection most commonly associated with the consumption of raw egg products but also with meat consumption including the consumption of poultry products. Turkey flocks in Europe have been reported to be affected by Salmonella infection, too. The present study examines the efficacy of a newly licensed Salmonella life vaccine in reducing infections with the Salmonella serovars Typhimurium and Enteritidis in turkeys. Turkeys were vaccinated the first day of life and at the age of 6 and 16 weeks. Groups of birds which had received different numbers of vaccinations were then submitted to challenge trials with either SE or ST. RESULTS: In vaccinated birds Salmonella counts in liver and spleen and, less effectively, in caecum were reduced compared to unvaccinated birds. In several groups serum antibody-titers were statistically significantly higher in vaccinated turkeys than in non-vaccinated ones at day seven post infection, but only in one out of six groups at day 14 post infection.

Antibody titers in turkeys increase after multiple booster vaccinations with an attenuated Salmonella live vaccine.

OBJECTIVE: Human Salmonellosis is one of the most frequently reported foodborne zoonoses in the European Union. The most common source of human infections is the consumption of poultry products. Besides management and hygiene practices vaccination of poultry livestock is seen as one way to reduce Salmonella infections in humans. Turkey flocks in Europe are frequently infected with Salmonella and until recently there was no live vaccine for turkeys available. The aim of the present study was to examine the development of humoral antibodies after repeated vaccination with a bivalent live Salmonella vaccine containing attenuated Salmonella Typhimurium and Salmonella Enteritidis strains. Furthermore the colonization of the caecum with the vaccine strains and their spread to liver and spleen as well as the course of their fecal excretion was observed. RESULTS: Antibody production was hardly detectable after the first vaccination but increased after booster vaccinations. Both the Salmonella Enteritidis and the Salmonella Typhimurium vaccine strain were reisolated from caecum contents and organ samples. After booster vaccinations the re-isolation rates were reduced. The shedding of the vaccine strains was most pronounced after the first vaccination.

Immune response to Salmonella infections in vaccinated and non-vaccinated turkeys.

Vaccination has been widely used to reduce the Salmonella burden in poultry and subsequently the transmission to humans. Concerning turkey, there is little knowledge on the immune response to colonization and invasion by Salmonella species or about efficacy of vaccination and involved immune mechanisms. In the present study, turkeys were vaccinated at the day of hatch and infected with Salmonella Typhimurium (ST) or Enteritidis (SE) field strains three weeks later. A control group was kept uninfected. After challenge infection, bacterial counts in the cecal content, liver and spleen were determined 7 and 14days post infection. They were often statistically significantly lower in vaccinated poults than in non-vaccinated ones. Production of iNOS, and the cytokines IL-8, IL-10 and IFN-γ were reduced in vaccinated birds. However, neither the influx of CD4+, CD8α+ and CD28+ cells into cecal mucosa after infection nor the antibody response were statistically significantly altered in vaccinated birds.

Immune response of turkey poults exposed at 1 day of age to either attenuated or wild Salmonella strains.

Salmonellosis is a foodborne zoonosis that is most often acquired by consuming poultry products such as eggs and poultry meat. Amongst other measures the vaccination of food-producing poultry is thought to contribute to a reduction in human salmonellosis. In the European Union (EU) in 2014 the licence of a commercially available Salmonella vaccine for chickens and ducks was extended to turkeys. In the present study, we examined the course of infection with a virulent Salmonella enterica ssp. enterica serovar Enteritidis (SE) strain, a virulent S. enterica ssp. enterica serovar Typhimurium (ST) strain, and the respective live vaccine containing attenuated strains of both serovars in turkey poults. Besides collecting microbiological data and detecting invading Salmonella in the caecal mucosa via immunohistochemistry, we also assessed immune reactions in terms of antibody production, influx of CD4-, CD8α- and CD28-positive cells into the caecal mucosa and the expression of four different immune-related proteins. We found that the attenuated strains were able to invade the caecum, but to a lower degree and for a shorter duration of time compared to virulent strains. Infections with virulent Salmonellae also caused an increase in CD4-, CD8α- and CD28-positive cells in the caecal mucosa and an increased transcription of iNOS, IL-8-like chemokines, and IFN-γ. In poults treated with attenuated bacteria we could not detect any evidence of immune responses. In conclusion, the vaccine showed a lower degree of caecal invasion and induced weaker immune reactions compared to the virulent Salmonella strains in turkeys. The efficiency of the vaccine has to be verified in future studies.

Differences in the tissue tropism to chicken oviduct epithelial cells between avian coronavirus IBV strains QX and B1648 are not related to the sialic acid binding properties of their spike proteins.

The avian coronavirus (AvCoV) infectious bronchitis virus (IBV) is a major poultry pathogen. A characteristic feature of IBV is the occurrence of many different strains belonging to different serotypes, which makes a complete control of the disease by vaccinations a challenging task. Reasons for differences in the tissue tropism and pathogenicity between IBV strains, e.g. a predilection for the kidneys or the oviduct are still an open question. Strains of the QX genotype have been major pathogens in poultry flocks in Asia, Europe and other parts of the world. They are the cause of severe problems with kidney disease and reproductive tract disorders. We analysed infectivity and binding properties of the QX strain and compared them with those of the nephropathogenic strain B1648. As most IBV strains do not infect permanent cell lines and show infection only in primary chicken cells of the target organs, we developed a culture system for chicken oviduct explants. The epithelial cells of the oviduct showed a high susceptibility to infection by the QX strain and were almost resistant to infection by the nephropathogenic B1648 strain. Binding tests with isolated primary oviduct epithelial cells and soluble S1 proteins revealed that S1 proteins of two IBV strains bound with the same efficiency to oviduct epithelial cells. This attachment was sialic acid dependent, indicating that the sugar binding property of IBV spike proteins is not the limiting factor for differences in infection efficiency for the oviduct of the corresponding viruses.

Sialic acid binding properties of soluble coronavirus spike (S1) proteins: differences between infectious bronchitis virus and transmissible gastroenteritis virus.

The spike proteins of a number of coronaviruses are able to bind to sialic acids present on the cell surface. The importance of this sialic acid binding ability during infection is, however, quite different. We compared the spike protein of transmissible gastroenteritis virus (TGEV) and the spike protein of infectious bronchitis virus (IBV). Whereas sialic acid is the only receptor determinant known so far for IBV, TGEV requires interaction with its receptor aminopeptidase N to initiate infection of cells. Binding tests with soluble spike proteins carrying an IgG Fc-tag revealed pronounced differences between these two viral proteins. Binding of the IBV spike protein to host cells was in all experiments sialic acid dependent, whereas the soluble TGEV spike showed binding to APN but had no detectable sialic acid binding activity. Our results underline the different ways in which binding to sialoglycoconjugates is mediated by coronavirus spike proteins.

Ablation of vitamin D signaling rescues bone, mineral, and glucose homeostasis in Fgf-23 deficient mice.

To explore further the role of the vitamin D axis for fibroblast growth factor-23 (FGF23) signaling, we mated Fgf-23 deficient (Fgf-23(-/-)) mice and vitamin D receptor (VDR) mutant mice with a non-functioning VDR. To prevent secondary hyperparathyroidism in VDR and compound mutant mice, all mice were kept on a rescue diet enriched with calcium, phosphorus, and lactose. Consistent with previous findings, Fgf-23(-/-) animals showed hypercalcemia, hyperphosphatemia, growth retardation, ectopic calcifications, severe osteoidosis, skin atrophy, and renal dysfunction. In addition, here we describe that Fgf-23(-/-) mice are hypoglycemic, and have profoundly increased peripheral insulin sensitivity and improved subcutaneous glucose tolerance, but normal renal expression of the aging suppressor gene Klotho. Although VDR and double mutants on the rescue diet still had moderately elevated parathyroid hormone serum levels and lower bone mineral density compared to wild-type mice, double mutant mice were normocalcemic and normophosphatemic, and had normal body weight, normal renal function, and no ectopic calcifications. Ablation of vitamin D signaling in compound mutants also normalized subcutaneous glucose tolerance tests and insulin secretory response. In conclusion, our results indicate that the alterations in mineral and carbohydrate metabolism present in Fgf-23(-/-) mice require an intact vitamin D signaling pathway.

Homozygous ablation of fibroblast growth factor-23 results in hyperphosphatemia and impaired skeletogenesis, and reverses hypophosphatemia in Phex-deficient mice.

Fibroblast growth factor-23 (FGF-23), a recently identified molecule that is mutated in patients with autosomal dominant hypophosphatemic rickets (ADHR), appears to be involved in the regulation of phosphate homeostasis. Although increased levels of circulating FGF-23 were detected in patients with different phosphate-wasting disorders such as oncogenic osteomalacia (OOM) and X-linked hypophosphatemia (XLH), it is not yet clear whether FGF-23 is directly responsible for the abnormal regulation of mineral ion homeostasis and consequently bone development. To address some of these unresolved questions, we generated a mouse model, in which the entire Fgf-23 gene was replaced with the lacZ gene. Fgf-23 null (Fgf-23-/-) mice showed signs of growth retardation by day 17, developed severe hyperphosphatemia with elevated serum 1,25(OH)2D3 levels, and died by 13 weeks of age. Hyperphosphatemia in Fgf-23-/- mice was accompanied by skeletal abnormalities, as demonstrated by histological, molecular, and various other morphometric analyses. Fgf-23-/-) mice had increased total-body bone mineral content (BMC) but decreased bone mineral density (BMD) of the limbs. Overall, Fgf-23-/- mice exhibited increased mineralization, but also accumulation of unmineralized osteoid leading to marked limb deformities. Moreover, Fgf-23-/- mice showed excessive mineralization in soft tissues, including heart and kidney. To further expand our understanding regarding the role of Fgf-23 in phosphate homeostasis and skeletal mineralization, we crossed Fgf-23-/- animals with Hyp mice, the murine equivalent of XLH. Interestingly, Hyp males lacking both Fgf-23 alleles were indistinguishable from Fgf-23/-/ mice, both in terms of serum phosphate levels and skeletal changes, suggesting that Fgf-23 is upstream of the phosphate regulating gene with homologies to endopeptidases on the X chromosome (Phex) and that the increased plasma Fgf-23 levels in Hyp mice (and in XLH patients) may be at least partially responsible for the phosphate imbalance in this disorder.