Beta-glucan enhanced immune response to Newcastle disease vaccine and changed mRNA expression of spleen in chickens

Yeast β-glucan promotes antiviral type I interferon response via dectin-1

Pseudorabies virus (PRV), an alphaherpesvirus, is a neglected zoonotic pathogen. Dectin-1 sensing of β-glucan (BG) induces trained immunity, which can possibly form a new strategy for the prevention of viral infection. However, alphaherpesvirus including PRV have received little to no investigation in the context of trained immunity. Here, we found that BG pretreatment improved the survival rate, weight loss outcomes, alleviated histological injury and decreased PRV copy number of tissues in PRV-infected mice. Type I interferons (IFNs) including IFN-α/β levels in serum were significantly increased by BG. However, these effects were abrogated in the presence of Dectin-1 antagonist. Dectin-1-mediated effect of BG was also confirmed in porcine and murine macrophages. These results suggested that BG have effects on type I IFNs with antiviral property involved in Dectin-1. In piglets, oral or injected immunization with BG and PRV vaccine could significantly elevated the level of PRV-specific IgG and type I IFNs. And it also increased the antibody levels of porcine reproductive and respiratory syndrome virus vaccine and classical swine fever vaccine that were later immunized, indicating a broad-spectrum effect on improving vaccine immunity. On the premise that the cost was greatly reducing, the immunological effect of oral was better than injection administration. Our findings highlighted that BG induced type I IFNs related antiviral effect against PRV involved in Dectin-1 and potential application value as a feed additive to help control the spread of PRV and future emerging viruses.

Response of broiler breeder pullets when fed hydrolyzed whole yeast from placement to 22 wk of age

The study examined the effects of feeding broiler breeder pullets hydrolyzed whole yeast (HY) from hatch to 22 wk of age (WOA). A total of 524-day-old Ross 708 pullets were placed in floor pens (∼24 birds/pen) for the starter (0-4 WOA) and grower (5-18 WOA) phases, then transferred to the egg production facility and redistributed to ∼20 birds/pen for the prelay phase (19-22 WOA). Two diets were allocated to pens (0-18 WOA; n = 11) and (19-22 WOA; n-12). The diets were a control corn and soybean meal diet formulated to meet specifications and control plus 0.05% HY (HY). Birds had ad libitum access to feed in the first week and daily feed allocation based on pen BW from 2 WOA. Birds had free access to water throughout the trial. Body weight (BW) and uniformity (BW CV) were monitored. Boosters for infectious bronchitis and New Castle disease vaccines were administered at 18 WOA, and samples of pullets bled for antibody titer 5-day later. One pullet/pen was randomly selected, weighed, bled for plasma biochemistry, and necropsied for organ weights, ceca digesta for short-chain fatty acids (SCFA), and leg bones morphometry. In the starter and grower phases, birds fed HY were lighter and gained less (P < 0.05) than control birds. However, there were no diet effects (P > 0.05) on growth, the BW prelay phase, or BW uniformity throughout the trial. There were no (P > 0.05) diet effects on breast, gastrointestinal, liver and bursa weights, serum antibody titers, plasma biochemistry, SCFA and bone attributes. However, pullets fed HY had heavier (P = 0.047) spleen and tended to have lower (P = 0.080) plasma concentrations of aspartate aminotransferase (AST) relative to control pullets. In conclusion, the parameters assessed showed no negative consequences of feeding HY to broiler breeder pullets. However, effects on the spleen and plasma AST may indicate modest modulation of immunity and metabolism. The impact of the provision of HY during broiler breeder pullet phase on reproductive performance and chick quality should be investigated.

The Immunological Basis for Vaccination

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.