A recent study has suggested that yeast cell wall product (YP) enhanced serum hemagglutination inhibition (HI) titers and intestinal sIgA responses in chickens immunized with Newcastle disease virus (NDV) vaccine. In the present study, the cell-mediated immune responses elicited by NDV and YP were investigated in commercial broilers. Broilers were fed 0 or 0.1% YP and immunized with a live NDV vaccine via an intraocular-and-intranasal route at 14 and 28 days old. After that, blood samples were collected for determination of HI titer, cytokine content, and blood analysis. Eight chickens were randomly selected from each group and sacrificed. Lymphocytes were harvested from the spleens for lymphocyte proliferation and flow cytometry analysis. Total RNA was extracted from spleen and jejunum for RT-qPCR analysis. The results showed that YP significantly increased serum concentration of IL-4, IL-6, IFN-γ, TNF-β, as well as promoted lymphocytes proliferation in broilers immunized with NDV vaccine. The enhanced cell-mediated immunity is correlated with the upregulated mRNA expression of TGF-β, IL-6, TLR5, GATA-3, and T-bet in the spleen and upregulated mRNA expression of CCR-9, J-chain, pIgR, and TLR3 in the jejunum of chickens. It is noteworthy that no significant side effect was observed after the administration of YP. Therefore, YP could be safely used as potential immunopotentiator assisting NDV vaccine for chickens.
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