Enhancement Of Immune Response By Yeast Cell Wall Products In Chickens Immunized With Newcastle Disease Vaccines

Yeast cell wall products(YP)is a polysaccharide complex extracted from yeast cell wall.It’s mainly composed of β-glucan and mannan-oligosaccharides in different proportions.A large number of studies have confirmed that YP can enhanced the humoral immunity in animals.However,there are few reports on the effects of YP on cellular immunity and intestinal mucosal immunity in chickens.In this study,chickens were selected as research subjects and explored the effects of YP on humoral immunity,cellular immunity,intestinal mucosal immunity and intestinal flora.This study will provide an experimental basis for further development of YP as immune enhancer.1.Effect of YP supplementation in diet on humoral immunity and intestinal mucosal immunity in chickensIn order to investigate the immunomodulatory effect of YP on humoral immunity and intestinal mucosal immunity of chickens immunized with Newcastle disease(ND),75 chickens were randomly divided into 5groups,15 layers in each group,namely YP 0.2%,0.1% and 0.05% dose groups(feed supplement),Vaccine group,control group.YP and Vaccine group were orally immunized with ND live vaccine at 2 week of age.Blood was collected 1 and 2 week postimmunization,and the titer of NDV specific antibody in serum was detected by HA-HI.Blood samples and feces were collected from all chickens before and 1,2,3,4 week postimmunization for determination of NDV-specific HI titers or NDV-specific SIg A levels.Chickens were sacrificed at 4 week postimmunization,and duodenum were collected,the number of Ig A+ cells was detected by immunohistochemistry.The results showed that compared with the Vaccine group,the HI titer in 0.05%group did not change significantly during the experiment(P>0.05).The serum HI titer in 0.1% group was significantly increased at 2 week after immunization(P<0.01),and the 0.2% group increased significantly(P<0.05).The content of specific NDV-SIg A and the number of Ig A + cells were significantly increased(P<0.05).These results indicate that dietary YP supplementation can significantly enhance the humoral and intestinal mucosal immunity of Newcastle disease vaccine in chickens,and the optimal supplemental dose is 0.1%.2.Effect of YP supplementation in diet on cellular immunity in chickensTo explore the effect of YP on the cellular immunity of chickens immunized with ND vaccine,60 chickens were randomly divided into 3 groups,20 broilers in each group,namely YP 0.1% dose groups(feed supplement),Vaccine group,control group.The broilers in group YP and Vaccine were received intraocularand-intranasal immunization with a ND live vaccine at 14 and 28 days old.Blood samples were collected before and 1,3 weeks after booster immunization for determination of cytokine content(IFN-γ,IL-6,IL-4,TNF-β and TGF-β1).Lymphocytes were harvested from the spleens for lymphocyte proliferation by MTT assay and flow cytometry analysis at 1 and 3 weeks after booster immunization.Spleen and jejunum were collected 1 week after booster immunization,and the relative expression levels of related genes were detected by real-time quantitative PCR(RT-q PCR)analysis.The results showed that when compared with the Vaccine group,dietary supplementation of YP could significantly increase the stimulation index of spleen lymphocytes to Newcastle disease antigen(P<0.05).And the CD4+/CD8+ ratio increased(P>0.05).IL-4,IL-6,TNF-β and IFN-γ were significantly increased(P<0.05).Results from RT-q PCR showed that YP upregulated the m RNA expression of IL-6,TGF-β,TLR-5,T-bet,GATA-3 genes in the spleen and CCR9,Jchain,p Ig R,TLR3 in the jejunum.It is suggested that the supplement of YP can promote cellular immunity by regulating transcription factors.3.Effect of YP supplementation in diet on cecum microbiome populations in chickensIn order to investigate the effect of YP on gut microbiota,the second generation 16 S sequencing technology was used to detect cecum microbiome populations.12 chickens were randomly divided into 2groups,6 layers in each group,namely YP group and control group.Chickens were orally immunized with ND live vaccine at 2 week of age.The layers in each group were sacrificed and cecum contents were collected for 16 S r RNA sequencing.The sequencing results revealed that there were significant differences in intestinal microflora Alpha diversity index(Chao1,observed species)between the YP group and the control group(P<0.05),and the difference between groups was obvious.At a phylum level,significantly increased abundance of Firmicutes(P<0.05)and Tenericutes(P<0.01)and significantly decreased abundance of Bacteroidetes(P<0.01),and Proteobacteria(P<0.05)were observed in the YP group in comparison with the control group.In the family level,significantly higher abundance of Ruminococcaceae(P<0.05)and significantly lower abundance of Bacteroidaceae(P<0.01),Desulfovibrionaceae(P<0.05),and Tannerellaceae(P<0.05)were detected in the YP group than control.These results suggested that YP supplementation in diet modulated the cecum microbiota to the advantage of the host in chickens.In summary,YP supplementation in diet significantly enhanced immune response in chickens immunized with live NDV vaccine.Supplementation of YP at a dose of 0.1% can significantly increase HI titers and cytokines concentration in serum,SIg A secretion,intestinal mucosal Ig A+ cells,spleen lymphocyte proliferative response and up-regulated immune-related gene level in chickens immunized with ND live vaccine.Meanwhile,supplementation of YP can also modulated the cecum microbiota in chickens.Therefore,YP could be an oral immune enhancer to improve NDV vaccine immunization in chickens.