The immune adjuvant effect of Astragalus polysaccharide on in ovo injection of Newcastle disease vaccine

Abstract In this study, immunogenic efficacies of in ovo administration of Astragalus polysaccharide (APS) along with live Newcastle disease vaccine (live ND vaccine) (live VG/GA strain) were evaluated. Four hundred fertilized eggs were randomly divided into four groups ( n = 100/group), and vaccinated in ovo, respectively, with solutions of APS, live ND vaccine, live ND vaccine combined with APS, and 0.9% physiological saline into their amniotic fluid on d 18.5 of incubation. Significant improvement of chicks’ development was displayed in those vaccinated with live ND vaccine adjuvanted with APS in ovo , manifested as enhanced hatchability and gaining weight. Moreover, in ovo administration of live NDV vaccine plus APS could significantly enhance the serum anti‐NDV antibody titres and interferon gamma (IFN‐γ), interleukin (IL)‐2, IL‐4 and IL‐6 concentrations, promote lymphocyte proliferative capability as well as improve the frequencies of CD4 + and CD8 + T cells in peripheral blood. Overall results indicated in ovo administration of live ND vaccine adjuvanted with APS could stimulate stronger humoral and cellular responses in newly hatched chicks.