Immunoenhancement on Newcastle disease virus La Sota strain attenuated vaccine by pig spleen transfer factor

Abstract:

[Objective] We evaluated the immunoenhancement effect and mechanism of pig spleen transfer factor (TF) on Newcastle disease virus (NDV) La Sota strain attenuated vaccine to provide a theoretical basis for the prevention and control of Newcastle disease (ND). [Methods] We inoculated La Sota strain alone and La Sota combined with TF into specific pathogen free (SPF) chickens at four different doses, and challenged SPF chickens by reference virulent NDV strain F₄₈E₉ (10^4.7 ELD₅₀) 14 days post vaccination. In addition, we determined the concentrations of IL-6, IL-10, IL-16, and IL-21 in chicken peripheral blood by protein chip technology, the hemagglutination inhibition (HI) antibody titer by HI assay, and the viremia level of F₄₈E₉ by RT-PCR. [Results] The challenge test showed that the protection rates of vaccination with La Sota strain alone at the doses of 10^5.17, 10^4.17, 10^3.17, and 10^2.17 EID₅₀ were 100%, 55%, 0%, and 0%, respectively, and the median protective dose (PD₅₀) was 12 023 EID₅₀. The protection rates of vaccination with La Sota strain combined with TF at the corresponding doses were 100%, 75%, 0%, and 0%, respectively, and the PD₅₀ was 6 918 EID₅₀. The mortality of control group (non-immunized but challenged) and blank group (non-immunized and non-challenged) were 100% and 0%. Upon vaccination at the dose of 10^4.17 EID₅₀, the IL-6, IL-10, IL-21, and ND HI antibody titer (log₂x) of the chicken exposed to combined vaccination increased at most by 254.95 pg/mL, 62.10 pg/mL, 1.51 pg/mL, and 2.6 (P<0.01), respectively, compared with those in the chicken vaccinated with La Sota strain alone. After challenge, the IL-10, IL-16, IL-21, and the viremia levels in the chicken under combined vaccination decreased at most by 428.61 pg/mL, 167.81 pg/mL (P<0.01), 1.48 pg/mL (P<0.01), and 20%, respectively, compared with those in the chicken vaccinated with La Sota strain alone. [Conclusion] TF improves the immune protection rate of NDV attenuated La Sota strain vaccine, the immune response mediated by IL-6, IL-10, and IL-21, and the ND HI antibody titer. In addition, TF reduces the PD₅₀, the inflammatory responses mediated by IL-16 and IL-21, the inhibition of immune response mediated by IL-10, and the viremia after challenge. It is clear that TF has a good immunoenhancement effect on the La Sota strain attenuated vaccine, which will provide a reference for research and development of vaccine adjuvant as well as prevention and control of ND.