Immune Regulatory Effects of Enteromorphaclathrata Polysaccharides on Nd Attenuated Vaccine in a Chicken Model Infected with Reticuloendotheliosis Virus

ABSTRACT Reticuloendotheliosis virus (REV) infection has frequently affected the poultry industry in recent years. The infection with REV weakens the immune responses of the infected poultry. It is reported that Enteromorphaclathrata polysaccharides are capable of regulating immune function. In order to investigate the immuno regulatory effects of Enteromorphaclathrata polysaccharides (EPS) on the response of REV-infected broilers to a live attenuated Newcastle disease (ND) vaccine. Broilers were intraperitoneally injected with REV at one day of age, subcutaneously infected with EPS at 2 days of age, and vaccinated by nasal drip with a live attenuated ND (Lasota strain) vaccine at 5 days of age. Immune organ index, secretory immunoglobulinA (SIgA), peripheral blood heterophil to lymphocyte ratios (H/L ratio), peripheral blood lymphocyte transformation rates, and interferon-gamma (IFN-γ) and interleukin-2 (IL-2) levels were measured at 3, 7, 14, 21, 28, 35, 42, and 56 days of age. The results showed that EPS increased the immune organ index, and the secretion of small intestine secretory immunoglobulin A, serum ND antibody titers, blood H/L ratio, peripheral blood lymphocyte transformation rates, and IL-2 and IFN-γ levels. These results indicate that EPS are able to enhance the immune responses of chickens both to REV infection and to ND vaccination. Therefore, Enteromorphaclathrata polysaccharides can be considered as an immune regulator in the future.