Cordyceps militaris polysaccharides can improve the immune efficacy of Newcastle disease vaccine in chicken

Abstract

Cordyceps militaris polysaccharide (CMP) was prepared by water decoction and ethanol precipitation. The fractional CMP40 and CMP50 were extracted from the CMP solution by stepwise precipitation with ethanol at 40% and 50% of working concentration, respectively. The immune-enhancing activities of two polysaccharides were researched. In vitro experiment, the effects of two polysaccharides on chicken peripheral lymphocyte proliferation were determined by MTT assay. The result displayed that two polysaccharides could significantly stimulate lymphocyte proliferation, the action of CMP40 was significantly or numerically stronger than those of CMP50. In vivo experiment, 320 14-day-old chickens were averagely divided into eight groups. The chickens, except blank control (BC) group, were vaccinated with Newcastle disease vaccine, repeated vaccination at 28 days old. At the same time of the first vaccination, the chickens in three CMP40 fraction groups and three CMP50 fraction groups were injected respectively with the polysaccharide at low, medium and high concentrations, in vaccination control (VC) and BC group, with equal volume of physiological saline, once a day for three successive days. On days 7, 14, 21, 28, 35 and 42 after the first vaccination, the lymphocyte proliferation, serum antibody titre and interferon-gamma and interleukin-4 were measured. The results showed that CMP40 and CMP50 at suitable dose could significantly promote lymphocyte proliferation, enhance serum antibody titre, and improve serum interferon-gamma and interleukin-4 concentrations. It indicated that CMP40 fraction and CMP50 fraction could significantly improve the immune efficacy of Newcastle disease vaccine, and would be as the candidate of a new-type immune adjuvant.