Sulfated modification can enhance the adjuvant activity of astragalus polysaccharide for ND vaccine

Two hundred 14-day-old chickens were divided randomly into 10 groups. At the same time of vaccination with Newcastle disease vaccine, the chickens in six experimental groups were intramuscularly injected with three sulfated astragalus polysaccharides (sAPSs), sAPS40, sAPS50 and sAPS60, at high or low doses, respectively, in two adjuvant control and two non-adjuvant control groups, non-sulfated APS and physiological saline, once a day for three successive days. On days 7, 14, 21 and 28 after vaccination, the blood samples were collected from brachial vein for determination of serum HI antibody. On days 14, 21, 28 and 35 after vaccination, the blood samples were collected by cardiopuncture for test of peripheral T lymphocyte proliferation. The results showed that three sAPSs could significantly enhance antibody titer and promote lymphocyte proliferation, which were better than that of non-sulfated APS with certain of dose– and time–effect relationships. At high dose, their effects on enhancing antibody titer were the better, at low dose, promoting lymphocyte proliferation. In general evaluation the efficacy of sAPS60 was best and would be expected as a candidate of new-type immunopotentiator.