Improved immune responses to a bivalent vaccine of Newcastle disease and avian influenza in chickens by ginseng stem-leaf saponins

Our previous investigation demonstrated that ginseng stem-leaf saponins (GSLS) derived from the stems and leaves of Panax ginseng C.A. Meyer promoted humoral and gut mucosal immunity in chickens vaccinated with live infectious bursa disease vaccine. The present study was designed to evaluate the effect of GSLS on the immune response to a bivalent inactive vaccine of Newcastle disease (ND) and avian influenza (AI) in chickens immunosuppressed by cyclophosphamide (Cy). One hundred and sixty-eight specific-pathogen-free (SPF) chickens were randomly divided into 7 groups, each containing 24 birds. Chickens in groups 3–7 received intramuscular injection of Cy at 100 mg/kg BW for 3 days to induce immunosuppression. Groups 1 and 2 were injected with saline solution in the same way as groups 3–7. Following injection of Cy, groups 4–7 were orally administrated GSLS (2.5, 5 and 10 mg/kg BW) or astragalus polysaccharide (APS) (200 mg/L) in drinking water for 7 days; groups 1–3 were not medicated and served as control birds. After administration of GSLS or APS, groups 2–7 were subcutaneously injected with a bivalent inactive vaccine of ND and AI. After that, serum was sampled for detecting antibody titers by HI, spleen was collected for lymphocyte proliferation assay, and duodenum tissues were collected for measurement of IgA-secreting (IgA+) cells and intestinal intraepithelial lymphocytes (iIELs). The results showed that injection of Cy significantly suppressed immunity in chickens; oral administration of GSLS before immunization recovered splenocyte proliferation induced by ConA and LPS, and the numbers of IgA+ cells and iIELs as well as the specific antibody response to a bivalent inactive vaccine of ND and AIin immunosuppressed chickens treated with Cy. Therefore, GSLS may be the potential agent to improve vaccination in immunosuppressed chickens.