Co-adjuvant effects of plant polysaccharide and propolis on chickens inoculated with Bordetella avium inactivated vaccine

Taishan Pinus massoniana pollen polysaccharide (TPPPS), propolis (PP) and aloe polysaccharide (AP), used as adjuvants, have been proven to possess immunity-enhancing functions. However, their collaborative immunomodulatory effects are largely unknown. To determine which combination can induce the best effects, the three adjuvants were separately or conjointly added into Bordetella avium inactivated vaccines to investigate their co-adjuvant effects on vaccinated chickens. We found that, among all six adjuvant-treated vaccine inoculated groups (TPPPS, PP, AP, TPPPS–PP, PP–AP and TPPPS–AP), the chickens inoculated with TPPPS, PP or TPPPS–PP adjuvant vaccines showed significantly higher levels of antibody titre, cytokine, lymphocyte transformation and peripheral blood T-lymphocyte count than those of non-adjuvant vaccine inoculated groups (P < 0.05), indicating the good immune-enhancing effects of TPPPS and PP. The TPPPS–PP group showed the highest levels of antibody titres and interleukin-2 (IL-2) at 14–28 days post the first inoculation (dpi), lymphocyte transformation rates (LTRs) at 14–35 dpi, CD4+ T-lymphocyte counts at 14–42 dpi, and CD8+ T-lymphocyte counts at 28 dpi. The results revealed that B. avium inactivated vaccine used conjointly with TPPPS and PP induced the strongest humoral and cellular immune responses. Thus, there was a synergistic effect between TPPPS and PP on enhancing immunity, which suggests that they can be used as a novel adjuvant formulation for the development of poultry vaccines.