Effects of Taishan Pinus massoniana pollen polysaccharide on the subunit vaccine of Proteus mirabilis in birds

Three adjuvants, namely, Taishan Pinus massoniana pollen polysaccharide (TPPPS), white mineral oil (WO) and propolis (PP), were added to the outer membrane protein (OMP) of Proteus mirabilis (P. mirabilis) and their effects were compared. Three hundred 1-day-old chicks were randomly divided into five groups (I–V), with 60 chicks per group, and injected subcutaneously with WO-OMP vaccine (I), PP-OMP vaccine (II), TPPPS-OMP vaccine (III), OMP-only vaccine (IV) and physiological saline (V) at 3, 7 and 12 days old. On days 3, 7, 14, 21, 28, 35, 42 and 49 after the first vaccination, the antibody titers, interleukin-2 levels (IL-2) and T-lymphocyte proliferation rates in the peripheral blood as well as the secreting-type IgA levels (SIgA) in the duodenum were measured. On day 7 after the third vaccination, the chicks were challenged with P. mirabilis strain Q1 and the protective effects of each group were observed. The highest protective rate was observed in group III. Moreover, the antibody titers as well as IL-2, SIgA and T-lymphocyte proliferation rates in this group significantly increased and were significantly higher than those in the other groups at most time points. The results indicate that TPPPS could significantly enhance the effects of the subunit vaccine of P. mirabilis; induced stronger humoral, cellular and mucosal immunity as compared with WO and PP; and should be developed as a vaccine adjuvant.