Effect of immunostimulation by detoxified E. coli lipopolysaccharide combined with inactivated Propionibacterium granulosum cells on porcine immunity.

The aim of this experiment was to evaluate the immunomodulating activities of inactivated Propionibacterium granulosum cell walls and E. coli lipopolysaccharide (PG/LPS) on porcine immunity. Piglets were intramuscularly administered PG/LPS (1 ml/10 kg body weight) once or twice. The function of natural killer cells, lymphocytes and neutrophils and the adjuvant effect on antibody induction by attenuated classical swine fever virus (CSFV) and inactivated Mycoplasma hyopneumoniae vaccination were evaluated. The results showed that the cytotoxicity of natural killer cells and proliferation of lymphocytes in response to mitogen stimulation were significantly enhanced (P<0.05) in those pigs receiving PG/LPS injection compared with the controls. However, there was no significant effect on the phagocytic activity of neutrophils (P>0.05). PG/LPS also displayed adjuvant effects with CSFV and Mycoplasma hyopneumoniae vaccines. Moreover, pigs receiving two injections of PG/LPS showed a 20.8% growth enhancement compared with untreated pigs. Thus, PG/LPS caused positive immunoregulation of porcine innate immune system effectors, non-specific activation of lymphocytes and antibody production.