Dietary arginine supplementation enhances immune responses to inactivated Pasteurella multocida vaccination in mice

The present study was conducted to determine the adjuvant effect of arginine in mice immunised with inactivated vaccine. Mice immunised with an inactivated Pasteurella multocida vaccine and fed diets supplemented with 0.2% (vaccine-0.2 %) or 0.5% (vaccine-0.5 %) arginine exhibited 100% protection from a challenge with P. multocida serotype A (CQ2) at a dose of 4.4x10(5) colony-forming units (2LD(50); median lethal dose), when compared with mice receiving no arginine supplementation. Meanwhile, antibody titres in the vaccine-0.2% arginine group were much higher than those in the vaccine-oil adjuvant group before challenge and at 36 h post-infection. Furthermore, immunisation with the inactivated vaccine and dietary supplementation with 0.2% arginine increased serum levels of glutathione peroxidase, in comparison with immunisation with the inactivated vaccine and an oil adjuvant. Collectively, dietary arginine supplementation confers an immunostimulatory effect in mice immunised with the inactivated P. multocida vaccine. The present results also indicate that optimal supplemental doses of arginine are 0.2-0.5% in the mouse model.