Dietary L-proline supplementation confers immunostimulatory effects on inactivated Pasteurella multocida vaccine immunized mice

This study was conducted to determine the immunostimulatory effect of L-proline on inactivated vaccine immunized mice. Ninety-five female KM mice were randomly divided into five groups: (1) mice received dietary supplementation with 0.4 % L-proline and immunized with inactivated vaccine (V–P group); (2) mice received dietary supplementation with 0.3 % L-alanine (isonitrogenous control) and immunized with inactivated vaccine (V–A group, negative control); (3) mice were immunized with inactivated vaccine with oil adjuvant (V–O group, positive control); (4) mice were immunized with inactivated vaccine with aluminum hydroxide adjuvant (V–H group, positive control); (5) mice immunized with phosphate-buffered saline (control group). All mice were dead in the control group between 36 and 48 h post infection. Mice in the V–P group showed 100 % protection after challenge with P. multocida serotype A (CQ2) at dose of 4.4 × 10⁵CFU (2LD50). Meanwhile, serum antibody titers in the V–P group were higher than those in the V–A group before infection and those in the V–A and V–O groups at 36 h post infection. Moreover, serum IL-1β levels in the V–P group were lower than those in V–O group. Furthermore, serum GSH-PX levels in the V–P group were higher than those in the V–A and V–O groups. Collectively, dietary proline supplementation confers beneficial immunostimulatory effects in inactivated P. multocida vaccine immunized mice.