Formalin and ferric chloride inactivated Pasteurella multocida type a adjuvanted with bacterial DNA and alum as a new vaccine candidate in sheep pasteurellosis.

The aim of the present study was to investigate humoral and cellular immune responses in sheep inoculated with inactivated P. multocida antigen with alum and bacterial DNA adjuvant by identifying IgG and cytokines from serum and cell culture. Sheep were immunized with iron and formalin-inactivated antigens at an interval of 2 weeks. These immunogens were mixed with alum adjuvant and P. multocida type A DNA (AbDNA). After injection and blood sampling, the serum antibody titer and cellular immune responses (IL-4, IFN-γ, and TNF-α) on serum samples and lymphocyte cell were tested by ELISA. The ELISA results showed a higher antibody titer in the bDNA adjuvant group compared to the alum adjuvant group and the control group. In general, the level of IgG in the serum of immunized animals was significantly increased compared to the control group. The peak antibody titer (1.794) was observed on the 28th day of injection in the IIV-AbDNA group. After immunization, inactivation with iron and bDNA adjuvant increased cytokine production compared to other experimental and control groups. High levels of lymphocyte and serum titers of IL-4, IFN-γ, and TNF-α were also obtained in the IIV-AbDNA group. The findings showed that killed P. multocida type A antigens formulated with bacterial DNA as an adjuvant are candidates for new immunogens against P. multocida infections in sheep. The inactivation of bacteria with iron also enhanced proper immune responses.

Pasteurella multocida inactivated with ferric chloride and adjuvanted with bacterial DNA is a potent and efficacious vaccine in Balb/c mice.

PURPOSE: Pasteurella multocida (P. multocida) is a principal pathogen of domestic animals and an opportunistic pathogen of humans. It is the causative agent of pneumonia and haemorrhagic septicaemia in cattle, sheep and goats, fowl cholera in chickens and progressive atrophic rhinitis in swine. In this study, we investigated the humoral and cellular immune responses and protective immunity conferred by an iron-inactivated vaccine with bacterial DNA (IIV+bDNA) as an adjuvant in mice. METHODOLOGY: P. multocida was grown in BHI broth, inactivated with formalin and FeCl3 and adjuvanted with alum and bDNA. Mice were immunized with two whole-cell inactivated vaccine doses 2 weeks apart. The animals were challenged 4 weeks after booster immunization. Immunogens (vaccines and bDNA) posed no safety problems when mice were injected subcutaneously (s/c) with these preparations. The serum antibody titres were tested by ELISA. At 28 days post immunization, cell-mediated immunity responses were determined. The responses were measured by assay of IL-6 and IL-12 in lymphocyte spleen culture supernatants. RESULTS: ELISA results showed that the levels of antibodies in iron inactivated with bDNA adjuvant groups were higher than in the formalin inactivated with alum adjuvant vaccine group. The protection rate of IIV+bDNA adjuvant vaccine was superior to that of the other vaccines and it protected 100 % of the challenge group mice. Following immunization, bDNA promoted increased production of interleukins compared to the control groups. CONCLUSION: These studies indicate that bDNA is effective as an immune adjuvant, and along with stimulatory bDNA represent promising new humoral and cellular immune enhancers for vaccination applications. In addition, this vaccine is able to provide long-term protection against infection.