Investigations on the role of the immune response in protection against Enterococcus cecorum infections in chickens

• Applicant: Dr. Arne Jung
• Subject Area: Veterinary Medical Science
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 467965937

Enterococcus cecorum (EC) infection in poultry can be regarded as a "New Emerging Disease". Since 15 years, disease outbreaks with considerable losses occur especially in broilers, in which EC is by now one of the most important bacterial pathogens. EC leads to skeletal infections of the chickens. The disease has an increasing importance for animal health and welfare and also social relevance, since a significant proportion of antibiotics in broilers may be used because of EC-infections. Despite its importance, in comparison to other bacterial diseases of poultry not very much is known about EC.In this research project, systematic investigations on the development and the role of the immune response during EC infections in meat type and layer type chickens will be conducted for the first time. Until now it is unknown, how the unspecific and specific immune system reacts on the infection. The research project consists of 2 subprojects. In the first subproject, an indirect ELISA system should be established and validated. Until now, no commercial detection system for antibodies is available. Furthermore, a hyperimmune serum will be produced and SPF chickens after vaccination. The hyperimmune serum will be injected to broiler type birds and afterwards birds will be experimentally infected with EC. Birds will be monitored for protection of the serum against EC infection. In the same animal trial, the immune response after experimental EC infection will be investigated. The ELISA system will be applied for the detection of anti-EC antibodies. Furthermore, immune cell populations in the blood (monocytes, granulocytes, CD4+ positive T-cells, CD8+ positive T-cells, lymphocytes, thrombocytes) will be detected using a fluorescence activated cell sorter (FACS). Additionally, the gen expression of following cytokines will be detected in blood and spleen using quantitative real-time PCR: IFN-γ for the th1 pathway, IL-4 and IL-13 for the th2 pathway, pro-inflammatory IL-6 and IL-8 and anti-inflammatory IL-10. An infection model for broilers is already established and can be used in this project. In the second subproject, it will be investigated which outcome an experimental EC-infection has in laying type birds and how the immune response differ from broiler type birds. Interestingly, EC infections are still unknown in laying type birds. This raises the question if besides differences in anatomy also differences in immune response play a role concerning low susceptibility of laying type birds. Until now, nearly no informations are available concerning the role of the immune response in protection against Enterococcus cecorum infections in chickens. The results of this research project may be fundamental for the development of vaccines against this very important pathogen of broiler type birds. These vaccines may help reducing antibiotic use in broilers.Furthermore, the project will help to understand why laying type birds are not affected by EC infection.

• DFG Programme: Research Grants