Assessing the role of the acute phase protein and opsonin MBL in protective immune responses against erysipelas in chickens

Erysipelas is an infectious disease that is a major problem in laying hens, especially in organic production. The disease is caused by the bacterium Erysipelothrix rhusiopathiae (ER), which can infect a wide range of species including humans. Basic knowledge on immune responses to ER in chickens has been lacking: however, we have recently monitored immune events during experimental infection of chickens and identified prominent responses of heterophils and the acute phase protein mannose-binding lectin (MBL) concurrent with bacteraemia during the early phases of infection. The ER capsule has mannose as a major component and MBL has a function as an opsonin for phagocytosis. Thus, it is likely that the observed MBL responses in infected chickens play a role in the successful clearance of experimental ER infection observed in our studies. In contrast, the disease is often fatal under field conditions, making the identification of protective immune responses critical. At VetBioNet partner AU there are two unique chicken lines (L10H and L10L) that have high and low MBL baseline levels and show high and low MBL responses upon microbial challenge. We therefore propose to perform an ER infection experiment at the AU facilities using these lines to further elucidate the role of MBL in the defence against ER infection.