MS KIENER¹, A BAUMANN¹, A SUMMERFIELD<sup>1

1</sup>Institute of Virology and Immunology, University of Bern, Länggassstrasse 122, 3012 Bern, Switzerland

Mastitis is an inflammation of the mammary gland usually caused by pathogens invading the lumen of the gland via the udder, and represents a major animal health concern of lactating cows. Antibiotic is the classical therapy but the massive use of such drugs have been associated with emergence of multi-resistant bacterial strains endangering both animal and human health. Cathelicidins represent a family of cationic peptides characterized by a strong antimicrobial activity and several effector functions in immunity. Understanding their induction and functions helps to identify new and sustainable antimicrobial strategies. Therefore, the antimicrobial activity of six synthetic bovine cathelicidins against mastitis pathogens was tested in vitro. The cathelicidin BMAP-27 was the most effective at killing bacteria, which was strictly dependent on its amphipathic structure. The modulatory functions were further investigated in an assay which consists to detect Mx expression after nucleic acids exposure in bovine turbinate cells. Interestingly, alpha-helical cathelicidins enhanced the sensing of very low concentration of nucleic acid. Strong bactericidal activity in the supernatants of stimulated neutrophils could be associated to bovine cathelicidins by western blot. Altogether, the present data support the role of cathelicidin in killing bacterial cells as well as helping the innate immune system in sensing of nucleic acids. These finding are relevant to develop future preventive strategies either as a potential alternative to antibiotics or as prophylactic strategy in animal health.