MYCOPLASMA BOVIS - IN VITRO AND IN VIVO MURINE MASTITIS MODEL

Mastitis due to Mycoplasma bovis (MB) is a worldwide problem leading to significant economic losses and affecting animal welfare. The successful establishment and persistence of intramammary (IMM) MB infection, which often evades clearance by host immune defense mechanisms, is governed by its virulence factors, which are largely unknown and the pathogenesis of the disease is poorly understood. Therefore, as a first step in characterization of MB-induced mastitis and future identification of MB virulence determinants we established (1) an in vitro cell-based model system using mouse mammary epithelial (EpH4) cell line and (2) in vivo model system using the murine mastitis model. Using NF-kappa-B reporter system and QPCR analysis in EpH4 cells we observed significant activation of inflammation in cells exposed to live MB, UV-killed MB and MB lipoproteins. In the murine mastitis model, lactating mammary glands were challenged by IMM injection via the teat canal with bacterial suspensions or MB lipoproteins. Mammary inflammation was analyzed using whole body imaging, QPCR analysis for cytokines and chemokines and histological analysis of the challenge glands. We observed inflammatory response starting 24 hours after challenge and peaking at 48 hours. Interestingly, challenge with UV-killed MB and MB lipoproteins elicited a milder and shorter inflammatory response underlying the importance of live whole MB in the pathogenesis of the disease. Moreover, infection with live MB was associated with the formation of MB microbial communities in the alveolar mammary epithelial cells. The cell-based and animal model systems will be used to investigate virulence mechanisms in the pathogenesis of MB mammary infection.