ARTICLE | doi:10.20944/preprints202210.0117.v1
Online: 10 October 2022 (09:56:09 CEST)
Ovine footrot is a complex multifactorial infectious disease, causing lameness in sheep with major welfare and economic consequences. Dichelobacter nodosus is the main causative bacterium, however, footrot is a polymicrobial disease with Fusobacterium necrophorum, Mycoplasma fermentans and Porphyromonas asaccharolytica also associated. There is limited understanding of the host response involved. Proinflammatory mediators interleukin (IL)-1β and C-X-C Motif Chemokine Ligand 8 (CXCL8) have been shown to play a role in the early response to D. nodosus in dermal fibroblasts and interdigital skin explant models. To further understand the response of ovine skin to bacterial stimulation, and to build the understanding of the role of the cytokines and chemokines identified in transcriptomic data, primary ovine interdigital fibroblasts and keratinocytes were isolated, cultured and stimulated with lipopolysaccharide (LPS), D. nodosus or F. necrophorum in the presence and absence of M. fermentans, whilst measuring mRNA expression and protein release of CXCL8 and, IL-1β. Stimulation with LPS, D. nodosus or F. necrophorum resulted in increased transcript levels of IL-1β and CXCL8 in M. fermentans free cells, however, only an increase in CXCL8 protein release was observed. No IL-1β protein release was detected despite increases in IL-1β mRNA, suggesting the signal for intracellular pre-IL-1β processing may be lacking when culturing primary cells in isolation. Keratinocytes and fibroblasts naturally infected with M. fermentans showed little response to LPS, a range of D. nodosus preparations or heat-inactivated F. necrophorum. Primary single cell culture models complement ex vivo organ culture models to study different aspects of the host response to D. nodosus. Ovine keratinocytes and fibroblasts infected with M. fermentans had a reduced response to experimental bacterial stimulation. However, in the case of footrot where Mycoplasma spp. are associated with diseased feet, this natural infection gives important insights into the impact of multiple pathogens on the host response.