Potential use of a canine whole blood culture system to evaluate the immune response to Leptospira.

In susceptible hosts, protection from Leptospira infection is mediated by the innate immune response at the point of entry and humoral immunity. Thus, identifying and segregating the initial host response at the representative host-pathogen interface is needed to understand the typical outcomes of Leptospira infection, clearance, persistence, or disease. An in vitro whole blood culture system to study the overall immune response using pathogenic and non-pathogenic Leptospira strains was explored in this study. Using an ELISA, increased IL-8, TNF alpha, and IL-1 in blood samples stimulated with pathogenic and nonpathogenic Leptospira compared to unstimulated controls were detected. In RT2 Profiler PCR Array assays, consistent upregulation of 22 genes and downregulation of 25 genes were observed. Few of the notable upregulated genes included BPI, CCL3, CXCL2, IL-6, IL-8, TLR1, TLR2, TLR6, and TNF and downregulated genes included, LBP, LYZ, MPO, MYD88. IFNβ was upregulated in samples treated with pathogenic Leptospira and IL-1β was upregulated in samples treated with nonpathogenic Leptospira. Toll- like Receptor signaling and expression of pattern recognition receptors were two of the five prominent canonical pathways observed. Individual deconvolution of each of the specific and significant pathways observed in this study may improve the understanding of the pathogenesis of this important zoonotic agent. The use of this system in conjunction with whole transcriptome analysis in a larger population, may unveil the robust nature of host/Leptospira interaction.