Proceedings of the 10th International Colloquium on Paratuberculosis

#75
Interleukin 17 and interleukin 23 gene expression differentiate severe pathology
in Johne’s disease
Mark William Robinson, Rory O’Brien, Frank Griffin
University <strong>of</strong> Otago, New Zealand
The gastrointestinal immune response to infectious agents such as Mycobacterium avium subspecies paratuberculosis
must be balanced in order to effectively contain <strong>the</strong> infection while at <strong>the</strong> same time avoiding
excessive tissue destruction. As such, differences in <strong>the</strong> host immune response to challenge can potentially
influence disease progression and outcome <strong>of</strong> Johne’s disease. Using an experimental infection model <strong>of</strong>
Johne’s disease in red deer (Cervus elaphus) we studied <strong>the</strong> immune responses during different pathological
states. A group <strong>of</strong> 30 red deer were challenged with ~10 9 colony forming units <strong>of</strong> bovine strain Mycobacterium
avium subspecies paratuberculosis and were monitored for Johne’s disease development over <strong>the</strong> course <strong>of</strong> 1
year. Peripheral blood samples were acquired at 20 weeks post-infection and post-jejunal lymph node (PJJLN)
samples following necropsy at ei<strong>the</strong>r 20-28 weeks post-infection for clinically diseased animals or at 50 weeks
post-infection for remaining animals. Animals were retrospectively grouped into 3 pathological outcomes (Infected,
Paucibacillary Diseased or Multibacillary Diseased) on <strong>the</strong> basis <strong>of</strong> histology scores and tissue culture
results. Gene expression <strong>of</strong> transcripts for IFNg, IL2, Tbet, IL1a, TNFa, TRAF1, GATA3, IL4, Foxp3, IL10, IL17,
IL23p19, IL6 and TGFb were detected using quantitative real time PCR and data was analysed using REST
s<strong>of</strong>tware to determine significant changes in gene expression levels. Stimulation <strong>of</strong> peripheral blood mononuclear
cells gave distinctive patterns <strong>of</strong> gene expression for all 3 groups with strong Type 1 responses in both
<strong>the</strong> Infected and Paucibacillary Diseased groups while <strong>the</strong> Multibacillary Diseased group showed a mixed
immune response with significant up-regulation <strong>of</strong> <strong>the</strong> IL23p19 gene transcript. The PJJLN gene expression
pr<strong>of</strong>iles <strong>of</strong> <strong>the</strong> Multibacillary Diseased group exhibited a highly inflammatory pr<strong>of</strong>ile with no evidence <strong>of</strong> a role
played by T regulatory or Type 2 immune responses. Gene expression pr<strong>of</strong>iles provide novel diagnostic markers
for different pathological states <strong>of</strong> Johne’s disease and support <strong>the</strong> hypo<strong>the</strong>sis that differing host immune
responses direct disease progression and pathological outcome.
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