Research, Connect, Protect



Interleukin 17A is an immune marker for chlamydial disease severity and pathogenesis in the koala (Phascolarctos cinereus)

Marina Mathew a, Courtney Waugh a,b, Kenneth W. Beagley a, Peter Timms a,b, Adam Polkinghorne a,b,

a Institute of Health & Biomedical Innovation, Queensland University of Technology, 60 Musk Avenue, Kelvin Grove 4059, Brisbane, Australia

b Faculty of Science, Health, Education and Engineering, University of the Sunshine Coast, 90 Sippy Downs Dr, Sippy Downs 4558, QLD, Australia


The koala (Phascolarctos cinereus) is an iconic Australian marsupial species that is facing many threats to its survival. Chlamydia pecorum infections are a significant contributor to this ongoing decline. A major limiting factor in our ability to manage and control chlamydial disease in koalas is a limited understanding of the koala’s cell-mediated immune response to infections by this bacterial pathogen. To identify immunological markers associated with chlamydial infection and disease in koalas, we used koalaspecific Quantitative Real Time PCR (qrtPCR) assays to profile the cytokine responses of Peripheral Blood Mononuclear Cells (PBMCs) collected from 41 koalas with different stages of chlamydial disease. Target cytokines included the principal Th1 (Interferon gamma; IFNc), Th2 (Interleukin 10; IL10), and proinflammatory cytokines (Tumor Necrosis Factor alpha; TNFa). A novel koala-specific IL17A qrtPCR assay was also developed as part of this study to quantitate the gene expression of this Th17 cytokine in koalas. A statistically significant higher IL17A gene expression was observed in animals with current chlamydial disease compared to animals with asymptomatic chlamydial infection. A modest up-regulation of proinflammatory cytokines, such as TNFa and IFNc, was also observed in these animals with signs of current chlamydial disease. IL10 gene expression was not evident in the majority of animals from both groups. Future longitudinal studies are now required to confirm the role played by cytokines in pathology and/or protection against C. pecorum infection in the koala.