Oral Presentation International Veterinary Immunology Symposium 2016

Characterisation of CD4+ T and CD8+ T Cells in healthy and diseased koalas (Phascolarctos cinereus) using cell-type-specific monoclonal antibodies (#49)

Chandan Mangar 1 , Charles W Armitage 1 , Peter Timms 2 , Lynn M Corcoran 3 , Kenneth W Beagley 1
  1. School of Biomedical Sciences, Queensland University of Technology, Brisbane, Queensland, Australia
  2. Faculty of Science, Health, Education and Engineering, University of Sunshine Coast, Sunshine Coast, Queensland, Australia
  3. Walter and Eliza Hall Institute of Medical Research, Melbourne, Victoria, Australia

The koala (Phascolarctos cinereus) is an arboreal herbivorous marsupial that is an Australian icon. Chlamydia pecorum and C. pneumoniae are obligate intracellular Gram-negative bacteria that infect koalas and can cause, infertility, arthritis, conjunctivitis, respiratory disease and in some cases death. Using the extracellular domain of koala CD8+ we produced a monoclonal antibody (mAb) targeting koala CD8+ T cells and used this to investigate the levels of CD8+ cytotoxic T cells in koala spleens, lymph nodes and peripheral blood by flow cytometry. CD8+ specific T cells were successfully identified in cells from all tissues and peripheral blood by both flow cytometry and by immunohistochemistry in tissue sections. In combination with our koala CD4+ mAb, both T cell populations in blood were characterised in healthy and diseased koalas. Both CD4 and CD8 single positive cells as well as a novel CD4+CD8+ double positive population proliferated in response to chlamydial antigen stimulation in vaccinated animals but not control animals, suggesting these cells may be important for protection against chlamydial infection in koalas. To investigate the importance of cytokines in protection against Chlamydia in koalas, a koala IFNg-specific mAb was used to identify IFNg-secreting CD4 and CD8 T cells in vaccinated and unvaccinated koalas following stimulation with chlamydial antigen. The results highlight the value of koala-specific immune reagents to analyse the immune response in diseased, healthy or vaccinated animals.