Development of a Chlamydia pecorum vaccine for koalas (Phascolarctos cinereus)

Sharon Nyari

doi:10.25907/00668

Chlamydial disease continues to be one of the main factors threatening the long-term survival of the koala (Phascolarctos cinereus). Chlamydia pecorum is a mucosal pathogen, causing debilitating disease of the urinary tract, reproductive tract and ocular sites of koalas, and can lead to infertility, and blindness. Antibiotics are the current treatment for chlamydial infection and disease in koalas however, antibiotics can be detrimental to the koala's gastrointestinal tract microbiota and in severe cases, can lead to dysbiosis and death. Alternatives to antibiotic treatment are desperately needed. The development of an anti-chlamydial vaccine is a logical treatment choice to overcome these unwanted side effects and provide long-term management of Chlamydia in wild koala populations. This was the major goal of this thesis project. Before developing a vaccine however, a better understanding of the prevalence, transmission and pathogenesis in wild koala populations is needed to improve control measures. Large epidemiological studies reporting the prevalence of infection and disease in wild koala populations are lacking. The prevalence of disease is often reported as overt signs, which does not include asymptomatic koalas experiencing sub-clinical disease. Furthermore, hospital-based studies are a biased subset of the wild koala population, as only sick and injured koalas are presented for treatment. To gain an accurate insight into the prevalence of C. pecorum infection and subsequent disease in koalas, I conducted a cross-sectional epidemiological study on 160 wild koalas residing in South East Queensland, Australia. During this project I developed two novel koala anti-Chlamydia vaccines. To overcome unwanted side effects often seen in koalas following antibiotic treatment, I assessed the therapeutic effects of a recombinant major outer membrane protein (rMOMP) vaccine on seven wild koalas with ocular disease. The possibility of a C. pecorum rMOMP vaccine that can provide a therapeutic effect is a promising prospect for wild koalas that have progressed to disease. This study assessed both humoral and cell-mediated responses at pre-vaccination and for six-weeks post-vaccination. In addition, this study also evaluated the infecting genotypes, MCH class II alleles and presence of koala retrovirus (KoRV) in ocular diseased koalas.

Development of a Chlamydia pecorum vaccine for koalas (Phascolarctos cinereus)

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