Oral Presentation Australian Society for Microbiology Annual Scientific Meeting 2022

Koala combination vaccine against Chlamydia and KoRV induces cellular immune response in wild free ranging koalas (82529)

Samuel Phillips 1 , Bonnie L Quigley 1 , Jon Hanger 2 , Sharon Nyari 1 , Peter Timms 1
  1. Centre for Bioinnovation, University of the Sunshine coast, Sippy Downs, QLD, Australia
  2. Endeavour Veterinary Ecology, Toorbul, Queensland, Australia

Chlamydia is a major threat facing koalas, with up to 40% of koalas at wildlife hospitals with serious illness [1,2]. USC, have developed a chlamydial vaccine for koalas that is safe, induces an immune response and reduces signs of chlamydial disease in koalas [3,4]. Although, the Chlamydia vaccine is safe and effective at reducing chlamydial disease, further efforts to improve these responses are still warranted. The Koala retrovirus (KoRV) is endemic throughout Queensland with 100% of koalas infected with the KoRV A subtype and up to 25% have KoRV B (unknown prevalence for other subtypes). KoRV has immunosuppressive properties and is believed to limit the koala’s ability to develop a strong protective anti-chlamydial immune response [5,6]. To combat this immunosuppression, USC has developed a vaccine for KoRV, with initial trials showing that this vaccine is safe and reduces the amount of circulating KoRV in vaccinated koalas [7,8].

The current study a vaccine trial was conducted with three groups of wild koalas, Chlamydia vaccine, combination Chlamydia/KoRV vaccine and un-vaccinated koalas. Each koala’s cellular immune responses were monitored for up to nine months post vaccination utilising Nanostring technology focusing on immune and infection related genes; CD4, CD8-beta, IL-1-beta, IL-10, IL-17A, IL-18, IL-4, IL-6, IL-8, INF-gamma, MHC-II-DAA, MHC-II-DBA, TRIM1, TNF-alpha, KoRV-pol, KoRV-A, B and D envelope and C. pecorum hsp60 and ompA.

Through differential gene expression analysis, clear differences were observed between the three vaccine groups. These differences were unique and novel between both vaccine groups and when compared to the unvaccinated group also. These key gene expression changes appear to be linked to improved chlamydial responses in koalas and remained significantly altered for over nine-months post vaccination.

These findings indicate that by vaccinating koalas with a combined Chlamydia and KoRV vaccine an altered cellular immune response can be generated. Further research into the protective effects of this combination vaccine is required to identify any positive outcomes for koalas.    

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