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Health & welfare management

A 5-year Chlamydia vaccination programme could reverse disease-related koala population decline: Predictions from a mathematical model using field data

Craig, AP, Hanger, J, Loader, J, Ellis, WAH, Callaghan, J, Dexter, C, Jones, D, Beagley, KW, Timms, P & Wilson, DP 2014, Vaccine, vol. 32, pp. 4163-4170.

Chlamydia vaccines are being developed to mitigate the impact the disease has on koala populations. Stochastic individual-based mathematical modelling suggests targeting female koalas aged 1-2 years old with a vaccine with 75% efficacy administered to approximately 10% of koalas per year could initiate a reversal in current population declines over a 5-6 year period.

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A guide for ecologists: detecting the role of disease in faunal declines and managing population recovery 

Preece, ND, Abell, SE, Grogan, L, Wayne, A, Skerratt, LF, van Oosterzee, P, Shima, AL, Daszak, P, Field, H, Reiss, A, Berger, L, Rymer, TL, Fisher, DO, Lawes. MJ, Laurance, SG, McCallum, H, Esson, C, & Epstein, JH, 2017, Biological Conservation, vol. 214, pp. 136-146. 

  Disease can drive population declines in many ways such as lowering reproductive success, direct mortality and altering population structure, dispersal and migratory patterns.  Its role in driving population decline, however, has received little attention.  The authors of the current study argue that its role in species decline is more important than has previously been appreciated.  A disease investigation framework consisting of ten steps was developed, with the help of scientists from multiple disciplines. This enabled investigators with diverse knowledge and experience in epidemiology to address disease as a potential factor in population declines. 

  The ten steps of disease determination were formulated based on knowledge and experience gained from three case studies of significant population crashes. These case studies included amphibian chytridiomycosis, Tasmanian devil facial tumour disease, and the effect of introduced predators on the wild population of Rufous Bettong.  The ten steps of disease determination are: 1) identify and clearly define outcome of interest, 2) verify that decline is real by incorporating the best understanding of species’ ecology and demography, 3) determine spatial, temporal and demographic characteristics which can potentially reveal likely causes of decline, 4) list all plausible hypotheses of threatening processes, risk factors and causes, 5) Determine risk factors by considering the association between the outcome of interest and host and environmental factors, 6) undertake health and pathological examinations to identify whether pathogens are present, 7) formulate a tentative diagnosis, 8) implement management actions, 9) use multiple competing hypotheses approach to evaluate the relative influence of each hypothesis, and lastly, 10) refine ongoing management through monitoring and adapting to new information. 

  Most studies of mammalian population declines that happen across Australia did not recognise disease as a cause.  In the Action Plan for Australian Mammals, disease is the putative cause in fewer than 20% of declining species. 

  Therefore, the development of this framework will ensure that disease as a source is acknowledged, and in turn will maximise the cost-effectiveness of diagnosis and management.  Apart from considering the role of disease in population crashes, the authors also emphasize the importance of collaboration between different responsible parties. The various sources utilized included wildlife management, epidemiologists, ecologists, and veterinarians in determining the causes of population decline and planning of management strategies. 

 

Summarised by Cherie Chan

 

Disclaimer: The summary of this report is provided for reference purposes only and does not represent the findings or opinions contained in the original report. Although every effort has been made to bring forward the main elements of the report, this review is no substitute for the full the report itself. Should you have any concerns or perceive any errors please contact us and we shall endeavour to rectify and improve the review.

A multi-subunit chlamydial vaccine induces antibody and cell-mediated immunity in immunised koalas (Phascolarctos cinereus): comparison of three different adjuvants

Carey, AJ, Timms, P, Rawlinson, G, Brumm, J, Nilsson, K, Harris, JM & Beagley, KW 2009, American Journal of Reproductive Immunology, vol. 63, no. 1, pp. 161-172.

An experimental vaccine against Chlamydia induced Chlamydia-specific cell-mediated and antibody responses in immunised koalas. Of three different adjuvants tested, each in combination with a selection of recombinant chlamydial antigens, one caused adverse reactions in immunised koalas and was therefore considered unsafe and removed from the experiment. The remaining two adjuvants had no adverse effects, and both resulted in long-term (270 days) neutralising antibody responses in plasma against the three antigens as well as Chlamydia-specific peripheral blood mononuclear cell proliferative responses. In an artificial environment, plasma antibodies inhibited infections from two different species of Chlamydia, suggesting the approach trialled may be effective for combating chlamydial infections in koalas.

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A non-invasive tool for assessing pathogen prevalence in koala (Phascolarctos cinereus) populations: detection of Chlamydia pecorum and koala retrovirus (KoRV) DNA in genetic material sourced from scats

Wedrowicz, F, Saxton, T, Mosse, J, Wright, W & Hogan, FE 2016, Conservation Genetics Resources, vol. 8, no. 1, pp. 511-521.

The major pathogens affecting koalas, Chlamydia pecorum and koala retrovirus (KoRV), can be reliably detected in DNA isolated from faecal samples.

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Antibody and cytokine responses of koalas (Phascolarctos cinereus) vaccinated with recombinant chlamydial major outer membrane protein (MOMP) with two different adjuvants

Khan, SA, Desclozeaux, M, Waugh, C, Hanger, J, Loader, J, Gerdts, V, Potter, A, Polkinghorne, A, Beagley, K & Timms, P 2016, PLoS ONE, vol. 11, no. 5, e0156094.

Two different adjuvants used in an anti-chlamydial recombinant major outer membrane protein (rMOMP) antigen-based vaccine for koalas both induced strong antigen-specific cellular responses and were equally able to produce Chlamydia pecorum-specific neutralising antibodies in vitro. The adjuvants differed in terms of the specificity of the MOMP epitope antibodies produced.

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Antigenic specificity of a monovalent versus polyvalent MOMP based Chlamydia pecorum vaccine in koalas (Phascolarctos cinereus)

Kollipara, A, Wan, C, Rawlinson, G, Brumm, J, Nilsson, K, Polkinghorne, A, Beagley, K & Timms, P 2013, Vaccine, vol. 31, no. 1, pp. 1217-1223.

A comparison of two koala anti-chlamydial vaccines containing either one or multiple target antigens demonstrated that both were equally effective at eliciting a strong cell-mediated and humoral immune response. Both vaccines elicited similar results in terms of developing plasma antibodies, neutralising different strains of C. pecorum infections, and proliferating lymphocytes against different C. pecorum recombinant major outer membrane proteins (MOMPs) and whole chlamydial elementary bodies (EBs). These findings imply that it is possible to develop a vaccine that can offer suitable protection against a range of chlamydial strains.

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Assessing the significance of endemic disease in conservation – koalas, chlamydia, and koala retrovirus as a case study

McCallum, H, Kerlin, DH, Ellis, W & Carrick, F 2017, Conservation Letters, e12425.

The value of disease management as a tool for biological conservation is often contested. The koala presents an ideal case study for examining this debate. Endemic diseases, most notably chlamydiosis and koala retrovirus (KoRV), are highly prevalent throughout koala populations. The extent to which disease contributes to population decline, however, is not agreed upon.

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Atypical presentation of Cryptococcus neoformans in a koala (Phascolarctos cinereus): a magnetic resonance imaging and computed tomography study

Martínez-Nevado, E, Alonso-Alegre, EG, Martínez, MÁ, Rodríguez-Álvaro, A, de Merlo, EM, García, JG & Real, IG 2017, Journal of Zoo and Wildlife Medicine, vol. 48, no. 1, pp. 250-254.

Magnetic resonance imaging (MRI) and computed tomography (CT) are valuable tools for diagnosing cryptococcosis in koalas as the techniques, used together, can assist in identifying the precise location and extent of a granuloma.

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Characterisation of CD4 T cells in healthy and diseased koalas (Phascolarctos cinereus) using cell-type-specific monoclonal antibodies

Manger, C, Armitage, CW, Timms, P, Corcoran, LM & Beagley, KW 2016, Developmental and Comparative Immunology, vol. 60, no. 1, pp. 80-90.

An initial cell-type-specific monoclonal antibody (mAb) for koalas has been developed. The anti-CD4 mAb is able to detect CD4+ T lymphocytes at various bodily sites using a range of analytical techniques. The mAb can also be used to detect vaccine-induced Chlamydia-specific CD4+ T cells in the peripheral blood mononuclear fragments of immunised koalas.

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Comparison of antigen detection and quantitative PCR in the detection of chlamydial infection in koalas (Phascolarctos cinereus)

Hanger, J, Loader, J, Wan, C, Beagley, KW, Timms, P & Polkinghorne, A 2013, The Veterinary Journal, vol. 195, no. 1, pp. 391-393.

Although an antigen detection method is less sensitive than quantitative polymerase chain reaction (qPCR) in the detection of Chlamydia pecorum infection in koalas, the former technique is suitable for rapidly diagnosing active chlamydial infections.

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Comparison of subcutaneous versus intranasal immunization of male koalas (Phascolarctos cinereus) for induction of mucosal and systemic immunity against Chlamydia pecorum

Waugh, CA, Timms, P, Andrew, D, Rawlinson, G, Brumm, J, Nilsson, K & Beagley, KW 2015, Vaccine, vol. 33, no. 1, pp. 855-860.

An anti-chlamydial vaccine delivered either subcutaneously or intranasally elicited significant and long-term immune responses in immunised male koalas. The subcutaneous, or systemic, route of delivery elicited a stronger cell-mediated response than the intranasal, or mucosal, route, which induced a greater humoral response including at the mucosal sites where chlamydial infections begin.

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Current trends and future directions in koala chlamydial disease research

Grogan, LF, Ellis, W, Jones, D, Hero, J, Kerlin, DH & McCallum, H 2017, Biological Conservation, vol. 215, no. 1, pp. 179-188.

A review of nearly five decades of peer-reviewed publications about koala chlamydiosis has revealed a significant gap in the research regarding studies of the disease at the population level. Such studies will be necessary in the future to inform conservation policies and programs for declining koala populations.

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Detection of Chlamydia pneumoniae DNA and antigen in the circulating mononuclear cell fractions of humans and koalas

Bodetti, TJ & Timms, P 2000, Infection and Immunity, vol. 68, no. 1, pp. 2744-2747.

DNA and antigens of the common respiratory pathogen Chlamydia pneumoniae were found in the peripheral blood mononuclear cell (PBMC) fractions of 30% of koalas from a sampled population at Lone Pine Koala Sanctuary. The presence of the pathogen in these cells confirms that C. pneumoniae can use PBMCs as a pathway for disseminating and subsequently infecting non-respiratory sites. A similar phenomenon was observed in the blood of human donors, suggesting that the dissemination of C. pneumoniae to non-respiratory sites is not unique in humans but rather is an inherent characteristic of the bacterium.

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Effects of capture on haematological values and plasma cortisol levels of free-range koalas (Phascolarctos cinereus)

Hajduk, P, Copland, MD & Schultz, DA 1992, Journal of Wildlife Diseases, vol. 28, no. 3, pp. 502-506.

Eight wild koalas were captured on Kangaroo Island, South Australia, placed in transport boxes, and then transported to the Adelaide Zoo by ferry and road. Blood samples were collected from these koalas at the time of their capture, and subsequently six hours, 24 hours and seven days following their capture. Significant differences in the following properties were observed between the samples: erythrocyte (red blood cell) number, haemoglobin concentration, packed cell volume, mean cell volumes, numbers of the white blood cell types leukocytes, neutrophils and lymphocytes, as well as lymphocyte: neutrophil ratio.  No significant differences could be found between sampling periods for the following properties: number of the white blood cell types monocytes and eosinophils, and plasma cortisol levels.

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Emergency and critical care of koalas

Blanshard, W 1993, Proceedings from the Annual Conference of the Australian Veterinary Association, Gold Coast.

In this report, Blanshard draws upon her experience in the veterinary care of koalas at Lone Pine Koala Sanctuary to describe how emergency and critical care protocols for koalas differ from those for other species. Blanshard details the physical and physiological characteristics of both healthy koalas and koalas with specific ailments in the context of the animal’s diet, behaviour, common conditions and appropriate health care.

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Fecal glucocorticoid metabolite response of captive koalas (Phascolarctos cinereus) to visitor encounters

Webster, K, Narayan, E & de Vos, N 2017, General and Comparative Endocrinology, vol. 244, pp. 157-163.

This study investigated the effect of visitor encounter experiences involving photography on the cortisol secretion response of captive koalas, which is an indicator of physiological stress. Overall, male koalas had higher mean faecal cortisol metabolite (FCM) concentrations compared to females. In male koalas the highest FCM concentrations were observed during an intensive photography treatment (as opposed to standard photography and control), whereas there was no apparent physiological response to photography regime observed in female koalas.

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Genetic diversity of Chlamydia pecorum strains in wild koala locations across Australia and the implications for a recombinant C. pecorum major outer membrane protein based vaccine

Kollipara, A, Polkinghorne, A, Wan, C, Kanyoka, P, Hanger, J, Loader, J, Callaghan, J, Bell, A, Ellis, W, Fitzgibbon, S, Melzer, A, Beagley, K & Timms, P 2013, Veterinary Microbiology, vol. 167, pp. 513-522.

The genetic diversity of Chlamydia pecorum strains in koalas has limited the production of an effective cross-strain vaccine. By examining C. pecorum isolates from koalas across their range, the most common major outer membrane protein (MOMP) amino type F was suggested to be a prime candidate for recombinant C. pecorum vaccine development.

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Humoral immune responses in koalas (Phascolarctos cinereus) either naturally infected with Chlamydia pecorum or following administration of a recombinant chlamydial major outer membrane protein vaccine

Khan, SA, Polkinghorne, A, Waugh, C, Hanger, J, Loader, J, Beagley, K & Timms, P 2016, Vaccine, vol. 34, no. 1, pp. 775-782.

Koalas that become infected with Chlamydia pecorum can produce a natural antibody response, but this response is not sufficient to adequately protect against the progression of the infection. Following immunisation with a recombinant chlamydial major outer membrane protein (rMOMP) vaccine, koalas exhibited a stronger humoral immune response to the infection than they were able to without the vaccine. Vaccinated koalas were also able to produce unique antibodies to epitopes, the parts of antigens that are recognised by the immune system, from non-vaccinated koalas. These unique antibodies effectively neutralised the C. pecorum bacterium in an artificial environment.

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In vitro activity of chloramphenicol, florfenicol and enrofloxacin against Chlamydia pecorum isolated from koalas (Phascolarctos cinereus)

Black, LA, Higgins, DP & Govendir, M 2015, Australian Veterinary Journal, vol. 93, no. 11, pp. 420-423.

Chloramphenicol and florfenicol were more effective treatments for chlamydiosis in koalas during in vitro experiments than enrofloxacin. The minimum inhibitory concentrations (MICs) were 0.25-0.50 μg/mL for enrofloxacin and 1-2 μg/mL for chloramphenicol and florfenicol. Minimum bactericidal concentration (MBC) values were also calculated to be within one two-fold dilution of the MICs.

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Koala (Phascolarctos cinereus) captive husbandry guidelines

Jackson, S, Perry, L, O’Callaghan, P, Spittal, D, Romer, L & Reid, K 1999

These guidelines for the husbandry of koalas in captive populations represent the combined insights of keepers from Lone Pine Koala Sanctuary, Healesville Sanctuary, Taronga Zoo and Currumbin Wildlife Sanctuary. The authors report on best practice principles in multiple aspects of the care and management of the species.

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Koala translocations and Chlamydia: Managing risk in the effort to conserve native species

Waugh, C, Hanger, J, Timms, P & Polkinghorne, A 2016, Biological Conservation, vol. 197, no. 1, pp. 247-253.

Despite becoming more commonly accepted as a ‘last-resort’ strategy for protecting at-risk animals, koala translocation may have a negative net impact upon the conservation of the species because of the associated risk of spreading chlamydial disease. In the context of recent scientific developments regarding the biology and epidemiology of Chlamydia pecorum infections in koalas, the authors of this report discuss the risks associated with koala translocations and potential management strategies for those risks.

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Non-invasive evaluation of physiological stress in an iconic Australian marsupial: the koala (Phascolarctos cinereus)

Narayan, EJ, Webster, K, Nicolson, V, Mucci, A & Hero, J 2013, General and Comparative Endocrinology, vol. 187, pp. 39-47.

In order to monitor physiological stress, the authors of this study used enzyme-immunoassay (EIA) to detect faecal cortisol metabolite (FCM) concentrations in both captive and wild koalas. An adrenocorticotropic hormone (ACTH) challenge was used for biological validation of the FCM EIA. For captive koalas, sex, lactation status and handling status significantly affected FCM levels. Additionally, FCM levels did not differ significantly between wild and captive koalas.

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Number of nearby visitors and noise level affect vigilance in captive koalas

Larsen, MJ, Sherwen, SL & Rault, J 2014, Applied Animal Behaviour Science, vol. 154, pp. 76-82.

Both proximity to and noise created by visitors to zoos and other facilities displaying captive koalas have been identified as causing increased vigilant behaviour of captive koalas. These findings have implications for the welfare management of captive koalas.

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One size does not fit all: Monitoring faecal glucocorticoid metabolites in marsupials

Fanson, KV, Best, EC, Bunce, A, Fanson, BG, Hogan, LA, Keeley, T, Narayan, EJ, Palme, R, Parrott, ML, Sharp, TM, Skogvold, K, Tuthill, L, Webster, KN & Bashaw, M 2017, General and Comparative Endocrinology, vol. 244, no. 1, pp. 146-156.

A comparison of five assays for monitoring adrenocortical activity in response to stress in thirteen marsupial species, including the koala, has shown that the suitability of assays varies greatly among species. This finding indicates that an effective assay for this purpose must be identified for each marsupial species individually.

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Post-fire survival and reproduction of rehabilitated and unburnt koalas

Lunney, D, Gresser, SM, Mahon, PS & Matthews, A 2004, Biological Conservation, vol. 120, pp. 567-575.

Comparisons of koalas rehabilitated after sustaining burn injuries following a fire event against uninjured koalas found no significant difference in post-release survival and reproductive success between the two groups, indicating human intervention and rehabilitation efforts can be beneficial to conservation efforts following fire.

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Serological assessment of chlamydial infection in the koala by a slide EIA technique

Ueno, H, Mizuno, S, Takashima, I, Osawa, R, Blanshard, W, Timms, P, White, N & Hashimoto, N 1991, Australian Veterinary Journal, vol. 68, no. 12, pp. 393-396

A slide enzyme immunosorbent assay (EIA) that can reliably detect Chlamydia psittaci antibody in koala blood serum is described in this study, presenting a rapid, simple and reliable alternative to existing methods.

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Surgical implantation of temperature-sensitive transmitters and data-loggers to record body temperature in koalas (Phascolarctos cinereus)

Adam, D, Johnston, SD, Beard, L, Nicholson, V, Lisle, A, Gaughan, J, Larkin, R, Theilemann, P, McKinnon, A & Ellis, W 2016, Australian Veterinary Journal, vol. 94, nos. 1-2, pp. 42-47.

With climate change predicted to influence the distribution of koala populations throughout Australia’s east coast, the individual responses of koalas to unsuitable temperatures may have important conservation implications. Accordingly, in this study, the suitability of temperature-sensitive intra-abdominal implants for tracking koala core body temperature was assessed. Findings were consistent across all koalas, revealing body temperatures ranging from 34.2﮿C to 37.7﮿C.

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The rescue and rehabilitation of koalas (Phascolarctos cinereus) in southeast Queensland

Burton, E & Tribe, A 2016, Animals, vol. 6, no. 56.

Data from koalas admitted to four wildlife hospitals in southeast Queensland from 2009 to 2014 were analysed to determine how the treatment and rehabilitation of koalas could be improved. It was found that clinical outcomes varied considerably between hospitals, particularly in terms of time spent in care and euthanasia and release rates, and these findings have implications for the improvement koala rehabilitation practices.

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Use of quantitative real-time PCR to monitor the shedding and treatment of chlamydiae in the koala (Phascolarctos cinereus)

Markey, B, Wan, C, Hanger, J, Phillips, C & Timms P 2007, Veterinary Microbiology, vol. 120, no. 1, pp. 334-342.

A quantitative real-time analysis revealed that antibiotic treatment for koalas with chlamydial infections caused chlamydiae to shed rapidly and in great numbers from both ocular and urogenital sites, with the majority of infections cleared after two weeks of treatment.

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Vaccination of healthy and diseased koalas (Phascolarctos cinereus) with a Chlamydia pecorum multi-subunit vaccine: Evaluation of immunity and pathology

Kollipara, A, George, C, Hanger, J, Loader, J, Polkinghorne, A, Beagley, K & Timms, P 2012, Vaccine, vol. 30, no. 1, pp. 1875-1885.

A multi-subunit chlamydial vaccine has been developed that was safe for administering to both healthy and diseased koalas, and that produced strong antibody and lymphocyte proliferation responses.

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Vaccination of koalas with a prototype chlamydial vaccine is safe, does not increase the incidence of lymphoma-related disease and maybe associated with increased lifespan in captive koalas

Hernandez-Sanchez, J, Brumm, J, Timms, P & Beagley, KW 2015, Vaccine, vol. 33, no. 1, pp. 4459-4463.

An experimental Chlamydia vaccination previously tested on a population of captive koalas at Lone Pine Koala Sanctuary has been shown not to increase the incidence of neoplasias, and may also increase the lifespan of captive koalas. The median lifespan for koalas treated with the prototype vaccine was 12.5 years; 3.7 years longer than that of unvaccinated koalas. A comparison of vaccinated and unvaccinated koalas revealed that the vaccine did not increase the incidence of lymphoma or leukemia, and the vaccination is therefore considered safe for koalas.

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Vaccination of koalas (Phascolarctos cinereus) with a recombinant chlamydial major outer membrane protein adjuvanted with poly I:C, a host defense peptide and polyphosphazine, elicits strong and long lasting cellular and humoral immune responses

Khan, SA, Waugh, C, Rawlinson, G, Brumm, J, Nilsson, K, Gerdts, V, Potter, A, Polkinghorne, A, Beagley, K & Timms, P 2014, Vaccine, http://dx.doi.org/10.1016/j.vaccine.2014.08/037

A single-dose Chlamydia vaccine induced significant and long-term cellular and humoral immune responses in six healthy female koalas. The vaccine was based on a three-component adjuvant consisting of polyinosinic-polycytidylic acid (poly I:C), polyphosphazine (PCEP) and a host defence peptide (HDP), combined with the Chlamydia pecorum recombinant chlamydial major outer membrane protein (rMOMP) antigen. Koalas immunised with the vaccine exhibited strong mucosal antibody and C. pecorum-specific neutralising antibody responses in the plasma and at mucosal sites. The vaccine also caused the proliferation of lymphocytes responding specifically to both whole chlamydial elementary bodies and C. pecorum rMOMP protein.

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