Antibody and Cytokine Responses of Koalas (Phascolarctos cinereus) Vaccinated with Recombinant Chlamydial Major Outer Membrane Protein (MOMP) with Two Different Adjuvants.

Shahneaz Ali Khan,Jon Hanger,Adam Polkinghorne,Kenneth Beagley,Courtney Waugh,Jo Loader,Marion Desclozeaux,Volker Gerdts,Peter Timms,Andrew Potter,Ashlesh K Murthy

doi:10.1371/journal.pone.0156094

Abstract

Developing a vaccine against Chlamydia is key to combating widespread mortalities and morbidities associated with this infection in koalas (Phascolarctos cinereus). In previous studies, we have shown that two or three doses of a Recombinant Major Outer Membrane Protein (rMOMP) antigen-based vaccine, combined with immune stimulating complex (ISC) adjuvant, results in strong cellular and humoral immune responses in koalas. We have also separately evaluated a single dose vaccine, utilising a tri-adjuvant formula that comprises polyphosphazine based poly I: C and host defense peptides, with the same antigen. This formulation also produced strong cellular and humoral immune responses in captive koalas. In this current study, we directly compared the host immune responses of two sub-groups of wild Chlamydia negative koalas in one population vaccinated with the rMOMP protein antigen and adjuvanted with either the ISC or tri-adjuvant formula. Overall, both adjuvants produced strong Chlamydia-specific cellular (IFN-γ and IL-17A) responses in circulating PBMCs as well as MOMP-specific and functional, in vitro neutralising antibodies. While the immune responses were similar, there were adjuvant-specific immune differences between the two adjuvants, particularly in relation to the specificity of the MOMP epitope antibody responses.

Highlights

Chlamydial infections are responsible for significant mortality and morbidity of mainland koalas (Phascolarctos cinereus) and are one major factor threatening the long term future of this iconic species [1,2,3,4]
We evaluated, in detail, both the cellular and humoral immune responses of wild koalas vaccinated with Recombinant Major Outer Membrane Protein (rMOMP), combined either with (a) the single-dose trivalent adjuvant (Tri-Adj) or (b) three doses of immune stimulating complex (ISC)
There was a non-significant trend towards stronger IFN-γ and IL-17A responses in animals immunised with the Tri-Adj compared to ISC immunised animals

Summary

Introduction

Chlamydial infections are responsible for significant mortality and morbidity of mainland koalas (Phascolarctos cinereus) and are one major factor threatening the long term future of this iconic species [1,2,3,4]. Several small animal studies have confirmed the protective role of IFN-γ secreting CD4+T cells in chlamydial infection [8]. There is re-emerging evidence supporting the prominent role of B cells to elicit protective anti-Chlamydia antibodies [9]. Once the bacterium parasitises the host’s cells, the cell mediated immune response pathway contributes significantly to protective immunity through IFN-γ secretion [11]. Whilst IL-17A is a strong recruiter of neutrophils which secrete antimicrobial peptides and promote a Th1 immune response against intracellular pathogens [12], other animal studies suggest that IL-17 plays a role in both immune pathology and protection [13]

Methods

Results

Conclusion