Vaccination of Koalas with a Recombinant Chlamydia
Major Outer Membrane Protein Induces
Antibodies of Different Specificity Compared to Those
Following a Natural Live Infection

Avinash Kollipara, Adam Polkinghorne, Kenneth W. Beagley, Peter Timms*

Institute of Health and Biomedical Innovation Queensland University of Technology, Kelvin Grove, Queensland, Australia

Chlamydial infection in koalas is common across the east coast of Australia and causes significant morbidity,
infertility and mortality. An effective vaccine to prevent the adverse consequences of chlamydial infections in koalas
(particularly blindness and infertility in females) would provide an important management tool to prevent further
population decline of this species. An important step towards developing a vaccine in koalas is to understand the
host immune response to chlamydial infection. In this study, we used the Pepscan methodology to identify B cell
epitopes across the Major Outer Membrane Protein (MOMP) of four
C. pecorum strains/genotypes that are
recognized, either following (a) natural live infection or (b) administration of a recombinant MOMP vaccine. Plasma
antibodies from the koalas naturally infected with a
C. pecorum G genotype strain recognised the epitopes located in
the variable domain (VD) four of MOMP G and also VD4 of MOMP H. By comparison, plasma antibodies from an
animal infected with a
C. pecorum F genotype strain recognised epitopes in VD1, 2 and 4 of MOMP F, but not from
other genotype MOMPs. When
Chlamydia-free koalas were immunised with recombinant MOMP protein they
produced antibodies not only against epitopes in the VDs but also in conserved domains of MOMP. Naturally infected
koalas immunised with recombinant MOMP protein also produced antibodies against epitopes in the conserved
domains. This work paves the way for further refinement of a MOMP-based
Chlamydia vaccine that will offer wide
cross-protection against the variety of chlamydial infections circulating in wild koala populations.