Characterisation of the immune compounds in koala milk using a combined transcriptomic and proteomic approach
Katrina M. Morris1, Denis O’Meally1, Thiri Zaw2, Xiaomin Song2, Amber Gillett3, Mark P. Molloy2, Adam Polkinghorne4 & Katherine Belov1
1Faculty of Veterinary Science, University of Sydney, Camperdown, NSW, 2006, Australia.
2Australian Proteome Analysis Facility, Dept. Chemistry and Biomolecular Sciences, E8C310, Research Park Drive, Macquarie University, NSW, 2109. Australia.
3Australia Zoo Wildlife Hospital, Beerwah, Queensland 4519, Australia.
4Centre for Animal Health Innovation, Faculty of Science, Health, Education and Engineering, University of the Sunshine Coast, Maroochydore, Qld, 4558, Australia.
Correspondence and requests for materials should be addressed to K.B. (email: )
Production of milk is a key characteristic of mammals, but the features of lactation vary greatly between monotreme, marsupial and eutherian mammals. Marsupials have a short gestation followed by a long lactation period, and milk constituents vary greatly across lactation. Marsupials are born immunologically naïve and rely on their mother’s milk for immunological protection. Koalas (Phascolarctos cinereus) are an iconic Australian species that are increasingly threatened by disease. Here we use a mammary transcriptome, two milk proteomes and the koala genome to comprehensively characterise the protein components of koala milk across lactation, with a focus on immune constituents. The most abundant proteins were well-characterised milk proteins, including β-lactoglobulin and lactotransferrin. In the mammary transcriptome, 851 immune transcripts were expressed, including immunoglobulins and complement components. We identifed many abundant antimicrobial peptides, as well as novel proteins with potential antimicrobial roles. We discovered that marsupial VELP is an ortholog of eutherian Glycam1, and likely has an antimicrobial function in milk. We also identifed highly-abundant koala endogenous-retrovirus sequences, identifying a potential transmission route from mother to young. Characterising the immune components of milk is key to understanding protection of marsupial young, and the novel immune compounds identifed may have applications in clinical research.