Pan-genome reverse vaccinology of Staphylococcus aureus bovine mastitis

Staphylococcus aureus is an important cause of hospital- and community-associated infections of humans. In addition, S. aureus causes economically-important infections of livestock such as bovine mastitis (infection of the udder) which is a major economic burden on the global dairy industry and an important animal welfare issue. Bovine mastitis is typically difficult to treat with antibiotics due in part to the capacity of S. aureus to become intracellular, and antibiotic-resistance is an increasing problem. Accordingly, a vaccine which protects against S. aureus mastitis would be highly desirable. Recently, the availability of the entire genetic code for pathogenic bacteria has been has been useful for identification of antigens predicted to induce a protective immune response. Such studies have resulting in promising vaccines for several important human pathogens. Here, we propose to utilise a similar approach based on the genetic code for all of the subtypes of S. aureus which cause bovine mastitis. This will allow us to identify antigens which are made by all strains, and which induce antibodies which promote bacterial killing and disrupt host-pathogen interactions. Importantly, the capacity to induce protective immunity will be examined in dairy cows. Overall, the study will result in a better understanding of how S. aureus causes bovine mastitis and which antigens may be useful as a vaccine to prevent disease, increase productivity and reduce animal suffering.

Staphylococcus aureus is a major pathogen responsible for life-threatening infections of humans and economically-important infections of livestock. In particular S. aureus is a leading cause of bovine mastitis, resulting in major economic losses to the dairy industry worldwide. The disease is often chronic and is difficult to treat effectively with antibiotics due in part to the capacity of S. aureus to invade epithelial cells, and to the recent emergence of antibiotic-resistant strains. Accordingly, a vaccine which protects against S. aureus bovine mastitis would be of considerable benefit to the global dairy industry. Recently, reverse vaccinology approaches utilising bacterial whole genome sequences for antigen identification have resulted in promising vaccines for several human pathogens. Currently, we are carrying out a large genome sequencing project of a total of ~60 isolates representing each of the common bovine-adapted S. aureus clones. This will provide a unique resource to facilitate identification of predicted antigens (including cell wall-associated and secreted proteins) which are encoded by all S. aureus clones associated with bovine mastitis. Bioinformatic identification of predicted conserved antigens will be followed by expression analysis and testing of the immune function of the antibodies induced by each antigen. The capacity of selected proteins to induce a protective immune response will then be tested in challenge experiments of dairy cows, and the the role of the selected antigens in host-pathogen interactions will be examined. It is anticipated that the project will result in new information regarding the nature of protective antigens which could be further evaluated as a potential vaccine for preventing S. aureus bovine mastitis.

The beneficiaries outside of the academic research community would include the pharmaceutical industry and in particular, the industrial partners Pfizer who will stand to benefit from a licensed vaccine or novel therapeutics which are developed as a result of the project. Veterinary clinicians will benefit directly from the development of approaches for the prevention of bovine mastitis as this should reduce or eliminate the requirement for antibiotic treatments which are often inadequate, lead to residues in milk, and may contribute to the emergence of antibiotic resistance. The dairy farmers will benefit from the project as an effective vaccine could result in reduced impact of the disease on productivity leading to greater economic returns. Recent evidence suggests that cows may represent a reservoir for the emergence of antibiotic resistance which could then be spread to human pathogenic bacteria. Accordingly, the wider public in general would stand to be a beneficiary of the project. It is expected that this preliminary vaccine work if successful, could lead to the development of a commercial product within a relatively short space of time, and it is anticipated that the benefits could be realised within several years after the completion of the grant. Within the research community, groups interested in the pathogenesis of bacterial infections, protein biologists, and immunologists will all benefit from the research as it is likely to result in new insights into host-bacterial interactions and the basis of protective immunity to S. aureus. The applicants are skilled in explaining complex scientific findings to lay audiences both in the UK and to international audiences. At The Roslin Institute, we provide information about our research through our web site, talks and discussion groups and direct interaction with the media. The Roslin Institute has a policy of promoting public engagement by means of interaction with the media, presentations, publications, exhibitions and schools activities. The authors plan to publish their results in a number of different formats including high impact academic publications and other publication materials such as popular science articles aimed at the general public. The PI, Dr Fitzgerald will oversee the project and its management and will coordinate the collaborations and be responsible for identification implementation of all impact opportunities. In terms of academic and public communication, each member of the team will contribute where appropriate with regard to writing research publications, public engagement material and liaising with the media. We have an agreement in place with Pfizer who would receive first licensing option for any commercial opportunities which derive from the project. The Roslin Institute is supported by Edinburgh Research and Innovation (ERI), which is a non-profit subsidiary company of the University of Edinburgh, owned entirely by the University. ERI provides a complete range of pre-award research and commercialisation services for researchers, inventors, consultants and entrepreneurs within the University of Edinburgh.