Pan-genome reverse vaccinology of Staphylococcus aureus bovine mastitis

Lead Research Organisation: University of Edinburgh
Department Name: The Roslin Institute

Abstract

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.

Technical Summary

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.

Planned Impact

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.

Publications

10 25 50
 
Description To date, we have identified a long-list of possible vaccine candidates which have been cloned and will be further screened for their potential. In the final year, a short-list will be tested for protective efficacy. We have now carried out different screening assays to provide a shortlist for testing including indirectly testing in vivo expression- Currently, antigens are being tested for protective efficacy in a dairy cow model of mastitis.

We now have a short list of vaccine candidates that are being tested in pools of antigens for protection against challenge. We will know the outcome within the next 2 months.
Once these data are obtained, we will be able to examine the possibility of any IP from the study and will decide on a publication strategy accordingly.
Exploitation Route Possible development as a commercial vaccine for S. aureus bovine mastitis

Limited publications to date due to potential IP outcome from the work (related to a novel vaccine)
Sectors Agriculture, Food and Drink,Healthcare,Pharmaceuticals and Medical Biotechnology

 
Title Bovine S. aureus sequence dataset and set of conserved vaccine antigens 
Description The reverse vaccinology approach has resulted in a representative sequence dataset and list of conserved predicted antigens 
Type Of Material Biological samples 
Year Produced 2017 
Provided To Others? No  
Impact Not yet publicly available but will be useful resource to research community 
 
Description Collaboration with Keun Seok Seo 
Organisation Mississippi State University
Country United States 
Sector Academic/University 
PI Contribution Collaborative research into the function of bacterial superantigens- sequence, evolutionary, and functional analysis
Collaborator Contribution functional analysis of bacterial superantigens
Impact 1: Moon BY, Park JY, Hwang SY, Robinson DA, Thomas JC, Fitzgerald JR, Park YH, Seo KS. Phage-mediated horizontal transfer of a Staphylococcus aureus virulence-associated genomic island. Sci Rep. 2015 Apr 20;5:9784. doi: 10.1038/srep09784. PubMed PMID: 25891795; PubMed Central PMCID: PMC4402969. 2: Wilson GJ, Seo KS, Cartwright RA, Connelley T, Chuang-Smith ON, Merriman JA, Guinane CM, Park JY, Bohach GA, Schlievert PM, Morrison WI, Fitzgerald JR. A novel core genome-encoded superantigen contributes to lethality of community-associated MRSA necrotizing pneumonia. PLoS Pathog. 2011 Oct;7(10):e1002271. doi: 10.1371/journal.ppat.1002271. PubMed PMID: 22022262; PubMed Central PMCID: PMC3192841.
Start Year 2010
 
Description Industrial partnership with Zoetis Animal Health 
Organisation Zoetis
Country United States 
Sector Private 
PI Contribution Identification of conserved antigens expressed during infection which represent candidate vaccine components
Collaborator Contribution Cash funding and challenge experiments in dairy cows
Impact Subject to confidentiality agreement
Start Year 2013
 
Description Conference presentations (Korea; UK) 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Third sector organisations
Results and Impact Poster presentations by PDRA describing the vaccine design
Year(s) Of Engagement Activity 2016
 
Description Media interviews for Nature Ecol evol paper 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Public/other audiences
Results and Impact Talking to various media including print and radio regarding our Nature Ecology and Evolution publication
Year(s) Of Engagement Activity 2018