Live attenuated vaccines to prevent against disease caused by A. pleuropneumoniae

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Actinobacillus pleuropneumoniae (APP) is a bacterium that causes lung disease in pigs, and is responsible for substantial deaths, morbidity and economic losses in the worldwide pig industry. After good husbandry practices are considered, antimicrobials and vaccines are used to control disease caused by APP. Antimicrobial resistance is a major concern, and the mostly widely used bacterin "inactivated whole cell" vaccines only protect against homologous or a few of the 16 APP serovars. The most promising are live attenuated vaccines (LAVs) as they are cheap to produce, and evidence suggests they give heterologous (other serovar) protection, and prevent colonisation. We will develop an LAV that consists of one or two APP strains that express the major ApxI-III toxins (for cross-serovar protection), will allow a differentiation of infected from vaccinated animals (DIVA) approach, and will not revert to wild-type virulence. Expression of one or two of ApxI-III is predominantly in a serovar-dependent manner., and an immune response to the toxins is considered important for protection. Two strategies will be used involving the construction of: (1) one APP LAV strain expressing inactivated ApxI-III; or (2) two APP LAV strains expressing combinations of ApxI-III. In each case inactivation of ApxI-III will be achieved by mutation of residues known to be important for their haemolytic and\or cytotoxic activities. Further gene deletions known to result in promising APP LAV strains willalso be tested. In all cases, the apxIV (encoding the APP-specific and immunogenic protein ApxIV) and the sxy (encoding Sxy required for natural transformation) genes will be deleted, enabling a DIVA approach, and preventing reversion of LAVs to their wild-type virulence, respectively. LAVs will be tested for homologous and heterologous protection in pigs. An effective APP LAV will result in a substantial decrease in deaths, suffering and economic losses in the worldwide pig industry.

There is an urgent need for effective vaccines to combat the highly contagious, and economically important, disease caused by Actinobacillus pleuropneumoniae (APP), which affects the UK and worldwide swine industry. Our research aims to meet this need through the development of a novel APP live attenuated vaccine (LAV) which targets all 16 serovars, can be used in a differentiating infected from vaccinated animals (DIVA) approach, will not revert to wild-type virulence, and can be used in the presence of maternally derived antibodies. Success would offer a step change in capability for combating APP, but would have far reaching impact for the treatment of other veterinary bacterial diseases more broadly. This work therefore closely addresses the key BBSRC Strategic Priorities of 'Animal Health', 'Welfare of Managed Animals' and 'Combating Antimicrobial Resistance', and the beneficiaries of this research and how they will benefit are as follows:

*Academic Researchers: through broad academic advancement and instigation of new research programmes
The data generated by this work will be of immediate benefit to researchers in Universities, Research Institutes and Industry with interests in bacterial pathogenicity, vaccines, host response to pathogens, as well as those interested in host-pathogen interactive biology research more broadly. Focusing on the immediate beneficiaries, these include, among others, scientists in the UK and abroad working directly on vaccines for APP. In particular, an immediate avenue of investigation will be to confirm whether the approach has broader applicability to other veterinary pathogenic bacterial species, leading to a potentially rapid evolution of related vaccines for bacterial infections.

* The veterinary commercial sector: through exploitation and commercialisation
Our research aims to provide the basis for an LAV approach will be readily exploitable by the vaccine industry. In the longer term, a successful conclusion of the project and introduction to the market has the potential to create wealth and economic prosperity through increased turn-over, profit and exports, and creating and safeguarding jobs for the company and workers involved.

* The swine industry: through the ability to effectively treat APP
In the longer term, a successful LAV to prevent APP disease will reduce medication costs, reduce pig suffering and mortality and overall reduce the significant economic impact on the swine industry of APP. In particular, a successful APP LAV to prevent bacterial disease overcomes the issue of antimicrobial resistance, a recognized global threat. In the UK the target for the pig industry is to reduce antibiotic use to 99 mg/population corrected unit in 2020, and further reductions beyond this. In the long term, given the use of antimicrobials in the control of APP, an APP LAV will facilitate meeting further reductions within the pig sector.

* The general public: through increasing public engagement with research.
Throughout it will be possible to engage with the general public and local schools to raise the profile of the research area and project. This will encourage interest in biosciences research and UK innovation and provide a context to local bioscience education.

* Researchers working directly on the project: thereby contributing to a highly trained workforce.
The skills gained by the researchers working on this innovative project will be highly transferable; providing an excellent training experience to enable them to embark on a successful future career in any setting including academia or industry. For example, working on a joint academia-industrial research project provides experience in collaboration and team working, participation in outreach activities, gives experience in communicating effectively with non-specialists, and through publishing manuscripts, patents, and presenting work at conferences they will hone their verbal and written skills.