Klebsiella pneumoniae type VI secretion system: a weapon for innate immunity warfare

The global problem of antimicrobial resistance (AMR) is fast becoming one of the major scientific and health issues of modern times. No surprisingly, AMR is included in the recently release UK government "National Risk Register of Civil Emergencies" that may directly affect the UK over the next 5 years. More than 80,000 deaths are estimated if there is a widespread outbreak of a resistant microbe. The development of new antibiotics is slow and difficult work but bacterial resistance is decreasing our arsenal of existing drugs. A post-antibiotic era - in which common infections and minor injuries can kill - far from being an apocalyptic fantasy, is a very real possibility for the 21st Century. The recent O'Neill review on AMR sets out the global threat by highliting that "drug-resistant infections already kill hundreds of thousands a year globally, and by 2050 that figure could be more than 10 million". Of particular concern is the mounting prevalence of infections caused by multidrug resistant Gram-negative bacteria, in particular Klebsiella pneumoniae. This pathogen has been singled out as an "urgent threat to human health" by the UK Government, the U.S. Centers for Disease Control and Prevention, and the World Health Organization due to extremely drug resistant strains. However, there is scant evidence on K. pneumoniae pathogenesis at the molecular and cellular level. Therefore, it is both urgent and necessary to better understand its pathophysiology to be able to design new strategies to treat Klebsiella infections.
Previous studies from the laboratory support the notion that Klebsiella subverts the activation of host defence mechanisms to survive in the lung. While we have progressed on understanding the cellular pathways manipulated by the pathogen to block inflammation, there is a major gap on decoding the anti-immune factors employed by Klebsiella. By applying a multidisciplinar approach encompassing cellular and molecular microbiology, innate immunity, structural bioinformatics; and exploiting Saccharomyces cerevisiae to express heterologous proteins, we will embark on harnessing basic knowledge about how Klebsiella pneumoniae type VI secretion system (T6SS)-delivered effectors block the activation of cell intrinsic immunity. T6SS is a recently discovered nanomachinery that bacteria use to deliver proteins to a recipient cell (either a competitor bacteria and/or an eukaryotic cell). We will characterize Klebsiella T6SS at the molecular level. We will dissect how T66S-delivered proteins antagonize the activation of the signalling pathway controlling the majority of host defense responses upon infection. And, finally, we will illuminate a hithertho unknown Klebsiella virulence strategy based on targeting mitochondrial dynamics.
Harnessing the host-pathogen interface opens the avenue for new antimicrobial therapeutics. Interference with pathogen virulence and/or signalling pathways hijacked by pathogens for their own benefit is an especially compelling approach, as it is thought to apply less selective pressure for the development of resistance than traditional strategies, which are aimed at killing pathogens or preventing their growth. It is therefore believed that such targets - if found and validated during the research - will meet big interest at pharmaceutical companies.

Subversion of host defence systems is considered important for pathogen survival during the early stages of infection. This proposal will investigate one of the most remarkable anti-host strategies: quenching host signalling pathways by translocation of bacterial proteins into the cell. By combining cellular and molecular microbiology, innate immunity, structural bioinformatics; and exploiting Saccharomyces cerevisiae to express heterologous proteins, we will embark on harnessing basic knowledge about how Klebsiella pneumoniae type VI secretion system (T6SS)-delivered effectors block the activation of cell intrinsic immunity. K. pneumoniae has been recently singled out as an "urgent threat to human health" by the UK Government, the U.S. Centers for Disease Control and Prevention, and the World Health Organization due to extremely drug resistant strains. However, there is scant evidence on K. pneumoniae pathogenesis at the molecular and cellular levels. Therefore, it is both urgent and necessary to better understand its pathophysiology to be able to design new strategies to treat Klebsiella infections. We will pursue the following question at the forefront of research in infection biology: (i) decoding Klebsiella factors involved in re-programming cell functions; (ii) uncovering the action of Klebsiella T6SS effectors to counteract cell intrinsic immunity; and (iii) illuminating new virulence strategies of Klebsiella (targeting mitochondrial dynamics and cytoskeleton). This innovative project rises to the challenges of improving our understanding of host immunity, enhancing antimicrobial stewardship and combatting multi-resistant infections. A better understanding of the host-pathogen interface, offers the potential to develop therapies based on targeting host factors manipulated by the pathogen for its own benefit (host directed therapeutics) and the Klebsiella factors needed for (anti-virulence therapeutics).

Who will benefit from this research? Academics will be the main short to medium term beneficiary. This state-of-the-art project represents a significant step forward on our understanding of Klebsiella infection biology and will illuminate general principles of microbial pathogenesis. The research will enhance the career development of Dr Palacios (named Researcher). Dr. Palacios was responsible for a significant amount of the background research. Industry: our investigations could result in the transfer of knowledge from academia to industry to develop new therapies and even products of commercial interest. Effectors and T6SS delivery system could become targets to develop new antimicrobials (anti-virulence therapeutics). Our study of Klebsiella effectors could potentially lead to the use of these proteins to re-programme cellular functions. The enormous potential of bacterial effectors to manipulate eukaryotic systems places these proteins at the center to develop cellular engineering science. Effectors offer great potential as biotechnological tools. It is also possible to use effectors and delivery systems for immunomodulation, vaccine development or gene therapy purposes.This knowledge transfer would increase wealth and foster economic competitiveness of UK-based industry. On top of this, this knowledge transfer could result in new therapies hence being benefitial for the UK health system. Public bodies: The project and the information generated will benefit UK based government bodies such as the Chief Medical Officer, the Dept of Health, and the Dept for Environment, Food and Rural Affaires as the data will provide an evidence-base for policy developments. This proposal is clearly aligned with the strategic action "supporting the development of new antimicrobials and alternative treatments" outline in the UK antimicrobial resistance strategy 2013-2018. General public: Antimcirobial resistance is one of the pressing health issues. It is advisable to increase public awareness about the potential threats and to provide the UK national regulatory bodies, with a top-class knowledge platform to maintain the unique position of UK as an area of research excellence on infection biology. This project offers also a unique opportunity to enhance the attractiveness of science for young people.

How will they benefit from this research?: Knowledge of value to the academic sector will be communicated by publication in peer-reviewed journals, oral and poster presentations at conferences and via invited lectures. Exchange of staff and students will promote knowledge transfer between collaborative groups. Staff working on the project will receive training on complementary skills (group management, know-how transfer, and entrepreneurship) which together with the cutting-edge research training received will give them all options for either an excellent career in academia, industry, or to develop a business plan for their own start-up enterprise. Knowledge transfer to industry on new targets to treat infections and biotechnological tools might have economic potential since royalty payments can reach numbers in the magnitude of several millions or tens of millions. The grant will have impact on the wider public sector by continuing our program of scientific communication. The laboratory hosts undergraduates to engage them in the fundamentals of scientific research. A video clip on infection biology will serve to disseminate our research work. Social media will be targeted via Twitter (@josebengoechea). Dr. Palacios will be involved in the public communication activities of this project.The planned symposium will disseminate our results to key stakeholders (scientists, clinitians and senior officials). There will be an outreach presentation covering the importance of microbiology for human health. This session will be opened to the general public.