Klebsiella anti-immunology: exploiting proteins with a eukaryotic SEFIR domain

Our struggle against infectious diseases is far from over. Globalization has increased the risk of pandemics, and the rise of antibiotic-resistant microbes threatens to render existing drugs useless. Public Health England has calculated that the lack of effective antibiotics will render more than the three million operations and cancer treatments life threatening, and more than 90,000 people are estimated to die in the UK over the next 30 years due to antibiotic resistant infections. Of particular concern is the mounting prevalence of respiratory infections caused by Gram-negative bacteria, in particular Klebsiella pneumoniae (the focus of this project), with a 12% increased in incidence in the last five years only in the UK.This is particularly alarming given the high rates of resistance to empirical antibiotics commonly recommended for Klebsiella treatment. In fact, the increasing isolation of strains resistant to "last resort" antimicrobials has significantly narrowed, or in some settings completely removed, the therapeutic options for the treatment of Klebsiella infections. Not surprisingly, 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. Unfortunately, at present, we cannot identify candidate compounds in late-stage development for treatment of multidrug Klebsiella infections; this pathogen is exemplary of the mismatch between unmet medical needs and the current antimicrobial research and development pipeline. Worryingly, recent studies have alerted that several Klebsiella virulent and multidrug resistant isolates have access to a mobile pool of virulence and antimicrobial resistance genes; hence making possible the emergence of a multidrug resistant, hypervirulent K. pneumoniae isolate capable of causing untreatable infections in healthy individuals. However, our understanding of Klebsiella pathogenesis still contains considerable gaps thereby making a compelling case to better understand Klebsiella infection biology in the context of the complex interactions between bacterial pathogens and their hosts.
In this proposal, by combining the distinct but synergistic expertise across the disciplines of molecular and cellular microbiology, immunology and biochemsitry of the Bengoechea, Moynagh and Schroeder laboratories, we will uncover a hitherto unknown Klebsiella immune evasion strategy directed to blunt IL17-governed host defenses, which have been shown to be essential for the clearance of Klebsiella infections. Our research will reveal that this immune evasion strategy also attenuates host defense signalling launched upon activation of the receptors implicated in sensing infections. Collectively, this proposal will shed new light into the sophisticated means exploited by pathogens to overcome host defenses while opening new opportunities to develop 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. There is extensive research on the pathways targeted by Klebsiella, and new drugs are currently under development. We anticipate that the outcomes of this proposal would lead to test these drugs in pre-clinical models of klebsiella disease, hence allowing a potential fast-track transition from the basic research to clinical development.

As a result of the pressure imposed by the immune system, pathogens have evolved sophisticated methods to overcome innate immune mechanisms. Many bacterial pathogens rely on immune-regulatory proteins blocking the activation of a small number of transcriptional factors, NF-kB, MAPKs, IRFs, which control the activation of host defense mechanisms. In this project, by exploiting the power of cellular microbiology and in vivo models, we will expose a bacterial immune evasion strategy based on prokaryotic proteins with eukaryotic domains to block the essential receptor-adaptor interaction. We will provide compelling evidence demonstrating that Klebsiella pneumoniae exploits an effector protein with a SEFIR domain, found in proteins of the IL17 signalling pathway, to antagonize host defenses. This proposal leverages the expertise of the Bengoechea, Moynagh and Schroeder laboratories on Klebsiella infection biology, innate immune signalling and effector biology, respectively, to provide mechanistic insights into (i) how pathogens undermine IL17 signalling, and (ii) how they control immune responses and cell-autonomous immunity. Altogether, our research will place Klebsiella as a cell biologist manipulating early events of innate immune signalling. K. pneumoniae is been recognized as an "urgent threat to human health", making imperative to to better understand its infection biology to design new strategies to treat Klebsiella infections. The findings of this proposal may serve as the foundation for novel therapeutic and prevention strategies based on enhancing innate host resistance to infection, and ameliorating pathophysiological tissue destruction.

Who will benefit from this research? Academics will be the main short to medium term beneficiary, as the research will provide knowledge to understand how pathogens counteract the activation of host defenses. This is one of the most competitive areas of research in the field of microbial pathogenesis and immunology. The main collaborative interactions will be groups interested on Klebsiella (Dr Kat Holt and Dr Sylvain Brisse), and international consortia such as the Norwegian Klebsiella network (http://nor-kleb.net/) and the JPIAMR SPARK project (Spread of Population-wide Antibiotic Resistance in Klebsiella). We anticipate exciting new collaborations with groups focusing on systems delivering bacterial effectors, and on proteins with eukaryotic domains. The research will enhance the career development of Dr sa Pessoa (named researcher). Dr. sa Pessoa was responsible for a significant amount of the background research. Industry: The growing number of organisms resistant to available antibiotics has become a public health threat worldwide, being Klebsiella a paradigm of an emerging pathogen. There are already drugs under development targeting the signalling pathways manipulated by Klebsiella which can be tested in our pre-clinical infection models. This will allow a fast-track transition from the basic research to clinical development. Public bodies: The project and the information generated may 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 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: Infections are one of the major global threats that are unfortunately very likely to become more urgent in the near future. It is not appropriate to generate an atmosphere of fear since medical care in UK is at a very high level. However, 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.
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. Pre prints will be deposited in bioRxiv archive. 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 Dr sa Pessoa 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 therapeutics to treat infections might have economic potential since royalty payments can reach numbers in the magnitude of several millions or tens of millions. This new treatment(s) will benefit the UK health system. 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. Social media will be targeted via Twitter (@josebengoechea, @gunnar_ns). Queen's University Belfast and the Institute web pages will be additional channels to promote this BBSRC-funded research.