Macrophage sabotage: undermining macrophage signalling by Klebsiella pneumoniae

Respiratory infections are the leading cause of infectious disease mortality and morbidity in UK, affecting roughly 1% of the adult population per year. This health burden is increasing due to ageing of the population, growing numbers of immunosuppressed patients and multidrug-resistant microorganisms. 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. 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. Furthermore, there is still scant evidence on K. pneumoniae pathogenesis at the molecular and cellular level. The development of new therapeutic strategies requires a better understanding of K. pneumoniae pathophysiology in the context of the complex interactions between bacterial pathogens and their hosts.
Macrophages have been at the heart of immune research for over a century and are an integral component of innate immunity. Not surprisingly, macrophages also play a critical role in the clearance of K. pneumoniae in vivo. However, in a landmark contribution of the laboratory we have discovered that K. pneumoniae survives inside macrophages hence suggesting that Klebsiella may exploit macrophages to enhance its survival while avoiding immune control. In this project, by bridging cellular microbiology and immunology, we will gain holistic understanding of the strategies used by K. pneumoniae to manipulate macrophages to survive during pneumonia. Furthermore, and by building up upon this knowledge platform, we also set out to provide evidence demonstrating that antagonism of this virulence strategy will favour pathogen clearance. 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. There are already drugs approved for use in humans which may target this Klebsiella virulence strategy. From the drug discovery point of view, this significantly circumvents the drug development process hence allowing a potential fast-track transition from the basic research to clinical development. Altogether, we envision that our results will encourage other academics as well as pharmaceutical companies to follow this avenue of research to tackle the problem of lack of therapies for microbes resistant to antibiotics.

Macrophages have been at the heart of immune research for over a century and are an integral component of innate immunity. This proposal will investigate one of the most remarkable anti-macrophage strategies identified to date: undermining macrophage antibacterial activity by co-opting macrophage systems dedicated to control the host immune balance. By bridging cellular microbiology and immunology, in this proposal we will provide compelling evidence demonstrating that a Klebsiella pneumoniae virulence strategy is the manipulation of macrophage plasticity to enhance its own survival. This proposal builds up upon a landmark study of the Bengoechea laboratory demonstrating that K. pneumoniae persists intracellularly in human and mouse macrophages within a unique compartment. K. pneumoniae has been recently singled out as an "urgent threat to human health" 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. To provide mechanistic insights into how K. pneumoniae manipulates macrophages, we will pursue the following questions: (i) to detail how K. pneumoniae subverts macropjhage signalling, (ii) to identify Klebsiella factors required for manipulating macrophage signalling; and (iii) to provide evidence for anti-virulence strategies against K. pneumoniae infections. Altogether, the study of Klebsiella infection biology offers unique opportunities to gain fundamental knowledge about mechanisms by which a pathogen overcomes innate immune mechanisms. The studies proposed in this application may serve as the foundation for novel therapeutic and prevention strategies targeting the host-pathogen interface.

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 main collaborative interactions will be with Prof Philippe J. Sansonetti (Institut Pasteur) on Klebsiella infection biology; however we anticipate exciting new collaborations with groups focusing on macrophage biology. The research will enhance the career development of the requested PDRA. S/he will receive training in some of the most novel aspects of host-pathogen interactions with emphasis on innate immune signaling. 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 is a need to develop effective therapeutics based on new targets and approaches. The anticipated results of this proposal will provide rationale to use cell therapy, particularly macrophage manipulation, to treat infectious diseases. This area is considered one of the next pillars in biomedicine It is therefore believed that validation of this approach will meet big interest at pharmaceutical companies. Public bodies: The UK Government is committed to taking an integrated approach to tackle the antimicrobial resistance challenge as part of the one health agenda at a national and international level. 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. 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 the PDRA 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, @dr_beckie). Queen's University Belfast and the Bengoechea laboratory web pages will be additional channels to promote this BBSRC-funded research