IMPACT OF FUNGAL ADAPTATION UPON HOST RECOGNITION AND PATHOGENESIS

Fungal infections have a major impact on human health. Pathogenic (disease causing) fungi cause life-changing oral, genital and skin infections, and life-threatening systemic infections affecting internal organs. Most individuals carry the fungus Candida albicans in their microflora. Normally our immune system recognises invading Candida cells and kills them, thereby protecting us from infection. However, Candida infections arise when the efficiency of this immune surveillance is compromised. Hence this fungus is a frequent cause of irritating yeast infections such as "thrush". It also causes life-threatening bloodstream infections in weak and vulnerable patients, often undoing the excellent work done by cancer treatment and intensive care medicine. Indeed, in some patient groups, over 40% of these infections are fatal. As well as having a significant impact on human health, these infections have a significant economic impact. Despite the availability of reasonably effective antifungal drugs, bloodstream infections are estimated to extend the hospitalisation of patients by 22 days, increasing health care costs by over £20,000 per patient. As yet, no antifungal vaccines are available. Their development depends on an understanding of the mechanisms by which our immune system recognises and kills Candida cells.

Significant progress has been made however. Research from a number of laboratories (including our own) has revealed that immune cells recognise specific types of molecule on the Candida cell surface as "foreign". After recognising these molecules ("pathogen-associated molecular patterns"), the immune cells generally swallow the Candida cells (a process called "phagocytosis"), and then kill them by subjecting the fungus to a battery of toxic chemicals, thereby clearing the infection. This generally accepted view is based largely on experiments involving Candida albicans cells grown in the laboratory under well-defined culture conditions on specific growth media, and not cells grown in an infected host. Unfortunately, these laboratory growth media differ significantly from the conditions that Candida experiences during an infection. We have shown recently that changes in growth conditions significantly affect: (a) the architecture of the Candida cell surface; (b) recognition by our immune system; and (c) Candida's capacity to cause disease. Therefore our hypothesis is that during the onset and progression of an infection, Candida cells encounter and adapt to changes in host niches, thereby affecting their growth. This affects the expression and exposure of "pathogen-associated molecular patterns" on the fungal cell surface. We predict that these changes strongly influence the effectiveness of local immune surveillance, allowing more fungal cells to survive these host defences, thereby influencing disease progression and the outcome of the infection. In other words, fungal physiology resists host immunology.

The over-arching goal of our research programme is to test this hypothesis by defining the effects of Candida adaptation mechanisms upon the efficacy of immune surveillance and infection outcome. With the help of the three postdoctoral researchers, plus two PhD students provided by Aberdeen University, we will achieve this by combining our synergistic expertise in the analysis of Candida albicans nutrient and stress adaptation, the Candida cell surface, Candida pathogen-associated molecular patterns and immune recognition, the dynamics of phagocytosis and fungal killing, and Candida infection biology. We will integrate well-established molecular approaches with powerful new genomic technologies and state-of-the-art cellular imaging (many of which were developed in our labs). This research is essential if we are to properly understand anti-Candida immunity in the context of disease onset and progression. This knowledge will facilitate the development of effective anti-Candida vaccines and novel immunotherapies.

An individual's susceptibility to fungal infection is heightened by factors that attenuate immune surveillance. Considerable progress has been made in defining the mechanisms by which innate immune cells recognise and clear Candida albicans, the major fungal pathogen of humans. These depend on the recognition of specific pathogen-associated molecular patterns (PAMPs) by host pathogen recognition receptors (PRRs). To date, C. albicans PAMPs have generally been defined using fungal cells grown under standardised conditions in vitro that do not accurately reflect dynamic host microenvironments. In reality, the fungus is a moving target. It adapts to host signals such as local nutrients, thermal fluctuations and iron limitation by altering its cell surface. We recently showed that the adaptation of C. albicans to physiologically relevant carbon sources triggers dramatic changes in cell wall architecture, immune recognition and virulence. Therefore, in this programme we will test our hypothesis that fungal adaptation within host niches influences the efficacy of local immune surveillance, thereby strongly impacts on disease progression. First, we will establish how fungal adaptation impacts on PAMP exposure at the C. albicans cell surface by combining targeted molecular dissection in C. albicans and the host with genomic-wide screens and biochemical characterisation. Next we will define how these changes influence the dynamics of Candida-phagocyte interactions by combining precise molecular intervention with state-of-the-art 4-D video microscopy. We will also exploit new synthetic reporters to determine the impact of these changes on disease progression in well-established infection models. Furthermore, the molecular characterisation of C. albicans cells from patient samples will establish the relevance of these major findings to human infection. In this way we will establish a key principle in infection biology - that fungal adaptation resists host immunology.

Our programme addresses an understudied issue of central importance to fungal infection. We will generate valuable new information about the impact of fungal adaptation upon host immunity and infection outcome. This will benefit companies interested in developing anti-Candida vaccines and therapies, clinicians specialising in medical microbiology, the general public, and our researchers. To maximise our impact in these areas we will continue to:
1. Ensure that our scientific observations and datasets are disseminated effectively.
2. Protect and exploit any valuable intellectual property that arises during the project.
3. Contribute to public outreach programmes with a view to enhancing the public understanding of science.
4. Further enhance our collaborations in the UK and abroad.
5. Provide an excellent and multidisciplinary training for our PDRAs.

DISSEMINATION:
We will continue to disseminate our findings to academics, companies and clinicians through: publications in leading journals; presentations at international conferences on molecular biology, immunology and infection biology; the release of large datasets to public repositories; collaborations with international colleagues, clinical mycologists and companies; and through our personal websites.

IP & TRANSLATION:
We will regularly review our work to identify potentially valuable IP with our Research and Innovation Office. In particular, we will protect information that might lead to the development of anti-Candida vaccines or novel immunotherapies that complement the limited number of antifungal drugs currently available to treat systemic fungal infections. The commercial translation of valuable findings will be achieved with help from our extensive and longstanding links with SMEs and pharmaceutical companies. These activities will be financed by our MRC Confidence in Concept Fund and Wellcome Trust-funded Institutional Strategic Support Fund and BBSRC Excellence With Impact award.

In the longer term, our programme will facilitate the development of more effective antifungal therapies. This clinical impact will be realised through Erwig (a practicing clinician), Mihai Netea and Adilia Warris (a clinical mycologist in the Aberdeen Fungal Group), and our many clinical colleagues in the medical mycology field.

PUBLIC OUTREACH:
This programme will be of interest to the general public because many individuals suffer Candida infections. [This fungus is a frequent cause of oral and vaginal thrush. (Most women suffer an episode of vaginitis in their lifetime. Over 75 million women suffer >4 episodes/year.) Also, C. albicans is a common cause of life-threatening systemic infections that, even with current antifungal drugs, display high morbidities (>40%).] We will continue our public outreach activities with support from our Aberdeen University Public Engagement Unit and Press Office. We disseminate information via our Aberdeen Fungal Group website and Facebook page, and through our Wellcome Trust Strategic Award website. This includes information about controversial issues as well as fungal immunology and medical mycology to counteract public exposure to misinformation and questionable treatments. In the longer term the public will benefit through the development of improved antifungal therapies (above).

COLLABORATION:
This programme involves new US collaborators. They extend our large collaborative network that includes partners in North America, European Networks, UK Wellcome Trust Strategic Consortia, and the Scottish Infectious Disease Research Initiative.

TRAINING:
Our researchers will receive an excellent multidisciplinary training in medical mycology, molecular biology, genomics, phagocyte biology and infection biology. Their career development will be enhanced by our collaborative networks, regular mentoring, and training in transferable skills of relevance to diverse sectors. This will build UK capacity in this under-represented field.