B24 is the soft X-ray tomography beamline at Diamond offering both high resolution tomography and super resolution fluorescence microscopy facilities for biological samples. The beamline is at the later commissioning stages with an active user community already in place. The methods developed onsite promise to provide unique insights into the ultrastructure of cells under a variety of near physiological scenarios.
The main focus of my research is the elucidation of the effects of microbial challenge to the distribution of immunity factors and the cellular ultrastructure of primary phagocytes. Macrophages are the first line of defense within the context of innate immunity, an evolutionary conserved germ-line coded host defense.
Staphylococcus aureus is a major human pathogen causing significant morbidity and mortality due to community and hospital obtained infections. This pathogen causes a variety of diseases, including cellulitis, food poisoning, toxic shock syndrome, necrotizing pneumonia, and endocarditis. For many years S. aureus was classified as a typical extracellular pathogen. However, recent experiments evaluating invasion and the intracellular survival of S. aureus in endothelial and epithelial cells suggest that such events may contribute to the persistence of S. aureus during infections such as endocarditis and bovine mastitis. Moreover, it has long been known that professional phagocytes may serve as intracellular reservoirs of this specific pathogen. Recent in vitro studies have further confirmed high levels of resistance by S. aureus to neutrophil and macrophage mediated killing. This project seeks to deliver a spatial understanding of the interactions between Drosophila primary macrophages and S. aureus with emphasis on tracking the infection following both microbe molecules and host receptors and connect time, bacterial load and macrophage fate.
Over the past decade the incidence of invasive fungal infection in immunocompromised individuals has dramatically increased, with candidiasis being the most common. Although largely due to Candida albicans, a shift towards non-albicans Candida species such as C. glabrata has been recently observed (C. glabrata has reduced susceptibility to commonly used antifungal agents).
Candida albicans and C. glabrata are the two most common pathogenic yeasts of humans, yet they are phylogenetically, genetically and phenotypically very different. In this study, we will compare and contrast the strategies they employ to evade the host immune response. Although their strategies share basic concepts they differ greatly in their outcome. While C. albicans follows an aggressive infection strategy leading to the death of engaged professional clearance cells, C. glabrata has evolved a strategy which is based on stealth, evasion and persistence without causing severe damage in host cells. However both fungi are successful as commensals and as pathogens in humans.
At B24 we have established a primary phagocytes infection model using plasmatocytes extracted from Drosophila melanogaster larvae. These have proved to be a reliable and accessible model for the visualisation and tracking of a wide range of pathogens through the clearance pathways of plasmatocyte host cells. We now focus our study on understanding distinct host-pathogen interactions of the closely related Candida species, C. albicans and C. glabrata with a view to relating our results in the longer term to the their respective proteomes.
We use correlative cryo-microscopy (within the resident capabilities at beamline B24) to associate cell morphology and ultrastructure with distinct stages of the phagocytosis process (recognition, engulfment, phagosome maturation, and clearance). Thus we aim to reveal novel insights into the mechanisms that hinder effective phagocytic clearance and ultimately provide credible molecular targets towards effective fungal elimination strategies.