Spatially Targeted Proteomics of the Host-Pathogen Interface during Staphylococcal Abscess Formation.
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ABSTRACT:
SUBMITTER: Guiberson ER
PROVIDER: S-EPMC7796985 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:Staphylococcus aureus is a major contributor of healthcare-associated infections and able to withstand numerous frequently used antibiotics. In order to develop novel treatment approaches, a deeper understanding of the complex interaction between host and pathogen is required. This is particularly true for the processes during development of tissue abscesses, which are important contributors to acute and persistent staphylococcal infections. Notably, the formation of staphylococcal abscesses takes place in distinct stages. Consequently, studies aiming to elucidate the underlying mechanisms of abscess development have to take temporal and spatial components into account. State-of-the-art proteomic technologies offer insight into complex biological systems. However, the pairing of spatial information and deep proteomic analysis is challenging, complicating the targeted analysis of relatively small-scale and heterogeneous structures like organ abscesses. To overcome existing technical limitations, we have previously introduced the use of a spatially targeted liquid extraction surface analysis (LESA) workflow termed “microLESA”. In our current study, we perform microLESA to investigate the processes at the host-pathogen interface during development of staphylococcal kidney abscesses in a murine model of systemic infection. For this investigation, regions from the abscess community, the interface surrounding the abscess, and the cortex of infected kidneys were extracted and analyzed at both 4- and 10-days post infection. By defining the proteome of different abscess regions across the course of infection, we followed the immune response and bacterial contribution to abscess development through spatial and temporal proteomic changes. The information gathered was then mapped through pathway analysis to characterize the metabolic processes at the host-pathogen interface during staphylococcal infection.
2020-11-30 | PXD019920 | Pride
Project description:Abscesses are a hallmark of invasive staphylococcal infections and the site of a dynamic struggle between pathogen and host. However, the precise host and bacterial factors that contribute to abscess formation and maintenance have not been completely described. In this work, we define the Staphylococcus aureus abscess proteome from both wild-type and neutropenic mice to elucidate the host response to staphylococcal infection and uncover novel S. aureus virulence factors. Among the proteins identified, the mouse protein histone H4 was enriched in the abscesses of wild-type compared with neutropenic animals. Histone H4 inhibits staphylococcal growth in vitro demonstrating a role for this protein in the innate immune response to staphylococcal infection. These analyses also identified staphylococcal proteins within the abscess, including known virulence factors and proteins with previously unrecognized roles in pathogenesis. Within the latter group was the universal stress protein Usp2, which was enriched in kidney lesions from neutropenic mice and required for the S. aureus response to stringent stress. Taken together, these data describe the S. aureus abscess proteome and lay the foundation for the identification of contributors to innate immunity and bacterial pathogenesis.
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Project description:The staphylococcal virulon is controlled largely by the agr locus, a global accessory gene regulator that is autoinduced by a self-coded peptide (AIP) and is therefore a quorum sensor. The agr locus has diverged within and between species, giving rise to AIP variants that inhibit heterologous agr activation, an effect with therapeutic potential against Staphylococcus aureus: a single dose of an inhibitory AIP blocks the formation of an experimental murine abscess. As the AIP is unstable at physiological pH, owing to its essential thiolactone bond, its single-dose efficacy seems paradoxical, which has led us to analyze the in vivo kinetics of agr activation and the consequences of its blockage by a heterologous AIP. Initially, the infecting bacteria grow rapidly, achieving sufficient population density within the first 3 h to activate agr, and then enter a neutrophil-induced metabolic eclipse lasting for 2-3 d, followed by agr reactivation concomitantly with the development of the abscess. The inhibitory AIP prevents agr expression only during its short in vivo lifetime, suggesting that the agr-induced and therefore quorum-dependent synthesis of virulence factors shortly after infection is necessary for the subsequent development of the abscess lesion and bacterial survival. We confirm this finding by showing that a sterile agr+ supernatant causes a sterile abscess similar to the septic abscess caused by live bacteria. These results may provide a biological rationale for regulation of virulence factor expression by quorum sensing rather than by response to specific host signals.
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Project description:Siglecs are sialic acid (Sia) recognizing immunoglobulin-like receptors expressed on the surface of all the major leukocyte lineages in mammals. Siglecs recognize ubiquitous Sia epitopes on various glycoconjugates in the cell glycocalyx and transduce signals to regulate immunological and inflammatory activities of these cells. The subset known as CD33-related Siglecs is principally inhibitory receptors that suppress leukocyte activation, and recent research has shown that a number of bacterial pathogens use Sia mimicry to engage these Siglecs as an immune evasion strategy. Conversely, Siglec-1 is a macrophage phagocytic receptor that engages GBS and other sialylated bacteria to promote effective phagocytosis and antigen presentation for the adaptive immune response, whereas certain viruses and parasites use Siglec-1 to gain entry to immune cells as a proximal step in the infectious process. Siglecs are positioned in crosstalk with other host innate immune sensing pathways to modulate the immune response to infection in complex ways. This chapter summarizes the current understanding of Siglecs at the host-pathogen interface, a field of study expanding in breadth and medical importance, and which provides potential targets for immune-based anti-infective strategies.
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Project description:Interactions among multiple infectious agents are increasingly recognized as a fundamental issue in the understanding of key questions in public health regarding pathogen emergence, maintenance, and evolution. The full description of host-multipathogen systems is, however, challenged by the multiplicity of factors affecting the interaction dynamics and the resulting competition that may occur at different scales, from the within-host scale to the spatial structure and mobility of the host population. Here we study the dynamics of two competing pathogens in a structured host population and assess the impact of the mobility pattern of hosts on the pathogen competition. We model the spatial structure of the host population in terms of a metapopulation network and focus on two strains imported locally in the system and having the same transmission potential but different infectious periods. We find different scenarios leading to competitive success of either one of the strain or to the codominance of both strains in the system. The dominance of the strain characterized by the shorter or longer infectious period depends exclusively on the structure of the population and on the the mobility of hosts across patches. The proposed modeling framework allows the integration of other relevant epidemiological, environmental and demographic factors, opening the path to further mathematical and computational studies of the dynamics of multipathogen systems.
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Project description:RNA seq experiment was perfomed in the presence and absence of 500uM indole
2019-01-05 | GSE119440 | GEO
Project description:CONSPECTUS: The human innate immune system has evolved the means to reduce the bioavailability of first-row late d-block transition metal ions to invading microbial pathogens in a process termed "nutritional immunity". Transition metals from Mn(II) to Zn(II) function as metalloenzyme cofactors in all living cells, and the successful pathogen is capable of mounting an adaptive response to mitigate the effects of host control of transition metal bioavailability. Emerging evidence suggests that Mn, Fe, and Zn are withheld from the pathogen in classically defined nutritional immunity, while Cu is used to kill invading microorganisms. This Account summarizes new molecular-level insights into copper trafficking across cell membranes from studies of a number of important bacterial pathogens and model organisms, including Escherichia coli, Salmonella species, Mycobacterium tuberculosis, and Streptococcus pneumoniae, to illustrate general principles of cellular copper resistance. Recent highlights of copper chemistry at the host-microbial pathogen interface include the first high resolution structures and functional characterization of a Cu(I)-effluxing P1B-ATPase, a new class of bacterial copper chaperone, a fungal Cu-only superoxide dismutase SOD5, and the discovery of a small molecule Cu-bound SOD mimetic. Successful harnessing by the pathogen of host-derived bactericidal Cu to reduce the bacterial load of reactive oxygen species (ROS) is an emerging theme; in addition, recent studies continue to emphasize the importance of short lifetime protein-protein interactions that orchestrate the channeling of Cu(I) from donor to target without dissociation into bulk solution; this, in turn, mitigates the off-pathway effects of Cu(I) toxicity in both the periplasm in Gram negative organisms and in the bacterial cytoplasm. It is unclear as yet, outside of the photosynthetic bacteria, whether Cu(I) is trafficked to other cellular destinations, for example, to cuproenzymes or other intracellular storage sites, or the general degree to which copper chaperones vs copper efflux transporters are essential for bacterial pathogenesis in the vertebrate host. Future studies will be directed toward the identification and structural characterization of other cellular targets of Cu(I) trafficking and resistance, the physical and mechanistic characterization of Cu(I)-transfer intermediates, and elucidation of the mutual dependence of Cu(I) trafficking and cellular redox status on thiol chemistry in the cytoplasm. Crippling bacterial control of Cu(I) sensing, trafficking, and efflux may represent a viable strategy for the development of new antibiotics.
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Project description:Autophagy is a fundamental cellular process used for the turnover and recycling of cytosolic components and damaged organelles. Originally characterized as a response to cellular stress, it now is well established that autophagy also is used as a defensive mechanism to combat the infection of host cells by intracellular pathogens. However, although this defensive strategy does limit the proliferation of most pathogens within their host cells, successful pathogens have evolved countermeasures that subvert or circumvent the autophagic response. In this review, we discuss the mechanisms used by a number of these pathogens to escape autophagy, with a particular focus on Salmonella enterica serovar Typhimurium, which has been the most extensively studied example. We also discuss the consequences of bacterial autophagy for the broader innate immune response.
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Project description:Microbial establishment within the gastrointestinal (GI) tract requires surveillance of the gut biogeography. The gut microbiota coordinates behaviors by sensing host- or microbiota-derived signals. Here we show for the first time that microbiota-derived indole is highly prevalent in the lumen compared to the intestinal tissue. This difference in indole concentration plays a key role in modulating virulence gene expression of the enteric pathogens enterohemorrhagic Escherichia coli (EHEC) and Citrobacter rodentium Indole decreases expression of genes within the locus of enterocyte effacement (LEE) pathogenicity island, which is essential for these pathogens to form attaching and effacing (AE) lesions on enterocytes. We synthetically altered the concentration of indole in the GI tracts of mice by employing mice treated with antibiotics to deplete the microbiota and reconstituted with indole-producing commensal Bacteroides thetaiotaomicron (B. theta) or a B. theta ΔtnaA mutant (does not produce indole) or by engineering an indole-producing C. rodentium strain. This allowed us to assess the role of self-produced versus microbiota-produced indole, and the results show that decreased indole concentrations promote bacterial pathogenesis, while increased levels of indole decrease bacterial virulence gene expression. Moreover, we identified the bacterial membrane-bound histidine sensor kinase (HK) CpxA as an indole sensor. Enteric pathogens sense a gradient of indole concentrations in the gut to probe different niches and successfully establish an infection.IMPORTANCE Pathogens sense and respond to several small molecules within the GI tract to modulate expression of their virulence repertoire. Indole is a signaling molecule produced by the gut microbiota. Here we show that indole concentrations are higher in the lumen, where the microbiota is present, than in the intestinal tissue. The enteric pathogens EHEC and C. rodentium sense indole to downregulate expression of their virulence genes, as a read-out of the luminal compartment. We also identified the bacterial membrane-bound HK CpxA as an indole sensor. This regulation ensures that EHEC and C. rodentium express their virulence genes only at the epithelial lining, which is the niche they colonize.
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