Curr Top Microbiol Immunol Impact Factor
Agata Schweiss
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Coronaviruses are pathogens with a serious impact on human and animal health. They mostly cause enteric or respiratory disease, which can be severe and life threatening, e.g., in the case of the zoonotic coronaviruses causing severe acute respiratory syndrome (SARS) and Middle East Respiratory Syndrome (MERS) in humans. Despite the economic and societal impact of such coronavirus infections, and the likelihood of future outbreaks of additional pathogenic coronaviruses, our options to prevent or treat coronavirus infections remain very limited. This highlights the importance of advancing our knowledge on the replication of these viruses and their interactions with the host. Compared to other +RNA viruses, coronaviruses have an exceptionally large genome and employ a complex genome expression strategy. Next to a role in basic virus replication or virus assembly, many of the coronavirus proteins expressed in the infected cell contribute to the coronavirus-host interplay. For example, by interacting with the host cell to create an optimal environment for coronavirus replication, by altering host gene expression or by counteracting the host's antiviral defenses. These coronavirus-host interactions are key to viral pathogenesis and will ultimately determine the outcome of infection. Due to the complexity of the coronavirus proteome and replication cycle, our knowledge of host factors involved in coronavirus replication is still in an early stage compared to what is known for some other +RNA viruses. This review summarizes our current understanding of coronavirus-host interactions at the level of the infected cell, with special attention for the assembly and function of the viral RNA-synthesising machinery and the evasion of cellular innate immune responses.
IMP hosts an annual retreat featuring our faculty and students presenting their more recent research, as well as an invited keynote speaker. The keynote speakers usually attend for the duration of the retreat and add a great perspective with their Q&A during talks and poster presentations. Recent keynote speakers have included Ramnik Xavier (MGH), Greg Barton (UC Berkeley) and Neal Alto (UTSW). In addition to the retreat, IMP organizes a robust, semester-long seminar program where outside experts in the field visit campus for a day, present their current research and interact with students and faculty. In addition, IMP organizes several social and informational sessions each fall to welcome new students.
PhD candidate Maureen Hester has experienced UMass Chan as an undergraduate intern, research laboratory technician and as a PhD student. Her research targets Cryptococcus neoformans, a fungal pathogen that can cause pneumonia and progress to meningitis.
Epigenetic inheritance is a process by which parental exposure to environmental factors influences offspring phenotype. This field of investigation has wide-ranging implications for human health. Epidemiologic studies have shown that exposure of parents or grandparents to starvation, trauma, cigarette smoke, or other stressors alters offspring susceptibility to cardiovascular disease, obesity, lung disease, or other conditions. Research with animal models has mirrored these findings and offers tools for disentangling the underlying mechanisms of epigenetic information transfer from parent to offspring. Such research has been greatly enabled by recent technological advances, including next generation sequencing and fundamental discoveries like microRNA biology. In vitro fertilization experiments demonstrate that sperm carry sufficient information to propagate epigenetic phenotypes across generations, and research with these paternal epigenetic inheritance models has identified sperm-associated small non-coding RNAs (sncRNA) as carriers of information from father to offspring. I have established an epigenetic inheritance model in which paternal influenza infection, with virus elimination and disease recovery prior to mating, results in an adaptive attenuation of disease severity (significantly decreased weight loss) in response to influenza infection in offspring, as well as a maladaptive altered glucose metabolism. While these phenotypes are robust, the underlying mechanism of information transfer to offspring remains to be determined. In preliminary experiments to address the mechanism I have found that influenza infection alters sperm-associated sncRNA. This proposal addresses the hypothesis that influenza virus-induced changes in sperm-associated sncRNA populations alter embryo development resulting in offspring metabolic and immune phenotypes. Aim 1 elucidates the underlying epigenetic inheritance mechanism through kinetic analysis of sperm sncRNA and early embryo development. Aim 2 determines the specificity of the offspring epigenetic inheritance phenotype to the paternal stressor both directly by challenging with a non-cross reactive strain of influenza virus, and indirectly by further metabolic phenotyping to determine if paternal influenza infection alters glucose homeostasis and liver gene expression in the offspring in ways similar to other paternal stressors. This research will provide valuable insight into the mechanism underlying epigenetic inheritance, and do so within the context of a novel epigenetic inheritance model with direct relevance to human health.
The mechanisms of pathogen sensing and immune effector induction in intestinal epithelial cells are not completely understood. Disruption in the mechanisms of pathogen sensing and immune homeostasis in intestinal epithelial cells can lead to dysbiosis and inflammation, as well as susceptibility to bacterial infection. Key insights into intestinal epithelial cell immunity and host-pathogen interactions have been made using the nematode C. elegans. Nematodes mount innate immune defenses against bacterial infection via conserved immune pathways, but the mechanisms of pathogen detection are unknown in this organism. In nematodes, the family of nuclear hormone receptors (NHRs) has dramatically expanded compared to other metazoans. NHRs are ligand-gated transcription factors that sense endogenous and exogenous signals to induce adaptive transcriptional responses. The C. elegans genome encodes 274 NHRs, of which 260 are homologs of human HNF4α. HNF4α is a key NHR involved in inflammatory bowel disease, though the mechanism through which HNF4α mediates inflammatory bowel disease in humans is unknown. The central hypothesis of this proposal is that C. elegans HNF4α homologs are an ancient family of pathogen sensors whose evolutionary expansion in C. elegans was driven by their function in detecting diverse pathogens. The following key findings support this hypothesis: (i) The nuclear hormone receptor, NHR-86/HNF4α, senses the cellular environment and activates C. elegans intestinal immune defenses; (ii) NHR-86/HNF4α is required for pathogen resistance and immune response towards the gram positive human pathogen E. faecalis; and (iii) A different C. elegans HNF4α homolog is required for pathogen defense and immune effector regulation against the gram negative pathogen P. aeruginosa. In this proposal, Aim 1 will define the role of C. elegans NHR-86/HNF4α in pathogen detection and immune effector induction during E. faecalis infection using a combination of transcriptomics, ChIP- sequencing, tissue-specific rescue and genetic epistasis. Aim 2 will characterize the function of a separate C. elegans HNF4α homolog in pathogen sensing during P. aeruginosa infection. The approach includes: transcriptomics, global NHR binding site identification, tissue specific rescue, and P. aeruginosa genetics. Collectively, these studies will characterize a fundamentally new paradigm of immune activation, which will solve a major conundrum of how pathogens are sensed in C. elegans. These findings will also establish NHRs as evolutionarily ancient pathogen sensors. Ultimately, the expectation is that detailed dissection of this mechanism will shed light on the role of HNF4α in mammalian pathogen sensing and inflammatory bowel disease.
Pulmonary lung fibrosis is a poorly understood process that can arise in pediatric patients with gain-of-function mutations that disrupt the regulation of the cytosolic double stranded DNA sensing pathway, cGAS-STING. This project will define the role that B cells play in mediating lung fibrosis in a mouse model of STING gain-of- function autoinflammation that recapitulates a human disease known as STING Associated Vasculopathy with onset in Infancy (SAVI). The expectation is that the results of these studies will offer insights into the mechanisms by which B cell contribute to fibrotic lung disease and assess, using murine models, whether targeting B cells is a valid strategy for prophylactically treating lung fibrosis.
The respiratory mucosa employs the innate and adaptive immune system to protect normal respiratory function from invading organisms. However, when there is a defect in one of these defenses the host becomes vulnerable to Aspergillus fumigatus (Af). This ubiquitous fungus enters the airways as a spore, or resting conidium but is generally cleared by intact respiratory defenses. However, when individuals are immunocompromised, Af conidia are more likely to germinate and form filamentous structures called hyphae. As this morphotype, Af can become invasive particularly in persons with low neutrophil counts. An estimated 200,000 people are diagnosed with invasive aspergillosis annually worldwide, and up to 90% die from the infection. Af can also colonize the airways of those who suffer from asthma or cystic fibrosis causing allergic bronchopulmonary aspergillosis (ABPA), which affects over 4 million people annually worldwide. Studies proposed here seek to further understand the intact innate immune response to Af conidia, particularly the involvement of interleukin-23 (IL-23) and interleukin-17 (IL-17). A better understanding of this response may uncover nuances associated with the host defects that predispose to infection with Af, as well as potentially inform rational vaccine design and immunotherapies against Af. Af conidia elicit IL-23 and IL-17 production from the host airways within the first 24 hours of infection. These cytokines are known to be important for the adaptive TH17 response. However their role in innate immunity against Af is largely unknown. IL-23 has been shown to augment IL-17 production, and in turn IL-17 elicits neutrophil recruitment. The relationship between IL-23 and IL-17 is referred to as the IL-23/IL-17 axis and this proposal aims to systematically characterize each portion of this axis in the innate response against Af conidia, and test whether this response is required for protection against this mycosis. In order to characterize the temporal production pattern of IL-23, we will measure levels of this cytokine at regular intervals in the fist 72 hours of infection by ELISA. From a preliminary screen, we have uncovered candidate cell types that may be involved in the production of IL-23. We aim to confirm these sources by in vivo and ex vivo intracellular cytokine staining. To test whether IL-23 production is protective against mortality in Af infection, the survival rates of wild-type (WT) mice will be compared to a functional IL-23 knock-out strain (IL-23p19-/-). Finally, we propose to create mixed bone marrow chimeras to test whether any specific cellular source of IL-23 is required for protection against Af (Specific Aim 1). The temporal pattern of production for IL-17 and its source will also be characterized in the first 72 hours of infection with Af using methods described above. To test whether IL-23 augments IL-17 production innately in response to Af, IL-17 levels will be assessed in IL-23p19-/- mice and WT mice. In addition, we have evidence that IL-23 and IL-17A are co-produced by one innate cell type in response Af, we propose to test and dissect any potential autocrine mechanisms in this cell type. Finally, the role of IL-17 in protection against f infection will also be tested by monitoring the survival of IL-17RA-/- mice and WT mice (Specific Aim 2). Because many at risk for IA are transplant patients who are iatrogenically immunosuppressed, knowledge of the factors leading to protection against aspergillosis could also inform development of targeted immunosuppressive agents that keep defenses against opportunistic infections intact.