Adler R. Dillman, Ph.D. - US grants

? DESCRIPTION (provided by applicant): Parasitic nematodes are able to avoid and suppress the immune system of their hosts so successfully that more than 25% of the global population is infected by nematode parasites. Current strategies to control nematode infections are inadequate and increased drug resistance is a global concern. One strategy to reduce the prevalence of nematode infections is to prevent these parasites from suppressing host immunity, thus allowing the host's immune response to counter or eliminate infections. However, little is known about how nematode parasites avoid detection or how they suppress immunity. A growing body of research suggests that nematode fatty acid- and retinol-binding (FAR) proteins are involved in parasitism and help the parasites suppress immunity. The most successful and widely used drug to treat nematode infections, Ivermectin, has been show to bind directly to or interfere with the binding of nematode FAR proteins. Here I propose to: 1) identify the arsenal of FAR proteins that parasitic nematodes secrete into hosts, 2) determine the binding affinity and specificity of these FAR proteins to fatty acid immune signaling molecules, and 3) determine the effect of FAR proteins in an in vivo infection model. I will investigate the role of FAR proteins i nematode infections using the insect-parasitic nematode Steinernema carpocapsae and the model insect host Drosophila melanogaster. These models overcome technical obstacles associated with studying human parasites and have been successfully used to increase our understanding of vertebrate parasites and innate immunity. This K22 award will provide the experimental resources, time, and training to identify the FAR proteins used in parasitism and to determine their functional role in infection. Specifically, this award will allow me to develop 1) skills in the purification and identification of secreted proteins, 2) tools and expertise in the cloning and expression of transgenic proteins and, 3) generate novel and important data that will establish the foundation of a new research program. These studies address an understudied area in immunology: how parasitic nematodes suppress host immunity. Moreover, by exploiting the powerful fruit fly and insect-parasitic nematode model systems I will establish a unique set of tools to define the molecular underpinnings of immune suppression that can then be taken and tested in an appropriate vertebrate system and used to develop and test treatments that target these parasitic immune effectors.

7. Project Summary/Abstract Parasitic nematodes continue to cause significant morbidity and mortality in humans and animals on a global scale. Central to their virulence is the ability to infect specific tissues and to evade and/or subvert the host?s immune response. A better understanding of the molecules and pathways triggered by the nematode parasite that govern its survival and migration through the host could allow identification of new therapeutic targets for nematode infection. It is widely recognized that helminth immune modulation and the pathology they cause is largely effected through the release of proteins and small molecules that interact with host cells and tissues, and that these molecules are key factors in tissue tropism. Previous and current helminth secretome and excreted/secreted protein (ESP) studies have been done in vitro, due to the difficulty of obtaining large volumes of ESPs from small helminth parasites. However, there has been no rigorous validation that the in vitro induction of ESPs mimics in vivo conditions. Additionally, the effects of host immune pressure on expression of ESPs and other nematode genes are unknown. To fill these current gaps in knowledge, we propose to perform high resolution transcriptomic profiling at the single nematode level of Nippostrongylus brasiliensis throughout its life cycle in a genetically susceptible or resistant rodent host. We will profile the transcription of parasites as they transition from free-living to being actively parasitic, and as they infect the lung and the intestine. N. brasiliensis is in the order Strongylida, closely related to hookworm, and it shares many life cycle features with hookworm, such as skin penetration, infection of the lungs, and infection of the intestine. Data from this project will provide stage-specific gene signatures that are associated with the tissue tropism of hookworms and determine how they are influenced by host immune pressure. Our proposed study will test the assumption that i) intestinal nematodes initiate specific genetic programs and ESPs that determine tissue tropism; ii) the context of host immune pressure affects parasite transcriptional programs. Further, by comparing transcriptional profiles of nematodes under in vivo culture conditions and comparing them to nematodes under in vitro conditions, we can directly test the assumption that in vitro conditions mimic in vivo infection. Data generated will lay the foundation for future studies on helminth tissue tropism, ESPs, and immune-targeted helminth pathways.

Project Summary/Abstract A central aspect of parasitic nematode success and prevalence is their ability to modify host biology, including evade and/or subvert the host?s immune response. In some cases, humans can host thousands of nematode parasites with little to no pathology, yet our understanding of this incredible evasion or suppression of the immune system remains limited. Modulation of host biology and the pathology they cause is largely effected through the release of proteins and small molecules that interact with host cells and tissues. There are hundreds of proteins released in nematode spit during an infection and only a few have been studied in any detail. My lab is focused on understanding host-parasite interactions, with an emphasis on elucidating the molecules that parasites release into the host, characterizing their interaction with host signaling pathways to modulate host biology, and learning from the evolution of the parasite arsenal how to manipulate the immune system. Over the next five years my lab will identify key genetic pathways in lipid-mediated immune signaling and identify molecular host- parasite interactions. Our specific focus will be to 1) establish experimental pipelines for identifying novel parasite-derived proteins and small molecules that modulate host biology, 2) determine the effects of the molecules we identify, beginning with members of the fatty acid- and retinol-binding (FAR) protein family, 3) elucidate molecular interactions between parasite molecules and host pathways, and 4) characterize eicosanoid signaling in Drosophila melanogaster, a genetic model of immunity. A major strategy of my lab's research is to combine in silico, in vitro, and in vivo experimental approaches with an established infection model that leverages our deep understanding of fruit fly biology and its powerful genetics, to reveal not only the binding targets of parasite proteins and molecules in an active infection, but also to define their effect on infection outcomes. Our overall goal is to understand how nematode parasites modify host biology in order to successfully infect them. This includes parasites? ability to evade and/or suppress host immunity, which is important to human health in at least two ways. First, nematode infections continue to be a major source of global morbidity and mortality, affecting more than 25% of the world?s population. Increasing drug resistance and recurring infections compound this problem. And second, there is mounting evidence that the immunomodulatory effects of nematode infections can dampen or even eliminate the pathologies that define autoimmune disorders such as Crohn?s disease, inflammatory bowel disease, and Celiac disease. Understanding how nematodes suppress the immune system will lead to new treatment and vaccination strategies against nematode infection, and may reveal new avenues for treating autoimmune disorders. We will employ a powerful model system to probe immune modulation by nematodes to identify specific secreted proteins and small molecules as well as the signaling pathways they target to effectively manipulate host immunity.