Author: Donna Huber

About the Speaker

Marc-Jan Gubbels received his Ph.D. at the University of Utrecht, the Netherlands, on diagnostics and vaccines for tick-transmitted Theileria and Babesia parasites of cattle. He then came to the CTEDG for a post-doc with Dr. Boris Striepen on Toxoplasma gondii. In 2005, he transitioned into an independent faculty position at Boston College and continued working on Toxoplasma. His lab is using and developing forward, reverse and functional genetic tools using enzymatic as well as fluorescent protein reporter assays in combination with cell sorting and fluorescence microscopy to learn more about the parasite’s cell biology.

Marc-Jan Gubbels’s Talk

Dr. Gubbels will give the following talk at 4:25 pm.

Of the Toxoplasma gondii Basal Complex Proteome: Cell Division, Apical Annuli and Beyond

Klemens Engelberg¹, Suyog Chavan¹, Tyler Bechtel², Victoria Sánchez-Guzmán¹, Allison Drozda¹, Eranthie Weerapana² and Marc-Jan Gubbels^1
1Department of Biology, Boston College, Chestnut Hill, MA, ²Department of Chemistry, Boston College, Chestnut Hill, MA

Toxoplasma gondii replicates by an internal budding mechanism producing two daughter parasites per division round. Budding is driven by cortical cytoskeleton assembly and concludes with the actions of the basal complex (BC). Although the BC is reminiscent of the contractile ring in higher eukaryotes, its composition, mechanism and controls differ substantially. To deepen our insights in this unusual cytokinesis apparatus, we dissected its proteomic composition by reciprocal proximity-dependent biotinylation experiments (BioID). This identified numerous undefined proteins, several of which with critical roles in cell division, next to hints at multiple phosphorylation-based controllers. Next, we assembled a protein-protein interaction network using interaction probability predictions, which defined several sub-complexes as well as protein hubs connecting the complexes. Furthermore, temporal resolution across the budding process revealed components uniquely associated with BC initiation, its expansion and, surprisingly, its mature phase, hinting at functions beyond cell division. Serendipitously, some of the BC proteins were also present in the enigmatic apical annuli, which comprise 5-6 donut shaped structures toward the basal end of the cytoskeleton. Assessment of the annuli resolved their architecture and provided hints toward a function in internal budding, thereby highlighting an underappreciated aspect of cell division.

More information about the Molecular Parasitology & Vector Biology Symposium and the schedule of presentions are available on our website. The deadline to register for the symposium is April 24.

About the Speaker

Macrophages are the major cell type infected by Leishmania parasites and the goal of my research is to define the relationship between Leishmania parasites, macrophages and the vasculature. Throughout my graduate studies and postdoctoral positions, I have dedicated my efforts toward understanding parasite-host interactions. As a graduate student at the University of Georgia carrying out research at the Centers for Disease Control and Prevention under Dr. Patrick Lammie, I was exposed to high caliber basic research in the CTEGD while simultaneously confronted with important public health issues in field settings related to neglected tropical diseases. My predoctoral research focused on the ability of monocytes to modulate lymphatic endothelial cell function and how this interaction contributed to the pathogenesis of human filarial disease. For my first postdoctoral position, I moved to the laboratory of Dr. Fabienne Tacchini-Cottier at the University of Lausanne in Switzerland. In Switzerland I gained experience using the mouse model to study the immunologic mechanisms involved in susceptibility to Leishmania infection. For my second postdoctoral position, I went to the laboratory of Phillip Scott at the University of Pennsylvania, a world-renowned professor and institution in the field of immunoparasitology. My initial project in the Scott lab, addressed the role of M2 macrophages as safe havens during Leishmania infection. For my second project in the Scott lab, I merged the knowledge and experience gained from my predoctoral research studying myeloid cells and vessels in filariasis with the technical experience of my first postdoctoral position to address the roles of innate cells in vivo in leishmaniasis. In the past months, I have transitioned to an Assistant Professor at the University of Arkansas for Medical Sciences (UAMS) where I have joined an elite group of vibrant and enthusiastic scientists with expertise in host-pathogen interactions. At UAMS, I am expanding upon previous studies examining vascular remodeling and the role of the VEGF-A/VEGFR-2 signaling pathway in lymphangiogenesis during Leishmania infection. In the future, I will work in collaboration with Dr. Camila Oliveira in Bahia, Brazil in a new project focusing on vascular remodeling during murine and human Leishmania braziliensis infection. These studies will provide important insights into our current understanding of the role of the vasculature during human disease.

Tiffany Weinkoff’s Talk

Dr. Weinkoff will give the following talk at 2:45 pm

The Role of Myeloid Cells in Vascular Remodeling during Leishmania major Infection

Tiffany Weinkopff
Department of Microbiology and Immunology, College of Medicine, University of Arkansas for Medical Sciences, Little Rock, AR, 72205, USA

Our lab investigates the mechanistic basis for the pathogenesis of disease driven by Leishmania, a protozoal parasite that causes cutaneous lesions. Following infection, lesion severity is often increased by an exaggerated inflammatory response. As a result, the inflammatory response can maintain disease even after the parasite infection has been controlled. Given vascular remodeling contributes to the magnitude of many inflammatory conditions, it is hypothesized that the manipulation of factors promoting angiogenesis or lymphangiogenesis would alter lesion severity in leishmaniasis. Our findings demonstrate that murine Leishmania major infection leads to dramatic changes in vessel morphology, number and permeability. At the peak of infection, VEGF-A and VEGFR-2 expression are upregulated and VEGFR-2 blockade led to a reduction in lymphatic endothelial cell proliferation and simultaneously increased lesion size without altering the parasite burden. We showed VEGF-A/VEGFR-2 signaling promotes lymphangiogenesis to restrict tissue inflammation in leishmaniasis. Given VEGF-A/VEGFR-2 signaling contributes to lesion resolution, we are currently investigating the cellular and molecular mediators driving VEGF-A production. We found that macrophages are the predominant cell type expressing VEGF-A during L. major infection and that parasites can directly induce VEGF-A production by macrophages in vitro. Given Leishmania parasites activate HIF-1α and this transcription factor induces VEGF-A expression, we analyzed the expression of HIF-1α during infection. We showed that macrophages are the major cell type expressing HIF-1α during infection and that parasite-induced VEGF-A production is mediated by HIF activation. We are presently examining VEGF-A expression in mice deficient in HIF signaling specifically in myeloid cells. To date, we have shown that LysMCre ARNTf/f mice express less VEGF-A than LysMCre ARNTf/+ control mice following infection, and we are exploring how decreased myeloid VEGF-A production influences vascular remodeling and lesion resolution in these animals. Altogether, these studies suggest macrophage HIF-dependent VEGF-A production contributes to lymphatic remodeling during L. major infection.

More information about the Molecular Parasitology & Vector Biology Symposium and the schedule of presentions are available on our website. The deadline to register for the symposium is April 24.

About the Speaker

James Morris is currently a Professor of Genetics and Biochemistry at Clemson University.  He earned his BS at The College of William and Mary in Williamsburg VA in 1990 and an M.S. in Entomology at the University of Georgia in Athens GA in 1992.  He completed his Ph.D. in Cellular Biology at the University of Georgia in 1997, characterizing the enzymology of a glycosylphosphatidylinositol phospholipase C from the African trypanosome, Trypanosoma brucei, under the supervision of Dr. Kojo Mensa-Wilmot.  Following his Ph.D., Jim moved to Baltimore MD to work in the laboratory of Dr. Paul T. Englund, where he was part of the team that developed the first RNAi-based library for forward genetics in any organism – in this case, the African trypanosome.  As part of this work, the team developed the vector pZJM (Jim is the “J”) that is still widely used for silencing genes in the parasite.

In 2003, Jim moved to Clemson University as an Assistant Professor in the Department of Genetics and Biochemistry, where he has remained to date.  His team has focused on resolving the mechanisms that protozoan parasites use to sense and metabolize the important sugar glucose during infection of their human host.  Through these studies, parasite-specific components of the sugar sensing and uptake pathway have been identified and, in an on-going collaborative effort, small molecule inhibitors of the pathways with anti-parasitic activity have been developed.  While his team has historically focused on the African trypanosome, more recent work on the malaria parasite Plasmodium falciparum and the brain-eating amoeba Naegleria fowleri suggests that exploiting the sugar metabolism pathways of these single-celled invaders may also prove useful in the development of new therapeutics.

James Morris’s Talk

Dr. Morris will give the following talk at 12:05 pm.

Pour Some Sugar on Me: Glucose, Development, Drug Discovery, and the African Trypanosome

James C. Morris
Eukaryotic Pathogens Innovation Center, Clemson University

Glucose is critical for the infectious blood stages of the African trypanosome, Trypanosoma brucei, serving as both a key metabolic agent and an important signaling molecule. While lack of the hexose is toxic to the proliferative long slender life stage of the parasite, the absence of glucose initiates differentiation in the non-dividing short stumpy (SS) form. These parasites demonstrate hallmarks of development into the next lifecycle stage, the procyclic form (PF) parasite, that include resumption of growth and expression of PF-specific antigens. Both SS differentiation and the growth of the resulting PF parasites is inhibited by glucose and non-metabolizable glucose analogs, with the latter observation suggesting a potential receptor-mediated mechanism for perception of the sugar. The importance of the hexose to the parasite for both metabolic a developmental needs suggests that glucose uptake or distribution inhibitors would be potentially useful anti-parasitic compounds. To identify small molecule inhibitors of glucose acquisition, we developed parasites that endogenously express FRET-based protein glucose sensors in the cytosol or glycosomes. Using these cells, we have completed a 25,000-compound pilot screen and have identified inhibitors with useful medicinal chemistry properties that have potential as a new line of lead compounds against the parasite.

More information about the Molecular Parasitology & Vector Biology Symposium and the schedule of presentions are available on our website. The deadline to register for the symposium is April 24.

About the Speaker

Matthew Collins obtained his Ph.D. studying under mentor Dr. Rick Tarleton at the University of Georgia; his thesis project focused on the role of CD8+ T cells in controlling chronic T. cruzi in nonlymphoid tissue. During Infectious Diseases fellowship at the University of North Carolina, he worked with Dr. Aravinda de Silva to study specificity and cross-reactivity of human antibody responses to flaviviruses such as dengue and Zika virus. He is now an Assistant Professor at Emory University where he leads a translational arbovirology research program. Goals of the group are to understand basic aspects of human adaptive immune responses to sequential related viral infection and to develop and implement serologic tools to support epidemiologic studies and the development of vaccines and diagnostic tests.

Matt Collins’s Talk

Dr. Collins will present the following talk at 9:55 am.

Epitope Targets of the Human Antibody Response to Zika Virus Infection

Matthew H. Collins^1,2, Huy A. Tu^3,4, Ciara Gimblet-Ochieng⁵, Guei-Jiun Alice Liou⁵, Ramesh S. Jadi⁵, Stefan W. Metz⁵, Ashlie Thomas⁵, Benjamin D. McElvany⁴, Edgar Davidson⁶, Benjamin J. Doranz⁶, Yaoska Reyes⁷, Natalie M. Bowman², Sylvia Becker-Dreps⁸, Filemón Bucardo⁷, Helen M. Lazear⁵, Sean A. Diehl^3,4, Aravinda M. de Silva^5
1Department of Medicine, Emory University ²Department of Medicine, University of North Carolina-Chapel Hill ³Cellular, Molecular, and Biomedical Sciences Program, University of Vermont ⁴Department of Microbiology and Molecular Genetics, University of Vermont ⁵Department of Microbiology and Immunology, University of North Carolina ⁶Integral Molecular, Inc. ⁷Department of Microbiology, National Autonomous University of Nicaragua ⁸Departments of Family Medicine and Epidemiology, University of North Carolina-Chapel Hill

Zika virus (ZIKV) transmission became a global public health emergency after the recent epidemic in Latin America and beyond revealed rare but dire manifestations of infection such as severe birth defects and Guillain-Barré syndrome. The emergence of ZIKV in areas where other related flaviviruses such as dengue are endemic creates challenges in accurately diagnosing infections, conducting reliable surveillance, as well as in understanding the distinguishing aspects of the host immune response to ZIKV due to antibody (Ab) cross-reactivity. Because vaccines represent a key strategy for prevention of infectious diseases and typically rely on robust antibody responses, we sought to analyze the durable antibody responses in individuals infected by ZIKV as a first flavivirus infection. We observed complex populations of antibodies that bind to epitopes on intact virions, simpler epitopes on envelope protein monomers as well as envelope subdomains. Moreover, strong neutralizing antibody responses that minimally cross-react with dengue viruses were consistently detected. To better understand the molecular determinants of the neutralizing antibody response to ZIKV and to develop tools that could aid vaccine development, we isolated two potently neutralizing monoclonal antibodies (mAbs) from one primary ZIKV case and mapped key amino acid residues involved in mAb binding and neutralization by multiple complimentary methods including generation of neutralization escape mutants and alanine scanning mutagenesis. The mAbs recognize different epitopes centered on domain I and domain II of the viral envelope protein. Functionally, both mAbs were protective in a lethal mouse model of ZIKV infection. Ongoing work is examining the prevalence of these specific Ab responses at the population level. This work provides new knowledge and tools that may be useful as diagnostic reagents or as therapeutics and will advance vaccine development.

More information about the Molecular Parasitology & Vector Biology Symposium and the schedule of presentions are available on our website. The deadline to register for the symposium is April 24.