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Tag: Dennis Kyle

Synthesis of Mono- and Bisperoxide-Bridged Artemisinin Dimers to Elucidate the Contribution of Dimerization to Antimalarial Activity

During the past decade, artemisinin as an antimalarial has been in the spotlight, in part due to the Nobel Prize in Physiology or Medicine awarded to Tu Youyou. While many studies have been completed detailing the significant increase in activity resulting from the dimerization of natural product artemisinin, activity increases unaccounted for by the peroxide bridge have yet to be researched. Here we outline the synthesis and testing for antimalarial activity of artemisinin dimers in which the peroxide bridge in one-half of the dimer is reduced, resulting in a dimer with one active and one deactivated artemisinin moiety.

Cynthia L Lichorowic, Yingzhao Zhao, Steven P Maher, Vivian Padín-Irizarry, Victoria C Mendiola, Sagan T de Castro, Jacob A Worden, Debora Casandra, Dennis E Kyle, Roman Manetsch. ACS Infect Dis. 2021 Apr 1. doi: 10.1021/acsinfecdis.1c00066

Naegleria fowleri: Protein structures to facilitate drug discovery for the deadly, pathogenic free-living amoeba

Naegleria fowleri is a pathogenic, thermophilic, free-living amoeba which causes primary amebic meningoencephalitis (PAM). Penetrating the olfactory mucosa, the brain-eating amoeba travels along the olfactory nerves, burrowing through the cribriform plate to its destination: the brain’s frontal lobes. The amoeba thrives in warm, freshwater environments, with peak infection rates in the summer months and has a mortality rate of approximately 97%. A major contributor to the pathogen’s high mortality is the lack of sensitivity of N. fowleri to current drug therapies, even in the face of combination-drug therapy. To enable rational drug discovery and design efforts we have pursued protein production and crystallography-based structure determination efforts for likely drug targets from N. fowleri. The genes were selected if they had homology to drug targets listed in Drug Bank or were nominated by primary investigators engaged in N. fowleri research. In 2017, 178 N. fowleri protein targets were queued to the Seattle Structural Genomics Center of Infectious Disease (SSGCID) pipeline, and to date 89 soluble recombinant proteins and 19 unique target structures have been produced. Many of the new protein structures are potential drug targets and contain structural differences compared to their human homologs, which could allow for the development of pathogen-specific inhibitors. Five of the structures were analyzed in more detail, and four of five show promise that selective inhibitors of the active site could be found. The 19 solved crystal structures build a foundation for future work in combating this devastating disease by encouraging further investigation to stimulate drug discovery for this neglected pathogen.

Logan Tillery, Kayleigh Barrett, Jenna Goldstein, Jared W Lassner, Bram Osterhout, Nathan L Tran, Lily Xu, Ryan M Young, Justin Craig, Ian Chun, David M Dranow, Jan Abendroth, Silvia L Delker, Douglas R Davies, Stephen J Mayclin, Brandy Calhoun, Madison J Bolejack, Bart Staker, Sandhya Subramanian, Isabelle Phan, Donald D Lorimer, Peter J Myler, Thomas E Edwards, Dennis E Kyle, Christopher A Rice, James C Morris, James W Leahy, Roman Manetsch, Lynn K Barrett, Craig L Smith, Wesley C Van Voorhis (2021) Naegleria fowleri: Protein structures to facilitate drug discovery for the deadly, pathogenic free-living amoeba. PLoS ONE 16(3): e0241738.

Discovery of repurposing drug candidates for the treatment of diseases caused by pathogenic free-living amoebae

Diseases caused by pathogenic free-living amoebae include primary amoebic meningoencephalitis (Naegleria fowleri), granulomatous amoebic encephalitis (Acanthamoeba spp.), Acanthamoeba keratitis, and Balamuthia amoebic encephalitis (Balamuthia mandrillaris). Each of these are difficult to treat and have high morbidity and mortality rates due to lack of effective therapeutics. Since repurposing drugs is an ideal strategy for orphan diseases, we conducted a high throughput phenotypic screen of 12,000 compounds from the Calibr ReFRAME library. We discovered a total of 58 potent inhibitors (IC50 <1 μM) against N. fowleri (n = 19), A. castellanii (n = 12), and B. mandrillaris (n = 27) plus an additional 90 micromolar inhibitors. Of these, 113 inhibitors have never been reported to have activity against Naegleria, Acanthamoeba or Balamuthia. Rapid onset of action is important for new anti-amoeba drugs and we identified 19 compounds that inhibit N. fowleri in vitro within 24 hours (halofuginone, NVP-HSP990, fumagillin, bardoxolone, belaronib, and BPH-942, solithromycin, nitracrine, quisinostat, pabinostat, pracinostat, dacinostat, fimepinostat, sanguinarium, radicicol, acriflavine, REP3132, BC-3205 and PF-4287881). These compounds inhibit N. fowleri in vitro faster than any of the drugs currently used for chemotherapy. The results of these studies demonstrate the utility of phenotypic screens for discovery of new drugs for pathogenic free-living amoebae, including Acanthamoeba for the first time. Given that many of the repurposed drugs have known mechanisms of action, these compounds can be used to validate new targets for structure-based drug design.

Christopher A Rice, Beatrice L Colon, Emily Chen, Mitchell V Hull, Dennis E Kyle. PLoS Negl Trop Dis. 2020 Sep 24;14(9):e0008353. doi: 10.1371/journal.pntd.0008353.

Dennis Kyle: Finding Solutions for Deadly Diseases

Dennis Kyle
Dennis Kyle leads the UGA Center for Tropical and Emerging Diseases, and his endowment enables him to run a 16-person lab of student researchers, postdocs, and research scientists fighting a host of parasitic diseases around the world. (Photo by Andrew Davis Tucker/UGA)

GRA Endowment helps researchers save lives through drug discovery

The Amoeba Summit in Orlando last year is where the importance of her work on drug discovery for deadly amoebae really hit home for Cassiopeia Russell.

It was there she learned the story of an 11-year-old boy who had gone on a family vacation to Costa Rica and was having a great time going down a waterslide at a hot spring there. Days later, he started complaining of a terrible headache. Then he started vomiting. Within a week, he was dead. The cause was a microscopic organism, Naegleria fowleri, living in the warm waters of the spring.

Cassiopeia Russell
Cassiopeia Russell is a doctoral student working in Dennis Kyle’s lab on treatments to combat Naegleria fowleri, a rare but deadly brain-eating microscopic organism that can be 99% fatal if contracted. “This parasite infects mainly young children,” she says. “Hundreds have died.”

Russell, a doctoral student, had been working in the lab of Dennis Kyle, director of the UGA Center for Tropical and Emerging Global Diseases, for about a year when she was able to attend the conference thanks to a Georgia Research Alliance (GRA) endowment and learn how the research she does in the lab is making a real impact on people’s lives. The GRA was founded with the goal of expanding Georgia universities’ ability to conduct high-level research with the potential of bringing new and innovative products to market. Kyle is the GRA Eminent Scholar in Antiparasitic Drug Discovery, and his endowment enables him to run a 16-person staff of student researchers, postdocs, and research scientists.

“I asked myself at the beginning if I really wanted to work on a parasite this rare,” Russell says. “But if you look at the statistics, this parasite infects mainly young children. Hundreds have died.” She thinks about that every day in the lab.

More commonly referred to as the brain-eating amoeba, Naegleria fowleri is a surprisingly common amoeba found in warm water lakes, ponds, and rivers. When water is forced up the nose—like when diving into a body of water or repeatedly riding a waterslide—the parasite travels to the brain, where it attacks the organ’s cells. Though infections are rare, the brain-eating amoeba kills almost everyone it infects.

One reason Naegleria fowleri is so deadly is because symptoms of the infection resemble those of viral meningitis, a much more common and more treatable disease. “That misdiagnosis and waiting to see if the patient gets better after beginning treatment is wasting valuable time,” says Russell. She’s committed to finding faster, more effective ways to diagnose the condition so patients can get the right medications in time to stop the disease’s progression.

The Georgia Research Alliance really helped me set up this whole operation when I got here. Without the GRA, there’s no way that I could have had this team going for three years.” — Dennis Kyle, GRA Eminent Scholar in Antiparasitic Drug Discovery

As a member of Kyle’s lab, Russell also tests drug compounds to see which ones can kill an amoeba without destroying the human cells it infects. Current drugs used to treat the infection aren’t very effective and are highly toxic.

Despite being almost 99% fatal, not many federal dollars go toward research on brain-eating and other kinds of amoebae. That’s where the Georgia Research Alliance comes in.

“The Georgia Research Alliance really helped me set up this whole operation when I got here,” says Kyle. “Without the GRA, there’s no way that I could have had this team going for three years. This is something that we have concerns about in Georgia. Every summer, we hear of Naegleria fowleri cases on the news. But we don’t have many people worldwide working on it and very few doing the drug discovery needed to come up with a new drug that could save lives. And that’s really our goal.”

The other main area of research in the Kyle lab is malaria and how the parasite becomes resistant to the drugs commonly used to treat it. Additionally, a less commonly studied strain of malaria can go dormant inside its host, effectively hiding in the liver until flaring up weeks, months, or even years later. Kyle and his team were able to develop a model that simulates that dormant phase to test a variety of drugs to find a way to kill the parasite.

But in order to use that model, researchers in the lab must collect parasites from the field. The endowment helped the lab send assistant research scientist Steven Maher to Asia 25 times over the past four years to work with partners in Cambodia and Thailand.

“International travel has definitely changed my life,” Maher says. “Right now, we’re supporting people in Asia and their families, and I think having that human connection is really important. I think all too often we do research and we forget about ‘how is what I’m doing helping real people?’ I think a lot of researchers would benefit from that type of experience.”

The Georgia Research Alliance, private donors, and the UGA Athletic Association are committed to providing researchers like Russell and Maher with opportunities to advance their work on deadly infectious diseases threatening nations around the world.

Steven Maher with Cambodian colleagues
Assistant research scientist Steven Maher (far right) with the team he works with in Cambodia. GRA funding has allowed him to travel to Asia 25 times over the past four years battling malaria.


This article was originally published at

Trainee Spotlight: Alona Botnar

Alona Botnar

T32 trainee Alona Botnar is entering her fifth year as a Ph.D. candidate in Dr. Dennis Kyle’s laboratory. She is from Doylestown, Pennsylvania and completed her B.S. in Chemistry with a minor in Biochemistry at the University of Georgia in 2015. During her undergraduate career, she also worked at Janssen, a pharmaceutical company of Johnson & Johnson as a Biologics R&D co-op.

As a graduate student, she was able to spend three semesters teaching Anatomy and Physiology labs here at UGA, and in 2019, she was awarded the Outstanding Teaching Assistant Award sponsored by the Office of the Vice President for Instruction. She also received a graduate school travel award to attend the 2018 annual meeting of the American Society of Tropical Medicine and Hygiene in New Orleans, Louisiana, and an Office for Vice President and Research travel award to attend the 2020 Molecular Approaches to Malaria meeting held in Lorne, Victoria, Australia.

Why did you choose UGA?

Having been at UGA for my undergraduate degree, I was already in love with UGA and Athens and all that they have to offer. I was attracted to the Integrated Life Sciences program because it gives incoming graduate students the freedom to explore a wide range of research topics among 14 different departments before choosing the lab they would ultimately like to join. Furthermore, I found the interdisciplinary approach of the program appealing. I love the Center for Tropical and Emerging Global Diseases because of all the resources available to us as scientists. Not only do we have state of the art microscopy and flow cytometry cores, but we also have very collaborative labs that are happy to share equipment, supplies, and expertise.

What is your research focus?

My research is focused on malaria and addressing significant problems at the stages of development at which the malaria parasite enters a drug-induced dormant period and evades the antimalarial. The mechanism by which the parasite enters drug-induced dormancy and later recrudesces to continue development is currently unknown.

Half the world’s population is at risk of malaria with about half a million people dying each year from it. A majority of these deaths are in children under the age of 5, located mainly in sub-Saharan Africa. While there are 5 species that can infect humans, Plasmodium falciparum is the most lethal and is responsible for a majority of the deaths. Our current arsenal of malaria drugs is failing at an alarming rate as drug-resistant strains of the parasite continue to emerge.

Thus I chose this research project because it is vital that we respond to the challenge of antimalarial drug resistance by not only developing novel drugs but also by understanding the mechanisms the parasite is using to evade the drugs.

What are your future career goals?

I plan on continuing my work in the field of infectious diseases. I am leaning towards industry research but I’m keeping an open mind. Lately, I have been interested in alternative careers available to life science Ph.D.’s such as consulting and being a medical science liaison.

What is your favorite thing about UGA?

UGA football. There’s nothing quite like a fall Saturday in Athens between the hedges. GO DAWGS!

Do you have any advice for a student interested in this field?

It’s never too early or too late to get into the field. Don’t be afraid to send those emails and get involved in research. And always ask questions.


Support trainees like Alona by giving today to the Center for Tropical & Emerging Global Diseases.

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Trainee Spotlight: Emma Troth

Emma Troth

Emma Troth, a Ph.D. trainee in Dennis Kyle‘s laboratory, is entering her fourth year at UGA. She is originally from Eureka, Illinois, and attended Bradley University where she majored in Biology with a minor in Ethics. While at UGA, Emma has served as president of the CTEGD Graduate Student Association (2019-2020) and is currently the CTEGD Graduate Student Association representative.

How did you get interested in neglected tropical diseases?

As an undergraduate, I participated in a Research Experience for Undergraduates program at the University of Notre Dame. At Notre Dame, I worked on a project characterizing malaria vectors in the Solomon Islands and Indonesia. My summer at Notre Dame sparked my interest in neglected tropical diseases.

Why did you choose UGA?

I chose UGA because of the diversity of research. Coming into graduate school, I knew I was interested in infectious diseases but did not have my heart set on a particular organism to work on. UGA works on the biggest selection of infectious organisms. With the Integrated Life Sciences Program, I had the opportunity to experience multiple labs working on different organisms, regardless of department, to help me identify where I would like to complete my doctoral degree.

What is your research focus? Why are you interested in this topic?

My project focuses on drug discovery for Naegleria fowleri, the brain-eating amoebae. My main project focuses on structure-based drug design to develop novel drug targets against N. fowleri. Additionally, I am working to develop phenotypic drug screening assays to complement our high-throughput drug discovery. I am fascinated by N. fowleri because it is such a mysterious, deadly organism. Though infections may not be as common as other parasitic diseases, nearly all cases of primary amebic meningoencephalitis (PAM) are fatal. This amoeba is grossly understudied; very few labs in the world research this organism. It is both a privilege and a challenge to be able to work on this neglected parasite.

Have you done any fieldwork or is there a collaborator/field site that you would like to visit in order to enhance your training?

I hope to complete an internship with the Task Force for Global Health. This internship will ideally include fieldwork with one of their neglected tropical disease programs.

What are your future professional plans?

Going forward, I would like to continue my career in neglected tropical diseases with an emphasis on global health. I am particularly interested in a career involving field research. Ultimately, I hope to work for a government agency like the Centers for Disease Control and Prevention (CDC) or a non-profit organization focused on neglected tropical diseases.

What is your favorite thing about Athens?

My favorite thing about Athens is the food! There is such a variety of local restaurants and new restaurants are continually opening. Coming from a small undergraduate institution, I really enjoy the atmosphere of a large university in a small college town. Athens is a very easy city to feel “at home”.

Any advice for a student interested in this field?

Never be afraid to reach out for help, wherever you need it! Coming into graduate school can be intimidating and at times, isolating. There are so many people eager to help you on your graduate school journey and ultimately want to see you succeed. Particularly within the CTEGD, I have always been met with kind and willing responses. All it takes is for you to take the step and reach out!

Support trainees like Emma by giving today to the Center for Tropical & Emerging Global Diseases.

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Bioactivity of Spongian Diterpenoid Scaffolds From the Antarctic Sponge Dendrilla antarctica

The Antarctic sponge Dendrilla antarctica is rich in defensive terpenoids with promising antimicrobial potential. Investigation of this demosponge has resulted in the generation of a small chemical library containing diterpenoid secondary metabolites with bioactivity in an infectious disease screening campaign focused on Leishmania donovaniPlasmodium falciparum, and methicillin-resistant Staphylococcus aureus (MRSA) biofilm. In total, eleven natural products were isolated, including three new compounds designated dendrillins B-D (1012). Chemical modification of abundant natural products led to three semisynthetic derivatives (1315), which were also screened. Several compounds showed potency against the leishmaniasis parasite, with the natural products tetrahydroaplysulphurin-1 (4) and dendrillin B (10), as well as the semisynthetic triol 15, displaying single-digit micromolar activity and low mammalian cytotoxicity. Triol 15 displayed the best profile against the liver-stage malaria parasites, while membranolide (5) and dendrillin C (11) were strong hits against MRSA biofilm cultures.

Alexandre Bory, Andrew J Shilling, Jessie Allen, Ala Azhari, Alison Roth, Lindsey N Shaw, Dennis E Kyle, John H Adams, Charles D Amsler, James B McClintock, Bill J Baker. Mar Drugs. 2020 Jun 23;18(6):E327. doi: 10.3390/md18060327.

Dynamics of Infection and Pathology Induced by the Aporocotylid, Cardicola Laruei, in Spotted Seatrout, Cynoscion Nebulosus (Sciaenidae)


The sciaenid Spotted Seatrout (Cynoscion nebulosus) are infected by blood flukes (Cardicola spp.). A 2 year survey in estuaries of South Carolina, USA, showed that adult flukes and granulomas occurred throughout the year but their prevalence was highest in summer (61% and 84%, respectively), indicating an unusually high level of infection for wild fish. Granulomas remained after adult flukes could no longer be found. PCR-Restriction Fragment Length Polymorphism (RFLP) of a subsample of specimens allowed identification of Cardicola laruei as the only species infecting these seatrout during the period of study. Mean intensity of infection by flukes was higher in female seatrout, suggesting endocrine and/or immune system involvement. The prevalence of granulomas declined sharply in winter, indicating possible mortality of infected seatrout as this species is known to be cold-sensitive. Granulomas were studied using histology, immunohistochemistry, and transmission electron microscopy. Eggs were encapsulated by an inner core of dark epithelioid cells, and an outer core of large epithelioid cells undergoing epithelialization. Fibrosis was observed around granulomas and some granulomas detached from the surrounding damaged myocardium. Numerous inflammatory cells appeared mobilized around granulomas and pathology could be severe, in some cases showing grossly visible blister-like extrusions scattered in the damaged epicardium. At the gross level, some granulomas possessing eggs with live miracidia were observed at the surface of the epicardium. These findings suggest that granulomas carrying both dead and live eggs can clear the fish heart by host-mediated transport through the myocardium, as is known to occur in related human Schistosoma infections.

Eric J. McElroy, Barbara Nowak, Kristina M. Hill-Spanik, Willard O. Granath, Vincent A. Connors, Jim Driver, C. Jonathan Tucker, Dennis E. Kyle, Isaurede Buron. Int J Parasitol. 2020 Jun 19;S0020-7519(20)30148-X. doi: 10.1016/j.ijpara.2020.03.016.

Discovery of Anti-Amoebic Inhibitors from Screening the MMV Pandemic Response Box on Balamuthia mandrillaris, Naegleria fowleri, and Acanthamoeba castellanii

Pathogenic free-living amoebae, Balamuthia mandrillarisNaegleria fowleri, and several Acanthamoeba species are the etiological agents of severe brain diseases, with case mortality rates > 90%. A number of constraints including misdiagnosis and partially effective treatments lead to these high fatality rates. The unmet medical need is for rapidly acting, highly potent new drugs to reduce these alarming mortality rates. Herein, we report the discovery of new drugs as potential anti-amoebic agents. We used the CellTiter-Glo 2.0 high-throughput screening methods to screen the Medicines for Malaria Ventures (MMV) Pandemic Response Box in a search for new active chemical scaffolds. Initially, we screened the library as a single-point assay at 10 and 1 µM. From these data, we reconfirmed hits by conducting quantitative dose–response assays and identified 12 hits against B. mandrillaris, 29 against N. fowleri, and 14 against A. castellanii ranging from nanomolar to low micromolar potency. We further describe 11 novel molecules with activity against B. mandrillaris, 22 against N. fowleri, and 9 against A. castellanii. These structures serve as a starting point for medicinal chemistry studies and demonstrate the utility of phenotypic screening for drug discovery to treat diseases caused by free-living amoebae.

Christopher A. Rice, Emma V. Troth, A. Cassiopeia Russell, Dennis E. Kyle. Pathogens. 2020 Jun 16;9(6):E476. doi: 10.3390/pathogens9060476.

Dennis Kyle elected as American Academy of Microbiology Fellow

American Academy of Microbiology Fellow Dennis Kyle

University of Georgia researcher Dennis Kyle has been elected as a 2020 fellow by the American Academy of Microbiology. He joins a class of 68 new fellows this year.

Kyle is a GRA Eminent Scholar in antiparasitic drug discovery, with appointments in the departments of cellular biology and infectious diseases.

“Election as a Fellow of the American Academy of Microbiology is a tremendous honor and one that was achieved by the success of all the great people I’ve work with over the years on antiparasitic drug discovery,” said Kyle, who joined UGA in 2017 as the director of the Center for Tropical and Emerging Global Diseases.

His research focuses on the discovery, development, and mechanisms of resistance to antiparasitic drugs. Currently, his laboratory is concentrating on malaria, which has become increasingly resistant to current treatments, and the brain-eating amoeba Naegleria fowleri. The Kyle laboratory has been instrumental in developing methods and tests to discover new drugs that act rapidly, effectively and can be combined with existing drugs used to treat these nearly incurable diseases.

Kyle’s work is largely funded by the National Institutes of Health, Medicines for Malaria Venture and a $9.4 million grant from the Bill & Melinda Gates Foundation. He has published more than 200 research papers, and his findings have been cited more than 14,000 times.

Kyle has received a number of awards over the course of his career, including the U.S. Army Achievement Medal in 1990, the U.S. Army Commendation Medal in 1988, and the U.S. Army Meritorious Service Award. He has been honored by the Southeastern Society of Parasitologists and is a fellow of the American Society for Tropical Medicine and Hygiene and the American Association for the Advancement of Science. In 2006, he was named Scientist of the Year by Malaria Foundation International.

Kyle joins more than 2,500 AAM fellows who are elected through a highly selective, peer-review process, based on their records of scientific achievement and original contributions that have advanced microbiology. Only 58 percent of this year’s nominees were elected to the Class of 2020, and the newly elected fellows hail from 11 different countries.