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Tag: malaria

Optimization of diastereomeric dihydropyridines as antimalarials

graphical abstract

The increase in research funding for the development of antimalarials since 2000 has led to a surge of new chemotypes with potent antimalarial activity. High-throughput screens have delivered several thousand new active compounds in several hundred series, including the 4,7-diphenyl-1,4,5,6,7,8-hexahydroquinolines, hereafter termed dihydropyridines (DHPs). We optimized the DHPs for antimalarial activity. Structure-activity relationship studies focusing on the 2-, 3-, 4-, 6-, and 7-positions of the DHP core led to the identification of compounds potent (EC50 < 10 nM) against all strains of P. falciparum tested, including the drug-resistant parasite strains K1, W2, and TM90-C2B. Evaluation of efficacy of several compounds in vivo identified two compounds that reduced parasitemia by >75 % in mice 6 days post-exposure following a single 50 mg/kg oral dose. Resistance acquisition experiments with a selected dihydropyridine led to the identification of a single mutation conveying resistance in the gene encoding for Plasmodium falciparum multi-drug resistance protein 1 (PfMDR1). The same dihydropyridine possessed transmission blocking activity. The DHPs have the potential for the development of novel antimalarial drug candidates.

Kurt S Van Horn, Yingzhao Zhao, Prakash T Parvatkar, Julie Maier, Tina Mutka, Alexis Lacrue, Fabian Brockmeier, Daniel Ebert, Wesley Wu, Debora R Casandra, Niranjan Namelikonda, Jeanine Yacoub, Martina Sigal, Spencer Knapp, David Floyd, David Waterson, Jeremy N Burrows, James Duffy, Joseph L DeRisi, Dennis E Kyle, R Kiplin Guy, Roman Manetsch. Eur J Med Chem. 2024 Jun 18:275:116599. doi: 10.1016/j.ejmech.2024.116599.

The influence of oviposition status on measures of transmission potential in malaria-infected mosquitoes depends on sugar availability

graphical abstract

Background: Like other oviparous organisms, the gonotrophic cycle of mosquitoes is not complete until they have selected a suitable habitat to oviposit. In addition to the evolutionary constraints associated with selective oviposition behavior, the physiological demands relative to an organism’s oviposition status also influence their nutrient requirement from the environment. Yet, studies that measure transmission potential (vectorial capacity or competence) of mosquito-borne parasites rarely consider whether the rates of parasite replication and development could be influenced by these constraints resulting from whether mosquitoes have completed their gonotrophic cycle.

Methods: Anopheles stephensi mosquitoes were infected with Plasmodium berghei, the rodent analog of human malaria, and maintained on 1% or 10% dextrose and either provided oviposition sites (‘oviposited’ herein) to complete their gonotrophic cycle or forced to retain eggs (‘non-oviposited’). Transmission potential in the four groups was measured up to 27 days post-infection as the rates of (i) sporozoite appearance in the salivary glands (‘extrinsic incubation period’ or EIP), (ii) vector survival and (iii) sporozoite densities.

Results: In the two groups of oviposited mosquitoes, rates of sporozoite appearance and densities in the salivary glands were clearly dependent on sugar availability, with shorter EIP and higher sporozoite densities in mosquitoes fed 10% dextrose. In contrast, rates of appearance and densities in the salivary glands were independent of sugar concentrations in non-oviposited mosquitoes, although both measures were slightly lower than in oviposited mosquitoes fed 10% dextrose. Vector survival was higher in non-oviposited mosquitoes.

Conclusions: Costs to parasite fitness and vector survival were buffered against changes in nutritional availability from the environment in non-oviposited but not oviposited mosquitoes. Taken together, these results suggest vectorial capacity for malaria parasites may be dependent on nutrient availability and oviposition/gonotrophic status and, as such, argue for more careful consideration of this interaction when estimating transmission potential. More broadly, the complex patterns resulting from physiological (nutrition) and evolutionary (egg-retention) trade-offs described here, combined with the ubiquity of selective oviposition behavior, implies the fitness of vector-borne pathogens could be shaped by selection for these traits, with implications for disease transmission and management. For instance, while reducing availability of oviposition sites and environmental sources of nutrition are key components of integrated vector management strategies, their abundance and distribution are under strong selection pressure from the patterns associated with climate change.

Justine C Shiau, Nathan Garcia-Diaz, Dennis E Kyle, Ashutosh K Pathak. Parasit Vectors. 2024 May 23;17(1):236. doi: 10.1186/s13071-024-06317-2.

Trainee Spotlight: Grace Vick

Ph.D. student Grace Woods

My name is Grace Vick and I am a 4th year infectious diseases PhD candidate in Vasant Muralidharan’s lab. I’m originally from North Carolina and received my Bachelor’s of Science in Biology from Western Carolina University. After graduating undergraduate, I completed an internship at the Defense Forensic Science Center doing forensic biology research. After that, I spent 2 years as an ORISE Fellow at the Centers for Disease Control and Prevention, studying and identifying genetic markers of multi-drug resistant strains of Neisseria gonorrhoeae. I came straight to UGA through the ILS program after my fellowship at CDC.

What made you want to study science?

Ever since I was little, I’ve always spent a lot of time being outside in nature and enjoyed figuring out the intricacies of how things work. During my undergraduate, I was able to explore the different areas of science and found the molecular biology of genetics to be an interesting field that is highly translatable and still vastly unknown. After I spent a few years gaining lab experience and an appreciation for the public health concerns of infectious diseases at the CDC, I knew I wanted to pursue a PhD in that field which brought me to UGA.

Why did you choose UGA?

My experience at the CDC offered the opportunity to learn about diseases and public health issues across all sectors and countries, which led me to learn more about parasitic diseases. Previously, I knew nothing about these diseases but as I learned more about their complex and fascinating life cycles and how these diseases of poverty impact people around the world, I was captivated by this research. Because I was really interested in spending my PhD studying infectious and parasitic diseases, I found out about the CTEGD at UGA and that is what brought me here. The CTEGD is a really wonderful environment for trainees to be exposed to exciting and diverse parasitology research, and I’ve really enjoyed my experience here.

What is your research focus and why did you choose it?

Our lab works on the deadliest form of malaria, Plasmodium falciparum. P. falciparum kills over half a million people each year, with the majority of those deaths being children under the age of 5. Our lab is interested in understanding the molecular mechanisms that are essential to asexual blood stage of this parasite. My work specifically focuses on determining the role of previously unknown proteins that we have discovered are essential for asexual stage invasion of merozoites into host red blood cells. Using a combination of genetic engineering, molecular, and cellular biology techniques, I aim to determine the molecular function of these proteins in the human asexual stage invasion of red blood cells.

Have you received any awards or honors?

In addition to receiving the NIH T32 Predoctoral Fellowship, I have been invited to present at multiple national and international conferences such as Molecular Parasitology Meeting in Massachusetts and Molecular Approaches in Malaria in Lorne, Australia where I won a poster award.

What are your career goals?

When I graduate with my doctoral degree, I hope to either join governmental research or the industry sector. If I decided to head into governmental work, I would choose a career at the CDC where I could continue working in the parasitology research field and apply current public health policies to the international parasitology field. If I decide to join the biomedical industry sector, I would want to work in Research and Design at a company that designs therapeutics and diagnostics for disease prevention and treatment.

What do you hope to do for your capstone experience?

I would really love to experience fieldwork in a malaria-endemic region. I think having the experience of meeting people and learning firsthand how this disease affects millions of people every day would be very eye-opening for me since I have only seen the lab side of malaria. The ability to experience fieldwork would give me a broader experience with how malaria is researched and treated outside of the lab environment and in rural lab environments. I would love to visit Africa or South East Asia to conduct fieldwork in a malaria-endemic environment.

What is your favorite thing about Athens?

Obviously, I love the food in Athens! I love going downtown to grab food and drinks on the weekend. Otherwise, I enjoy getting out and exploring the green spaces and parks that Athens has to offer such as Sandy Creek and the North Oconee Greenway with my husband and dog.

Any advice for a student interested in this field?

I would say the best advice is to read and soak up as much as you can about parasitology both before you get into the field and after. A lot of research has overlap between different parasites and it’s helpful to know about other parasitic diseases that might not be your main focus. Plus, parasites are fun! 🙂 My other advice in general for starting graduate school is to always reach out to students in labs you’re interested in joining. Students are pretty much always willing to help give clear insight into lab dynamics, mentorship of the PI, and generally how life working in that lab is. That information is all really helpful to know when choosing which lab to join!

 

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

Hepatocytes and the art of killing Plasmodium softly

Figure 1. The gap in our understanding of how hepatocytes eliminate Plasmodium.
Figure 1. The gap in our understanding of how hepatocytes eliminate Plasmodium.

 

The Plasmodium parasites that cause malaria undergo asymptomatic development in the parenchymal cells of the liver, the hepatocytes, prior to infecting erythrocytes and causing clinical disease. Traditionally, hepatocytes have been perceived as passive bystanders that allow hepatotropic pathogens such as Plasmodium to develop relatively unchallenged. However, now there is emerging evidence suggesting that hepatocytes can mount robust cell-autonomous immune responses that target Plasmodium, limiting its progression to the blood and reducing the incidence and severity of clinical malaria. Here we discuss our current understanding of hepatocyte cell-intrinsic immune responses that target Plasmodium and how these pathways impact malaria.

Camila Marques-da-Silva, Clyde Schmidt-Silva, Samarchith P Kurup. Trends Parasitol. 2024 May 6:S1471-4922(24)00086-2. doi: 10.1016/j.pt.2024.04.004.

UGA researchers received prestigious grant to develop malaria drug

by Amy Horton

Chet Joyner and Steven Maher
Principal Investigators Chet Joyner (left) and Steven Maher (right). Photo credit: Donna Huber

 

New compound targets P. vivax, source of recent U.S. infections

Two University of Georgia researchers have been awarded approximately $770,000 from the Global Health Initiative Technology (GHIT) Fund to develop a new drug to kill the dormant liver stages of Plasmodium vivax, the most widespread of the malaria parasites. This amount is part of a total of JPY 334,238,778 awarded by the GHIT Fund to a partnership consisting of UGA, Medicine for Malaria Venture and Mitsubishi Tanabe Pharma Corporation.

P. vivax often persists in the liver of patients, causing a relapse infection following treatment of the symptomatic blood infection,” said Steven Maher, associate research scientist in the Office of Research’s Center for Tropical and Emerging Global Diseases (CTEGD). “In many parts of the world, relapses account for the majority of total P. vivax cases.”

The announcement comes on the heels of reports of the first locally acquired cases of malaria in the United States in 20 years. In the summer of 2023, seven cases of locally acquired P. vivax malaria were reported in Sarasota, Fla., and one in Cameron County, Texas. These are in addition to a case of P. falciparum diagnosed in a Maryland resident living in the National Capital Region.

Most malaria cases diagnosed in the United States occur in people who have traveled to countries in South America, Africa, and southeast Asia where malaria is endemic. While locally acquired mosquito-transmitted malaria cases can occur, as Anopheles mosquito vectors exist throughout the United States, they are rare. The last reported outbreak was in 2003 when eight cases of locally acquired P. vivax malaria were identified in Palm Beach County, Fla.

The GHIT award will allow Maher and Chet Joyner to develop a compound series drug-screening program. Joyner is an assistant professor in the College of Veterinary Medicine’s Department of Infectious Diseases and Center for Vaccines and Immunology and jointly appointed to CTEGD.

Microscopy image of Plasmodium vivax
Microscopy image of a P. vivax dormant (left, green) and growing (right, green) liver parasites inside of human liver cells (nuclei in purple). Image taken using 100x magnification. The dormant form survives most antimalarial treatments, but the new series of antimalarials kills both forms of the parasite. (Image credit: Wayne Cheng)

The compound series identified by Maher, the result of testing more than 100,000 samples using infected liver cells, is the first new chemical class discovered in more than 70 years with efficacy against the persisting liver stage. Over the next two years, Maher and Joyner will be collaborating with Medicine for Malaria Venture and Mitsubishi Tanabe Pharma Corporation to alter the chemistry of the compound to improve drug-like properties, including half-life and potency, necessary to achieve single dose criteria.

“Discovering a drug to kill dormant, non-proliferating cells is extremely difficult, yet with the novel assay the team developed we now have the first new target and drug class with potential to accelerate global malaria elimination efforts,” said Dennis Kyle, director of the CTEGD.

The current drug class used to treat P. vivax malaria, 8-aminoquinolines, often results in serious side effects and cannot be administered to pregnant women, who are one of the patient groups most in need of treatment.

“We have the first validated compound that kills vivax while it lies dormant in the liver,” Joyner said. “We hope in the next two years to help advance the new compounds to clinical testing.”

Lisa K. Nolan, dean of the College of Veterinary Medicine, said the work Maher and Joyner are doing could deliver a better quality of life to millions of people around the world.

“This great research is a shining example of our commitment to translational research, which will take this drug from the lab to preclinical testing to the patient rapidly,” Nolan said.

Time-resolved proximity biotinylation implicates a porin protein in export of transmembrane malaria parasite effectors

Figure 1 Generation of SBP1TbID mutants.
Generation of SBP1TbID mutants.

The malaria-causing parasite, Plasmodium falciparum completely remodels its host red blood cell (RBC) through the export of several hundred parasite proteins, including transmembrane proteins, across multiple membranes to the RBC. However, the process by which these exported membrane proteins are extracted from the parasite plasma membrane for export remains unknown. To address this question, we fused the exported membrane protein, skeleton binding protein 1 (SBP1), with TurboID, a rapid, efficient, and promiscuous biotin ligase (SBP1TbID). Using time-resolved, proximity biotinylation, and label-free quantitative proteomics, we identified two groups of SBP1TbID interactors: early interactors (pre-export) and late interactors (post-export). Notably, two promising membrane-associated proteins were identified as pre-export interactors, one of which possesses a predicted translocon domain, that could facilitate the export of membrane proteins. Further investigation using conditional mutants of these candidate proteins showed that these proteins were essential for asexual growth and localize to the host-parasite interface during early stages of the intraerythrocytic cycle. These data suggest that they may play a role in ushering membrane proteins from the PPM for export to the host RBC.

David Anaguano, Watcharatip Dedkhad, Carrie F Brooks, David W Cobb, Vasant Muralidharan. J Cell Sci. 2023 Sep 29;jcs.260506. doi: 10.1242/jcs.260506

Sheptide A: an antimalarial cyclic pentapeptide from a fungal strain in the Herpotrichiellaceae

Structure and amino acid sequence of the cyclic pentapeptide, sheptide A (1)

As part of ongoing efforts to isolate biologically active fungal metabolites, a cyclic pentapeptide, sheptide A (1), was discovered from strain MSX53339 (Herpotrichiellaceae). The structure and sequence of 1 were determined primarily by analysis of 2D NMR and HRMS/MS data, while the absolute configuration was assigned using a modified version of Marfey’s method. In an in vitro assay for antimalarial potency, 1 displayed a pEC50 value of 5.75 ± 0.49 against malaria-causing Plasmodium falciparum. Compound 1 was also tested in a counter screen for general cytotoxicity against human hepatocellular carcinoma (HepG2), yielding a pCC50 value of 5.01 ± 0.45 and indicating a selectivity factor of ~6. This makes 1 the third known cyclic pentapeptide biosynthesized by fungi with antimalarial activity.

Robert A Shepherd, Cody E Earp, Kristof B Cank, Huzefa A Raja, Joanna Burdette, Steven P Maher, Adriana A Marin, Anthony A Ruberto, Sarah Lee Mai, Blaise A Darveaux, Dennis E Kyle, Cedric J Pearce, Nicholas H Oberlies. J Antibiot (Tokyo). 2023 Sep 20. doi: 10.1038/s41429-023-00655-6.

Generating Genetically Modified Plasmodium berghei Sporozoites

Malaria is a deadly disease caused by the parasite Plasmodium and is transmitted through the bite of female Anopheles mosquitoes. The sporozoite stage of Plasmodium deposited by mosquitoes in the skin of vertebrate hosts undergoes a phase of mandatory development in the liver before initiating clinical malaria. We know little about the biology of Plasmodium development in the liver; access to the sporozoite stage and the ability to genetically modify such sporozoites are critical tools for studying the nature of Plasmodium infection and the resulting immune response in the liver. Here, we present a comprehensive protocol for the generation of transgenic Plasmodium berghei sporozoites. We genetically modify blood-stage P. berghei and use this form to infect Anopheles mosquitoes when they take a blood meal. After the transgenic parasites undergo development in the mosquitoes, we isolate the sporozoite stage of the parasite from the mosquito salivary glands for in vivo and in vitro experimentation. We demonstrate the validity of the protocol by generating sporozoites of a novel strain of P. berghei expressing the green fluorescent protein (GFP) subunit 11 (GFP11), and show how it could be used to investigate the biology of liver-stage malaria.

Carson Bowers, Samarchith P Kurup. J Vis Exp. 2023 May 5;(195). doi: 10.3791/64992.

All the pieces matter: UGA researchers collaborate to solve malaria puzzle

malaria parasites
Super-resolution microscopy showing malaria parasites infecting human red blood cells. credit: Muthugapatti Kandasamy, Biomedical Microscopy Core

They say what doesn’t kill you makes you stronger. Whoever coined that adage had probably never heard of Plasmodium.

It’s a microscopic parasite, invisible to the naked eye but common in tropical and subtropical regions throughout the world. Each year, millions of people are infected by Plasmodium and exposed to an even more debilitating—and often deadly—disease: malaria.

Malaria is one of the deadliest diseases known to man. It can lead to extreme illness, marked by fever, chills, headaches and fatigue. More than half the world’s population is at risk of contracting the disease, and those who develop relapsing infections suffer a host of associated costs.

Limited educational opportunities and wage loss lead to an often unbreakable cycle of poverty. Vulnerable populations are most at risk.

“When I’m teaching in an endemic area like Africa, it isn’t unusual to find a student who needs to sleep during part of the workshop because they have malaria,” researcher Jessica Kissinger said.

It’s a challenge she and her collaborators in the University of Georgia’s Center for Tropical and Emerging Global Diseases (CTEGD) are trying to combat.

When the Center was established in 1998, there were only a couple of faculty members studying Plasmodium. Now, 25 years later, it has become a world-class powerhouse of multidisciplinary malaria research. Scientists examine various species of the dangerous parasite, studying its life cycle and the mosquito that transmits it.

While Plasmodium seems to have superpowers that allow it to evade detection and resist treatment, CTEGD researchers are working together to innovate and transfer science from the lab to interventions on the ground.

A 50,000-piece puzzle with no edges

Plasmodium is a complex organism, and studying it is like putting together a jigsaw puzzle. Some researchers contribute pieces related to the blood or liver stages of the parasite’s lifecycle, while others provide insights about hosts interactions. One way UGA’s research connects with the global effort to eradicate malaria is PlasmoDb—a resource derived in part from Kissinger’s research that is now part of a host of databases under the umbrella of The Eukaryotic Pathogen, Vector and Host information Resource (VEuPathDB).

“Our group has been able to help many others when their research question crosses into an –omic,” Kissinger said, referring to in-house shorthand for domains like genomics, proteomics and metabolomics.

Kissinger, Distinguished Research Professor of genetics in the Franklin College of Arts & Sciences, became interested in malaria and Plasmodium during her postdoctoral training at the National Institutes of Health (NIH). Working from an evolutionary biology perspective, she’s interested in how the parasite has changed over time.

PlasmoDb, a database of Plasmodium informatics resources, is a tool developed in part by the work of Distinguished Research Professor Jessica Kissinger, who became interested in malaria during her postdoctoral training at the National Institutes of Health.

“I see it as an arms race,” Kissinger said. “I want to understand what moves they have and can make.”

To understand the parasite, you must dive deep into its genetic code.

Kissinger paired her work in Plasmodium genomics with her interest in computing by helping create the database with information from the Plasmodium genome project completed in 2002. The Malaria Host-Pathogen Interaction Center, one of her projects at UGA, was a seven-year, multi-institutional effort funded, in part, by NIH to create data sets that could be used in systems biology of the host-pathogen interaction during the development of disease.

“Wouldn’t it be neat if, from the beginning of infection all the way to cure, you knew everything that was going on in the organism all the time?” Kissinger said, noting the project’s goal.

They generated terabytes of data that, along with data from the global research community, are publicly accessible and reusable through PlasmoDB and other resources.

Being part of a group that is studying so many different aspects of malaria helps put Kissinger’s research into perspective. Now, in addition to understanding the parasite, she also thinks about tools needed to facilitate research from peers.

High-tech solutions rely on basic research

David Peterson, professor of infectious diseases in the College of Veterinary Medicine, noted that low-tech solutions have mitigated malaria’s human costs. He acknowledged, however, that their long-term goals required more.

“We have to acknowledge that low-tech solutions, such as mosquito nets, have saved lives,” Peterson said. “But to develop the high-tech solutions that will one day end malaria, we need basic research.”

Pregnant women are particularly vulnerable to malaria because their existing immunity to malaria fails to protect them during pregnancy. Placental malaria often results in  premature birth and low birth weight.

Peterson is interested in a binding protein that allows the parasite to adhere to the placenta. While many P. falciparum parasites have only one gene copy that encodes the placental binding protein,  Peterson is investigating Plasmodiumisolates with two or more slightly different copies.

But why isn’t one copy enough?

David Peterson
Professor David Peterson of the College of Veterinary Medicine acknowledges the importance of low-tech solutions like mosquito nets but said to mitigate its effects required better understanding at the genetic level.

That is the primary question Peterson is focused on. He wants to understand how Plasmodium uses extra copies to evade the immune system, distinguishing the role of each requires tools that Vasant Muralidharan, associate professor of cellular biology, has.

Muralidharan’s interest began when he contracted malaria himself. Through access to good health care, he made a full recovery, but the pain he endured remained. He wanted to understand this parasite. Even more, he wanted to make an impact with research.

His graduate training focused on biophysics, but soon his interest in Plasmodium resurfaced. He discovered there was a lack of tools to study the parasite on a genetic level.

“It’s like a house of cards, and each card is a gene,” Muralidharan said. “You can remove one and see what happens—does the house fall or remain standing?”

This is an illustration of the life cycle of the parasites of the genus, Plasmodium, that are causal agents of malaria.(Illustration by CDC/ Alexander J. da Silva, PhD; Melanie Moser)

In the days before CRISPR/Cas9, there wasn’t a precise way to remove genes. Muralidharan is among the pioneers of gene-editing techniques in Plasmodium.

Like Peterson, Muralidharan focuses on proteins secreted by the parasite. He studies the largely unknown process that allows the parasite to invade a red blood cell (RBC), replicate and escape. The lack of tools was a major hindrance, so Muralidharan created new ones.

These tools have been used by Muralidharan’s CTEGD and CDC colleagues to see how drugs might fail. Muralidharan’s laboratory can create mutant Plasmodium parasites that become resistant to a particular drug, and genome sequence databases allow researchers to check if that mutant is already circulating in malaria endemic regions.

Vasant Quote

Building a research bridge to endemic regions

Plasmodium vivax is the predominant malaria parasite in Southeast Asia. It causes “relapsing malaria” during which some parasites go “dormant” after entering the liver instead of reproducing. This phase is a major obstacle for current treatments.

CTEGD Director Dennis Kyle, GRA Eminent Scholar Chair in Antiparasitic Drug Discovery and head of the Department of Cellular Biology, became fascinated with the Plasmodium parasite early in his career, spending time living in Thailand and working in refugee camps where malaria is prevalent.

Dennis Kyle
CTEGD Director Dennis Kyle was moved to follow through with his work as a researcher on a trip to a refugee camp in Thailand. Upon seeing the challenges residents faced, he thought perhaps he should have become a physician. Instead, a local leader impressed upon him the impact you could have in generating new treatments that could benefit everyone. (Photo by Andrew Davis Tucker/UGA)

“When I first got to the refugee camp and saw the situation people were living in, I questioned my decision to become a scientist in the lab instead of becoming a physician,” Kyle said, recalling a camp he worked in that housed about 1,300 kids between the ages of 2 and 15. “There was a guy who was a leader in the group who probably had no more than an early high school education. He said, ‘Look at what you can do—you might generate something that would benefit all of us. The physicians we have in the camp can only work on a few people at a time.’”

Kyle’s laboratory is looking to repurpose medications that have antimalarial properties, a safe way to reduce the development time from lab to clinical use. He’s optimistic we will see a drug treatment that eliminates vivax malaria.

“That’s where UGA is playing a major role,” he said. “The Gates Foundation funded us to develop tools to study the dormant parasite in the liver. And we’ve been successful.”

One of Kyle’s collaborators is Samarchith Kurup, assistant professor of cellular biology, who studies the human immune response to Plasmodium infection.

“We use mouse models to delve into the fundamental host-parasite interactions, which you cannot do practicallyin humans,” Kurup said. “Our understanding of these fundamental processes gives rise to newer and better vaccination approaches and drugs.”

Another important CTEGD addition is Chet Joyner, assistant professor of infectious diseases, whose work has helped make it easier to study dormant parasites stateside.

Like other Plasmodium researchers, Joyner became interested in parasites at an early age. During an undergraduate parasitology class, he discovered how little was known about P. vivax. He was already interested in how diseases develop, so for graduate school he focused on the liver stage of vivax malaria. However, it was a difficult task.

Samarchith Kurup is an assistant professor of cellular biology studying the human immune response to Plasmodium infection. (photo credit: Lauren Corcino)
Samarchith Kurup is an assistant professor of cellular biology studying the human immune response to Plasmodium infection. (photo credit: Lauren Corcino)
Chet Joyner
Assistant Professor Chet Joyner discovered how little was known about Plasmodium vivax as an undergraduate student.

“At the time, the technologies weren’t there,” Joyner said. “Dennis was working on his system, but it wasn’t on the scene yet. I changed from studying the parasite to studying the animal model to understand pathogenesis and immunology in humans.”

Joyner joined UGA after completing his postdoctoral training at Emory University, where he developed a non-mouse animal model to study vivax malaria.

“We have to go to [Thailand] where people are infected and collect blood samples and then feed mosquitoes these samples to do the necessary studies,” Kyle said. “That’s been very impactful. We’ve gotten a lot of data out of it, and now with Chet’s model it all can be done under one roof.”

Joyner wants to understand the human immune response with a focus on vaccine development. Building on Muralidharan’s and other researchers’ findings of how the parasite interacts with the RBCs, Joyner’s vaccine program targets a specific protein in the parasite that inhibits the development of immunity.

“My colleagues have shown that if you knock this protein out in the parasite, the immune response in mice is actually great, and we are now working together to evaluate this in non-mouse models.” Joyner said.

Joyner also has collaborated with Belen Cassera, professor of biochemistry, to screen drug compounds. Cassera’s training focused on metabolism to find drug targets. She is particularly interested in how a drug functions.

“If we understand how the drug works, it will help us predict potential side effects in humans,” Cassera said. “We can’t predict everything, but knowing how it works gives you some confidence in whether it will work in humans.”

Cassera is focused on finding drugs that will treat the more lethal Plasmodium falciparum, the predominant species in Africa, which is rapidly becoming resistant to current treatments. Her work is complementary to Kyle’s.

“They run certain assays for the liver-stage infection, and our lab benefits because we want to know if the drug we are developing is specific for the blood stage or can tackle all stages,” Cassera said.

M. Belen Cassera
Professor Belen Cassera is identifying drugs that will treat the lethal Plasmodium falciparum, a predominant species of the parasite in Africa that has become resistant to many current treatments.

Don’t forget the mosquito

“Malaria is a vector-borne disease transmitted by a mosquito. You need to tackle not only the parasite in the human but also stop its transmission,” Cassera said. “CTEGD is unique because we can study the whole life cycle, including the mosquito.”

Michael Strand, H.M. Pulliam Chair of Entomology in the College of Agricultural and Environmental Sciences and a National Academy of Sciences Fellow, is an expert on parasite-host interactions. Instead of the human host, he is interested in mosquitoes. Recent work indicates blood feeding behavior of mosquitoes strongly affects malaria parasite development while the gut microbiota of mosquitos could lead to new ways to control populations. Having the SporoCore insectory on campus aids his research.

Michael Strand is an expert on parasite-host interactions. His research focuses on mosquitoes and their effects on malaria parasite development.
Michael Strand is an expert on parasite-host interactions. His research focuses on mosquitoes and their effects on malaria parasite development.

Established in 2020, SporoCore, under the management of Ash Pathak, assistant research scientist in the Department of Infectious Diseases, provides both uninfected and Plasmodium-infected Anopheles stephensi mosquitoes to researchers at UGA and other institutions. Like Joyner’s animal model, the insectory allows for research to be done in the U.S. that would otherwise require field work in an endemic country.

Old-school interventions like mosquito nets, combined with new drug therapies, have reduced the number of malaria deaths, which declined over the last 30 years before rising slightly during the COVID-19 pandemic. Great strides have been made to control and treat malaria—but not enough. New tools, like the ones being developed at CTEGD, are needed to keep pushing malaria’s morbidity and mortality rates in the right direction.

“The hard part—what can’t be done easily with the tools we already have—is being done,” Kyle said. “We just need new tools, which is one of the things that our center is really a leader in.”

 

This story was first published at https://research.uga.edu/news/all-the-pieces-matter-uga-researchers-collaborate-to-solve-malaria-puzzle/