Chet Joyner Archives - Center for Tropical and Emerging Global Diseases

UGA researchers received prestigious grant to develop malaria drug

Donna Huber on October 12, 2023

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.

Understanding heterogeneity of human bone marrow plasma cell maturation and survival pathways by single-cell analyses

Donna Huber on June 23, 2023

Human bone marrow (BM) plasma cells are heterogeneous, ranging from newly arrived antibody-secreting cells (ASCs) to long-lived plasma cells (LLPCs). We provide single-cell transcriptional resolution of 17,347 BM ASCs from five healthy adults. Fifteen clusters are identified ranging from newly minted ASCs (cluster 1) expressing MKI67 and high major histocompatibility complex (MHC) class II that progress to late clusters 5–8 through intermediate clusters 2–4. Additional ASC clusters include the following: immunoglobulin (Ig) M predominant (likely of extra-follicular origin), interferon responsive, and high mitochondrial activity. Late ASCs are distinguished by G2M checkpoints, mammalian target of rapamycin (mTOR) signaling, distinct metabolic pathways, CD38 expression, utilization of tumor necrosis factor (TNF)-receptor superfamily members, and two distinct maturation pathways involving TNF signaling through nuclear factor κB (NF-κB). This study provides a single-cell atlas and molecular roadmap of LLPC maturation trajectories essential in the BM microniche. Altogether, understanding BM ASC heterogeneity in health and disease enables development of new strategies to enhance protective ASCs and to deplete pathogenic ones.

Meixue Duan, Doan C Nguyen, Chester J Joyner, Celia L Saney, Christopher M Tipton, Joel Andrews, Sagar Lonial, Caroline Kim, Ian Hentenaar, Astrid Kosters, Eliver Ghosn, Annette Jackson, Stuart Knechtle, Stalinraja Maruthamuthu, Sindhu Chandran, Tom Martin, Raja Rajalingam, Flavio Vincenti, Cynthia Breeden, Ignacio Sanz, Greg Gibson, F Eun-Hyung Lee. Cell Rep. 2023 Jun 23;42(7):112682. doi: 10.1016/j.celrep.2023.112682

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

Donna Huber on April 25, 2023

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?

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.

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.

“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)

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.

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/

Chet Joyner receives $1.1 million grant to study malaria vaccine

Donna Huber on March 28, 2023

RESEARCH WILL BE IN COLLABORATION WITH YALE UNIVERSITY

Chet Joyner, PhD, a faculty member in the Center for Vaccines and Immunology and the Center for Tropical and Emerging Diseases in the College of Veterinary Medicine (CVM) at the University of Georgia, is the recipient of a $1.1 million grant from Open Philanthropy to perform preclinical testing of a vaccine designed to prevent reinfection from malaria.

“A vaccine that lessens the impact of this disease will have incalculable value in terms of lives saved and the quality of life of those in the affected areas,” said Lisa K. Nolan, DVM, PhD, dean of the CVM. “We are proud of Dr. Joyner’s work and that he has chosen to do it in the College of Veterinary Medicine at the University of Georgia.”

Joyner is collaborating with Dr. Richard Bucala, MD, PhD, of Yale University to test the vaccine that targets Plasmodium-encoded Macrophage Migration Inhibitory Factor (pMIF), a protein secreted by Plasmodium falciparum, a pathogen that causes malaria.

The science team for Open Philanthropy, which recommended grants to Joyner and Bucala for the three-year study, believes that vaccinating against pMIF may provide an important boost to the efficacy of existing malaria vaccines, according to a statement on its website, openphilanthropy.org.

Open Philanthropy is a Silicon Valley-based nonprofit which aims to use its resources to help others as much as possible. They fund work in many areas, including global health.

Joyner, who was recruited from Emory University to join the CVM in January of 2020, said the college is uniquely positioned to test the efficacy of the vaccine developed by Bucala at Yale.

“We are a strong malaria group with unique infrastructure and facilities that can support this necessary research within the CVM,” Joyner said.

Immunity to malaria is acquired naturally after exposure, but the disease can be fatal to children younger than five and debilitating up to age 10 because malaria parasites disrupt the immune system’s response with their own proteins that mimic the human Macrophage Migration Inhibitory Factor (MIF).

Not only does the resulting illness cause children to miss school, but it also leads to long-term cognitive decline due to nutritional deficiencies. Parents miss work to care for children and the economic impacts compound.

According to the World Health Organization’s 2022 World Malaria report, an estimated 247 million cases of malaria occurred worldwide in 2021 and 619,000 people died, mostly children under the age of five in sub-Saharan Africa.

This story was originally published at https://vet.uga.edu/cvm-researcher-wins-1-1-million-grant-to-study-malaria-vaccine/

Malaria disrupts the rhesus macaque gut microbiome

Donna Huber on January 13, 2023

Previous studies have suggested that a relationship exists between severity and transmissibility of malaria and variations in the gut microbiome, yet only limited information exists on the temporal dynamics of the gut microbial community during a malarial infection. Here, using a rhesus macaque model of relapsing malaria, we investigate how malaria affects the gut microbiome. In this study, we performed 16S sequencing on DNA isolated from rectal swabs of rhesus macaques over the course of an experimental malarial infection with Plasmodium cynomolgi and analyzed gut bacterial taxa abundance across primary and relapsing infections. We also performed metabolomics on blood plasma from the animals at the same timepoints and investigated changes in metabolic pathways over time. Members of Proteobacteria (family Helicobacteraceae) increased dramatically in relative abundance in the animal’s gut microbiome during peak infection while Firmicutes (family Lactobacillaceae and Ruminococcaceae), Bacteroidetes (family Prevotellaceae) and Spirochaetes amongst others decreased compared to baseline levels. Alpha diversity metrics indicated decreased microbiome diversity at the peak of parasitemia, followed by restoration of diversity post-treatment. Comparison with healthy subjects suggested that the rectal microbiome during acute malaria is enriched with commensal bacteria typically found in the healthy animal’s mucosa. Significant changes in the tryptophan-kynurenine immunomodulatory pathway were detected at peak infection with P. cynomolgi, a finding that has been described previously in the context of P. vivax infections in humans. During relapses, which have been shown to be associated with less inflammation and clinical severity, we observed minimal disruption to the gut microbiome, despite parasites being present. Altogether, these data suggest that the metabolic shift occurring during acute infection is associated with a concomitant shift in the gut microbiome, which is reversed post-treatment.

Danielle N Farinella, Sukhpreet Kaur, ViLinh Tran, Monica Cabrera-Mora, Chester J Joyner, Stacey A Lapp, Suman B Pakala, Mustafa V Nural, Jeremy D DeBarry, Jessica C Kissinger, Dean P Jones, Alberto Moreno, Mary R Galinski, Regina Joice Cordy. Front Cell Infect Microbiol. 2023 Jan 13;12:1058926. doi: 10.3389/fcimb.2022.1058926. eCollection 2022.

MaHPIC malaria systems biology data from Plasmodium cynomolgi sporozoite longitudinal infections in macaques

Donna Huber on November 24, 2022

Plasmodium cynomolgi causes zoonotic malarial infections in Southeast Asia and this parasite species is important as a model for Plasmodium vivax and Plasmodium ovale. Each of these species produces hypnozoites in the liver, which can cause relapsing infections in the blood. Here we present methods and data generated from iterative longitudinal systems biology infection experiments designed and performed by the Malaria Host-Pathogen Interaction Center (MaHPIC) to delve deeper into the biology, pathogenesis, and immune responses of P. cynomolgi in the Macaca mulatta host. Infections were initiated by sporozoite inoculation. Blood and bone marrow samples were collected at defined timepoints for biological and computational experiments and integrative analyses revolving around primary illness, relapse illness, and subsequent disease and immune response patterns. Parasitological, clinical, haematological, immune response, and -omic datasets (transcriptomics, proteomics, metabolomics, and lipidomics) including metadata and computational results have been deposited in public repositories. The scope and depth of these datasets are unprecedented in studies of malaria, and they are projected to be a F.A.I.R., reliable data resource for decades.

Jeremy D DeBarry, Mustafa V Nural, Suman B Pakala, Vishal Nayak, Susanne Warrenfeltz, Jay Humphrey, Stacey A Lapp, Monica Cabrera-Mora, Cristiana F A Brito, Jianlin Jiang, Celia L Saney, Allison Hankus, Hannah M Stealey, Megan B DeBarry, Nicolas Lackman, Noah Legall, Kevin Lee, Yan Tang, Anuj Gupta, Elizabeth D Trippe, Robert R Bridger, Daniel Brent Weatherly, Mariko S Peterson, Xuntian Jiang, ViLinh Tran, Karan Uppal, Luis L Fonseca, Chester J Joyner, Ebru Karpuzoglu, Regina J Cordy, Esmeralda V S Meyer, Lance L Wells, Daniel S Ory, F Eun-Hyung Lee, Rabindra Tirouvanziam, Juan B Gutiérrez 1, Chris Ibegbu, Tracey J Lamb, Jan Pohl, Sarah T Pruett, Dean P Jones, Mark P Styczynski, Eberhard O Voit, Alberto Moreno, Mary R Galinski, Jessica C Kissinger. Sci Data. 2022 Nov 24;9(1):722. doi: 10.1038/s41597-022-01755-y.

Single-cell RNA profiling of Plasmodium vivax-infected hepatocytes reveals parasite- and host- specific transcriptomic signatures and therapeutic targets

Donna Huber on August 25, 2022

The resilience of Plasmodium vivax, the most widely-distributed malaria-causing parasite in humans, is attributed to its ability to produce dormant liver forms known as hypnozoites, which can activate weeks, months, or even years after an initial mosquito bite. The factors underlying hypnozoite formation and activation are poorly understood, as is the parasite’s influence on the host hepatocyte. Here, we shed light on transcriptome-wide signatures of both the parasite and the infected host cell by sequencing over 1,000 P. vivax-infected hepatocytes at single-cell resolution. We distinguish between replicating schizonts and hypnozoites at the transcriptional level, identifying key differences in transcripts encoding for RNA-binding proteins associated with cell fate. In infected hepatocytes, we show that genes associated with energy metabolism and antioxidant stress response are upregulated, and those involved in the host immune response downregulated, suggesting both schizonts and hypnozoites alter the host intracellular environment. The transcriptional markers in schizonts, hypnozoites, and infected hepatocytes revealed here pinpoint potential factors underlying dormancy and can inform therapeutic targets against P. vivax liver-stage infection.

Anthony A Ruberto, Steven P Maher, Amélie Vantaux, Chester J Joyner, Caitlin Bourke, Balu Balan, Aaron Jex, Ivo Mueller, Benoit Witkowski, Dennis E Kyle. Front Cell Infect Microbiol. 2022 Aug 25;12:986314. doi: 10.3389/fcimb.2022.986314. eCollection 2022.

Plasmodium knowlesi Cytoadhesion Involves SICA Variant Proteins

Donna Huber on June 23, 2022

Plasmodium knowlesi poses a health threat throughout Southeast Asian communities and currently causes most cases of malaria in Malaysia. This zoonotic parasite species has been studied in Macaca mulatta (rhesus monkeys) as a model for severe malarial infections, chronicity, and antigenic variation. The phenomenon of Plasmodium antigenic variation was first recognized during rhesus monkey infections. Plasmodium-encoded variant proteins were first discovered in this species and found to be expressed at the surface of infected erythrocytes, and then named the Schizont-Infected Cell Agglutination (SICA) antigens. SICA expression was shown to be spleen dependent, as SICA expression is lost after P. knowlesi is passaged in splenectomized rhesus. Here we present data from longitudinal P. knowlesi infections in rhesus with the most comprehensive analysis to date of clinical parameters and infected red blood cell sequestration in the vasculature of tissues from 22 organs. Based on the histopathological analysis of 22 tissue types from 11 rhesus monkeys, we show a comparative distribution of parasitized erythrocytes and the degree of margination of the infected erythrocytes with the endothelium. Interestingly, there was a significantly higher burden of parasites in the gastrointestinal tissues, and extensive margination of the parasites along the endothelium, which may help explain gastrointestinal symptoms frequently reported by patients with P. knowlesi malarial infections. Moreover, this margination was not observed in splenectomized rhesus that were infected with parasites not expressing the SICA proteins. This work provides data that directly supports the view that a subpopulation of P. knowlesi parasites cytoadheres and sequesters, likely via SICA variant antigens acting as ligands. This process is akin to the cytoadhesive function of the related variant antigen proteins, namely Erythrocyte Membrane Protein-1, expressed by Plasmodium falciparum.

Mariko S Peterson, Chester J Joyner, Stacey A Lapp, Jessica A Brady, Jennifer S Wood, Monica Cabrera-Mora, Celia L Saney, Luis L Fonseca, Wayne T Cheng, Jianlin Jiang, Stephanie R Soderberg, Mustafa V Nural, Allison Hankus, Deepa Machiah, Ebru Karpuzoglu, Jeremy D DeBarry, Rabindra Tirouvanziam, Jessica C Kissinger, Alberto Moreno, Sanjeev Gumber, Eberhard O Voit, Juan B Gutierrez, Regina Joice Cordy, Mary R Galinski. Front Cell Infect Microbiol. 2022 Jun 23;12:888496. doi: 10.3389/fcimb.2022.888496. eCollection 2022.

Clinical recovery of Macaca fascicularis infected with Plasmodium knowlesi

Donna Huber on December 30, 2021

Background: Kra monkeys (Macaca fascicularis), a natural host of Plasmodium knowlesi, control parasitaemia caused by this parasite species and escape death without treatment. Knowledge of the disease progression and resilience in kra monkeys will aid the effective use of this species to study mechanisms of resilience to malaria. This longitudinal study aimed to define clinical, physiological and pathological changes in kra monkeys infected with P. knowlesi, which could explain their resilient phenotype.

Methods: Kra monkeys (n = 15, male, young adults) were infected intravenously with cryopreserved P. knowlesi sporozoites and the resulting parasitaemias were monitored daily. Complete blood counts, reticulocyte counts, blood chemistry and physiological telemetry data (n = 7) were acquired as described prior to infection to establish baseline values and then daily after inoculation for up to 50 days. Bone marrow aspirates, plasma samples, and 22 tissue samples were collected at specific time points to evaluate longitudinal clinical, physiological and pathological effects of P. knowlesi infections during acute and chronic infections.

Results: As expected, the kra monkeys controlled acute infections and remained with low-level, persistent parasitaemias without anti-malarial intervention. Unexpectedly, early in the infection, fevers developed, which ultimately returned to baseline, as well as mild to moderate thrombocytopenia, and moderate to severe anaemia. Mathematical modelling and the reticulocyte production index indicated that the anaemia was largely due to the removal of uninfected erythrocytes and not impaired production of erythrocytes. Mild tissue damage was observed, and tissue parasite load was associated with tissue damage even though parasite accumulation in the tissues was generally low.

Conclusions: Kra monkeys experimentally infected with P. knowlesi sporozoites presented with multiple clinical signs of malaria that varied in severity among individuals. Overall, the animals shared common mechanisms of resilience characterized by controlling parasitaemia 3-5 days after patency, and controlling fever, coupled with physiological and bone marrow responses to compensate for anaemia. Together, these responses likely minimized tissue damage while supporting the establishment of chronic infections, which may be important for transmission in natural endemic settings. These results provide new foundational insights into malaria pathogenesis and resilience in kra monkeys, which may improve understanding of human infections.

Mariko S Peterson, Chester J Joyner, Jessica A Brady, Jennifer S Wood, Monica Cabrera-Mora, Celia L Saney, Luis L Fonseca, Wayne T Cheng, Jianlin Jiang, Stacey A Lapp, Stephanie R Soderberg, Mustafa V Nural, Jay C Humphrey, Allison Hankus, Deepa Machiah, Ebru Karpuzoglu, Jeremy D DeBarry, MaHPIC-Consortium; Rabindra Tirouvanziam, Jessica C Kissinger, Alberto Moreno, Sanjeev Gumber, Eberhard O Voit, Juan B Gutiérrez, Regina Joice Cordy, Mary R Galinski. Clinical recovery of Macaca fascicularis infected with Plasmodium knowlesi. Malar J 20, 486 (2021). https://doi.org/10.1186/s12936-021-03925-6

Generation of human long-lived plasma cells by developmentally regulated epigenetic imprinting

Donna Huber on December 24, 2021

Antibody secreting cells (ASCs) circulate after vaccination and infection and migrate to the BM where a subset known as long-lived plasma cells (LLPCs) persists and secrete antibodies for a lifetime. The mechanisms by which circulating ASCs become LLPCs are not well elucidated. Here, we show that human blood ASCs have distinct morphology, transcriptomes, and epigenetics compared with BM LLPCs. Compared with blood ASCs, BM LLPCs have decreased nucleus/cytoplasm ratio but increased endoplasmic reticulum and numbers of mitochondria. LLPCs up-regulate pro-survival genes MCL1, BCL2, and BCL-XL while simultaneously down-regulating pro-apoptotic genes HRK1, CASP3, and CASP8 Consistent with reduced gene expression, the pro-apoptotic gene loci are less accessible in LLPCs. Of the pro-survival genes, only BCL2 is concordant in gene up-regulation and loci accessibility. Using a novel in vitro human BM mimetic, we show that blood ASCs undergo similar morphological and molecular changes that resemble ex vivo BM LLPCs. Overall, our study demonstrates that early-minted blood ASCs in the BM microniche must undergo morphological, transcriptional, and epigenetic changes to mature into apoptotic-resistant LLPCs.

Chester J Joyner, Ariel M Ley, Doan C Nguyen, Mohammad Ali, Alessia Corrado, Christopher Tipton, Christopher D Scharer, Tian Mi, Matthew C Woodruff, Jennifer Hom, Jeremy M Boss, Meixue Duan, Greg Gibson, Danielle Roberts, Joel Andrews, Sagar Lonial, Inaki Sanz, F Eun-Hyung Lee. Life Sci Alliance. 2021 Dec 24;5(3):e202101285. doi: 10.26508/lsa.202101285.

Tag: Chet Joyner