Donna Huber, Author at Center for Tropical and Emerging Global Diseases

A combination of four Toxoplasma gondii nuclear-targeted effectors protects against interferon gamma-driven human host cell death

Donna Huber on September 18, 2024

Fig 1 IFNγ stimulation following infection is countered by MYR1, preventing early tachyzoite egress and host cell death.

In both mice and humans, Type II interferon gamma (IFNγ) is crucial for the regulation of Toxoplasma gondii (T. gondii) infection, during acute or chronic phases. To thwart this defense, T. gondii secretes protein effectors hindering the host’s immune response. For example, T. gondii relies on the MYR translocon complex to deploy soluble dense granule effectors (GRAs) into the host cell cytosol or nucleus. Recent genome-wide loss-of-function screens in IFNγ-primed primary human fibroblasts identified MYR translocon components as crucial for parasite resistance against IFNγ-driven vacuole clearance. However, these screens did not pinpoint specific MYR-dependent GRA proteins responsible for IFNγ signaling blockade, suggesting potential functional redundancy. Our study reveals that T. gondii depends on the MYR translocon complex to prevent parasite premature egress and host cell death in human cells stimulated with IFNγ post-infection, a unique phenotype observed in various human cell lines but not in murine cells. Intriguingly, inhibiting parasite egress did not prevent host cell death, indicating this mechanism is distinct from those described previously. Genome-wide loss-of-function screens uncovered TgIST, GRA16, GRA24, and GRA28 as effectors necessary for a complete block of IFNγ response. GRA24 and GRA28 directly influenced IFNγ-driven transcription, GRA24’s action depended on its interaction with p38 MAPK, while GRA28 disrupted histone acetyltransferase activity of CBP/p300. Given the intricate nature of the immune response to T. gondii, it appears that the parasite has evolved equally elaborate mechanisms to subvert IFNγ signaling, extending beyond direct interference with the JAK/STAT1 pathway, to encompass other signaling pathways as well.

Henry B, Phillips AJ, Sibley LD, Rosenberg A. 2024. mBio 0:e02124-24. https://doi.org/10.1128/mbio.02124-24

Inorganic Polyphosphate Is in the Surface of Trypanosoma cruzi but Is Not Significantly Secreted

Donna Huber on September 9, 2024

Figure 2. Presence of surface polyP in T. cruzi different stages.

Trypanosoma cruzi is the etiologic agent of Chagas disease, an infection that can lead to the development of cardiac fibrosis, which is characterized by the deposition of extracellular matrix (ECM) components in the interstitial region of the myocardium. The parasite itself can induce myofibroblast differentiation of cardiac fibroblast in vitro, leading to increased expression of ECM. Inorganic polyphosphate (polyP) is a linear polymer of orthophosphate that can also induce myofibroblast differentiation and deposition of ECM components and is highly abundant in T. cruzi. PolyP can modify proteins post-translationally by non-enzymatic polyphosphorylation of lysine residues of poly-acidic, serine-(S) and lysine (K)-rich (PASK) motifs. In this work, we used a bioinformatics screen and identified the presence of PASK domains in several surface proteins of T. cruzi. We also detected polyP in the external surface of its different life cycle stages and confirmed the stimulation of host cell fibrosis by trypomastigote infection. However, we were not able to detect significant secretion of the polymer or activation of transforming growth factor beta (TGF-β), an important factor for the generation of fibrosis by inorganic polyP- or trypomastigote-conditioned medium.

Logan P Crowe, Anna Gioseffi, Mayara S Bertolini, Roberto Docampo. Pathogens. 2024 Sep 9;13(9):776. doi: 10.3390/pathogens13090776.

Trainee Spotlight: Kaelynn Parker

Donna Huber on July 30, 2024

I’m Kaelynn Parker and I’m from Virginia where I received my BS in biology from the University of Mary Washington. I’m a cellular biology Ph.D. student in Deigo Huet‘s laboratory.

What made you want to study science?

I took a genetic course at Germanna Community College as an elective while pursuing an associate’s degree part-time and working as an assistant barn manager. We did an experiment where we transformed E. coli with GFP and I thought it was the coolest thing I had ever done. It was a turning point where I decided I wanted to be in science.

Why did you choose UGA?

I chose UGA because of my undergraduate research advisor, Dr. Swati Agrawal, a CTEGD alum. I fell in love with parasitology (something I never imagined would happen) working with her, which inspired me to continue in the field. She also organized a seminar series featuring graduate students from CTEGD labs. After hearing from the graduate students at CTEGD, UGA was the only place I wanted to go for graduate school.

What is your project and why did you choose this research focus?

My project focuses on understanding interorganellar communication in Toxoplasma gondii through discovery and characterization of membrane contact sites between the ER, mitochondrion, and apicoplast. I am also investigating mitochondrial dynamics and stress response in T. gondii. I came to UGA with the desire to work on T. gondii because my original undergraduate project was supposed to be characterizing proteins important for egress in T. gondii. However, the COVID-19 pandemic put a halt on that plan and I wanted to return to Toxoplasma for graduate school.

What are your career goals?

I would like to remain in academic parasitology.

What do you hope to do for your capstone experience? Is there a collaborator/field site you would like to visit?

For my capstone experience, my plan is to utilize the opportunity to go to another lab to learn techniques to apply to membrane contact site research.

What is your favorite thing about UGA and/or Athens?

I love to go bird watching at the botanical gardens and local parks.

Any advice for a student interested in this field?

Talk to people, take every opportunity to present your work and build connections.

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

Seeing the unseen: illuminating Toxoplasma gondii’s metabolic manipulation

Donna Huber on July 12, 2024

Intracellular infection by a pathogen induces significant rewiring of host cell signaling and biological processes. Understanding how an intracellular pathogen such as Toxoplasma gondii modulates host cell metabolism with single-cell resolution has been challenged by the variability of infection within cultures and difficulties in separating host and parasite metabolic processes. A new study from Gallego-Lopez and colleagues (G. M. Gallego-López, E. C. Guzman, D. E. Desa, L. J. Knoll, M. C. Skala, mBio e00727-24, 2024, https://doi.org/10.1128/mbio.00727-24) applies a quantitative imaging approach to evaluate the host cell metabolism during intracellular infection with Toxoplasma. This study provides important insights into host metabolic responses to Toxoplasma infection and offers a valuable tool to dissect the mechanisms underlying parasite infection and pathophysiology.

Diego Huet, Victoria Jeffers. mBio. 2024 Jul 12:e0121124. doi: 10.1128/mbio.01211-24.

In the news: Dennis Kyle

Donna Huber on July 8, 2024

Dennis Kyle is the Director of CTEGD and the GRA Eminent Scholar in Antiparasitic Drug Discovery in the Departments of Cellular Biology and Infectious Diseases.

Brain-eating amoeba: Will the warming climate bring more cases? (MSN)

In the news: Michael Strand

Donna Huber on July 8, 2024

Michael Strand is a Regents Professor in the Department of Entomology and member of the Center for Tropical and Emerging Global Diseases. His mosquito research has recently been featured in a number of news stories.

What drives mosquitoes’ bloodlust? Their hormones (Nature)

The Science Behind What Makes Mosquitoes Bite You! Explained (News 9)

Mosquito bloodlust controlled by two hormones (The Naked Scientists)

Domestic Dog Infection with Trypanosoma cruzi from Northern and Southern Regions of Mexico

Donna Huber on July 1, 2024

Reactive StatPak immunochromatography test results from dogs sampled between December 2018 and October 2019 in Reynosa, Tamaulipas and Tuxtla Gutierrez, Chiapas, Mexico.

Background: Chagas disease or American trypanosomiasis, caused by Trypanosoma cruzi and vectored by triatomines, affects millions of people worldwide. In endemic countries including Mexico, infections in domestic animals, such as dogs, may affect the risk of human disease when they serve as a source of infection to vectors that subsequently infect humans. Materials and Methods: We conducted a cross-sectional study of 296 dogs from two cities near the northern and southern borders of Mexico: Reynosa, Tamaulipas, and Tuxtla Gutierrez, Chiapas. Infection was measured based on testing of blood using T. cruzi quantitative PCR (qPCR) and up to three antibody detection assays. The StatPak immunochromatographic assay was used to screen samples and the indirect fluorescent antibody (IFA) and multiplex microsphere immunoassay (MIA) tests were used as secondary tests on all samples that screened positive and a subset of negatives. Serologic positivity was defined based on reactivity on at least two independent tests. Results: Of the 280 samples tested for parasite DNA, two (0.7%) were positive, one of which (0.4%) was confirmed as T. cruzi discrete typing unit TcIV. Overall, 72 (24.3%) samples were reactive for T. cruzi antibodies via StatPak of which 8 were also positive using MIA and 2 were also positive using IFA (including one of the PCR-positive dogs). Overall, nine dogs (3.4%) met study criteria of positivity based on either/both serology or PCR tests. Positive dogs were found in both regions of Mexico; five (2.7%) from Reynosa and four (3.6%) from Tuxtla Gutierrez. We found no association between infection status and state of origin, sex, age group, breed group, neighborhood, and whether other pets lived in the home. Conclusion: Our results re-emphasize dogs’ utility as sentinels for T. cruzi in Mexico and underscore the need for improved veterinary diagnostic tests and parasite surveillance at the household level in endemic countries.

Edward Davila, Nadia A Fernandez-Santos, José Guillermo Estrada-Franco, Lihua Wei, Doireyner Daniel Velázquez-Ramírez, Rosario García-Miranda, Cesar Irecta Nájera, Raúl Cruz-Cadena, Carlos Guichard-Romero, Carlos Rodriguez, Rick Tarleton, Mario A Rodríguez-Pérez, Héctor Ochoa-Díaz-López, Gabriel L Hamer, Sarah A Hamer. Vector Borne Zoonotic Dis. 2024 Jul 1. doi: 10.1089/vbz.2023.0110

Reciprocal interactions between neuropeptide F and RYamide regulate host attraction in the mosquito Aedes aegypti

Donna Huber on July 1, 2024

NPF accumulates in EECs of the posterior midgut after adult emergence but rapidly depletes after blood feeding.

Female mosquitoes produce eggs in gonadotrophic cycles that are divided between a previtellogenic and vitellogenic phase. Previtellogenic females consume water and sugar sources like nectar while also being attracted to hosts for blood feeding. Consumption of a blood meal activates the vitellogenic phase, which produces mature eggs and suppresses host attraction. In this study, we tested the hypothesis that neuropeptide Y-like hormones differentially modulate host attraction behavior in the mosquito Aedes aegypti. A series of experiments collectively indicated that enteroendocrine cells (EECs) in the posterior midgut produce and release neuropeptide F (NPF) into the hemolymph during the previtellogenic phase which stimulates attraction to humans and biting behavior. Consumption of a blood meal, which primarily consists of protein by dry weight, down-regulated NPF in EECs until mature eggs developed, which was associated with a decline in hemolymph titer. NPF depletion depended on protein digestion but was not associated with EEC loss. Other experiments showed that neurons in the terminal ganglion extend axons to the posterior midgut and produce RYamide, which showed evidence of increased secretion into circulation after a blood meal. Injection of RYamide-1 and -2 into previtellogenic females suppressed host attraction, while coinjection of RYamides with or without short NPF-2 also inhibited the host attraction activity of NPF. Overall, our results identify NPF and RYamide as gut-associated hormones in A. aegypti that link host attraction behavior to shifts in diet during sequential gonadotrophic cycles.

Xiaoyi Dou, Kangkang Chen, Mark R Brown, Michael R Strand. Proc Natl Acad Sci U S A. 2024 Jul 9;121(28):e2408072121. doi: 10.1073/pnas.2408072121.

An Overview of Management Considerations for Mongolian Gerbils (Meriones unguiculatus), Cats (Felis catus), and Dogs (Canis familiaris) as Hosts for Brugia Infection

Donna Huber on June 26, 2024

Lymphatic filariasis is a mosquito-borne parasitic infection affecting an estimated 51.4 million people. Brugia malayi and Brugia pahangi are used in research because common nonprimate research species such as Mongolian gerbils (Meriones unguiculatus), cats (Felis catus), and dogs (Canis familiaris) can maintain the life cycle of these species of filarial nematodes. Although overall care and management of animals infected with Brugia spp. is relatively straightforward, there are some unique challenges and special considerations that must be addressed when managing a research colony infected with these parasites. In this review, we discuss our experience, share insight into biosafety and clinical management, and describe the expected clinical signs associated with Brugia infection in gerbils, cats, and dogs.

Catherine A Chambers, Christopher C Evans, Gianni A Campellone, Mary A McCrackin, Andrew R Moorhead, Leanne C Alworth. Comp Med. 2024 Jun 26. doi: 10.30802/AALAS-CM-24-034.

Optimization of diastereomeric dihydropyridines as antimalarials

Donna Huber on June 18, 2024

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.

Author: Donna Huber