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

Reduced Trypanosoma cruzi-specific humoral response and enhanced T cell immunity after treatment interruption with benznidazole in chronic Chagas disease

Donna Huber on March 7, 2021

Background: Interruption of benznidazole therapy due to the appearance of adverse effects, which is presumed to lead to treatment failure, is a major drawback in the treatment of chronic Chagas disease.

Methods: Trypanosoma cruzi-specific humoral and T cell responses, T cell phenotype and parasite load were measured to compare the outcome in 33 subjects with chronic Chagas disease treated with an incomplete benznidazole regimen and 58 subjects treated with the complete regimen, during a median follow-up period of 48 months.

Results: Both treatment regimens induced a reduction in the T. cruzi-specific antibody levels and similar rates of treatment failure when evaluated using quantitative PCR. Regardless of the regimen, polyfunctional CD4+ T cells increased in the subjects, with successful treatment outcome defined as a decrease of T. cruzi-specific antibodies. Regardless of the serological outcome, naive and central memory T cells increased after both regimens. A decrease in CD4+ HLA-DR+ T cells was associated with successful treatment in both regimens. The cytokine profiles of subjects with successful treatment showed fewer inflammatory mediators than those of the untreated T. cruzi-infected subjects. High levels of T cells expressing IL-7 receptor and low levels of CD8+ T cells expressing the programmed cell death protein 1 at baseline were associated with successful treatment following benznidazole interruption.

Conclusions: These findings challenge the notion that treatment failure is the sole potential outcome of an incomplete benznidazole regimen and support the need for further assessment of the treatment protocols for chronic Chagas disease.

Melisa D Castro Eiro, María A Natale, María G Alvarez, Huifeng Shen, Rodolfo Viotti, Bruno Lococo, Jacqueline Bua, Myriam Nuñez, Graciela L Bertocchi, María C Albareda, Gonzalo Cesar, Rick L Tarleton, Susana A Laucella. J Antimicrob Chemother. 2021 Mar 7;dkab054. doi: 10.1093/jac/dkab054

Trainee Spotlight: Nathan Chasen

Donna Huber on March 5, 2021

Nathan Chasen is a post-doctoral fellow in Drew Etheridge’s laboratory (submitted photo)

Nathan Chasen, a postdoctoral fellow in Drew Etheridge’s laboratory, is originally from Richmond, Virginia. After receiving his undergraduate degree from Emory University, he worked as a research technician at UGA. He then decided to attend UGA for graduate school. Under the mentorship of Silvia Moreno, Chasen received two American Heart Association Predoctoral Fellowship Awards and earned his Ph.D. in December of 2017.

Why did you choose UGA?

I chose UGA because it is one of the best places in the world to study parasites for both the quality of the work and the collaborative research environment.

What is your research focus/project and why are you interested in the topic?

My current research focus is the poorly understood endocytic organelle of the parasite Trypanosoma cruzi, which is the causal agent of Chagas disease.

What are your future professional plans?

I plan to establish an academic lab that continues to unravel the nature of this neglected parasite, using state-of-the-art molecular tools and microscopy methods.

What is your favorite thing about UGA and Athens?

The area is a great low-cost living area, with little traffic and essentially everything you need within a 15-minute drive, including great food and a lively downtown area. The ability to live affordably within a short bike ride of campus is also a plus.

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

[button size=’large’ style=” text=’Give Now’ icon=” icon_color=’BA0C2F’ link=’https://ctegd.uga.edu/give/’ target=’_self’ color=” hover_color=” border_color=” hover_border_color=” background_color=” hover_background_color=” font_style=” font_weight=” text_align=’center’ margin=”]

Whole blood and blood components from vertebrates differentially affect egg formation in three species of anautogenous mosquitoes

Donna Huber on February 24, 2021

Background: Most female mosquitoes are anautogenous and must blood feed on a vertebrate host to produce eggs. Prior studies show that the number of eggs females lay per clutch correlates with the volume of blood ingested and that protein is the most important macronutrient for egg formation. In contrast, how whole blood, blood fractions and specific blood proteins from different vertebrates affect egg formation is less clear. Since egg formation is best understood in Aedes aegypti, we examined how blood and blood components from different vertebrates affect this species and two others: the malaria vector Anopheles gambiae and arbovirus vector Culex quinquefasciatus.

Methods: Adult female mosquitoes were fed blood, blood fractions and purified major blood proteins from different vertebrate hosts. Markers of reproductive response including ovary ecdysteroidogenesis, yolk deposition into oocytes and number of mature eggs produced were measured.

Results: Ae. aegypti, An. gambiae and C. quinquefasciatus responded differently to meals of whole blood, plasma or blood cells from human, rat, chicken and turkey hosts. We observed more similarities between the anthropophiles Ae. aegypti and An. gambiae than the ornithophile C. quinquefasciatus. Focusing on Ae. aegypti, the major plasma-derived proteins (serum albumin, fibrinogen and globulins) differentially stimulated egg formation as a function of vertebrate host source. The major blood cell protein, hemoglobin, stimulated yolk deposition when from pigs but not humans, cows or sheep. Serum albumins from different vertebrates also variably affected egg formation. Bovine serum albumin (BSA) stimulated ovary ecdysteroidogenesis, but more weakly induced digestive enzyme activities than whole blood. In contrast, BSA-derived peptides and free amino acids had no stimulatory effects on ecdysteroidogenesis or yolk deposition into oocytes.

Conclusions: Whole blood, blood fractions and specific blood proteins supported egg formation in three species of anautogenous mosquitoes but specific responses varied with the vertebrate source of the blood components tested.

Harrison, R.E., Brown, M.R. & Strand, M.R. Whole blood and blood components from vertebrates differentially affect egg formation in three species of anautogenous mosquitoes. Parasites Vectors 14, 119 (2021). https://doi.org/10.1186/s13071-021-04594-9

Silvia Moreno elected as American Academy of Microbiology Fellow

Donna Huber on February 18, 2021

University of Georgia researcher, a member of the Center for Tropical and Emerging Global Diseases and a Distinguished Research Professor in cellular biology, has been elected as a 2021 American Academy of Microbiology Fellow. Holding courtesy appointments in microbiology and infectious diseases, Silvia N. Moreno also serves as director of the NIH-funded Training in Tropical and Emerging Global Diseases program.

“This is an honor that represents the hard work and commitment of the members of my lab, past and present,” said Moreno.

Her research focuses on the parasite Toxoplasma gondii, which can cause encephalitis and cardiogenic shock in immunocompromised patients and can result in devastating birth defects in children born from infected pregnant women. Almost a third of the human population is infected. The parasite also infects cats, dogs and cattle.

In particular, Moreno’s laboratory is interested in discovering unique metabolic differences that can be used as targets for chemotherapy as current treatment options are for only one phase of the disease and have harmful side effects.

In 2018, she was named a corresponding member of the Latin American Academy of Sciences. Since 2015, she has been leading the Training in Tropical and Emerging Global Diseases program which is funded by an NIH T32 training grant. In the most recent competing renewal of the grant, CTEGD was awarded $1.9 million.

Under Moreno’s leadership the program has expanded to provide fellowships to seven graduate students and two post-doctoral fellows, a mini-sabbatical program for faculty members of local colleges with a higher proportion of diversity students to offer undergraduates and faculty research experience, and organize a number of professional development workshops.

Moreno joins more than 2,500 AAM fellows who are elected through a highly selective, peer-reviewed process, based on their record of scientific achievement and original contributions that have advanced the field of microbiology. Of the 150 researchers nominated this year, only 65 were elected to the 2021 Fellowship Class.

Evaluation of changes in drug susceptibility and population genetic structure in Haemonchus contortus following worm replacement as a means to reverse the impact of multiple-anthelmintic resistance on a sheep farm

Donna Huber on February 18, 2021

A population of Haemonchus contortus that was highly resistant to benzimidazoles and avermectin/milbemycins with a subpopulation that was resistant to levamisole, was replaced with a susceptible laboratory isolate of H. contortus in a flock of sheep. The anthelmintic susceptibility and population genetics of the newly established population were evaluated for 3.5 years using in vivo, in vitro, and molecular methods. Successful replacement of the resistant population with a susceptible population was confirmed using phenotypic and genotypic measurements; larval development assay indicated full anthelmintic susceptibility; albendazole treatment yielded 98.7% fecal egg count reduction; pyrosequence genotyping of single nucleotide polymorphisms in positions 167 and 200 of the isotype-1 beta tubulin gene were present at 0.0 and 1.7%, respectively; microsatellite genotyping indicated the background haplotype was similar to the susceptible isolate; and haplotypes of the isotype-1 beta tubulin gene were similar to the susceptible isolate. To sustain the susceptibility of the new population, targeted selective treatment was implemented using albendazole. Surprisingly, within 1.5 years post-replacement, the population reverted to a resistant phenotype. Resistance to albendazole, ivermectin, and moxidectin was confirmed via fecal egg count reduction test, larval development assay, and pyrosequencing-based genotyping. Targeted selective treatment was then carried out using levamisole. However, within one year, resistance was detected to levamisole. Population genetics demonstrated a gradual change in the genetic structure of the population until the final population was similar to the initial resistant population. Genetic analyses showed a lack of diversity in the susceptible isolate, suggesting the susceptible isolate had reduced environmental fitness compared to the resistant population, providing a possible explanation for the rapid reversion to resistance. This work demonstrates the power of combining molecular, in vitro, and in vivo assays to study phenotypic and genotypic changes in a field population of nematodes, enabling improved insights into the epidemiology of anthelmintic resistance.

Melissa M George, Adriano F Vatta, Sue B Howell, Bob E Storey, Ciaran J McCoy, Adrian J Wolstenholme, Elizabeth M Redman, John S Gilleard, Ray M Kaplan. International Journal for Parasitology: Drugs and Drug Resistance. 15, April 2021, 134-143. https://doi.org/10.1016/j.ijpddr.2021.02.004

MdBVe46 is an envelope protein that is required for virion formation by Microplitis demolitor bracovirus

Donna Huber on February 16, 2021

Bracoviruses (BVs) are endogenized nudiviruses that braconid parasitoid wasps have coopted for functions in parasitizing hosts. Microplitis demolitor is a braconid wasp that produces Microplitis demolitor bracovirus (MdBV) and parasitizes the larval stage of the moth Chrysodeixis includens. Some BV core genes are homologs of genes also present in baculoviruses while others are only known from nudiviruses or other BVs. In this study, we had two main goals. The first was to separate MdBV virions into envelope and nucleocapsid fractions before proteomic analysis to identify core gene products that were preferentially associated with one fraction or the other. Results indicated that nearly all MdBV baculovirus-like gene products that were detected by our proteomic analysis had similar distributions to homologs in the occlusion-derived form of baculoviruses. Several core gene products unknown from baculoviruses were also identified as envelope or nucleocapsid components. Our second goal was to functionally characterize a core gene unknown from baculoviruses that was originally named HzNVorf64-like. Immunoblotting assays supported our proteomic data that identified HzNVorf64-like as an envelope protein. We thus renamed HzNVorf64-like as MdBVe46, which we further hypothesized was important for infection of C. includens. Knockdown of MdBVe46 by RNA interference (RNAi) greatly reduced transcript and protein abundance. Knockdown of MdBVe46 also altered virion morphogenesis, near-fully inhibited infection of C. includens, and significantly reduced the proportion of hosts that were successfully parasitized by M. demolitor.

Michael J Arvin, Ange Lorenzi, Gaelen R Burke, Michael R Strand. J Gen Virol. 2021 Feb 16. doi: 10.1099/jgv.0.001565.

A redox-active crosslinker reveals an essential and inhibitable oxidative folding network in the endoplasmic reticulum of malaria parasites

Donna Huber on February 3, 2021

Malaria remains a major global health problem, creating a constant need for research to identify druggable weaknesses in P. falciparum biology. As important components of cellular redox biology, members of the Thioredoxin (Trx) superfamily of proteins have received interest as potential drug targets in Apicomplexans. However, the function and essentiality of endoplasmic reticulum (ER)-localized Trx-domain proteins within P. falciparum has not been investigated. We generated conditional mutants of the protein PfJ2-an ER chaperone and member of the Trx superfamily-and show that it is essential for asexual parasite survival. Using a crosslinker specific for redox-active cysteines, we identified PfJ2 substrates as PfPDI8 and PfPDI11, both members of the Trx superfamily as well, which suggests a redox-regulatory role for PfJ2. Knockdown of these PDIs in PfJ2 conditional mutants show that PfPDI11 may not be essential. However, PfPDI8 is required for asexual growth and our data suggest it may work in a complex with PfJ2 and other ER chaperones. Finally, we show that the redox interactions between these Trx-domain proteins in the parasite ER and their substrates are sensitive to small molecule inhibition. Together these data build a model for how Trx-domain proteins in the P. falciparum ER work together to assist protein folding and demonstrate the suitability of ER-localized Trx-domain proteins for antimalarial drug development.

David W. Cobb, Heather M. Kudyba, Alejandra Villegas, Michael R. Hoopmann, Rodrigo P. Baptista, Baylee Bruton, Michelle Krakowiak, Robert L. Moritz, Vasant Muralidharan. PLoS Pathog. 2021 Feb 3;17(2):e1009293. doi: 10.1371/journal.ppat.1009293.

Strain-specific genome evolution in Trypanosoma cruzi, the agent of Chagas disease

Donna Huber on January 28, 2021

The protozoan Trypanosoma cruzi almost invariably establishes life-long infections in humans and other mammals, despite the development of potent host immune responses that constrain parasite numbers. The consistent, decades-long persistence of T. cruzi in human hosts arises at least in part from the remarkable level of genetic diversity in multiple families of genes encoding the primary target antigens of anti-parasite immune responses. However, the highly repetitive nature of the genome-largely a result of these same extensive families of genes-have prevented a full understanding of the extent of gene diversity and its maintenance in T. cruzi. In this study, we have combined long-read sequencing and proximity ligation mapping to generate very high-quality assemblies of two T. cruzi strains representing the apparent ancestral lineages of the species. These assemblies reveal not only the full repertoire of the members of large gene families in the two strains, demonstrating extreme diversity within and between isolates, but also provide evidence of the processes that generate and maintain that diversity, including extensive gene amplification, dispersion of copies throughout the genome and diversification via recombination and in situ mutations. Gene amplification events also yield significant copy number variations in a substantial number of genes presumably not required for or involved in immune evasion, thus forming a second level of strain-dependent variation in this species. The extreme genome flexibility evident in T. cruzi also appears to create unique challenges with respect to preserving core genome functions and gene expression that sets this species apart from related kinetoplastids.

Wang W, Peng D, Baptista RP, Li Y, Kissinger JC, Tarleton RL (2021) Strain-specific genome evolution in Trypanosoma cruzi, the agent of Chagas disease. PLoS Pathog 17(1): e1009254. https://doi.org/10.1371/journal.ppat.1009254

CTEGD Emerging Fellows Symposium

Donna Huber on January 20, 2021

We invite recent and soon-to-graduate students (from any biological discipline) to apply for funded postdoctoral fellowships and positions to study parasitic diseases at the University of Georgia. Selected applicants will present their research to the CTEGD community on May 3, 2021 via Zoom at CTEGD Emerging Fellows Symposium. The applicants will get to meet with several faculty at CTEGD, as well as former and current trainees of the T32 program. We strongly support and encourage scholars from historically excluded or underrepresented groups to apply.

To apply, please send a cover letter and your CV by April 2, 2021 to ctegdt32@uga.edu

Program Goals

Since 2004, the Center for Tropical and Emerging Global Diseases at UGA has received funding from the NIH for an institutional training grant with the purpose of training researchers to become independent scientists who study parasitic diseases in the context of global health.

Eligibility

US citizen or permanent resident (if applying for T32 fellowship)
PhD received on or before August 1, 2021

Program Highlights

The Training in Tropical and Emerging Global Diseases program seeks fundamental insights into protozoan and helminth parasites and their interactions with mammalian hosts and invertebrate vectors. The CTEGD is an exceptional place to do a postdoc with an invigorating and supportive environment. Athens is a quirky, fun, and affordable city to live in.

The role of potassium and host calcium signaling in Toxoplasma gondii egress

Donna Huber on January 19, 2021

Toxoplasma gondii is an obligate intracellular parasite and replicates inside a parasitophorous vacuole (PV) within the host cell. The membrane of the PV (PVM) contains pores that permits for equilibration of ions and small molecules between the host cytosol and the PV lumen. Ca²⁺ signaling is universal and both T. gondii and its mammalian host cell utilize Ca²⁺ signals to stimulate diverse cellular functions. Egress of T. gondii from host cells is an essential step for the infection cycle of T. gondii, and a cytosolic Ca²⁺ increase initiates a Ca²⁺ signaling cascade that culminates in the stimulation of motility and egress. In this work we demonstrate that intracellular T. gondii tachyzoites are able to take up Ca²⁺ from the host cytoplasm during host cell signaling events. Both intracellular and extracellular Ca²⁺ sources are important in reaching a threshold of parasite cytosolic Ca²⁺ needed for successful egress. Two peaks of Ca²⁺ were observed in egressing single parasites with the second peak resulting from Ca²⁺ entry. We patched infected host cells to allow the delivery of precise concentrations of Ca²⁺ for the stimulation of motility and egress. Using this approach of patching infected host cells, allowed us to determine that increasing the host cytosolic Ca²⁺ to a specific concentration can trigger egress, which is further accelerated by diminishing the concentration of potassium (K⁺).

Stephen A Vella, Christina A Moore, Zhu-Hong Li, Miryam A Hortua Triana, Evgeniy Potapenko, Silvia N J Moreno. Cell Calcium. 2021 Jan 19;94:102337. doi: 10.1016/j.ceca.2020.102337

Author: Donna Huber