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

New Confocal Microscope at the Biomedical Microscopy Core

Donna Huber on November 16, 2022

The University of Georgia’s Biomedical Microscopy Core has recently acquired a Zeiss LSM 980 confocal microscope with Airyscan2 and Multiplex Mode for confocal and super-resolution imaging.

This new state-of-art microscope is capable of fast, gentle, and simultaneous imaging of live and fixed samples with up to 5 colors (Blue, green, Red, Far-Red & NIR), and resolving structures up to 120 nm. It can be used for a wide array of imaging applications including protein co-localization, cytoskeletal studies, tiling of large tissue samples or a lot of cells, spectral imaging and unmixing of diverse fluorophores, and Z-stack 3D/4D imaging. It has an inverted microscope stand and environmental chamber with temperature control and CO₂ for long-term live imaging. Moreover, the LSM 980 is fitted with seven different laser lines (405, 458, 488, 514, 543, 633, and 730 nm) and 32 channel GaAsP PMT + 2 channels MA-PMT detectors for performing spectral detection of a wealth of fluorescent labels from 380 nm to NIR range. The presence of Airyscan2 and Multiplex Mode allows fast imaging of samples at super-resolution levels.

The new instrument was purchased with funding from the UGA Office of Research and BMC (lease). It has been installed already at the Core and is available for training and use. Please contact Dr. M. Kandasamy, the Director of BMC for training, and refer to the Core website for further details about the instrument and fees.

The Biomedical Microscopy Core is open to all UGA researchers as well as researchers outside of UGA.

Avoiding clinical trial failures in neglected tropical diseases: The example of Chagas disease

Donna Huber on November 14, 2022

Human clinical trials are expensive, and when they fail, they create the impression that a problem is intractable, thus depressing interest in future attempts. For neglected tropical diseases, where there are likely limited numbers of “shots on goal”, such failures need to be assiduously avoided. Chagas disease drug discovery efforts have experienced more than its share of human clinical trial failures. Here Here are some guidelines, many specific for Chagas, but some which might also have application for other neglected tropical diseases. Chagas disease has major challenges (e.g., the lack of a definitive test of cure) but also has outstanding advantages, among these the unmatched multi-species natural infection systems that can be exploited to de-risk compounds before human trials. Fully utilizing these advantages while frankly acknowledging and addressing the challenges should bring better options to patients, sooner.

Rick Tarleton. Clin Infect Dis. 2022 Nov 14;ciac884. doi: 10.1093/cid/ciac884. Online ahead of print.

Evaluation of delayed LNFPIII treatment initiation protocol on improving long-term behavioral and neuroinflammatory pathology in a mouse model of Gulf War Illness

Donna Huber on November 8, 2022

Chemical overexposures and war-related stress during the 1990-1991 Gulf War (GW) are implicated in the persisting pathological symptoms that many GW veterans continue to endure. These symptoms culminate into a disease known as Gulf War Illness (GWI) and affect about a third of the GW veteran population. Currently, comprehensive effective GWI treatment options are unavailable. Here, an established GWI mouse model was utilized to explore the (1) long-term behavioral and neuroinflammatory effects of deployment-related GWI chemicals exposure and (2) ability of the immunotherapeutic lacto-N-fucopentaose III (LNFPIII) to improve deficits when given months after the end of exposure. Male C57BL6/J mice (8-9 weeks old) were administered pyridostigmine bromide (PB) and DEET for 14 days along with corticosterone (CORT; latter 7 days) to emulate wartime stress. On day 15, a single injection of the nerve agent surrogate diisopropylfluorophosphate (DFP) was given. LNFPIII treatment began 7 months post GWI chemicals exposure and continued until study completion. A battery of behavioral tests for assessment of cognition/memory, mood, and motor function in rodents was performed beginning 8 months after exposure termination and was then followed by immunohistochemcal evaluation of neuroinflammation and neurogenesis. Within tests of motor function, prior GWI chemical exposure led to hyperactivity, impaired sensorimotor function, and altered gait. LNFPIII attenuated these motor-related deficits and improved overall grip strength. GWI mice also exhibited more anxiety-like behavior that was reduced by LNFPIII; this was test-specific. Short-term, but not long-term memory, was impaired by prior GWI exposure; LNFPIII improved this measure. In the brains of GWI mice, but not in mice treated with LNFPIII, glial activation was increased. Overall, it appears that months after exposure to GWI chemicals, behavioral deficits and neuroinflammation are present. Many of these deficits were attenuated by LNFPIII when treatment began long after GWI chemical exposure termination, highlighting its therapeutic potential for veterans with GWI.

Jessica M Carpenter, Kyle A Brown, Lukas Veltmaat, Helaina D Ludwig, Kendall B Clay, Thomas Norberg, Donald A Harn, John J Wagner, Nikolay M Filipov. Brain Behav Immun Health. 2022 Nov 8;26:100553. doi: 10.1016/j.bbih.2022.100553. eCollection 2022 Dec.

Gastrointestinal helminths increase Bordetella bronchiseptica shedding and host variation in supershedding

Donna Huber on November 8, 2022

Co-infected hosts, individuals that carry more than one infectious agent at any one time, have been suggested to facilitate pathogen transmission, including the emergence of supershedding events. However, how the host immune response mediates the interactions between co-infecting pathogens and how these affect the dynamics of shedding remains largely unclear. We used laboratory experiments and a modeling approach to examine temporal changes in the shedding of the respiratory bacterium Bordetella bronchiseptica in rabbits with one or two gastrointestinal helminth species. Experimental data showed that rabbits co-infected with one or both helminths shed significantly more B. bronchiseptica, by direct contact with an agar petri dish, than rabbits with bacteria alone. Co-infected hosts generated supershedding events of higher intensity and more frequently than hosts with no helminths. To explain this variation in shedding an infection-immune model was developed and fitted to rabbits of each group. Simulations suggested that differences in the magnitude and duration of shedding could be explained by the effect of the two helminths on the relative contribution of neutrophils and specific IgA and IgG to B. bronchiseptica neutralization in the respiratory tract. However, the interactions between infection and immune response at the scale of analysis that we used could not capture the rapid variation in the intensity of shedding of every rabbit. We suggest that fast and local changes at the level of respiratory tissue probably played a more important role. This study indicates that co-infected hosts are important source of variation in shedding, and provides a quantitative explanation into the role of helminths to the dynamics of respiratory bacterial infections.

Nhat TD Nguyen, Ashutosh K Pathak, Isabella M Cattadori (2022) Gastrointestinal helminths increase Bordetella bronchiseptica shedding and host variation in supershedding eLife 11:e70347. https://doi.org/10.7554/eLife.70347

Cephalotane-type C20 diterpenoids from Cephalotaxus fortunei var. alpina

Donna Huber on November 4, 2022

Seventeen new cephalotane-type diterpenoids, fortalides A-Q (1-17), along with five known analogues, were isolated from the seeds of Cephalotaxus fortunei var. alpina. Their structures were determined by extensive spectroscopic methods, as well as electronic circular dichroism (ECD) and X-ray crystallographic data analyses. Some isolates exhibited unusual structural features that were first found in cephalotane-type diterpenoids, such as the occurrence of the 7-oxabicyclo[4.1.1]octane moiety in 14 and 15 and the cis-arrangement of 3-OH and Me-19 in 9. Besides, the antiplasmodial activity of these compounds was evaluated in this study.

Zhan-Peng Ge, Bin Zhou, Flavia M Zimbres, Reagan S Haney, Qun-Fang Liu, Yan Wu, Maria B Cassera, Jin-Xin Zhao, Jian-Min Yue. Org Biomol Chem. 2022 Nov 4. doi: 10.1039/d2ob01748b

Pseudokinase NRP1 facilitates endocytosis of transferrin in the African trypanosome

Donna Huber on November 3, 2022

Trypanosoma brucei causes human African trypanosomiasis (HAT) and nagana in cattle. During infection of a vertebrate, endocytosis of host transferrin (Tf) is important for viability of the parasite. The majority of proteins involved in trypanosome endocytosis of Tf are unknown. Here we identify pseudokinase NRP1 (Tb427tmp.160.4770) as a regulator of Tf endocytosis. Genetic knockdown of NRP1 inhibited endocytosis of Tf without blocking uptake of bovine serum albumin. Binding of Tf to the flagellar pocket was not affected by knockdown of NRP1. However the quantity of Tf per endosome dropped significantly, consistent with NRP1 promoting robust capture and/or retention of Tf in vesicles. NRP1 is involved in motility of Tf-laden vesicles since distances between endosomes and the kinetoplast were reduced after knockdown of the gene. In search of possible mediators of NRP1 modulation of Tf endocytosis, the gene was knocked down and the phosphoproteome analyzed. Phosphorylation of protein kinases forkhead, NEK6, and MAPK10 was altered, in addition to EpsinR, synaptobrevin and other vesicle-associated proteins predicted to be involved in endocytosis. These candidate proteins may link NRP1 functionally either to protein kinases or to vesicle-associated proteins.

Gaurav Kumar, Bryanna Thomas, Kojo Mensa-Wilmot. Sci Rep. 2022 Nov 3;12(1):18572. doi: 10.1038/s41598-022-22054-x.

Prophylactic low-dose, bi-weekly benznidazole treatment fails to prevent Trypanosoma cruzi infection in dogs under intense transmission pressure

Donna Huber on October 31, 2022

Trypanosoma cruzi naturally infects a wide variety of wild and domesticated mammals, in addition to humans. Depending on the infection dose and other factors, the acute infection can be life-threatening, and in all cases, the risk of chagasic heart disease is high in persistently infected hosts. Domestic, working, and semi-feral dogs in the Americas are at significant risk of T. cruzi infection and in certain settings in the southern United States, the risk of new infections can exceed 30% per year, even with the use of vector control protocols. In this study, we explored whether intermittent low-dose treatment with the trypanocidal compound benznidazole (BNZ) during the transmission season, could alter the number of new infections in dogs in an area of known, intense transmission pressure. Preliminary studies in mice suggested that twice-weekly administration of BNZ could prevent or truncate infections when parasites were delivered at the mid-point between BNZ doses. Pre-transmission season screening of 126 dogs identified 53 dogs (42.1%) as T. cruzi infection positive, based upon blood PCR and Luminex-based serology. Serial monitoring of the 67 uninfected dogs during the high transmission season (May to October) revealed 15 (22.4%) new infections, 6 in the untreated control group and 9 in the group receiving BNZ prophylaxis, indicating no impact of this prophylaxis regimen on the incidence of new infections. Although these studies suggest that rigorously timed and more potent dosing regimen may be needed to achieve an immediate benefit of prophylaxis, additional studies would be needed to determine if drug prophylaxis reduced disease severity despite this failure to prevent new infections.

Juan M Bustamante, Angel M Padilla, Brooke White, Lisa D Auckland, Rachel E Busselman, Stephanie Collins, Elizabeth L Malcolm, Briana F Wilson, Ashley B Saunders, Sarah A Hamer, Rick L Tarleton. PLoS Negl Trop Dis. 2022 Oct 31;16(10):e0010688. doi: 10.1371/journal.pntd.0010688.

Assessing seroprevalence and associated risk factors for multiple infectious diseases in Sabah, Malaysia using serological multiplex bead assays

Donna Huber on October 25, 2022

Background: Infectious diseases continue to burden populations in Malaysia, especially among rural communities where resources are limited and access to health care is difficult. Current epidemiological trends of several neglected tropical diseases in these populations are at present absent due to the lack of habitual and efficient surveillance. To date, various studies have explored the utility of serological multiplex beads to monitor numerous diseases simultaneously. We therefore applied this platform to assess population level exposure to six infectious diseases in Sabah, Malaysia. Furthermore, we concurrently investigated demographic and spatial risk factors that may be associated with exposure for each disease.

Methods: This study was conducted in four districts of Northern Sabah in Malaysian Borneo, using an environmentally stratified, population-based cross-sectional serological survey targeted to determine risk factors for malaria. Samples were collected between September to December 2015, from 919 villages totaling 10,100 persons. IgG responses to twelve antigens of six diseases (lymphatic filariasis- Bm33, Bm14, BmR1, Wb123; strongyloides- NIE; toxoplasmosis-SAG2A; yaws- Rp17 and TmpA; trachoma- Pgp3, Ct694; and giardiasis- VSP3, VSP5) were measured using serological multiplex bead assays. Eight demographic risk factors and twelve environmental covariates were included in this study to better understand transmission in this community.

Results: Seroprevalence of LF antigens included Bm33 (10.9%), Bm14+ BmR1 (3.5%), and Wb123 (1.7%). Seroprevalence of Strongyloides antigen NIE was 16.8%, for Toxoplasma antigen SAG2A was 29.9%, and Giardia antigens GVSP3 + GVSP5 was 23.2%. Seroprevalence estimates for yaws Rp17 was 4.91%, for TmpA was 4.81%, and for combined seropositivity to both antigens was 1.2%. Seroprevalence estimates for trachoma Pgp3 + Ct694 were 4.5%. Age was a significant risk factors consistent among all antigens assessed, while other risk factors varied among the different antigens. Spatial heterogeneity of seroprevalence was observed more prominently in lymphatic filariasis and toxoplasmosis.

Conclusions: Multiplex bead assays can be used to assess serological responses to numerous pathogens simultaneously to support infectious disease surveillance in rural communities, especially where prevalences estimates are lacking for neglected tropical diseases. Demographic and spatial data collected alongside serosurveys can prove useful in identifying risk factors associated with exposure and geographic distribution of transmission.

YuYen L Chan, Catriona L Patterson, Jeffrey W Priest, Gillian Stresman, Timothy William, Tock H Chua, Kevin Tetteh, Patrick Lammie, Chris Drakeley, Kimberly M Fornace. Front Public Health. 2022 Oct 25;10:924316. doi: 10.3389/fpubh.2022.924316. eCollection 2022.

The mystery of massive mitochondrial complexes: the apicomplexan respiratory chain

Donna Huber on October 24, 2022

The mitochondrial respiratory chain is an essential pathway in most studied eukaryotes due to its roles in respiration and other pathways that depend on mitochondrial membrane potential. Apicomplexans are unicellular eukaryotes whose members have an impact on global health. The respiratory chain is a drug target for some members of this group, notably the malaria-causing Plasmodium spp. This has motivated studies of the respiratory chain in apicomplexan parasites, primarily Toxoplasma gondii and Plasmodium spp. for which experimental tools are most advanced. Studies of the respiratory complexes in these organisms revealed numerous novel features, including expansion of complex size. The divergence of apicomplexan mitochondria from commonly studied models highlights the diversity of mitochondrial form and function across eukaryotic life.

Andrew E Maclean, Jenni A Hayward, Diego Huet, Giel G van Dooren, Lilach Sheiner. Trends Parasitol. 2022 Oct 24;S1471-4922(22)00219-7. doi: 10.1016/j.pt.2022.09.008. Online ahead of print.

Spindly is a nucleocytosolic O-fucosyltransferase in Dictyostelium and related proteins are widespread in protists and bacteria

Donna Huber on October 17, 2022

O-GlcNAcylation is a prominent modification of nuclear and cytoplasmic proteins in animals and plants, and is mediated by a single O-GlcNAc transferase (OGT). Spindly (Spy), a paralog of OGT first discovered in higher plants, has an ortholog in the apicomplexan parasite Toxoplasma gondii, and both enzymes are now recognized as O-fucosyltransferases (OFTs). Here we investigate the evolution of spy-like genes and experimentally confirm OFT activity in the social amoeba Dictyostelium – a protist that is more related to fungi and metazoa. Immunofluorescence probing with the fucose-specific Aleuria aurantia lectin (AAL) and biochemical cell fractionation combined with western blotting suggested the occurrence of nucleocytoplasmic fucosylation. The absence of reactivity in mutants deleted in spy or gmd (unable to synthesize GDP-Fuc) suggested monofucosylation mediated by Spy. Genetic ablation of the modE locus, previously predicted to encode a GDP-fucose transporter, confirmed its necessity for fucosylation in the secretory pathway but not for the nucleocytoplasmic proteins. Affinity capture of these proteins combined with mass spectrometry confirmed monofucosylation of Ser and Thr residues of several known nucleocytoplasmic proteins. As in Toxoplasma, the Spy OFT was required for optimal proliferation of Dictyostelium under laboratory conditions. These findings support a new phylogenetic analysis of OGT and OFT evolution that indicates their occurrence in the last eukaryotic common ancestor but mostly complementary presence in its eukaryotic descendants with the notable exception that both occur in red algae and plants. Their generally exclusive expression, high degree of conservation and shared monoglycosylation targets suggest overlapping roles in physiological regulation.

Hanke Wel, Ana Maria Garcia, Elisabet Gas-Pascual, Macy M Willis, Hyun W Kim, Giulia Bandini, Maissa Mareme Gaye, Catherine E Costello, John Samuelson, Christopher M West. Glycobiology. 2022 Oct 17;cwac071. doi: 10.1093/glycob/cwac071.

Author: Donna Huber