Generic selectors
Exact matches only
Search in title
Search in content
Post Type Selectors

Category: publications

Probing the B- & C-rings of the antimalarial tetrahydro-β-carboline MMV008138 for steric and conformational constraints

The antimalarial candidate MMV008138 (1a) is of particular interest because its target enzyme (IspD) is absent in human. To achieve higher potency, and to probe for steric demand, a series of analogs of 1a were prepared that featured methyl-substitution of the B- and C-rings, as well as ring-chain transformations. X-ray crystallography, NMR spectroscopy and calculation were used to study the effects of these modifications on the conformation of the C-ring and orientation of the D-ring. Unfortunately, all the B- and C-ring analogs explored lost in vitro antimalarial activity. The possible role of steric effects and conformational changes on target engagement are discussed.

Sha Ding, Maryam Ghavami, Joshua H.Butler, Emilio F. Merino, Carla Slebodnick, Maria B. Cassera, Paul R. Carlier. Bioorg Med Chem Lett. 2020 Sep 5;127520. doi: 10.1016/j.bmcl.2020.127520

p53 Hinders CRISPR/Cas9-Mediated Targeted Gene Disruption in Memory CD8 T Cells In Vivo

CRISPR/Cas9 technology has revolutionized rapid and reliable gene editing in cells. Although many cell types have been subjected to CRISPR/Cas9-mediated gene editing, there is no evidence of success in genetic alteration of Ag-experienced memory CD8 T cells. In this study, we show that CRISPR/Cas9-mediated gene editing in memory CD8 T cells precludes their proliferation after Ag re-encounter in vivo. This defect is mediated by the proapoptotic transcription factor p53, a sensor of DNA damage. Temporarily inhibiting p53 function offers a window of opportunity for the memory CD8 T cells to repair the DNA damage, facilitating robust recall responses on Ag re-encounter. We demonstrate this by functionally altering memory CD8 T cells using CRISPR/Cas9-mediated targeted gene disruption under the aegis of p53siRNA in the mouse model. Our approach thus adapts the CRISPR/Cas9 technology for memory CD8 T cells to undertake gene editing in vivo, for the first time, to our knowledge.

Samarchith P. KurupSteven J. MoiofferLecia L. Pewe and John T. Harty. J Immunol. 2020 Sep 4;ji2000654. doi: 10.4049/jimmunol.2000654.

IP3 receptor-mediated Ca2+ release from acidocalcisomes regulates mitochondrial bioenergetics and prevents autophagy in Trypanosoma cruzi

In contrast to animal cells, the inositol 1,4,5-trisphosphate receptor of Trypanosoma cruzi (TcIP3R) localizes to acidocalcisomes instead of the endoplasmic reticulum. Here, we present evidence that TcIP3R is a Ca2+ release channel gated by IP3 when expressed in DT40 cells knockout for all vertebrate IP3 receptors, and is required for Ca2+ uptake by T. cruzi mitochondria, regulating pyruvate dehydrogenase dephosphorylation and mitochondrial O2 consumption, and preventing autophagy. Localization studies revealed its co-localization with an acidocalcisome marker in all life cycle stages of the parasite. Ablation of TcIP3R by CRISPR/Cas9 genome editing caused: a) a reduction in O2 consumption rate and citrate synthase activity; b) decreased mitochondrial Ca2+ transport without affecting the membrane potential; c) increased ammonia production and AMP/ATP ratio; d) stimulation of autophagosome formation, and e) marked defects in growth of culture forms (epimastigotes) and invasion of host cells by infective stages (trypomastigotes). Moreover, TcIP3R overexpressing parasites showed decreased metacyclogenesis, trypomastigote host cell invasion and intracellular amastigote replication. In conclusion, the results suggest a modulatory activity of TcIP3R-mediated acidocalcisome Ca2+ release on cell bioenergetics in T. cruzi.

Miguel A. Chiurillo, Noelia Lander, Anibal E. Vercesi, Roberto Docampo, 2020. Cell Calcium; 92:102284, https://doi.org/10.1016/j.ceca.2020.102284.

Fine-scale heterogeneity in Schistosoma mansoni force of infection measured through antibody response

Schistosomiasis is among the most common parasitic diseases in the world, with over 142 million people infected in low- and middle-income countries. Measuring population-level transmission is centrally important in guiding schistosomiasis control programs. Traditionally, human Schistosoma mansoni infections have been detected using stool microscopy, which is logistically difficult at program scale and has low sensitivity when people have low infection burdens. We compared serological measures of transmission based on antibody response to S. mansoni soluble egg antigen (SEA) with stool-based measures of infection among 3,663 preschool-age children in an area endemic for S. mansoni in western Kenya. We estimated force of infection among children using the seroconversion rate and examined how it varied geographically and by age. At the community level, serological measures of transmission aligned with stool-based measures of infection (ρ = 0.94), and serological measures provided more resolution for between-community differences at lower levels of infection. Force of infection showed a clear gradient of transmission with distance from Lake Victoria, with 94% of infections and 93% of seropositive children in communities <1.5 km from the lake. Force of infection increased through age 3 y, by which time 65% (95% CI: 53%, 75%) of children were SEA positive in high-transmission communities—2 y before they would be reached by school-based deworming programs. Our results show that serologic surveillance platforms represent an important opportunity to guide and monitor schistosomiasis control programs, and that in high-transmission settings preschool-age children represent a key population missed by school-based deworming programs.

Benjamin F. Arnold, Henry Kanyi, Sammy M. Njenga, Fredrick O. Rawago, Jeffrey W. Priest, W. Evan Secor, Patrick J. Lammie, Kimberly Y. Won, and Maurice R. Odiere. Proc Natl Acad Sci U S A. 2020 Aug 31;202008951. doi: 10.1073/pnas.2008951117.

Noncoding RNAs in Apicomplexan Parasites: An Update

Illustration of Long Noncoding RNA (lncRNA) Functions in Apicomplexan Parasites.

Recent breakthroughs in high-throughput technologies, transcriptomics, and advances in our understanding of gene regulatory networks have enhanced our perspective on the complex interplay between parasite and host. Noncoding RNA molecules have been implicated in critical roles covering a broad range of biological processes in the Apicomplexa. Processes that are affected range from parasite development to host–parasite interactions and include interactions with epigenetic machinery and other regulatory factors. Here we review recent progress involving noncoding RNAs and their functions in the Apicomplexa, with a focus on three parasites: PlasmodiumToxoplasma, and Cryptosporidium. We discuss the limitations and challenges of current methods applied to apicomplexan noncoding RNA study and discuss future directions in this exciting field.

 

 

 

Yiran Li, Rodrigo P. Baptista, Jessica C. Kissinger. Trends Parasitol. 2020 Aug 19;S1471-4922(20)30189-6. https://doi.org/10.1016/j.pt.2020.07.006

Metabolomics profiling reveals new aspects of dolichol biosynthesis in Plasmodium falciparum

The cis-polyisoprenoid lipids namely polyprenols, dolichols and their derivatives are linear polymers of several isoprene units. In eukaryotes, polyprenols and dolichols are synthesized as a mixture of four or more homologues of different length with one or two predominant species with sizes varying among organisms. Interestingly, co-occurrence of polyprenols and dolichols, i.e. detection of a dolichol along with significant levels of its precursor polyprenol, are unusual in eukaryotic cells. Our metabolomics studies revealed that cis-polyisoprenoids are more diverse in the malaria parasite Plasmodium falciparum than previously postulated as we uncovered active de novo biosynthesis and substantial levels of accumulation of polyprenols and dolichols of 15 to 19 isoprene units. A distinctive polyprenol and dolichol profile both within the intraerythrocytic asexual cycle and between asexual and gametocyte stages was observed suggesting that cis-polyisoprenoid biosynthesis changes throughout parasite’s development. Moreover, we confirmed the presence of an active cis-prenyltransferase (PfCPT) and that dolichol biosynthesis occurs via reduction of the polyprenol to dolichol by an active polyprenol reductase (PfPPRD) in the malaria parasite.

Flavia M Zimbres, Ana Lisa Valenciano, Emilio F Merino, Anat Florentin, Nicole R Holderman, Guijuan He, Katarzyna Gawarecka, Karolina Skorupinska-Tudek, Maria L Fernández-Murga, Ewa Swiezewska, Xiaofeng Wang, Vasant Muralidharan, Maria Belen Cassera. Sci Rep. 2020 Aug 6;10(1):13264. doi: 10.1038/s41598-020-70246-0.

Age influences the thermal suitability of Plasmodium falciparum transmission in the Asian malaria vector Anopheles stephensi

Models predicting disease transmission are vital tools for long-term planning of malaria reduction efforts, particularly for mitigating impacts of climate change. We compared temperature-dependent malaria transmission models when mosquito life-history traits were estimated from a truncated portion of the lifespan (a common practice) versus traits measured across the full lifespan. We conducted an experiment on adult female Anopheles stephensi, the Asian urban malaria mosquito, to generate daily per capita values for mortality, egg production and biting rate at six constant temperatures. Both temperature and age significantly affected trait values. Further, we found quantitative and qualitative differences between temperature–trait relationships estimated from truncated data versus observed lifetime values. Incorporating these temperature–trait relationships into an expression governing the thermal suitability of transmission, relative R0(T), resulted in minor differences in the breadth of suitable temperatures for Plasmodium falciparum transmission between the two models constructed from only An. stephensi trait data. However, we found a substantial increase in thermal niche breadth compared with a previously published model consisting of trait data from multiple Anopheles mosquito species. Overall, this work highlights the importance of considering how mosquito trait values vary with mosquito age and mosquito species when generating temperature-based suitability predictions of transmission.

K. L. Miazgowicz, M. S. Shocket, S. J. Ryan, O. C. Villena, R. J. Hall, J. Owen, T. Adanlawo, K. Balaji, L. R. Johnson, E. A. Mordecai and C. C. Murdock. Proc Biol Sci. 2020 Jul 29;287(1931):20201093. doi: 10.1098/rspb.2020.1093.

Pre-Erythrocytic Vaccines against Malaria

Malaria, caused by the protozoan Plasmodium, is a devastating disease with over 200 million new cases reported globally every year. Although immunization is arguably the best strategy to eliminate malaria, despite decades of research in this area we do not have an effective, clinically approved antimalarial vaccine. The current impetus in the field is to develop vaccines directed at the pre-erythrocytic developmental stages of Plasmodium, utilizing novel vaccination platforms. We here review the most promising pre-erythrocytic stage antimalarial vaccine candidates.

Camila Marques-da-Silva, Kristen Peissig, and Samarchith P. Kurup. Pre-Erythrocytic Vaccines against Malaria. Vaccines 20208, 400. https://doi.org/10.3390/vaccines8030400

Test, Treat, Track, Test, and Treat Active Surveillance toward Elimination of Schistosomiasis: A Feasibility Study

We assessed the feasibility of using a test, treat, track, test, and treat (5T) active surveillance strategy to identify and treat individuals with schistosomiasis in three very low-prevalence villages in Kafr El Sheikh Governorate, Egypt. Primary index cases (PICs) were identified using the point-of-care circulating cathodic antigen (POC-CCA) assay in schools, in rural health units (retesting individuals with positive Kato-Katz examinations over the previous 6 months), and at potential water transmission sites identified by PICs and field observations. Primary cases identified potential second-generation cases-people with whom they shared water activities-who were then tracked, tested, and treated if infected. Those sharing water activities with second-generation cases were also tested. The yield of PICs from the three venues were 128 of 3,576 schoolchildren (3.6%), 42 of 696 in rural health units (6.0%), and 83 of 1,156 at water contact sites (7.2%). There were 118 second- and 19 third-generation cases identified. Persons testing positive were treated with praziquantel. Of 388 persons treated, 368 (94.8%) had posttreatment POC-CCA tests 3-4 weeks after treatment, and 81.8% (301) became negative. The 67 persons remaining positive had negative results after a second treatment. Therefore, all those found positive, treated, and followed up were negative following one or two treatments. Analysis of efforts as expressed in person-hours indicates that 4,459 person-hours were required for these 5T activities, with nearly 65% of that time spent carrying out interviews, treatments, and evaluations following treatment. The 5T strategy appears feasible and acceptable as programs move toward elimination.

Reda M R Ramzy, Amal Rabiee, Khaled M Abd Elaziz, Carl H Campbell, Nupur Kittur, Daniel G Colley, Ayat A Haggag. Am J Trop Med Hyg. 2020 Jul 13. doi: 10.4269/ajtmh.20-0156.

Flavanones From the Twigs and Barks of Artocarpus Lakoocha Having Antiplasmodial and Anti-TB Activities

Chromatographic separation of the acetone extracts from the twigs and barks of Artocarpus lakoocha led to the isolation of the one new flavanone, lakoochanone (1), together with eleven known compounds (2-12). Lakoochanone (1) and moracin C (4) exhibited weak antiplasmodial activity against Plasmodium falciparum Dd2 with IC50 values of 36.7 and 33.9 µM, respectively. Moreover, moracin C (4) and sanggenofuran B (5) showed cytotoxic activity against A2780 cell line with the respective IC50 values of 15.0 and 57.1 µM. In addition, cyclocommunin (7) displayed strong antimycobacterial activity against Mycobacterium tuberculosis H37Ra with the minimum inhibitory concentration (MIC) value of 12.3 µM.

Sirada Boonyaketgoson, Yongle Du, Ana L. Valenciano Murillo, Maria B. Cassera, David G. I. Kingston, Kongkiat Trisuwan. Chem Pharm Bull (Tokyo). 2020;68(7):671-674. doi: 10.1248/cpb.c20-00080.