The efficacy of avermectins (ivermectin, doramectin and abamectin) as treatments for infestation with the tick Haemaphysalis longicornis on rabbits in Korea

Model nematodes as a practical innovation to promote high throughput screening of natural products for anthelmintics discovery in South Asia: Current challenges, proposed practical and conceptual solutions

With the increasing prevalence of anthelmintic resistance in animals recorded globally, and the threat of resistance in human helminths, the need for novel anthelmintic drugs is greater than ever. Most research aimed at discovering novel anthelmintic leads relies on high throughput screening (HTS) of large libraries of synthetic small molecules in industrial and academic settings in developed countries, even though it is the tropical countries that are most plagued by helminth infections. Tropical countries, however, have the advantage of possessing a rich flora that may yield natural products (NP) with promising anthelmintic activity. Focusing on South Asia, which produces one of the world's highest research outputs in NP and NP-based anthelmintic discovery, we find that limited basic research and funding, a lack of awareness of the utility of model organisms, poor industry-academia partnerships and lack of technological innovations greatly limit anthelmintics research in the region. Here we propose that utilizing model organisms including the free-living nematode Caenorhabditis elegans, that can potentially allow rapid target identification of novel anthelmintics, and Oscheius tipulae, a closely related, free-living nematode which is found abundantly in soil in hotter temperatures, could be a much-needed innovation that can enable cost-effective and efficient HTS of NPs for discovering compounds with anthelmintic/antiparasitic potential in South Asia and other tropical regions that historically have devoted limited funding for such research. Additionally, increased collaborations at the national, regional and international level between parasitologists and pharmacologists/ethnobotanists, setting up government-industry-academia partnerships to fund academic research, creating a centralized, regional collection of plant extracts or purified NPs as a dereplication strategy and HTS library, and holding regional C. elegans/O. tipulae-based anthelmintics workshops and conferences to share knowledge and resources regarding model organisms may collectively promote and foster a NP-based anthelmintics landscape in South Asia and beyond.

Cheminformatics-Based Study Identifies Potential Ebola VP40 Inhibitors

The Ebola virus (EBOV) is still highly infectious and causes severe hemorrhagic fevers in primates. However, there are no regulatorily approved drugs against the Ebola virus disease (EVD). The highly virulent and lethal nature of EVD highlights the need to develop therapeutic agents. Viral protein 40 kDa (VP40), the most abundantly expressed protein during infection, coordinates the assembly, budding, and release of viral particles into the host cell. It also regulates viral transcription and RNA replication. This study sought to identify small molecules that could potentially inhibit the VP40 protein by targeting the N-terminal domain using an in silico approach. The statistical quality of AutoDock Vina’s capacity to discriminate between inhibitors and decoys was determined, and an area under the curve of the receiver operating characteristic (AUC-ROC) curve of 0.791 was obtained. A total of 29,519 natural-product-derived compounds from Chinese and African sources as well as 2738 approved drugs were successfully screened against VP40. Using a threshold of −8 kcal/mol, a total of 7, 11, 163, and 30 compounds from the AfroDb, Northern African Natural Products Database (NANPDB), traditional Chinese medicine (TCM), and approved drugs libraries, respectively, were obtained after molecular docking. A biological activity prediction of the lead compounds suggested their potential antiviral properties. In addition, random-forest- and support-vector-machine-based algorithms predicted the compounds to be anti-Ebola with IC50 values in the micromolar range (less than 25 μM). A total of 42 natural-product-derived compounds were identified as potential EBOV inhibitors with desirable ADMET profiles, comprising 1, 2, and 39 compounds from NANPDB (2-hydroxyseneganolide), AfroDb (ZINC000034518176 and ZINC000095485942), and TCM, respectively. A total of 23 approved drugs, including doramectin, glecaprevir, velpatasvir, ledipasvir, avermectin B1, nafarelin acetate, danoprevir, eltrombopag, lanatoside C, and glycyrrhizin, among others, were also predicted to have potential anti-EBOV activity and can be further explored so that they may be repurposed for EVD treatment. Molecular dynamics simulations coupled with molecular mechanics Poisson–Boltzmann surface area calculations corroborated the stability and good binding affinities of the complexes (−46.97 to −118.9 kJ/mol). The potential lead compounds may have the potential to be developed as anti-EBOV drugs after experimental testing.

Study of the degradation in aqueous solution of a refractory organic compound: avermectin type used as pesticide in agriculture

We examined the removal of abamectin by the electro-Fenton (EF) process and the feasibility of biological treatment after degradation. The effect of the operating parameters showed that abamectin (Aba) degradation was enhanced with increasing temperature. Response surface analysis of the central composite design led to the following optimal conditions for the abatement of chemical oxygen demand: 45.5 °C, 5 mg L^-1, 150 mA, and 0.15 mmol L^-1 for the temperature, initial Aba concentration, current intensity, and catalyst concentration, respectively. Under these conditions, 68.01% of the organic matter was removed and 94% of Aba was degraded after 5 h and 20 min of electrolysis, respectively. A biodegradability test, which was performed on a solution electrolyzed at 47 °C, 9 mg L^-1, 150 mA, and 0.15 mmol L^-1, confirms that the ratio of biological oxygen demand/chemical oxygen demand increased appreciably from 0.0584 to 0.64 after 5 h of electrolysis. This increased ratio is slightly above the limit of biodegradability (0.4). These results show the relevance of the EF process and its effectiveness for abamectin degradation. We conclude that biological treatment can be combined with the EF process for total mineralization.

Identification of responsive proteins in Panonychus citri exposed to abamectin by a proteomic approach

Abamectin is a microbial-derived pesticide widely used for control of agricultural pests. However, sustained use of abamectin has led to the development of resistance in some target species. Previous studies on arthropod resistance to abamectin have mainly used traditional biochemical and molecular approaches. To understand the responses of citrus red mite, Panonychus citri, exposed to abamectin, comparative proteomic analysis was conducted using two-dimensional electrophoresis (2-DE). A total of 26 distinct protein spots were present in response to abamectin exposure. Tandem mass spectrometry (MS/MS) identified 16 proteins that were mainly involved in energy metabolism and detoxification. Some remaining proteins were not identifiable, suggesting that they may be novel. The expression levels of transcripts associated with proteins were analyzed by quantitative reverse transcription PCR (qRT-PCR). Furthermore, to validate the proteomic data obtained in the present study, Western-blot experiment was performed and the expression of sHsp and PcE1 proteins were confirmed, respectively.

BIOLOGICAL SIGNIFICANCE

The citrus red mite has developed resistance to many acaricides, including abamectin. In the current study, we used the proteomic approaches involving 2-DE, matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF), and MS/MS to document changes in adult P. citri during 24h of abamectin exposure. Abamectin stress induced a total of 16 differentially regulated proteins. The proteomic results were validated in mRNA expression patterns using qRT-PCR. This is the first analysis of differentially expressed proteins in P. citri exposed to abamectin. The results help clarify the physiological mechanisms of P. citri responses to abamectin exposure.

Transcriptomics and proteomic studies reveal acaricidal mechanism of octadecanoic acid-3, 4 - tetrahydrofuran diester against Sarcoptes scabiei var. cuniculi

In our previous study, a new compound, octadecanoic acid-3, 4-tetrahydrofuran diester, possessing potent acaricidal activity was obtained from neem oil. This study performed RNA-seq transcriptomics and iTRAQ proteomics to uncover the acaricidal mechanism of the compound against Sarcoptes scabiei var. cuniculi. The results of transcriptomics indicated that after treatment with octadecanoic acid-3, 4-tetrahydrofuran diester, genes related to “Energy metabolism” were significantly up-/down-regulated, including citrate cycle, oxidative phosphorylation pathway and fatty acid metabolism. Proteomics analysis showed accordant changes of proteins related to oxidative phosphorylation pathway. The target proteins of the compound were NADH dehydrogenase, Ubiquinol-cytochrome c reductase, Cytochrome c oxidase, ATP synthase, enolase and superoxide dismutase. In transcriptomics-proteomics correlation analysis, the concordance rate between protein abundances and their corresponding mRNAs was 57%, while others (43%) were discordant changes, suggesting divergent regulating effects of octadecanoic acid-3, 4-tetrahydrofuran diester. These results suggested that the acaricidal mechanism of octadecanoic acid-3, 4-tetrahydrofuran diester attributed to interference with energy metabolism, especially oxidative phosphorylation pathway.

Bacteria associated with Amblyomma cajennense tick eggs

Ticks represent a large group of pathogen vectors that blood feed on a diversity of hosts. In the Americas, the Ixodidae ticks Amblyomma cajennense are responsible for severe impact on livestock and public health. In the present work, we present the isolation and molecular identification of a group of culturable bacteria associated with A. cajennense eggs from females sampled in distinct geographical sites in southeastern Brazil. Additional comparative analysis of the culturable bacteria from Anocentor nitens, Rhipicephalus sanguineus and Ixodes scapularis tick eggs were also performed. 16S rRNA gene sequence analyses identified 17 different bacterial types identified as Serratia marcescens, Stenotrophomonas maltophilia, Pseudomonas fluorescens, Enterobacter spp., Micrococcus luteus, Ochrobactrum anthropi, Bacillus cereus and Staphylococcus spp., distributed in 12 phylogroups. Staphylococcus spp., especially S. sciuri, was the most prevalent bacteria associated with A. cajennense eggs, occurring in 65% of the samples and also frequently observed infecting A. nitens eggs. S. maltophilia, S. marcescens and B. cereus occurred infecting eggs derived from specific sampling sites, but in all cases rising almost as pure cultures from infected A. cajennense eggs. The potential role of these bacterial associations is discussed and they possibly represent new targets for biological control strategies of ticks and tick borne diseases.