Biology subjects

Michaelakis, A.

Publications and source records attributed to Michaelakis, A..

7 recordsLinked to original sources

bioRxiv2026

AgamOBP4-targeted drug repurposing identifies novel mosquito repellent scaffolds

Odorant-binding proteins (OBPs) play central roles in insect chemoreception and represent attractive molecular targets for the discovery of novel behavior-modifying compounds. We report two crystal structures of Anopheles gambiae OBP4: one complexed with the fluorescent probe N-phenyl-1-naphthylamine and a second containing two indole molecules simultaneously bound within the ligand-binding cavity. Structural comparison revealed two binding subsites accommodating the aromatic moieties of 1-NPN or two indole molecules, while identifying Thr58 and Thr70 as key residues in ligand recognition. A structure-based virtual screening campaign was performed against a volatility-filtered library from DrugBank, FooDB, BioNet, and natural-volatiles datasets. Twenty-three ligands were selected for fluorescence competitive binding assays, identifying four AgamOBP4 binders with micromolar affinities (Ki = 2.4-21.8 M). Among them were benzoyl peroxide, an active anti-acne ingredient, Avex-73 (blarcamesine), a clinical-stage drug candidate, and 2-phenylethyl benzoate, a food- and fragrance-associated ester. Additional candidates include O,p'-DDE, a metabolite of the insecticide DDT, and fluorene, a polycyclic aromatic hydrocarbon detected in foods as environmental or processing-derived contaminants. Seven selected compounds were subsequently evaluated against Aedes albopictus in in-vivo behavioral assays, with benzoyl peroxide displaying the highest repellency (RI = 81.8% at 0.2 mg cm-2). AI-based protein-ligand modeling provided insights into ligand recognition and suggested relationships among binding mode, binding affinity, and bioactivity. Collectively, these findings establish the structural basis of ligand recognition by AgamOBP4, highlight the potential of drug-repurposing and food-derived chemical space as sources of next-generation mosquito repellents, and open new opportunities for the development of OBP4-based biosensors for food-quality and environmental monitoring applications.

biochemistry↗

bioRxiv2024

Mitogenome Diversity and Phylogenetic Insights of Aedes albopictus in Greece

The invasive mosquito species Aedes albopictus, commonly known as the Asian Tiger Mosquito, is a significant global health concern due to its role as a vector for diseases such as Dengue, Zika, and Chikungunya. In Greece, Ae. albopictus was first detected in 2005, with subsequent widespread establishment across the country. This study investigates the genetic diversity and phylogeography of Greek Ae. albopictus populations by analyzing mitochondrial cytochrome oxidase I (COI) gene sequences. A total of 488 female individuals were analyzed, revealing six haplotypes in samples collected from 2016 to 2018 using the LCO 1490 and HCO 2198 primer pair, including instances of identical haplotypes across years, while only one haplotype was consistently detected across all 2019 to 2022 samples using the UBC6 and UBC9 primer pair. These findings underscore the importance of molecular tools in understanding invasion dynamics and informing targeted surveillance and control measures. Further research is needed to assess additional worldwide populations and expand phylogeographic comparisons to elucidate global dispersal patterns.

genetics↗

bioRxiv2024

Winter Survival of Culex pipiens f. pipiens Adults in Central Greece

Winter survival consists a major component of insect vectors life history in temperate environments that is directly related with early and later population growth next season with major consequences in the epidemiology of vectored diseases. The common European mosquito Culex pipiens is a major vector of the West Nile Virus (WNV) in Europe, including Greece. West Nile Virus outbreaks are frequently reported in Greece over the last 2 decades and Thessaly, Central Greece, is included in the affected areas. Here we report on overwintering trials conducted in three regions of Thessaly to investigate the overwintering dynamics of the subspecies of the Cx. pipiens complex, Cx. pipiens f. pipiens. Two overwintering experiments regarding adults of Cx. pipiens f. pipiens carried out in two coastal areas of Thessaly (Nea Anchialos and Volos) and an inland area (Kalamaki). Results demonstrated the successful overwintering of Cx. pipiens f. pipiens females, as well as the failure of males to survive in all three regions considered. Successful overwintering females were capable of initiating egg laying following a blood meal in spring onsetting the first summer generation. Nonetheless, mortality patterns differ between the coastal and the inland area as well as among different cohorts of adults.

ecology↗

bioRxiv2024

Natural volatiles causing inhibition of mosquito biting behaviors: development of a virtual screening platform predicting antagonists of ORco function for accelerated discovery

Insect olfactory receptors are heteromeric ligand-gated cation channels composed of an obligatory receptor subunit, ORco, and one of many variable subunits, ORx, in as yet undefined molar ratios. When expressed alone ex vivo, ORco forms homotetrameric channels gated by ORco-specific ligands acting as channel agonists. Using an insect cell-based system as a functional platform for expressing mosquito odorant receptors ex vivo, we identified small molecules of natural origin acting as specific ORco channel antagonists, orthosteric or allosteric relative to a postulated ORco agonist binding site, and causing severe inhibition of olfactory function in mosquitoes. In the present communication, we are reporting on the compilation of common structural features of such orthosteric antagonists and development of a ligand-based pharmacophore whose properties are deemed necessary for binding to the agonist binding site and inhibition of ORcos biological function. In silico screening of an available collection of natural volatile compounds with this pharmacophore resulted in identification of several ORco antagonist hits. Cell-based functional screening of the same compound collection resulted in the identification of several compounds acting as orthosteric and allosteric antagonists of ORco channel function ex vivo and inducing anosmic behaviors to Aedes albopictus mosquitoes in vivo. Comparison of the in silico screening results with those of the functional assays revealed that the pharmacophore predicted correctly 7 out of the 8 confirmed orthosteric antagonists and none of the allosteric ones. Because the pharmacophore screen also produced additional hits that did not cause inhibition of the ORco channel function, we generated a Support Vector Machine (SVM) model based on two descriptors of all pharmacophore hits. Training of the SVM on the ex vivo validated compound collection resulted in the selection of the confirmed orthosteric antagonists with a very low cross-validation out-of-sample misclassification rate. Employment of the combined pharmacophore-SVM platform for in silico screening of a larger collection of olfaction-relevant volatiles produced several new hits. Functional validation of randomly selected hits and rejected compounds from this screen confirmed the power of this virtual screening platform as convenient tool for identifying novel vector control agents. To the best of our knowledge, this study is the first one that combines a pharmacophore with a SVM model for identification of AgamORco antagonists and specifically orthosteric ones.

molecular biology↗

bioRxiv2020

Volatile allosteric antagonists of mosquito odorant receptors inhibit normal odor-dependent behaviors

Odorant-dependent behaviors in insects are triggered by the binding of odorant ligands to the variable subunits of heteromeric olfactory receptors. Previous studies have shown, however, that specific odor binding to ORco, the common subunit of odorant receptor heteromers, may alter allosterically olfactory receptor function and affect profoundly subsequent behavioral responses. Here we report on the identification of several antagonists of the odorant receptor co-receptor of the African malaria vector Anopheles gambiae, AgamORco, in a small collection of natural volatile organic compounds (VOCs) using a relevant insect cell-based screening platform. Because some of the identified antagonists were previously shown to strongly repel Anopheles and Culex mosquitoes, here we examined the bioactivities of the identified antagonists against Aedes, the third major genus of the Culicidae family. The tested antagonists were found to inhibit the function of Ae. aegypti ORco ex vivo and repel Asian tiger, Ae. albopictus, adult mosquitoes. Specific antagonist binary mixtures elicited higher repellency than single antagonists. Binding competition assays suggested antagonist binding to distinct ORco sites as a likely cause for the enhanced repellence of the blends. These findings demonstrate that a simple screening assay may be used for the identification of allosteric modifiers of olfactory-driven behaviors capable of providing enhanced indoor and outdoor protection against multiple mosquito borne infectious diseases.

neuroscience↗

bioRxiv2019

The abundance and diversity of West Nile virus mosquito vectors in two Regional Units of Greece during the onset of the 2018 transmission season

BackgroundWest Nile virus (WNV) is a zoonotic arbovirus of great medical and veterinary importance, threatening the health of humans and equines worldwide. Mosquitoes belonging to the Culex (Cx.) pipiens complex are major vectors but numerous other mosquito species have also been implicated as vectors of WNV. Due to variations in blood-feeding behaviour, the different biotypes and hybrids of Cx. pipiens influence the transmission of WNV, from enzootic cycles (between mosquitoes and birds), to spill-over transmission to humans and equines.\n\nMethodsIn this study, mosquitoes were collected and analysed from two regional units (RUs) of Greece with reported cases of WNV within the past 4 years; Palaio Flairo and Argolida (in Attica and Peloponnese regions, respectively). Collections using different types of mosquito surveillance traps were undertaken in May-June 2018 during the early period of the WNV transmission season.\n\nResultsA total of 1062 mosquitoes were collected, with Biogents Sentinel traps (BG traps) collecting both a greater number of mosquitoes across all species and Cx. pipiens complex individuals than Centres for Disease Control miniature light traps (CDC traps) or Heavy Duty Encephalitis Vector Survey traps (EVS traps). Identification of collected mosquitoes (using both morphological keys and molecular barcoding) confirmed the presence of additional species including Aedes (Ae.) albopictus, Ae. caspius and Culiseta (Cs.) longiareolata. The prevalence of Cx. pipiens biotypes in the RU of Palaio Faliro was 54.5% pipiens type, 20.0% molestus type and 25.5% hybrids. In the RU of Argolida, the collection comprised 68.1% pipiens type, 8.3% molestus type and 23.6% hybrids. Screening individual unfed female mosquitoes for WNV (molecular xenomonitoring) resulted in detection in three females of the pipiens type and in one hybrid; all collected from the RU of Argolida.\n\nConclusionsAs hybrids play an important role in spill-over transmission of WNV to humans and equines, these findings highlight the importance of undertaking entomological surveillance programs incorporating molecular xenomonitoring at the onset of the transmission season to provide an early warning system for health authorities aiming to prevent WNV outbreaks in Greece.

ecology↗

bioRxiv2018

Reducing Aedes albopictus breeding sites through education: a study in urban area

Aedes albopictus tends to proliferate in small, often man-made bodies of water, largely present in urban private areas. For this reason, education and community participation are considered crucial for source reduction and mosquito control. In the current study, we tried to relate for the first time in Greece, the effectiveness of resident education in an urban area with the number of breeding sites based on previous KAP (knowledge, attitudes and practices) studies. Our study examines the relationship between mosquito breeding sources and socioeconomic or demographic characteristics of different households in a Greek municipality and evaluates efficacy of resident education. The results revealed that only a minority of residents knew where mosquitoes breed (18.6%) and only 46% felt that residents had any responsibility for managing breeding habitat. Our findings strongly suggest that only the presence of scientific staff inspecting possible habitats in their properties, could be enough to stimulate practices towards source reduction. However, educational interventions alone with printed education material cannot enhance significant community participation and source reduction.

zoology↗