Serological biomarker for assessing human exposure to Aedes mosquito bites during a randomized vector control intervention trial in northeastern Thailand

BackgroundAedes mosquitoes are vectors for several major arboviruses of public health concern including dengue viruses. The relationships between Aedes infestation and disease transmission are complex wherein the epidemiological dynamics can be difficult to discern because of a lack of robust and sensitive indicators for predicting transmission risk. This study investigates the use of anti-Aedes saliva antibodies as a serological biomarker for Aedes mosquito bites to assess small scale variations in adult Aedes density and dengue virus (DENV) transmission risk in northeastern Thailand. Individual characteristics, behaviors/occupation and socio-demographics, climatic and epidemiological risk factors associated with human-mosquito exposure are also addressed.MethodsThe study was conducted within a randomized clustered control trial in Roi Et and Khon Kaen provinces over a consecutive 19 months period. Thirty-six (36) clusters were selected, each of ten houses. Serological and entomological surveys were conducted in all houses every four months and monthly in three sentinel households per cluster between September 2017 and April 2019 for blood spot collections and recording concurrent immature and adult Aedes indices. Additionally, the human exposure to Aedes mosquito bites (i.e., Mosquito Exposure Index or MEI) was estimated by ELISA measuring levels of human antibody response to the specific Nterm-34 kDa salivary antigen. The relationships between the MEI, vector infestation indices (adult and immature stages) and vector DENV infection were evaluated using a two-level (house and individual levels) mixed model analysis with one-month lag autoregressive correlation.ResultsThere was a strong positive relationship between the MEI and adult Aedes (indoor and outdoor) density. Individuals from households with a medium mosquito density (mean difference: 0.091, p<0.001) and households with a high mosquito density (mean difference: 0.131, p<0.001) had higher MEI’s compared to individuals from households without Aedes. On a similar trend, individuals from households with a low, medium or high indoor Aedes densities (mean difference: 0.021, p<0.007, 0.053, p<0.0001 and 0.037, p<0.0001 for low, medium and high levels of infestation, respectively) had higher MEI than individuals from houses without indoor Aedes. The MEI was driven by individual characteristics, such as gender, age and occupation/behaviors, and varied according to climatic, seasonal factors and vector control intervention (p<0.05). Nevertheless, the study did not demonstrate a clear correlation between MEI and the presence of DENV-infected Aedes.ConclusionThis study represents an important step toward the validation of the specific IgG response to the Aedes salivary peptide Nterm-34kDa as a proxy measure for Aedes infestation levels and human-mosquito exposure risk in a dengue endemic setting. The use of the IgG response to the Nterm-34 kDa peptide as a viable diagnostic tool for estimating dengue transmission requires further investigations and validation in other geographical and transmission settings.     

Granulocyte-colony stimulating factor attenuates mitochondrial dysfunction induced by oxidative stress in cardiac mitochondria

During cardiac ischemia-reperfusion injury, reactive oxygen species (ROS) level is markedly increased, leading to oxidative stress and mitochondrial dysfunction. Although granulocyte-colony stimulating factor (G-CSF) is known to be cardioprotective, its effects on cardiac mitochondria during oxidative stress have never been investigated. In this study, we discovered that G-CSF completely prevented mitochondrial swelling and depolarization, and markedly reduced ROS production caused by H(2)O(2)-induced oxidative stress in isolated cardiac mitochondria. Its effects were similar to those treated with cyclosporine A and 4'-chlorodiazepam. These findings suggest that G-CSF could act directly on cardiac mitochondria to prevent mitochondrial dysfunction caused by oxidative stress.     

Toxoplasma gondii: Inhibitory activity and encystation effect of securinine and pyrrolidine derivatives on Toxoplasma growth

Securinine, an alkaloid originally isolated from Securinega suffruticosa, exhibits a wide range of biological activities, including anti-malarial activity. Along with securinine, 10 pyrrolidine derivatives, generated via the retrosynthesis of (−)-securinine, were selected and tested for their inhibitory activity against Toxoplasma gondii growth in vitro. Anti-Toxoplasma activity correlated to hydrophobicity of the tested compounds. Three pyrrolidine derivatives along with securinine inhibit Toxoplasma proliferation at the micromolar range. These compounds act on parasite proliferation in different capacities, either by slowing the growth rate or inhibiting invasion of host cells. Securinine induces bradyzoite differentiation at comparable levels to treatment with alkali media in vitro.     

Ecdysone and retinoid-X receptors of the blue crab, Callinectes sapidus: Cloning and their expression patterns in eyestalks and Y-organs during the molt cycle

Crustacean molting is known to be regulated largely by ecdysteroids and crustacean hyperglycemic hormone (CHH) neuropeptide family including molt-inhibiting hormone (MIH) and CHH. The surge of 20-OH ecdysone and/or ponasterone A initiates the molting process through binding to its conserved heterodimeric nuclear receptor: Ecdysone Receptor (EcR) and Ultraspiracle (USP)/Retinoid-X Receptor (RXR). To better understand the role of ecdysteroids in the molt regulation, the full-length cDNAs of the blue crab, Callinectes sapidus EcR1 and RXR1 were isolated from the Y-organs and their expression levels were determined in both Y-organs and eyestalks at various molt stages. Y-organs show the expression of four putative isoforms of CasEcRs and CasRXRs which differ in the length of the open reading frame but share the same domain structures as in typical nuclear receptors: AF1, DBD, HR, LBD, and AF2. The putative CasEcR isoforms are derived from a 27-aa insert in the HR and a 49-aa residue substitution in the LBD. In contrast, an insertion of a 5-aa and/or a 45-aa in the DBD and LBD gives rise to CasRXR isoforms. The eyestalks and Y-organs show the co-expression of CasEcRs and CasRXRs but at the different levels. In the eyestalks, the expression levels of CasRXRs are 3–5 times higher than those of CasEcRs, while in Y-organs, CasRXRs are 2.5–4 times higher than CasEcRs. A tissue-specific response to the changes in the levels of hemolymphatic ecdysteroids indicates that these tissues may have differences in the sensitivity or responsiveness to ecdysteroids. The presence of upstream open reading frame and internal ribosome entry site in 5′ UTR sequences of C. sapidus and other arthropod EcR/RXR/USP analyzed by in silico indicates a plausible, strong control(s) of the translation of these receptors.     

Single argonaute protein from Toxoplasma gondii is involved in the double-stranded RNA induced gene silencing

Here, we report the characterization of the argonaute protein from Toxoplasma gondii. This is the first report on the function of an argonaute protein with structural features overlapping between argonaute proteins of archaeal bacteria and eukaryotes. The full-length cDNA clone has an open reading frame of 1575 bp, which encodes a 524 amino acid protein with a calculated molecular weight of 58.5 kDa and an estimated isoelectric point of 9.4. This argonaute protein, called TgAgo, exhibits unique features: (i) TgAgo is smaller than reported argonaute proteins derived from higher eukaryotic organisms (i.e. Arabidopsis, human and nematodes) but has a similar size to those from archaeal bacteria (i.e. Pyrococcus furiosus and Archaeoglobus fulgidus); (ii) TgAgo contains a conserved PIWI domain and non-conserved PAZ domain; (iii) TgAgo is mainly localized in the cytoplasm; and (iv) despite its small size, TgAgo participates in the double-stranded RNA induced gene silencing. Using a transgenic parasite line, in which TgAgo expression is lowered, we showed that the expression of TgAgo is required for the double-stranded RNA induced gene silencing, RNA interference mechanism.     

Photosensitizer effects on cancerous cells: a combined study using synchrotron infrared and fluorescence microscopies

Hypocrellin A (HA), a lipid-soluble peryloquinone derivative, isolated from natural fungus sacs of Hypocrella bambusae, has been reported to be a highly potential photosensitizer in photodynamic therapy (PDT). It has been studied increasingly because of its anticancer activities when irradiated with light. We have studied the interaction mechanisms of HA with HeLa cells as a function of incubation time. Fluorescence microscopy confirmed that HA localisation is limited in the cytoplasm before eventually concentrating in clusters around the nucleus. The IR spectra of HA-treated, PDT-treated and control HeLa cells were recorded at the ESRF Infrared beamline (ID21). Principal component analysis has been used to assess the IR spectral changes between the various HeLa cells spectral data sets (The Unscrambler software, CAMO). PCA revealed that there is a frequency shift of protein amide I and amide II vibrational bands, indicating changes in the protein secondary structures of the HA-treated and PDT-treated cancer cells compared to the control cells. In addition, the relative DNA intensity in HA-treated cells decreases gradually along the incubation time. The use of synchrotron infrared microscopy is shown to be of paramount importance for targeting specifically the biochemical modification induced in the cell nucleus.     

Plasma membrane cholesterol content affects nitric oxide diffusion dynamics and signaling

Nitric oxide (NO) signaling is inextricably linked to both its physical and chemical properties. Due to its preferentially hydrophobic solubility, NO molecules tend to partition from the aqueous milieu into biological membranes. We hypothesized that plasma membrane ordering provided by cholesterol further couples the physics of NO diffusion with cellular signaling. Fluorescence lifetime quenching studies with pyrene liposome preparations showed that the presence of cholesterol decreased apparent diffusion coefficients of NO approximately 20-40%, depending on the phospholipid composition. Electrochemical measurements indicated that the diffusion rate of NO across artificial bilayer membranes were inversely related to cholesterol content. Sterol transport-defective Niemann-Pick type C1 (NPC1) fibroblasts exhibited increased plasma membrane cholesterol content but decreased activation of both intracellular soluble guanylyl cyclase and vasodilator-stimulated phosphoprotein (VASP) phosphorylation at Ser(239) induced by exogenous NO exposure relative to their normal human fibroblast (NHF) counterparts. Augmentation of plasma membrane cholesterol in NHF diminished production of both cGMP and VASP phosphorylation elicited by NO to NPC1-comparable levels. Conversely, decreasing membrane cholesterol in NPC1 resulted in the augmentation in both cGMP and VASP phosphorylation to a level similar to those observed in NHF. Increasing plasma membrane cholesterol contents in NHF, platelets, erythrocytes and tumor cells also resulted in an increased level of extracellular diaminofluorescein nitrosation following NO exposure. These findings suggest that the impact of cholesterol on membrane fluidity and microdomain structure contributes to the spatial heterogeneity of NO diffusion and signaling.