We explored acquired immunity resulting from vaccination in 3 to 7-year-old children, chronically exposed to multiple heavy metals and metalloids, in an e-waste recycling area (Guiyu, China). Child blood levels of ten heavy metals and metalloids, including lead (Pb), arsenic (As), mercury (Hg), chromium (Cr), cadmium (Cd), manganese (Mn), nickel (Ni), copper (Cu), zinc (Zn) and selenium (Se), and seven vaccine antibodies (diphtheria, pertussis, tetanus, hepatitis B, Japanese encephalitis, polio, measles) were measured. The exposed group had higher levels of blood Pb, Mn, Cu, Zn and Cr compared to the reference group (P < 0.05). Levels of all vaccine antibodies in the exposed group were significantly lower than in the reference group (P < 0.01). All vaccine antibodies negatively correlated with blood concentrations of Cu, Zn and Pb, based on spearman rank correlation analysis. Multiple logistic regression and univariate analyses identified the location of residence (Guiyu), high blood Pb (>10 μg/dL) and high blood Cu and Zn (upper median value of each group) to be inversely associated with seven antibody titers. Antibody titers increased with age, BMI, high blood Mn (>15 μg/L), and high blood Cd and Ni (upper median value of each group). Results suggest multiple heavy metal and metalloid exposure, especially to Pb, Zn and Cu, may be a risk factor inhibiting the development of child immunity, resulting in decreased child antibody levels against vaccines.

There are no specific drugs for the treatment of Japanese Encephalitis. Thus, new chemical entities or exploration of existing molecules is required. We have tested the antiviral potential of abscisic acid and aloe-emodin against protease of the Japanese encephalitis virus (JEV) using the computational and target-based assay. Maestro Schrödinger glide suite 2019 was used for molecular docking and dynamic studies, and NS2B-NS3A JEV protease kit was used to confirm protease inhibitory activity of abscisic acid and aloe-emodin. The abscisic acid and aloe-emodin have shown optimum binding affinity towards NS2B-NS3A protease of JEV. Furthermore, molecular dynamic simulation results have also shown the stability of abscisic acid and aloe-emodin within the binding pocket of NS2B-NS3A protease. The ADME parameters of both compounds were also found in an acceptable range. The IC50 values were found to be 100 μg/ml and 7.3 μg/ml for abscisic acid and aloe-emodin respectively which indicate more potency of aloe-emodin over the abscisic acid. However, the toxicity prediction results have shown a good safety profile of abscisic acid as compared to aloe-emodin. Thus, further, more detailed experimental studies are required to develop abscisic acid and aloe-emodin as a specific protease inhibitor of JEV.

Mosquitoes transmit major communicable diseases such as dengue, malaria, filariasis, Japanese encephalitis, chikungunya, and so on. Vector control is important in epidemic disease situations as there is an urgent need to develop new and improved mosquito control methods that are economical and effective yet safe for non-targeted organisms. In the present study, silver nanoparticles (AgNPs) were synthesized from the aqueous leaf extract of neem plant (Azadirachta indica), and their effects on mosquito vectors (Aedes aegypti and Culex quinquefasciatus) were assessed. The synthesised AgNPs were characterized by UV–vis spectroscopy, scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FT-IR), and X-ray diffraction analysis (XRD). The nanoparticles have maximum absorption at 442 ± 1.5 nm with an average size of 41–60 nm. The XRD data showed six well-defined diffraction peaks, corresponding to a relative intensity of the crystal structure of metallic silver 36.42, 100.00, 53.70, 14.20, 16.05, and 6.79, respectively. The FT-IR data showed strong prominent peaks in different ranges, reflecting its complex nature. The mosquito larvae were exposed to varying concentrations of AgNPs synthesized from the neem leaves under investigation (0.07–25 mg/l) for 24 h; this revealed larvicidal activity of AgNPs with LC₅₀and LC₉₀values of 0.006 and 0.04 mg/l for A. aegypti, respectively. Further, the LC₅₀and LC₉₀values were also identified as 0.047 and 0.23 mg/l for Cx. quinquefasciatus, respectively. The result obtained from this study presents biosynthesized silver nanoparticle from A. indica as the biolarvicidal agent with the most potential for mosquito control.

Mosquitoes are principal vector of several vector-borne diseases affecting human beings leading to thousands of deaths per year and responsible for transmitting diseases like malaria, dengue, chikungunya, yellow fever, Zika virus, Japanese encephalitis, and lymphatic filariasis. In the present study, we evaluated the different solvent extracts of mangrove Avicennia marina for their toxicity against larvae of three major mosquito vectors, as well as selected microbial pathogens. The larvicidal mortality of third instars was observed after 24 h. Highest larval mortality was found for the acetone extract of A. marina against Culex quinquefasciatus (LC₅₀ = 0.197 mg/ml; LC₉₀ = 1.5011 mg/ml), Anopheles stephensi (LC₅₀ = 0.176 mg/ml; LC₉₀ = 3.6290 mg/ml), and Aedes aegypti (LC₅₀ = 0.164 mg/ml; LC₉₀ = 4.3554 mg/ml). GC-MS analysis of acetone extract revealed 5 peaks, i.e., 1-hexyl-2-nitrocyclohexane (3.229%), eicosanoic acid (40.582%), cis-9-hexadecenal (70.54%), oleic acid (4.646%), and di-N-decylsulfone (5.136%). Parallel to larvicidal assay, sub-lethal dosage acetone extracts severely affected the enzyme regulations (α,β-carboxylesterase, GST and CYP450) of third instars. Larval and pupal durations increased in all treatment sub-lethal dosage (0.127, 0.151, 0.177, and 0.197 mg/ml), whereas egg hatchability and means of fecundity decreased compared to control. The survival rate was reduced statistically in Cx. quinquefasciatus (χ² = 23.77, df = 1, P = 0.001) in all the treatment dosages as compared to the control. Antimicrobial activity assays showed significant growth inhibition post treatment with acetone and methanol extracts against Salmonella typhimurium, Klebsiella pneumoniae, Pseudomonas aeruginosa, Staphylococcus pneumoniae, Escherichia coli, and Shigella flexneri. Overall, these results indicated the potential employment of A. marina extracts as a source of natural mosquitocidal and antimicrobial compounds of green-based environment.

The rapid spread of highly aggressive arboviruses, parasites, and bacteria along with the development of resistance in the pathogens and parasites, as well as in their arthropod vectors, represents a huge challenge in modern parasitology and tropical medicine. Eco-friendly vector control programs are crucial to fight, besides malaria, the spread of dengue, West Nile, chikungunya, and Zika virus, as well as other arboviruses such as St. Louis encephalitis and Japanese encephalitis. However, research efforts on the control of mosquito vectors are experiencing a serious lack of eco-friendly and highly effective pesticides, as well as the limited success of most biocontrol tools currently applied. Most importantly, a cooperative interface between the two disciplines is still lacking. To face this challenge, we have reviewed a wide number of promising results in the field of green-fabricated pesticides tested against mosquito vectors, outlining several examples of synergy with classic biological control tools. The non-target effects of green-fabricated nanopesticides, including acute toxicity, genotoxicity, and impact on behavioral traits of mosquito predators, have been critically discussed. In the final section, we have identified several key challenges at the interface between "green" nanotechnology and classic biological control, which deserve further research attention.