Vectorial Capacity Research Articles

Bloodmeal regulation in mosquitoes curtails dehydration-induced mortality, altering vectorial capacity

Mosquitoes readily lose water when exposed to any humidity less than that of near saturated air unless mitigated, leading to shifts in behavior, survival, distribution, and reproduction. In this study, we conducted a series of physiological experiments on two prominent species in the Culicinae subfamily: Culex pipiens, a vector of West Nile virus, and Aedes aegypti, a vector of yellow fever and Zika to examine the effects of dehydration. We exposed C. pipiens and A. aegypti to non-dehydrating conditions (saturated air), dehydrating conditions (air at a 0.89 kPa saturation vapor pressure deficit), several recovery conditions, as well as to bloodfeeding opportunities. We show that dehydrated mosquitoes increase bloodfeeding propensity, improve retention, and decrease excretion of a post-dehydration bloodmeal. In addition, mosquitoes that take a bloodmeal prior to dehydration exposure show increased survival over non-bloodfed counterparts. Dehydration-induced alterations in survival, reproduction, and bloodfeeding propensity of C. pipiens and A. aegypti resulted in marked changes to vectorial capacity. Ultimately, these results become increasingly important as drought intensifies in association with climate change and mosquitoes become more likely to experience arid periods.

Evaluation of the dystrophin carboxy-terminal domain for micro-dystrophin gene therapy in cardiac and skeletal muscles in the DMDmdx rat model.

Duchenne muscular dystrophy (DMD) is a muscle wasting disorder caused by mutations in the gene encoding dystrophin. Gene therapy using micro-dystrophin (MD) transgenes and recombinant adeno-associated virus (rAAV) vectors hold great promise. To overcome the limited packaging capacity of rAAV vectors, most MD do not include dystrophin carboxy-terminal (CT) domain. Yet, the CT domain is known to recruit α1- and β1-syntrophins and α-dystrobrevin, a part of the dystrophin-associated protein complex (DAPC), which is a signaling and structural mediator of muscle cells. In this study, we explored the impact of inclusion of the dystrophin CT domain on ΔR4-23/ΔCT MD (MD1), in DMDmdx rats, which allows for relevant evaluations at muscular and cardiac levels. We showed by LC-MS/MS that MD1 expression is sufficient to restore the interactions at a physiological level of most DAPC partners in skeletal and cardiac muscles, and that inclusion of the CT domain increases the recruitment of some DAPC partners at supra-physiological levels. In parallel, we demonstrated that inclusion of the CT domain does not improve MD1 therapeutic efficacy on DMD muscle and cardiac pathologies. Our work highlights new evidences of the therapeutic potential of MD1 and strengthens the relevance of this candidate for gene therapy of DMD.

Influence of Host Blood Meal Source on Gut Microbiota of Wild Caught Aedes aegypti, a Dominant Arboviral Disease Vector.

Blood feeding is an important behavior of Aedes aegypti, a dominant arboviral disease vector, as it can establish and transmit viruses to humans. Bacteria associated with the mosquito gut can modulate the biological characteristics and behavior of disease vectors. In this study, we characterized the gut microbiota composition of human-blood-fed (HF), non-human-blood-fed (NHF) and non-fed (NF) field-collected Ae. aegypti mosquitoes, using a 16S metagenomic approach, to assess any association of bacterial taxa with the blood-feeding behavior of Ae. aegypti. A significant difference in the microbiota composition between the HF and NF mosquito group was observed. A significant association was observed in the relative abundance of families Rhodobacteraceae, Neisseriaceae and Dermacoccaceae in the HF group in contrast to NF and NHF Ae. aegypti mosquitoes, respectively. At the class level, two classes (Rhodobacterales and Neisseriales) were found to be in higher abundance in the HF mosquitoes compared to a single class of bacteria (Caulobacterales) in the NF mosquitoes. These results show that human-blood feeding may change the gut microbiota in wild Ae. aegypti populations. More research is needed to determine how changes in the midgut bacterial communities in response to human-blood-feeding affect the vectorial capacity of Ae. aegypti.

Trypanosomes of the Trypanosoma theileri Group: Phylogeny and New Potential Vectors

Trypanosomes belonging to Trypanosoma theileri group are mammalian blood parasites with keds and horse fly vectors. Our aim is to study to vector specificity of T. theileri trypanosomes. During our bloodsucking Diptera survey, we found a surprisingly high prevalence of T. theileri trypanosomes in mosquitoes (154/4051). Using PCR and gut dissections, we detected trypanosomes of T. theileri group mainly in Aedes mosquitoes, with the highest prevalence in Ae. excrucians (22%), Ae. punctor (21%), and Ae. cantans/annulipes (10%). Moreover, T. theileri group were found in keds and blackflies, which were reported as potential vectors for the first time. The vectorial capacity was confirmed by experimental infections of Ae. aegypti using our isolates from mosquitoes; sand fly Phlebotomus perniciosus supported the development of trypanosomes as well. Infection rates were high in both vectors (47–91% in mosquitoes, 65% in sandflies). Furthermore, metacyclic stages of T. theileri trypanosomes were observed in the gut of infected vectors; these putative infectious forms were found in the urine of Ae. aegypti after a second bloodmeal. On the contrary, Culex pipiens quinquefasciatus was refractory to experimental infections. According to a phylogenetic analysis of the 18S rRNA gene, our trypanosomes belong into three lineages, TthI, ThII, and a lineage referred to as here a putative lineage TthIII. The TthI lineage is transmitted by Brachycera, while TthII and ThIII include trypanosomes from Nematocera. In conclusion, we show that T. theileri trypanosomes have a wide range of potential dipteran vectors, and mosquitoes and, possibly, sandflies serve as important vectors.

Survival rate, blood feeding habits and sibling species composition of Aedes simpsoni complex: Implications for arbovirus transmission risk in East Africa.

Aedes simpsoni complex has a wide distribution in Africa and comprises at least three described sub-species including the yellow fever virus (YFV) vector Ae. bromeliae. To date, the distribution and relative contributions of the sub-species and/or subpopulations including bionomic characteristics in relation to YF transmission dynamics remain poorly studied. In this study conducted in two areas with divergent ecosystems: peri-urban (coastal Rabai) and rural (Rift Valley Kerio Valley) in Kenya, survival rate was estimated by parity in Ae. simpsoni s.l. mosquitoes sampled using CO2-baited BG Sentinel traps. We then applied PCR targeting the nuclear internal transcribed spacer 2 (ITS2), region followed by sequencing and phylogenetic analytics to identify the sibling species in the Ae. simpsoni complex among parous and blood fed cohorts. Our results show that Ae. bromeliae was the most dominant sub-species in both areas, exhibiting high survival rates, human blood-feeding, and potentially, high vectorial capacity for pathogen transmission. We document for the first time the presence of Ae. lilii in Kenya and potentially yet-to-be described species in the complex displaying human feeding tendencies. We also infer a wide host feeding range on rodents, reptile, and domestic livestock besides humans especially for Ae. bromeliae. This feeding trend could likely expose humans to various zoonotic pathogens. Taken together, we highlight the utility of genotype-based analyses to generate precision surveillance data of vector populations for enhanced disease risk prediction and to guide cost-effective interventions (e.g. YF vaccinations).

Anopheles gambiae Actively Metabolizes Uric Acid Following Plasmodium Infection to Limit Malaria Parasite Survival.

Characterizing the physiological changes that accompany malaria parasite infection of the mosquito host is crucial to our understanding of vectorial capacity in Anopheles mosquitoes, yet has not fully been explored. In this study, we examine the role of uric acid metabolism in the mosquito, Anopheles gambiae, following malaria parasite infection. We demonstrate that levels of uric acid are significantly decreased in the excreta and the mosquito at 24 and 48 h post-Plasmodium infection when compared to controls fed on naïve mouse blood. When we examine the expression of well-known enzymes responsible for uric acid metabolism, we see a significant increase in both urate oxidase (UO) and allatoicase (ALLC) expression following Plasmodium infection. Targeting the essential first step in uric acid metabolism by silencing UO resulted in elevated levels of uric acid, enhancing malaria parasite survival. With implications from other insect systems that bacteria can modulate UO expression, we examined the possibility that the mosquito microbiota and its expansion following blood-feeding may contribute to increased UO levels. However, there was no difference in uric acid metabolism between septic and aseptic mosquitoes, indicating that the mosquito microbiome is not associated with the manipulation of UO expression. Together, our study provides new evidence that Plasmodium infection causes the mosquito host to actively metabolize uric acid by increasing UO expression to limit Plasmodium oocyst survival, suggesting that nitrogen metabolism is an essential pathway in defining mosquito vector competence.

Evidence of pyrethroid resistance in Anopheles amharicus and Anopheles arabiensis from Arjo-Didessa irrigation scheme, Ethiopia.

Indoor residual spraying and insecticide-treated nets are among the key malaria control intervention tools. However, their efficacy is declining due to the development and spread of insecticide resistant vectors. In Ethiopia, several studies reported resistance of An. arabiensis to multiple insecticide classes. However, such data is scarce in irrigated areas of the country where insecticides, pesticides and herbicides are intensively used. Susceptibility of An. gambiae s.l. to existing and new insecticides and resistance mechanisms were assessed in Arjo-Didessa sugarcane plantation area, southwestern Ethiopia. Adult An. gambiae s.l. reared from larval/pupal collections of Arjo-Didessa sugarcane irrigation area and its surrounding were tested for their susceptibility to selected insecticides. Randomly selected An. gambiae s.l. (dead and survived) samples were identified to species using species-specific polymerase chain reaction (PCR) and were further analyzed for the presence of knockdown resistance (kdr) alleles using allele-specific PCR. Among the 214 An. gambiae s.l. samples analyzed by PCR, 89% (n = 190) were An. amharicus and 9% (n = 20) were An. arabiensis. Mortality rates of the An. gambiae s.l. exposed to deltamethrin and alphacypermethrin were 85% and 86.8%, respectively. On the other hand, mortalities against pirmiphos-methyl, bendiocarb, propoxur and clothianidin were 100%, 99%, 100% and 100%, respectively. Of those sub-samples (An. amharicus and An. arabiensis) examined for presence of kdr gene, none of them were found to carry the L1014F (West African) allelic mutation. Anopheles amharicus and An. arabiensis from Arjo-Didessa sugarcane irrigation area were resistant to pyrethroids which might be synergized by extensive use of agricultural chemicals. Occurrence of pyrethroid resistant malaria vectors could challenge the ongoing malaria control and elimination program in the area unless resistance management strategies are implemented. Given the resistance of An. amharicus to pyrethroids, its behavior and vectorial capacity should be further investigated.

Dengue virus infections among European travellers, 2015 to 2019.

BackgroundDengue is a disease with major impacts on public health in tropical and subtropical countries. In Europe, in the past decade, few autochthonous outbreaks were described.AimWe aimed to identify factors associated with frequency of dengue virus infection among European travellers and at assessing how surveillance data could support preparedness against autochthonous outbreaks within Europe.MethodsWe performed a descriptive analysis of travel-related dengue cases reported by European countries from 2015 through 2019. Using flight passenger data, we calculated travellers’ infection rates (TIR). We investigated the following associations: (i) between TIR and incidence rate in selected countries of infection and (ii) between number of travel-related cases and occurrence of autochthonous outbreaks within Europe.ResultsThere were 11,478 travel-related dengue cases and the TIR was 2.8 cases per 100,000 travellers. Most cases were infected in Asia (71%), predominantly in south-eastern Asia. The TIR was highest among travellers returning from Asia (6.1/100,000). There was an association between the incidence rate in the country of infection and the TIR but no association between the number of travel-related cases and occurrence of autochthonous outbreaks in Europe.ConclusionsThe likelihood of infection in travellers is a function of the ongoing epidemiological situation in the country of exposure. The number of travel-related cases alone is not sufficient to estimate the likelihood of autochthonous outbreaks where vectors are present in Europe. Additional contributing factors such as adequate vectorial capacity and suitable environmental conditions are required.

Blood meal analysis of Anopheles vectors of simian malaria based on laboratory and field studies

Blood feeding and host-seeking behaviors of a mosquito play an imperative role in determining its vectorial capacity in transmitting pathogens. Unfortunately, limited information is available regarding blood feeding behavior of Anopheles species in Malaysia. Collection of resting Anopheles mosquitoes for blood meal analysis poses a great challenge especially for forest dwelling mosquitoes. Therefore, a laboratory-based study was conducted to evaluate the potential use of mosquitoes caught using human landing catch (HLC) for blood meal analysis, and subsequently to document blood feeding behavior of local Anopheles mosquitoes in Peninsular Malaysia. The laboratory-based experiment from this study revealed that mosquitoes caught using HLC had the potential to be used for blood meal analysis. Besides HLC, mosquitoes were also collected using manual aspirator and Mosquito Magnet. Overall, 47.4% of 321 field-caught Anopheles mosquitoes belonging to six species were positive for vertebrate host DNA in their blood meal. The most frequent blood meal source was human (45.9%) followed by wild boar (27.4%), dog (15.3%) and monkey (7.5%). Interestingly, only Anopheles cracens and Anopheles introlatus (Leucosphyrus Group) fed on monkey. This study further confirmed that members of the Leucosphyrus Group are the predominant vectors for knowlesi malaria transmission in Peninsular Malaysia mainly due to their simio-anthropophagic feeding behavior.

Molecular and morphological identification of a reptile-associated tick, Amblyomma geoemydae (Acari: Ixodidae), infesting wild yellow-margined box turtles (Cuora flavomarginata) in northern Taiwan

The genetic identity and morphological features of a reptile-associated tick, Amblyomma geoemydae, were examined for the first time in Taiwan. The key morphological characters of male and female Am. geoemydae were photographed using a stereo microscope. The genetic identity was analyzed by comparing the 16S mitochondrial DNA gene sequences obtained from 11 Taiwan Am. geoemydae ticks with other Amblyomma species and three Ixodes species as outgroups. All the Taiwan specimens were genetically affiliated to a monophyletic group of Am. geoemydae and could be discriminated from other Amblyomma species. Our results provide the first distinguished colour figures and first genetic identification of adult Am. geoemydae ticks infesting turtles in Taiwan. The host range and vectorial capacity of Am. geoemydae for various tick-borne pathogens need to be further clarified in Taiwan.

Dengue virus infection modifies mosquito blood-feeding behavior to increase transmission to the host

Mosquito blood-feeding behavior is a key determinant of the epidemiology of dengue viruses (DENV), the most-prevalent mosquito-borne viruses. However, despite its importance, how DENV infection influences mosquito blood-feeding and, consequently, transmission remains unclear. Here, we developed a high-resolution, video-based assay to observe the blood-feeding behavior of Aedes aegypti mosquitoes on mice. We then applied multivariate analysis on the high-throughput, unbiased data generated from the assay to ordinate behavioral parameters into complex behaviors. We showed that DENV infection increases mosquito attraction to the host and hinders its biting efficiency, the latter resulting in the infected mosquitoes biting more to reach similar blood repletion as uninfected mosquitoes. To examine how increased biting influences DENV transmission to the host, we established an invivo transmission model with immuno-competent mice and demonstrated that successive short probes result in multiple transmissions. Finally, to determine how DENV-induced alterations of host-seeking and biting behaviors influence dengue epidemiology, we integrated the behavioral data within a mathematical model. We calculated that the number of infected hosts per infected mosquito, as determined by the reproduction rate, tripled when mosquito behavior was influenced by DENV infection. Taken together, this multidisciplinary study details how DENV infection modulates mosquito blood-feeding behavior to increase vector capacity, proportionally aggravating DENV epidemiology. By elucidating the contribution of mosquito behavioral alterations on DENV transmission to the host, these results will inform epidemiological modeling to tailor improved interventions against dengue.

Chemically Modified mocRNAs for Highly Efficient Protein Expression in Mammalian Cells.

mRNA has recently been established as a new class of therapeutics, due to its programmability and ability to produce proteins of interest rapidly in vivo. Despite its demonstrated utility, mRNA as a protein expression platform remains limited by its translational capacity and RNA stability. Here, we introduce messenger-oligonucleotide conjugated RNAs (mocRNAs) to enable site-specific, robust, and modularized encoding of chemical modifications for highly efficient and stable protein expression. In mocRNA constructs, chemically synthesized oligonucleotides are ligated to the 3' terminus of mRNA substrates to protect poly(A) tails from degradation, without compromising their potency in stimulating translation. As a proof-of-concept, mocRNAs modified by deadenylase-resistant oligonucleotides result in augmented protein production by factors of 2-4 in human HeLa cells and by 10-fold in primary rat cortical neuronal cultures. By directly linking enzymatic and organic synthesis of mRNA, we envision that the mocRNA design will open new avenues to expand the chemical space and translational capacity of RNA-based vectors in basic research and therapeutic applications.

Phylogenetic relationships of the supercontig of sodium channel subunit I (NaV) in 17 species of Anopheles (Diptera: Culicidae).

Malaria is a global health problem and is transmitted by the Anopheles species. Due to the epidemiological importance of the genus, studies on biological, phylogenetic, and evolutionary aspects have contributed to the understanding of adaptation, vector capacity, and resistance to insecticides. The latter may result from different causes such as mutations in the gene that encodes the sodium channel (NaV). In this study, the NaV subunit I scaffold of 17 anopheline species was used to infer phylogenetic relationships of the genus Anopheles using Bayesian inference. The evolutionary phylogenetic tree of the NaV gene was aligned in the AliView program and analyzed utilizing Bayesian inference, using the software MrBayes. The anophelines were grouped into five well-supported clusters: 1 - Anopheles darlingi and Anopheles albimanus; 2 - Anopheles sinensis and Anopheles atroparvus; 3 - Anopheles dirus; 4 - Anopheles minimus, Anopheles culicifacies, Anopheles funestus, Anopheles maculatus, and Anopheles stephensi; and 5 - Anopheles christyi, Anopheles epiroticus, Anopheles merus, Anopheles melas, Anopheles gambiae, Anopheles coluzzii, and Anopheles arabiensis. The topology confirms the phylogenetic relationships proposed in studies based on the genome of some anophelines and reflects the current taxonomy of the genus, which suggests that NaV undergoes selection pressure during the evolution of the species. These data are useful tools for inferring their ability to resist insecticides and also help in better understanding the evolutionary processes of the genus Anopheles.

Establishment and mass breeding of Phlebotomus papatasi (Diptera:Pshychodidae) in Orzouieh county in Kerman Province, Southeast of Iran

Background & objectives: Sand flies are important carriers of Leishmania parasites. Leishmaniosis, spread by sand fly vectors, is a major public health problem worldwide Particular in the tropics and the subtropics. The parasite transmission capacity of vectors, life cycle of parasites in the body of vectors, disease transmission, and the physiology and behavior of carrier vectors can be extensively studied by establishing insect colonies in the insectarium. In addition, response of vectors to repellents and insecticides, mating behaviors, blood feeding habits, interaction between parasites, and vectors, and taxonomic studies can be investigated by establishing insect colonies. The goal of the present study was to establish a colony of Phlebotomus papatasi in the insectarium in a ZCL endemic area in the Kerman Province of Iran. Methods: The Killick -Kendrick and Killick -Kendrick method (1991) was used for individual rearing and the volf and volfa (2011) method was used for mass rearing of the collected sand flies. The larvaewere fed by a diet with liver powder, which is the recommended diet for Phlebotomus papatasi larvae. Adult sand flies were allowed to feed on Balb/c mice blood in the laboratory. Results: 80 sand flies specimens (75 female+5 male) were collected with aspirator and reared for f1 and f2 generations in the laboratory. Interpretation & conclusion: The Phlebotomus sand flies were colonized in laboratory condition. Then sand flies successfully maintained for the first time as a laboratory species in Kerman Province.

Transposable element variants and their potential adaptive impact in urban populations of the malaria vector Anopheles coluzzii.

Anopheles coluzzii is one of the primary vectors of human malaria in sub-Saharan Africa. Recently, it has spread into the main cities of Central Africa threatening vector control programs. The adaptation of An. coluzzii to urban environments partly results from an increased tolerance to organic pollution and insecticides. Some of the molecular mechanisms for ecological adaptation are known, but the role of transposable elements (TEs) in the adaptive processes of this species has not been studied yet. As a first step toward assessing the role of TEs in rapid urban adaptation, we sequenced using long reads six An. coluzzii genomes from natural breeding sites in two major Central Africa cities. We de novo annotated TEs in these genomes and in an additional high-quality An. coluzzii genome, and we identified 64 new TE families. TEs were nonrandomly distributed throughout the genome with significant differences in the number of insertions of several superfamilies across the studied genomes. We identified seven putatively active families with insertions near genes with functions related to vectorial capacity, and several TEs that may provide promoter and transcription factor binding sites to insecticide resistance and immune-related genes. Overall, the analysis of multiple high-quality genomes allowed us to generate the most comprehensive TE annotation in this species to date and identify several TE insertions that could potentially impact both genome architecture and the regulation of functionally relevant genes. These results provide a basis for future studies of the impact of TEs on the biology of An. coluzzii.

Peptide OPTX-1 From Ornithodoros papillipes Tick Inhibits the pS273R Protease of African Swine Fever Virus.

African swine fever virus (ASFV) is a large double-stranded DNA virus and causes high mortality in swine. ASFV can be transmitted by biological vectors, including soft ticks in genus Ornithodoros but not hard ticks. However, the underlying mechanisms evolved in the vectorial capacity of soft ticks are not well-understood. Here, we found that a defensin-like peptide toxin OPTX-1 identified from Ornithodoros papillipes inhibits the enzyme activity of the ASFV pS273R protease with a Ki=0.821±0.526μM and shows inhibitory activity on the replication of ASFV. The analogs of OPTX-1 from hard ticks show more inhibitory efficient on pS273R protease. Considering that ticks are blood-sucking animals, we tested the effects of OPTX-1 and its analogs on the coagulation system. At last, top 3D structures represented surface analyses of the binding sites of pS273R with different inhibitors that were obtained by molecular docking based on known structural information. In summary, our study provides evidence that different inhibitory efficiencies between soft tick-derived OPTX-1 and hard tick-derived defensin-like peptides may determine the vector and reservoir competence of ticks.

Incidence and consequences of damage to insecticide-treated mosquito nets in Kenya

BackgroundEfforts to improve the impact of long-lasting insecticidal nets (LLINs) should be informed by understanding of the causes of decay in effect. Holes in LLINs have been estimated to account for 7–11% of loss in effect on vectorial capacity for Plasmodium falciparum malaria in an analysis of repeated cross-sectional surveys of LLINs in Kenya. This does not account for the effect of holes as a cause of net attrition or non-use, which cannot be measured using only cross-sectional data. There is a need for estimates of how much these indirect effects of physical damage on use and attrition contribute to decay in effectiveness of LLINs.MethodsUse, physical integrity, and survival were assessed in a cohort of 4514 LLINs followed for up to 4 years in Kenya. Flow diagrams were used to illustrate how the status of nets, in terms of categories of use, physical integrity, and attrition, changed between surveys carried out at 6-month intervals. A compartment model defined in terms of ordinary differential equations (ODEs) was used to estimate the transition rates between the categories. Effects of physical damage to LLINs on use and attrition were quantified by simulating counterfactuals in which there was no damage.ResultsAllowing for the direct effect of holes, the effect on use, and the effect on attrition, 18% of the impact on vectorial capacity was estimated to be lost because of damage. The estimated median lifetime of the LLINs was 2.9 years, but this was extended to 5.7 years in the counterfactual without physical damage. Nets that were in use were more likely to be in a damaged state than unused nets but use made little direct difference to LLIN lifetimes. Damage was reported as the reason for attrition for almost half of attrited nets, but the model estimated that almost all attrited nets had suffered some damage before attrition.ConclusionsFull quantification of the effects of damage will require measurement of the supply of new nets and of household stocks of unused nets, and also of their impacts on both net use and retention. The timing of mass distribution campaigns is less important than ensuring sufficient supply. In the Kenyan setting, nets acquired damage rapidly once use began and the damage led to rapid attrition. Increasing the robustness of nets could substantially increase their lifetime and impact but the impact of LLIN programmes on malaria transmission is ultimately limited by levels of use. Longitudinal analyses of net integrity data from different settings are needed to determine the importance of physical damage to nets as a driver of attrition and non-use, and the importance of frequent use as a cause of physical damage in different contexts.

Exploiting Dengue Virus Protease as a Therapeutic Target: Current Status, Challenges and Future Avenues.

Dengue, the oldest and the most prevalent mosquito-borne illness, is caused by the dengue virus (DENV), from the family of Flaviviridae. It infects approximately 400 million individuals per annum, with approximately half of the global population residing in high-risk areas. The factors attributed to the geographic expansion of dengue, include urbanization, population density, modern means of transportation, international travels, habit modification, climate change, virus genetics, vector capacity, and poor vector control. Despite the significant progress made in the past against dengue, no effective antiviral therapy is currently available. Among the structural and non-structural proteins encoded by DENV genome, the NS2B-NS3 protease complex is amongst the extensively studied targets for the development of antiviral therapeutics owing to its multiple roles in virus life cycle. Furthermore, protease inhibitors were found to be successful in Hepatitis C Virus (HCV) and Human Immunodeficiency Virus (HIV). Likewise, several peptidic, peptide derived/peptidomimetic, and small molecules inhibitors have been identified as DENV protease inhibitors. Unfortunately, none of them have resulted in a clinically approved drug. Considering all the abovementioned facts, this review descriptively explains the molecular mechanism and therapeutic potential of DENV protease along with an up to date information on various competitive inhibitors reported against DENV protease. This review might be helpful for the researchers working in this area to understand the critical aspects of DENV protease that will help them develop effective and novel inhibitors against DENV to protect lives of millions of people worldwide.

Evaluation of the interaction between insecticide resistance-associated genes and malaria transmission in Anopheles gambiae sensu lato in central C\xf4te d\u2019Ivoire

BackgroundThere is evidence that the knockdown resistance gene (Kdr) L1014F and acetylcholinesterase-1 gene (Ace-1R) G119S mutations involved in pyrethroid and carbamate resistance in Anopheles gambiae influence malaria transmission in sub-Saharan Africa. This is likely due to changes in the behaviour, life history and vector competence and capacity of An. gambiae. In the present study, performed as part of a two-arm cluster randomized controlled trial evaluating the impact of household screening plus a novel insecticide delivery system (In2Care Eave Tubes), we investigated the distribution of insecticide target site mutations and their association with infection status in wild An. gambiae sensu lato (s.l.) populations.MethodsMosquitoes were captured in 40 villages around Bouaké by human landing catch from May 2017 to April 2019. Randomly selected samples of An. gambiae s.l. that were infected or not infected with Plasmodium sp. were identified to species and then genotyped for Kdr L1014F and Ace-1R G119S mutations using quantitative polymerase chain reaction assays. The frequencies of the two alleles were compared between Anopheles coluzzii and Anopheles gambiae and then between infected and uninfected groups for each species.ResultsThe presence of An. gambiae (49%) and An. coluzzii (51%) was confirmed in Bouaké. Individuals of both species infected with Plasmodium parasites were found. Over the study period, the average frequency of the Kdr L1014F and Ace-1R G119S mutations did not vary significantly between study arms. However, the frequencies of the Kdr L1014F and Ace-1R G119S resistance alleles were significantly higher in An. gambiae than in An. coluzzii [odds ratio (95% confidence interval): 59.64 (30.81–131.63) for Kdr, and 2.79 (2.17–3.60) for Ace-1R]. For both species, there were no significant differences in Kdr L1014F or Ace-1R G119S genotypic and allelic frequency distributions between infected and uninfected specimens (P > 0.05).ConclusionsEither alone or in combination, Kdr L1014F and Ace-1R G119S showed no significant association with Plasmodium infection in wild An. gambiae and An. coluzzii, demonstrating the similar competence of these species for Plasmodium transmission in Bouaké. Additional factors including behavioural and environmental ones that influence vector competence in natural populations, and those other than allele measurements (metabolic resistance factors) that contribute to resistance, should be considered when establishing the existence of a link between insecticide resistance and vector competence.Graphical

Tick Immunobiology and Extracellular Traps: An Integrative Vision to Control of Vectors.

Ticks are hematophagous ectoparasites that infest a diverse number of vertebrate hosts. The tick immunobiology plays a significant role in establishing and transmitting many pathogens to their hosts. To control tick infestations, the acaricide application is a commonly used method with severe environmental consequences and the selection of tick-resistant populations. With these drawbacks, new tick control methods need to be developed, and the immune system of ticks contains a plethora of potential candidates for vaccine design. Additionally, tick immunity is based on an orchestrated action of humoral and cellular immune responses. Therefore, the actors of these responses are the object of our study in this review since they are new targets in anti-tick vaccine design. We present their role in the immune response that positions them as feasible targets that can be blocked, inhibited, interfered with, and overexpressed, and then elucidate a new method to control tick infestations through the development of vaccines. We also propose Extracellular Traps Formation (ETosis) in ticks as a process to eliminate their natural enemies and those pathogens they transmit (vectorial capacity), which results attractive since they are a source of acting molecules with potential use as vaccines.