Development of an Enzyme-Linked Immunosorbent Assay (ELISA) as a tool to detect NS1 of dengue virus serotype 2 in female Aedes aegypti eggs for the surveillance of dengue fever transmission.

Dengue is a significant disease transmitted by Aedes mosquitoes in the tropics and subtropics worldwide. The disease is caused by four virus (DENV) serotypes and is transmitted to humans by female Aedes aegypti mosquito bites infected with the virus and vertically to their progeny. Current strategies to control dengue transmission focus on the vector. In this study, we describe an indirect Enzyme-Linked Immunosorbent Assay (ELISA), using a monoclonal antibody against the non-structural dengue virus protein 1 (NS1), to detect DENV2 in Ae. aegypti eggs. The assay detects NS1 in eggs homogenates with 87.5% sensitivity and 75.0% specificity and it is proposed as a tool for the routine entomovirological surveillance of DENV 2 in field mosquito populations.

Arbovirus surveillance on the Mexico-USA border: West Nile virus identification in various species of field mosquitoes.

West Nile virus (WNV) has been documented in human and/or mosquito samples near the border with Mexico in El Paso, Texas, and Doña Ana County, New Mexico. However, on the Mexican side of the border, particularly in the State of Chihuahua, no such cases of WNV-infected mosquitoes have been documented. We tested 367 mosquitoes of four species (Culex quinquefasciatus, Cx. tarsalis, Aedes aegypti, and Aedes (Ochlerotatus) epactius) and found a high rate of WNV-positivity, including the first record of Ae. (Ochlerotatus) epactius infection with WNV. These results call for intensifying WNV surveillance efforts on the border between the United States and Mexico, with particular emphasis on vector control and monitoring of the species included in this study.

The costs of transgenerational immune priming for homologous and heterologous infections with different serotypes of dengue virus in Aedes aegypti mosquitoes.

The immune system is a network of molecules, signaling pathways, transcription, and effector modulation that controls, mitigates, or eradicates agents that may affect the integrity of the host. In mosquitoes, the innate immune system is highly efficient at combating foreign organisms but has the capacity to tolerate vector-borne diseases. These implications lead to replication, dissemination, and ultimately the transmission of pathogenic organisms when feeding on a host. In recent years, it has been discovered that the innate immune response of mosquitoes can trigger an enhanced immunity response to the stimulus of a previously encountered pathogen. This phenomenon, called immune priming, is characterized by a molecular response that prevents the replication of viruses, parasites, or bacteria in the body. It has been documented that immune priming can be stimulated through homologous organisms or molecules, although it has also been documented that closely related pathogens can generate an enhanced immune response to a second stimulus with a related organism. However, the cost involved in this immune response has not been characterized through the transmission of the immunological experience from parents to offspring by transgenerational immune priming (TGIP) in mosquitoes. Here, we address the impact on the rates of oviposition, hatching, development, and immune response in Aedes aegypti mosquitoes, the mothers of which were stimulated with dengue virus serotypes 2 and/or 4, having found a cost of TGIP on the development time of the progeny of mothers with heterologous infections, with respect to mothers with homologous infections. Our results showed a significant effect on the sex ratio, with females being more abundant than males. We found a decrease in transcripts of the siRNA pathway in daughters of mothers who had been exposed to an immune challenge with DV. Our research demonstrates that there are costs and benefits associated with TGIP in Aedes aegypti mosquitoes exposed to DV. Specifically, priming results in a lower viral load in the offspring of mothers who have previously been infected with the virus. Although some results from tests of two dengue virus serotypes show similarities, such as the percentage of pupae emergence, there are differences in the percentage of adult emergence, indicating differences in TGIP costs even within the same virus with different serotypes. This finding has crucial implications in the context of dengue virus transmission in endemic areas where multiple serotypes circulate simultaneously.

Detection of NS1 protein from dengue virus in excreta and homogenates of wild-caught Aedes aegypti mosquitoes using monoclonal antibodies.

Dengue fever is one of the most devastating infectious diseases worldwide. Development of methods for dengue virus (DENV) detection in mosquitoes to assess prevalence as a preliminary screen for entomological surveillance in endemic regions of DENV will certainly contribute to the control of the disease. A monoclonal antibody against the NS1 (nonstructural protein 1) viral protein was generated using recombinant NS1 protein and used to detect and analyze DENV in both excreta and total homogenates from Aedes aegypti mosquitoes. Results demonstrated expression of NS1 in excreta of DENV laboratory-infected mosquitoes and homogenates from field mosquitoes infected with DENV. The immunodetection method reported here represents a first-line strategy for assessing the prevalence of DENV in mosquitoes, for entomological surveillance in endemic regions of dengue. Detection of DENV prevalence in field mosquitoes could have an impact on vector surveillance measures to interrupt dengue transmission.

Adult damselflies as possible regulators of mosquito populations in urban areas.

BACKGROUND: Dragonfly and damselfly larvae have been considered as possible biocontrol agents against young instars of mosquito vectors in urban environments. Yet our knowledge about adult odonate predation against mosquito adults is scarce. We quantified daily and annual predation rates, consumption rates and prey preferences of adult Hetaerina vulnerata male damselflies in an urban park. A focus on predation of mosquito species was provided, quantified their arbovirus (dengue, chikungunya and Zika) infection rates and biting activity. RESULTS: Foraging times of H. vulnerata overlapped with those of the maximum activity of hematophagous mosquitoes. The most consumed preys were Diptera and Hymenoptera and, in lower quantities, Hemiptera, Coleoptera, Trichoptera, Psocoptera and Neuroptera. Of note, 7% of the diet was represented by hematophagous dipterans, with 2.4% being Aedes aegypti and Aedes albopictus. Prey abundance in the diet coincided with that of the same species in the environment. The arboviral infection rate (dengue, chikungunya and Zika) was 1.6% for A. aegypti and A. albopictus. The total biting rate of these mosquito vectors was 16 bites per person per day, while the annual rate of infectious bites was 93.4. CONCLUSION: Although 2.4% for both Aedes species seems a low consumption, considering the presence of 12 odonate species at the park, it can be argued that adult odonates may play a relevant role as mosquito vector regulators, therefore impacting the spread of mosquito-borne diseases. Our study outlines the need for further research on the topic of the possible role of adult odonates for mosquito biocontrol. © 2021 Society of Chemical Industry.

Dietary and Plasmodium challenge effects on the cuticular hydrocarbon profile of Anopheles albimanus.

The cuticular hydrocarbon (CHC) profile reflects the insects' physiological states. These include age, sex, reproductive stage, and gravidity. Environmental factors such as diet, relative humidity or exposure to insecticides also affect the CHC composition in mosquitoes. In this work, the CHC profile was analyzed in two Anopheles albimanus phenotypes with different degrees of susceptibility to Plasmodium, the susceptible-White and resistant-Brown phenotypes, in response to the two dietary regimes of mosquitoes: a carbon-rich diet (sugar) and a protein-rich diet (blood) alone or containing Plasmodium ookinetes. The CHCs were analyzed by gas chromatography coupled to mass spectrometry or flame ionization detection, identifying 19 CHCs with chain lengths ranging from 20 to 37 carbons. Qualitative and quantitative changes in CHCs composition were dependent on diet, a parasite challenge, and, to a lesser extent, the phenotype. Blood-feeding caused up to a 40% reduction in the total CHC content compared to sugar-feeding. If blood contained ookinetes, further changes in the CHC profile were observed depending on the Plasmodium susceptibility of the phenotypes. Higher infection prevalence caused greater changes in the CHC profile. These dietary and infection-associated modifications in the CHCs could have multiple effects on mosquito fitness, impacts on disease transmission, and tolerance to insecticides.

Transcriptome analysis uncover differential regulation in cell cycle, immunity, and metabolism in Anopheles albimanus during immune priming with Plasmodium berghei.

In invertebrates, "immunological priming" is considered as the ability to acquire a protective (adaptive) immune response against a pathogen due to previous exposure to the same organism. To date, the mechanism by which this type of adaptive immune response originates in insects is not well understood. In the Anopheles albimanus - Plasmodium berghei model, a DNA synthesis that probably indicates an endoreplication process during priming induction has been evidenced. This work aimed to know the transcriptomic profile in the midguts of An. albimanus after priming induction. Our analysis indicates the participation of regulatory elements of the cell cycle in the immunological priming and points out the importance of the cell cycle regulation in the mosquito midgut.

Experimental infection and vector competence of Zika virus in Aedes aegypti mosquitoes from Acapulco, Guerrero, Mexico.

OBJECTIVE: To gain a better understanding of the Zika virus (ZIKV) vector transmission in Mexico, we determined the vector competence of a local population of Ae. aegypti (Acapulco, Guerrero) for a strain of ZIKV isolated from a Mexican febrile patient. MATERIALS AND METHODS: Eggs were hatched and larvae were reared under controlled conditions. After five days post-emergence, female mosquitoes were fed an infectious blood-meal containing ZIKV. Mosquitoes were analyzed at 4, 7 and 14-day post-infection (dpi). Infection (gut), dissemination (wings, legs and heads) and potential transmission (salivary glands) were assessed by RT-qPCR. The Rockefeller Ae. aegypti strain was used as ZIKV infection control. RESULTS: ZIKV infection, dissemination, and potential transmission rates were 96.2, 96.1 and 93.2%, respectively. CONCLUSIONS: Ae. aegypti (F1) from Acapulco were very susceptible to ZIKV infection, and showed similar vector competence to that of the susceptible Rockefeller strain. To our knowledge, this is the first report of vector competence for ZIKV performed in a Mexican laboratory.

OBJETIVO: Determinar la competencia vectorial de una población local de Ae. aegypti para transmitir el virus Zika (ZIKV) aislado de un paciente febril mexicano. MATERIAL Y MÉTODOS: Se desarrolló la primera generación (F1) de mosquitos Ae. aegypti en el insectario a partir de huevos colectados mediante ovitrampas en la Colonia Renacimiento, Acapulco, Guerrero. Después de cinco días de la emergencia, los mosquitos hembras fueron alimentados con sangre infecciosa con ZIKV. La infección (intestino), la diseminación (alas, piernas y cabezas) y la transmisión potencial (glándulas salivales) se evaluaron mediante RT-qPCR, a los 4, 7 y 14 días después de la alimentación. RESULTADOS: La infección por ZIKV, la diseminación y las tasas potenciales de transmisión fueron de 96.2, 96.1 y 93.2%, respectivamente. CONCLUSIONES: Los mosquitos Ae. aegypti (F1) de Acapulco presentan una alta competencia vectorial (93.2%). Según los autores de este estudio, este es el primer informe de competencia vectorial para ZIKV realizado en un laboratorio mexicano.

Immune priming with inactive dengue virus during the larval stage of Aedes aegypti protects against the infection in adult mosquitoes.

Several studies have observed that the immune response in insects can be conserved, a phenomenon known as immune priming, which has been mostly tested in adult stages. However, it is unknown if induction of immune priming in larval stages protects against dengue virus (DENV) infections in adult mosquitoes. In this work, we primed larval instar 3rd of Aedes aegypti with inactive dengue virus, producing adult mosquitoes with i) an enhanced antiviral-immune response; ii) a reduction in the load and replication of RNA of dengue virus (DENV); iii) a decline in viral infective particles production. Adult mosquitoes previously primed during larval stages over-expressed RNA interference (RNAi) markers Argonaute-2 (AGO-2) and Dicer-2 (DCR-2). We also observed inter-individual variations of DENV infection in adult mosquitoes, indicating a heterogeneous response to DENV infection in the same mosquito strain. However, mosquitoes primed during larval stages appear to control the infection, reducing the viral load. The over-expression of interferon-like factors (VAGO) and AGO-2 in the pupa stage suggests a fast activation of antiviral mechanisms after immune priming in larvae, creating a condition in which adult mosquitoes are resistant to the pathogen in the posterior exposure.

Experimental infection and vector competence of Zika virus in Aedes aegypti mosquitoes from Acapulco, Guerrero, Mexico / Infección experimental y competencia vectorial del virus Zika en mosquitos Aedes aegypti de Acapulco, Guerrero, México

Abstract: Objective: To gain a better understanding of the Zika virus (ZIKV) vector transmission in Mexico, we determined the vector competence of a local population ofAe. aegypti(Acapulco, Guerrero) for a strain of ZIKV isolated from a Mexican febrile patient. Materials and methods: Eggs were hatched and larvae were reared under controlled conditions. After five days post-emergence, female mosquitoes were fed an infectious blood-meal containing ZIKV. Mosquitoes were analyzed at 4, 7 and 14-day post-infection (dpi). Infection (gut), dissemination (wings, legs and heads) and potential transmission (salivary glands) were assessed by RT-qPCR. The RockefellerAe. aegyptistrain was used as ZIKV infection control. Results: ZIKV infection, dissemination, and potential transmission rates were 96.2, 96.1 and 93.2%, respectively. Conclusions: Ae. aegypti(F1) from Acapulco were very susceptible to ZIKV infection, and showed similar vector competence to that of the susceptible Rockefeller strain. To our knowledge, this is the first report of vector competence for ZIKV performed in a Mexican laboratory.

Resumen: Objetivo: Determinar la competencia vectorial de una población local deAe. aegyptipara transmitir el virus Zika (ZIKV) aislado de un paciente febril mexicano. Material y métodos: Se desarrolló la primera generación (F1) de mosquitosAe. aegyptien el insectario a partir de huevos colectados mediante ovitrampas en la Colonia Renacimiento, Acapulco, Guerrero. Después de cinco días de la emergencia, los mosquitos hembras fueron alimentados con sangre infecciosa con ZIKV. La infección (intestino), la diseminación (alas, piernas y cabezas) y la transmisión potencial (glándulas salivales) se evaluaron mediante RT-qPCR, a los 4, 7 y 14 días después de la alimentación. Resultados: La infección por ZIKV, la diseminación y las tasas potenciales de transmisión fueron de 96.2, 96.1 y 93.2%, respectivamente. Conclusiones: Los mosquitos Ae. aegypti (F1) de Acapulco presentan una alta competencia vectorial (93.2%). Según los autores de este estudio, este es el primer informe de competencia vectorial para ZIKV realizado en un laboratorio mexicano.

DNA Synthesis Is Activated in Mosquitoes and Human Monocytes During the Induction of Innate Immune Memory.

Endoreplication is a cell cycle program in which cells replicate their genomes without undergoing mitosis and cytokinesis. For the normal development of many organisms (from fungi to humans) and the formation of their organs, endoreplication is indispensable. The aim of the present study was to explore whether endoreplication and DNA synthesis are relevant processes during the induction of trained innate immunity in human monocytes and in the Anopheles albimanus mosquito cell line. During the induction of trained immunity in both models, endoreplication markers were overexpressed and we observed an increase in DNA synthesis with an augmented copy number of genes essential for trained immunity. Blocking DNA synthesis prevented trained immunity from being established. Overall, these findings suggest that DNA synthesis and endoreplication are important mechanisms involved in inducing innate immune memory. They have probably been conserved throughout evolution from invertebrates to humans.

Sialic acid expression in the mosquito Aedes aegypti and its possible role in dengue virus-vector interactions.

Dengue fever (DF) is the most prevalent arthropod-borne viral disease which affects humans. DF is caused by the four dengue virus (DENV) serotypes, which are transmitted to the host by the mosquito Aedes aegypti that has key roles in DENV infection, replication, and viral transmission (vector competence). Mosquito saliva also plays an important role during DENV transmission. In this study, we detected the presence of sialic acid (Sia) in Aedes aegypti tissues, which may have an important role during DENV-vector competence. We also identified genome sequences encoding enzymes involved in Sia pathways. The cDNA for Aedes aegypti CMP-Sia synthase (CSAS) was amplified, cloned, and functionally evaluated via the complementation of LEC29.Lec32 CSAS-deficient CHO cells. AedesCSAS-transfected LEC29.Lec32 cells were able to express Sia moieties on the cell surface. Sequences related to α-2,6-sialyltransferase were detected in the Aedes aegypti genome. Likewise, we identified Sia-α-2,6-DENV interactions in different mosquito tissues. In addition, we evaluated the possible role of sialylated molecules in a salivary gland extract during DENV internalization in mammalian cells. The knowledge of early DENV-host interactions could facilitate a better understanding of viral tropism and pathogenesis to allow the development of new strategies for controlling DENV transmission.

Modification of the cytoprotective protein C pathway during Dengue virus infection of human endothelial vascular cells.

Dengue fever (DF) is the most prevalent arthropod-borne viral disease of humans. No safe vaccine is available, there is no experimental animal model and no specific treatment (antiviral) for Dengue virus (DV) infection exists. The pathogenic mechanisms of the severe forms of the disease, such as Dengue shock syndrome (DSS) and Dengue haemorrhagic fever (DHF), in which endothelial damage is the pathognomonic sign, are not fully understood. Clinical observations have revealed significant abnormalities in the coagulation and inflammation systems, with increased levels of soluble thrombomodulin (sTM) in the plasma of patients with DHF/DSS (grade III or IV). Blood sTM was proposed as an early predictor of DSS during the febrile stage. However, the role of the DV in endothelial injury during DSS is unclear. Here, we present novel insights into the participation of DV in the downregulation of the thrombomodulin-thrombin-protein C complex formation at the endothelial surface, with a reduction in activated protein C (APC). APC is the most important vasoprotective protein because it downregulates thrombin generation (by the inactivation of procoagulant factors Va and VIIIa) and has anti-inflammatory, antiapoptotic, and barrier protection properties. These biological functions of APC are associated with the endothelial protein C receptor (EPCR) and protease-activated receptor 1 (PAR-1) signalling pathways, which link the coagulation-inflammation responses. We found alterations in the antithrombotic and cytoprotective protein C pathways during DV infection of human endothelial vascular cells, which may explain the vasculopathy observed during DHF/DSS. Clarification of the basic principles that underlie these processes has important implications for the design of new therapeutic strategies for DHF/DSS.

Crosstalk between coagulation and inflammation during Dengue virus infection.

Dengue fever is the most prevalent viral disease transmitted by vectors (Aedes aegypti, Aedes albopictus) in worldwide. More than 100 million cases occur annually with a mortality rate of 5% and no safe vaccine is available. The pathogenesis of Dengue, where host and viral factors participate in the establishment of Dengue haemorrhagic fever (DHF) and Dengue shock syndrome (DSS) remains unresolved. Clinical observations have revealed significant abnormalities in coagulation and inflammation systems, with increased levels of tissue factor (TF) and the chemokine IL-8, correlating with the severity of the disease and implicating damage to endothelial vascular cells (EVC). Here we present novel insights concerning the crosstalk between the regulatory signaling pathways of the coagulation-inflammation processes, during Dengue virus (DV) infection of EVC. We found that DV up-regulates Protease Activated receptor type-1 (inflammation) and TF (coagulation) receptors, via the phosphorylation of p38 and ERK1/2 MAPKs, which favor the activation of NF-kappaB transcription factor. This induces pro-inflammatory (IL-8) or pro-adhesive (VCAM-1) gene expression which may lead to EVC activation. The elucidation of the basic principles that signal these processes has important implications for the design of new therapeutic strategies for DHF/DSS.