Mosquito adaptations to hematophagia impact pathogen transmission

Bloodmeals fuel dengue virus replication in the female mosquito Aedes aegypti

Vector competence defines the ability of a vector to acquire, host, and transmit a pathogen. Understanding the molecular determinants of the mosquitos' competence to host dengue virus (DENV) holds promise to prevent its transmission. To this end, we employed RNA-seq to profile mRNA transcripts of the female Aedes aegypti mosquitos feeding on naïve vs viremic mouse. While most transcripts (12,634) did not change their abundances, 360 transcripts showed decreases. Biological pathway analysis revealed representatives of the decreased transcripts involved in the wnt signaling pathway and hippo signaling pathway. One thousand three hundred fourteen transcripts showed increases in abundance and participate in 21 biological pathways including amino acid metabolism, carbon metabolism, fatty acid metabolism, and oxidative phosphorylation. Inhibition of oxidative phosphorylation with antimycin A reduced oxidative phosphorylation activity and ATP concentration associated with reduced DENV replication in the Aedes aegypti cells. Antimycin A did not affect the amounts of the non-structural proteins 3 and 5, two major components of the replication complex. Ribavirin, an agent that reduces GTP concentration, recapitulated the effects of reduced ATP concentration on DENV replication. Knocking down one of the oxidative phosphorylation components, ATP synthase subunit β, reduced DENV replication in the mosquitos. In summary, our results suggest that DENV enhances metabolic pathways in the female Aedes aegypti mosquitos to supply nutrients and energy for virus replication. ATP synthase subunit β knockdown might be exploited to reduce the mosquitos' competence to host and transmit DENV.

IMPORTANCE

Through evolution, the mosquito-borne viruses have adapted to the blood-feeding behaviors of their opportunist hosts to fulfill a complete lifecycle in humans and mosquitos. Disruption in the mosquitos' ability to host these viruses offers strategies to prevent diseases caused by them. With the advent of genomic tools, we discovered that dengue virus (DENV) benefited from the female mosquitos' bloodmeals for metabolic and energetic supplies for replication. Chemical or genetic disruption in these supplies reduced DENV replication in the female mosquitos. Our discovery can be exploited to produce genetically modified mosquitos, in which DENV infection leads to disruption in the supplies and thereby reduces replication and transmission. Our discovery might be extrapolated to prevent mosquito-borne virus transmission and the diseases they cause.

Quorum sensing-activated phenylalanine metabolism drives OMV biogenesis to enhance mosquito commensal colonization resistance to Plasmodium

Gut microbiota and its symbiotic relationship with the host are crucial for preventing pathogen infection. However, little is known about the mechanisms that drive commensal colonization. Serratia bacteria, commonly found in Anopheles mosquitoes, potentially mediate mosquito resistance to Plasmodium. Using S. ureilytica Su_YN1 as a model, we show that a quorum sensing (QS) circuit is crucial for stable colonization. After blood ingestion, the QS synthase SueI generates the signaling molecule N-hexanoyl-L-homoserine lactone (C6-HSL). Once C6-HSL binds to the QS receptor SueR, repression of the phenylalanine-to-acetyl-coenzyme A (CoA) conversion pathway is lifted. This pathway regulates outer membrane vesicle (OMV) biogenesis and promotes Serratia biofilm-like aggregate formation, facilitating gut adaptation and colonization. Notably, exposing Serratia Su_YN1-carrying Anopheles mosquitoes to C6-HSL increases Serratia gut colonization and enhances Plasmodium transmission-blocking efficacy. These findings provide insights into OMV biogenesis and commensal gut colonization and identify a powerful strategy for enhancing commensal resistance to pathogens.

Shotgun Metagenomic Sequencing Reveals Virome Composition of Mosquitoes from a Transition Ecosystem of North-Northeast Brazil

A wide diversity of pathogenic mosquito-borne viruses circulate in the Brazilian Amazon, and the intense deforestation can contribute to the spread of these viruses. In this context, this study aimed to investigate the viral diversity in mosquitoes of the genera Aedes, Culex, Haemagogus, and Sabethes from a transition area between the Amazon, Cerrado, and Caatinga biomes in Brazil. Metagenomic high-throughput sequencing was used to characterize the virome of 20 mosquito pools. A total of 15 virus-like genomes were identified, comprising species genomically close to insect-specific viruses of the families Iflaviridae, Metaviridae, Lispiviridae, Rhabdoviridae, Xinmoviridae, and Parvoviridae and species of plant viruses of the families Solemoviridae, Virgaviridae, and Partitiviridae. However, sequences of viruses associated with human and animal diseases were not detected. Most of the recovered genomes were divergent from those previously described. These findings reveal that there are a large number of unknown viruses to be explored in the middle-north of Brazil.

Blood feeding habits of mosquitoes: hardly a bite in South America

Mosquito blood feeding plays a key role in epidemiology. Despite its importance and large number of studies worldwide, less attention has been paid in South America. We summarized some general concepts and methodological issues related to the study of mosquito blood feeding habits, and compiled and analyzed all published information regarding the subject in the continent until 2020. Available literature comprised 152 scientific studies, that pursued different approaches: human landing catches (102 studies), baited trap (19), and blood meal analyses of collected specimens (38). Among the latter, 23 used serological and 15 molecular techniques. Species most frequently studied were those incriminated in malaria transmission, whereas relevant vectors such as Aedes aegypti, Ae. albopictus, and Haemagogus janthinomys were surprisingly neglected. Brazil was the leading country both in number of works and species studied. For over 70% of the species and three out of 13 South American countries there is no single information on mosquito blood feeding habits. Data from baited traps included 143 mosquito species, 83.9% of which were attracted to humans, either exclusively (10.5%) or in combination with other vertebrates (73.4%). Host blood identification of field collected specimens provided data on 102 mosquito species, and 60.8% of these fed on humans (55.9% combined with other vertebrates). Only 17 of the 73 species assessed by both methods yielded similar feeding patterns. Finally, supplementary tables are provided in a comprehensive summary of all information available and information gaps are highlighted for future research in the continent.

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 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. Production of a monoclonal antibody against the NS1 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.

Non-immune Traits Triggered by Blood Intake Impact Vectorial Competence

Blood-feeding arthropods are considered an enormous public health threat. They are vectors of a plethora of infectious agents that cause potentially fatal diseases like Malaria, Dengue fever, Leishmaniasis, and Lyme disease. These vectors shine due to their own physiological idiosyncrasies, but one biological aspect brings them all together: the requirement of blood intake for development and reproduction. It is through blood-feeding that they acquire pathogens and during blood digestion that they summon a collection of multisystemic events critical for vector competence. The literature is focused on how classical immune pathways (Toll, IMD, and JAK/Stat) are elicited throughout the course of vector infection. Still, they are not the sole determinants of host permissiveness. The dramatic changes that are the hallmark of the insect physiology after a blood meal intake are the landscape where a successful infection takes place. Dominant processes that occur in response to a blood meal are not canonical immunological traits yet are critical in establishing vector competence. These include hormonal circuitries and reproductive physiology, midgut permeability barriers, midgut homeostasis, energy metabolism, and proteolytic activity. On the other hand, the parasites themselves have a role in the outcome of these blood triggered physiological events, consistently using them in their favor. Here, to enlighten the knowledge on vector-pathogen interaction beyond the immune pathways, we will explore different aspects of the vector physiology, discussing how they give support to these long-dated host-parasite relationships.

Leaning Into the Bite: The piRNA Pathway as an Exemplar for the Genetic Engineering Need in Mosquitoes

The piRNA pathway is a specialized small RNA interference that in mosquitoes is mechanistically distant from analogous biology in the Drosophila model. Current genetic engineering methods, such as targeted genome manipulation, have a high potential to tease out the functional complexity of this intricate molecular pathway. However, progress in utilizing these methods in arthropod vectors has been geared mostly toward the development of new vector control strategies rather than to study cellular functions. Herein we propose that genetic engineering methods will be essential to uncover the full functionality of PIWI/piRNA biology in mosquitoes and that extending the applications of genetic engineering on other aspects of mosquito biology will grant access to a much larger pool of knowledge in disease vectors that is just out of reach. We discuss motivations for and impediments to expanding the utility of genetic engineering to study the underlying biology and disease transmission and describe specific areas where efforts can be placed to achieve the full potential for genetic engineering in basic biology in mosquito vectors. Such efforts will generate a refreshed intellectual source of novel approaches to disease control and strong support for the effective use of approaches currently in development.

Anopheles metabolic proteins in malaria transmission, prevention and control: a review

The increasing resistance to currently available insecticides in the malaria vector, Anopheles mosquitoes, hampers their use as an effective vector control strategy for the prevention of malaria transmission. Therefore, there is need for new insecticides and/or alternative vector control strategies, the development of which relies on the identification of possible targets in Anopheles. Some known and promising targets for the prevention or control of malaria transmission exist among Anopheles metabolic proteins. This review aims to elucidate the current and potential contribution of Anopheles metabolic proteins to malaria transmission and control. Highlighted are the roles of metabolic proteins as insecticide targets, in blood digestion and immune response as well as their contribution to insecticide resistance and Plasmodium parasite development. Furthermore, strategies by which these metabolic proteins can be utilized for vector control are described. Inhibitors of Anopheles metabolic proteins that are designed based on target specificity can yield insecticides with no significant toxicity to non-target species. These metabolic modulators combined with each other or with synergists, sterilants, and transmission-blocking agents in a single product, can yield potent malaria intervention strategies. These combinations can provide multiple means of controlling the vector. Also, they can help to slow down the development of insecticide resistance. Moreover, some metabolic proteins can be modulated for mosquito population replacement or suppression strategies, which will significantly help to curb malaria transmission.