A human-blood-derived microRNA facilitates flavivirus infection in fed mosquitoes

Host 5-HT affects Plasmodium transmission in mosquitoes via modulating mosquito mitochondrial homeostasis

Malaria parasites hijack the metabolism of their mammalian host during the blood-stage cycle. Anopheles mosquitoes depend on mammalian blood to lay eggs and to transmit malaria parasites. However, it remains understudied whether changes in host metabolism affect parasite transmission in mosquitoes. In this study, we discovered that Plasmodium infection significantly decreased the levels of the tryptophan metabolite, 5-hydroxytryptamine (5-HT), in both humans and mice. The reduction led to the decrease of 5-HT in mosquitoes. Oral supplementation of 5-HT to Anopheles stephensi enhanced its resistance to Plasmodium berghei infection by promoting the generation of mitochondrial reactive oxygen species. This effect was due to the accumulation of dysfunctional mitochondria caused by 5-HT-mediated inhibition of mitophagy. Elevating 5-HT levels in mouse serum significantly suppressed parasite infection in mosquitoes. In summary, our data highlight the critical role of metabolites in animal blood in determining the capacity of mosquitoes to control parasite infection.

Role of Gut Microbiota in Dengue

Dengue is a disease caused by a flavivirus (DENV) and transmitted by the bite of a mosquito, primarily the Aedes aegypti and Aedes albopictus species. Previous studies have demonstrated a relationship between the host gut microbiota and the evolution of dengue. It seems to be a bidirectional relationship, in which the DENV can affect the microbiota by inducing alterations related to intestinal permeability, leading to the release of molecules from microbiota dysbiosis that can influence the evolution of dengue. The role of angiotensin II (Ang II) in the microbiota/dengue relationship is not well understood, but it is known that the renin-angiotensin system (RAS) is present in the intestinal tract and interacts with the gut microbiota. The possible effect of Ang II on the microbiota/Ang II/dengue relationship can be summarised as follows: the presence of Ang II induced hypertension, the increase in angiotensinogen, chymase, and microRNAs during the disease, the induction of vascular dysfunction, the production of trimethylamine N-oxide and the brain/microbiota relationship, all of which are elements present in dengue that could be part of the microbiota/Ang II/dengue interactions. These findings suggest the potential use of Ang II synthesis blockers and the use of AT1 receptor antagonists as therapeutic drugs in dengue.

The Role of Noncoding RNA in the Transmission and Pathogenicity of Flaviviruses

Noncoding RNAs (ncRNAs) constitute a class of RNA molecules that lack protein-coding capacity. ncRNAs frequently modulate gene expression through specific interactions with target proteins or messenger RNAs, thereby playing integral roles in a wide array of cellular processes. The Flavivirus genus comprises several significant members, such as dengue virus (DENV), Zika virus (ZIKV), and yellow fever virus (YFV), which have caused global outbreaks, resulting in high morbidity and mortality in human populations. The life cycle of arthropod-borne flaviviruses encompasses their transmission between hematophagous insect vectors and mammalian hosts. During this process, a complex three-way interplay occurs among the pathogen, vector, and host, with ncRNAs exerting a critical regulatory influence. ncRNAs not only constitute a crucial regulatory mechanism that has emerged from the coevolution of viruses and their hosts but also hold potential as antiviral targets for controlling flavivirus epidemics. This review introduces the biogenesis of flavivirus-derived ncRNAs and summarizes the regulatory roles of ncRNAs in viral replication, vector-mediated viral transmission, antiviral innate immunity, and viral pathogenicity. A profound comprehension of the interplay between ncRNAs and flaviviruses will help formulate efficacious prophylactic and therapeutic strategies against flavivirus-related diseases.

Advances in research on arboviral acquisition from hosts to mosquitoes

Arboviral acquisition is a critical step in virus transmission. In this review, we present an overview of the interactions between viruses and host blood-derived factors, highlighting the diverse ways in which they interact. Moreover, the review outlines the impact of host blood on gut barriers during viral acquisition, emphasizing the crucial role of this physiological process in virus dissemination. Additionally, the review investigates the responses of symbioses to invading arboviruses, providing insights into the dynamic reactions of these vital relationships to the presence of arboviruses.

Signaling between mammalian adiponectin and a mosquito adiponectin receptor reduces Plasmodium transmission

IMPORTANCE

When a female mosquito takes a blood meal from a mammalian host, components of the blood meal can affect mosquito fitness and indirectly influence pathogen infectivity. We identified a pathway involving an Anopheles gambiae adiponectin receptor, which, triggered by adiponectin from an incoming blood meal, decreases Plasmodium infection in the mosquito. Activation of this pathway negatively regulates lipophorin expression, an important lipid transporter that both enhances egg development and Plasmodium infection. This is an unrecognized cross-phyla interaction between a mosquito and its vertebrate host. These processes are critical to understanding the complex life cycle of mosquitoes and Plasmodium following a blood meal and may be applicable to other hematophagous arthropods and vector-borne infectious agents.

Adiponectin in the mammalian host influences ticks' acquisition of the Lyme disease pathogen Borrelia

Arthropod-borne pathogens cause some of the most important human and animal infectious diseases. Many vectors acquire or transmit pathogens through the process of blood feeding. Here, we report adiponectin, the most abundant adipocyte-derived hormone circulating in human blood, directly or indirectly inhibits acquisition of the Lyme disease agent, Borrelia burgdorferi, by Ixodes scapularis ticks. Rather than altering tick feeding or spirochete viability, adiponectin or its associated factors induces host histamine release when the tick feeds, which leads to vascular leakage, infiltration of neutrophils and macrophages, and inflammation at the bite site. Consistent with this, adiponectin-deficient mice have diminished pro-inflammatory responses, including interleukin (IL)-12 and IL-1β, following a tick bite, compared with wild-type animals. All these factors mediated by adiponectin or associated factors influence B. burgdorferi survival at the tick bite site. These results suggest a host adipocyte-derived hormone modulates pathogen acquisition by a blood-feeding arthropod.

Insights into the microRNA landscape of Rhodnius prolixus, a vector of Chagas disease

The growing interest in microRNAs (miRNAs) over recent years has led to their characterization in numerous organisms. However, there is currently a lack of data available on miRNAs from triatomine bugs (Reduviidae: Triatominae), which are the vectors of the protozoan parasite Trypanosoma cruzi, the causative agent of Chagas disease. A comprehensive understanding of the molecular biology of vectors provides new insights into insect-host interactions and insect control approaches, which are key methods to prevent disease incidence in endemic areas. In this work, we describe the miRNome profiles from gut, hemolymph, and salivary gland tissues of the Rhodnius prolixus triatomine. Small RNA sequencing data revealed abundant expression of miRNAs, along with tRNA- and rRNA-derived fragments. Fifty-two mature miRNAs, previously reported in Ecdysozoa, were identified, including 39 ubiquitously expressed in the three tissues. Additionally, 112, 73, and 78 novel miRNAs were predicted in the gut, hemolymph, and salivary glands, respectively. In silico prediction showed that the top eight most highly expressed miRNAs from salivary glands potentially target human blood-expressed genes, suggesting that R. prolixus may modulate the host's gene expression at the bite site. This study provides the first characterization of miRNAs in a Triatominae species, shedding light on the role of these crucial regulatory molecules.

Analyses of Mosquito Species Composition, Blood-Feeding Habits and Infection with Insect-Specific Flaviviruses in Two Arid, Pastoralist-Dominated Counties in Kenya

Insect-specific flaviviruses (ISFs), although not known to be pathogenic to humans and animals, can modulate the transmission of arboviruses by mosquitoes. In this study, we screened 6665 host-seeking, gravid and blood-fed mosquitoes for infection with flaviviruses and assessed the vertebrate hosts of the blood-fed mosquitoes sampled in Baringo and Kajiado counties; both dryland ecosystem counties in the Kenyan Rift Valley. Sequence fragments of two ISFs were detected. Cuacua virus (CuCuV) was found in three blood-fed Mansonia (Ma.) africana. The genome was sequenced by next-generation sequencing (NGS), confirming 95.8% nucleotide sequence identity to CuCuV detected in Mansonia sp. in Mozambique. Sequence fragments of a potential novel ISF showing nucleotide identity of 72% to Aedes flavivirus virus were detected in individual blood-fed Aedes aegypti, Anopheles gambiae s.l., Ma. africana and Culex (Cx.) univittatus, all having fed on human blood. Blood-meal analysis revealed that the collected mosquitoes fed on diverse hosts, primarily humans and livestock, with a minor representation of wild mammals, amphibians and birds. The potential impact of the detected ISFs on arbovirus transmission requires further research.

Neighboring mutation-mediated enhancement of dengue virus infectivity and spread

Frequent turnover of dengue virus (DENV) clades is one of the major forces driving DENV persistence and prevalence. In this study, we assess the fitness advantage of nine stable substitutions within the envelope (E) protein of DENV serotypes. Two tandem neighboring substitutions, threonine to lysine at the 226th (T226K) and glycine to glutamic acid at the 228th (G228E) residues in the DENV2 Asian I genotype, enhance virus infectivity in either mosquitoes or mammalian hosts, thereby promoting clades turnover and dengue epidemics. Mechanistic studies indicate that the substitution-mediated polarity changes in these two residues increase the binding affinity of E for host C-type lectins. Accordingly, we predict that a G228E substitution could potentially result in a forthcoming epidemic of the DENV2 Cosmopolitan genotype. Investigations into the substitutions associated with DENV fitness in hosts may offer mechanistic insights into dengue prevalence, thus providing a warning of potential epidemics in the future.

Expression of mosquito miRNAs in entomopathogenic fungus induces pathogen-mediated host RNA interference and increases fungal efficacy

The growing threat of insecticide resistance prompts the urgent need to develop additional tools for mosquito control. Entomopathogenic fungi provide an eco-friendly alternative to chemical insecticides. One limitation to the use of mycoinsecticides is their relatively low virulence. Here, we report an approach for suppressing mosquito immunity and increasing fungal virulence. We engineered Beauveria bassiana to express Aedes immunosuppressive microRNAs (miRNAs) to induce host RNA interference (RNAi) immune responses. We show that engineered strains can produce and deliver the miRNAs into host cells to activate cross-kingdom RNAi during infection and suppress mosquito immunity by targeting multiple host genes, thereby dramatically increasing fungal virulence against Aedes aegypti and Galleria mellonella larvae. Importantly, expressing host miRNAs also significantly increases fungal virulence against insecticide-resistant mosquitoes, creating potential for insecticide-resistance management. This pathogen-mediated RNAi (pmRNAi)-based approach provides an innovative strategy to enhance the efficacy of fungal insecticides and eliminate the likelihood of resistance development.

Regulatory Role of Host MicroRNAs in Flaviviruses Infection

MicroRNAs (miRNAs) are small non-coding RNA that affect mRNA abundance or translation efficiency by binding to the 3′UTR of the mRNA of the target gene, thereby participating in multiple biological processes, including viral infection. Flavivirus genus consists of small, positive-stranded, single-stranded RNA viruses transmitted by arthropods, especially mosquitoes and ticks. The genus contains several globally significant human/animal pathogens, such as Dengue virus, Japanese encephalitis virus, West Nile virus, Zika virus, Yellow fever virus, Tick-borne encephalitis virus, and Tembusu virus. After flavivirus invades, the expression of host miRNA changes, exerting the immune escape mechanism to create an environment conducive to its survival, and the altered miRNA in turn affects the life cycle of the virus. Accumulated evidence suggests that host miRNAs influence flavivirus replication and host–virus interactions through direct binding of viral genomes or through virus-mediated host transcriptome changes. Furthermore, miRNA can also interweave with other non-coding RNAs, such as long non-coding RNA and circular RNA, to form an interaction network to regulate viral replication. A variety of non-coding RNAs produced by the virus itself exert similar function by interacting with cellular RNA and viral RNA. Understanding the interaction sites between non-coding RNA, especially miRNA, and virus/host genes will help us to find targets for antiviral drugs and viral therapy.

Cross-species microRNA transmission modulates flavivirus growth in mosquitoes

Mosquitoes can be infected with a variety of RNA viruses. Recently,Zhu et al. demonstrated that human microRNA hsa-miR-150-5p is acquired by mosquitoes during blood meals and protects the Dengue virus by downregulation of chymotrypsin AaCT-1 mRNA. This finding suggests the use of microRNA antagomirs as an antiviral approach in mosquitoes.