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Discussions of host–microbe interactions in mosquito vectors are frequently dominated by a focus on the human pathogens they transmit (e.g.Plasmodiumparasites and arboviruses). Underlying the interactions between a vector and its transmissible pathogens, however, is the physiology of an insect living and interacting with a world of bacteria and fungi including commensals, mutualists and primary and opportunistic pathogens. Here we review what is known about the bacteria and fungi associated with mosquitoes, with an emphasis on the members of theAedesgenus. We explore the reciprocal effects of microbe on mosquito, and mosquito on microbe. We analyse the roles of bacterial and fungal symbionts in mosquito development, their effects on vector competence, and their potential uses as biocontrol agents and vectors for paratransgenesis. We explore the compartments of the mosquito gut, uncovering the regionalization of immune effectors and modulators, which create the zones of resistance and immune tolerance with which the mosquito host controls and corrals its microbial symbionts. We examine the anatomical patterning of basally expressed antimicrobial peptides. Finally, we review the relationships between inducible antimicrobial peptides and canonical immune signalling pathways, comparing and contrasting current knowledge on each pathway in mosquitoes to the model insectDrosophila melanogaster. This article is part of the theme issue ‘Sculpting the microbiome: how host factors determine and respond to microbial colonization’.
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This content will become publicly available on December 1, 2026
Gut bacteria induce heterologous immune priming in Rhodnius prolixus encompassing both humoral and cellular immune responses
Insects lack the adaptive, antibody mediated responses of vertebrates, yet they possess a robust innate immune system capable of defending themselves against pathogens. Immune priming has been observed in multiple insect species, wherein exposure to a pathogen provides protection against subsequent infections by the pathogen. Heterologous immune priming has also been described, where presence of one bacterial species provides protection against another. We determined thatRhodococcus rhodnii, a gut symbiont of the kissing bugRhodnius prolixus,induces strong heterologous immune priming, while axenic bugs lacking gut bacteria are highly susceptible to pathogens. CommensalEscherichia coliprovides less robust protection.R. rhodniimust be alive within the insect as dead bacteria do not stimulate immune priming and pathogen resistance. Removal ofR. rhodniifrom the gut reduces resistance to pathogens while restoring it to axenic bugs improves pathogen resistance, though not completely. Unlike most other examples of symbiont-mediated immune priming, we find no evidence thatR. rhodniiever leaves the gut, despite activating a potent immune response in the hemocoel and fat body.R. rhodniiandE. coliactivate both the IMD and Toll pathways indicating cross-activation of the pathways, while silencing of either pathway leads to a loss of the protective effect. Several antimicrobial peptides are induced in the fat body by presence of gut bacteria. WhenE. coliis in the gut, expression of antimicrobial peptides is often higher than whenR. rhodniiis present, whileR. rhodniiinduces proliferation of hemocytes and induces a stronger melanization response thanE. coli. Hemolymph fromR. rhodniibugs has a greater ability to convert the melanin precursor DOPA to melanization products than axenic orE. coli-harboring bugs. These results demonstrate thatR. rhodnii’sbenefits to its host extend beyond nutritional provisioning, playing an important role in the host immune system.
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- Award ID(s):
- 2239595
- PAR ID:
- 10660069
- Editor(s):
- Vale, Pedro F
- Publisher / Repository:
- Public Library of Science
- Date Published:
- Journal Name:
- PLOS Pathogens
- Volume:
- 21
- Issue:
- 12
- ISSN:
- 1553-7374
- Page Range / eLocation ID:
- e1012947
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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