Infection Routes and Their Role in Insect-Microbe Interactions

Dear Colleagues,

Insect–microbe interactions represent highly dynamic and complex relationships that profoundly influence insect physiology, immunity, ecology, and evolution. Pathogens and symbiotic microorganisms can colonize insects through multiple infection routes, including oral ingestion, penetration through the cuticle, and direct systemic entry into the hemocoel. Each route exposes microbes to distinct physical barriers and immune environments, shaping both pathogen virulence strategies and host defense responses.

Oral infections are among the most common natural routes of pathogen entry. In this context, invading microorganisms must overcome gut-associated defenses such as digestive enzymes, reactive oxygen and nitrogen species, antimicrobial peptides, and structural barriers including the peritrophic matrix and midgut epithelium.

Cuticular infections, frequently associated with wounds or entomopathogenic fungi, activate local immune mechanisms such as melanization, clotting, and epidermal antimicrobial responses. By contrast, systemic infections directly expose pathogens to the hemolymph, triggering strong cellular and humoral immune responses mediated by hemocytes and fat body tissues. Importantly, mounting evidence indicates that immune activation may begin even before pathogens reach the hemocoel, highlighting the importance of early recognition mechanisms and tissue-specific immune signaling.

Understanding how infection routes influence insect–microbe interactions is essential for clarifying pathogen transmission dynamics, host susceptibility, microbiota modulation, and immune system activation. Furthermore, experimental infection models based on different routes of administration have become fundamental tools for studying innate immunity, host–pathogen interactions, microbial virulence, and the development of antimicrobial strategies.

This Special Issue aims to provide an updated overview of current advances in the study of infection routes in insects and their consequences for insect–microbe interactions. We welcome original research articles, reviews, and perspectives addressing, but not limited to, the following topics:

• Oral, cuticular, and systemic infections in insects;
• Gut immunity and intestinal barrier functions;
• Hemocyte and fat body immune responses;
• Reactive oxygen species and oxidative stress during infection;
• Host–pathogen and host–symbiont interactions;
• Microbial virulence mechanisms and immune evasion strategies;
• Crosstalk between microbiota and insect immunity;
• Experimental infection models in insect systems;
• Comparative analyses of natural versus artificial infection routes;
• Ecological and evolutionary implications of infection dynamics.

We encourage contributions employing molecular, cellular, physiological, ecological, and omics-based approaches, as well as studies using emerging insect model systems. 

This Special Issue will provide a multidisciplinary platform to advance our understanding of how infection routes shape the outcome of insect-microbe interactions and influence insect health and disease.

Dr. Maurizio Francesco Brivio
Dr. Maristella Mastore
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 250 words) can be sent to the Editorial Office for assessment.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-anonymized peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Insects is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

• insect immunity
• host–pathogen interactions
• host–symbiont interactions
• insect–microbe interactions
• Infection routes
• experimental infection
• infection dynamics