Co-evolved Partners of Immunity: A Trait-Based Map of Human Keystone Organisms

Area of Science:

• Immunology
• Microbiology
• Evolutionary Biology

Background:

• Persistent microbes can function as immunological keystones, influencing host defense and vulnerability to immune changes.
• Keystone organisms require coordinated immune responses for containment and exhibit structured anatomical niche occupancy.

Purpose of the Study:

• To operationalize keystone organisms based on immune engagement and anatomical niche structure.
• To identify and characterize keystone pathogens using immunological and evolutionary traits.
• To develop a framework for predicting pathogen emergence under immune perturbation.

Main Methods:

• Unsupervised analysis of 18 immunological and evolutionary traits across 43 organisms.
• Development of a pathogen × immune-perturbation × niche tensor from clinical literature.
• Quantification of diagnostic breadth using immune breadth and niche breadth metrics.

Main Results:

• Four reproducible archetypes were resolved, with persistent herpesviruses and Mycobacterium tuberculosis identified as a compact keystone set.
• Expanded niche breadth, representing diverse anatomical sites, was the primary discriminator for keystone pathogens.
• Clinical emergence patterns accurately separated trait-defined keystones from non-keystones.

Conclusions:

• Keystone pathogens are characterized by expanded niche breadth, linking evolutionary adaptation to reactivation patterns.
• Findings motivate archetype-aware surveillance strategies for immunosuppressed individuals.
• A predictive framework for pathogen emergence and immunogen design was established.