Coevolutionary immune system dynamics driving pathogen speciation

TL;DR

This paper presents a dynamical model of pathogen-immune coevolution within hosts, showing how pathogen mutation and immune constraints lead to chronic infections and pathogen speciation, ultimately risking immune system collapse.

Contribution

It introduces a novel within-host coevolutionary model demonstrating how pathogen speciation and immune system fragility emerge from their interactions.

Findings

Chronic infections arise from pathogen mutation and immune constraints.

Pathogen speciation occurs through branching patterns driven by coevolution.

Immune system fragility increases over time, leading to potential collapse.

Abstract

We introduce and analyze a within-host dynamical model of the coevolution between rapidly mutating pathogens and the adaptive immune response. Pathogen mutation and a homeostatic constraint on lymphocytes both play a role in allowing the development of chronic infection, rather than quick pathogen clearance. The dynamics of these chronic infections display emergent structure, including branching patterns corresponding to asexual pathogen speciation, which is fundamentally driven by the coevolutionary interaction. Over time, continued branching creates an increasingly fragile immune system, and leads to the eventual catastrophic loss of immune control.