Integrative model of the immune response to a pulmonary macrophage infection: what determines the infection duration?

Area of Science:

• Immunology
• Mathematical Biology
• Veterinary Virology

Background:

• Immune mechanisms controlling pathogen infection duration, especially those targeting pulmonary macrophages, remain poorly understood.
• Variability in pathogen virulence and host susceptibility significantly impacts infection outcomes.
• Mathematical models offer a powerful approach to explore complex host-pathogen and immune dynamics.

Purpose of the Study:

• To develop and apply an original mathematical model detailing macrophage-pathogen interactions, adaptive immune response orientation, and cytokine regulation.
• To investigate the impact of varying Porcine Respiratory and Reproductive Syndrome virus (PRRSv) virulence and host susceptibility on infection dynamics.
• To identify key immune mechanisms influencing infection duration and to inform the design of improved vaccination strategies.

Main Methods:

• Development of a novel mathematical model simulating macrophage-pathogen interactions, adaptive immunity, and cytokine networks.
• Application of the model to Porcine Respiratory and Reproductive Syndrome virus (PRRSv) infection dynamics.
• Parameter value extraction from existing modeling and experimental studies on respiratory pathogens.
• Sensitivity analysis to identify influential model parameters.
• Simulation of scenarios with graduated levels of PRRSv strain virulence and host susceptibility.

Main Results:

• High levels of antiviral cytokines and a dominant cellular response can lead to both short and prolonged infection durations, contrary to common assumptions.
• The interplay between antiviral cytokines (e.g., IFNγ) and IL10 is crucial for determining the adaptive immune response orientation.
• IL10 levels serve as a reliable indicator of infected macrophage burden, aiding in understanding immune status.
• The developed model provides a framework to explore complex immune interactions influencing PRRSv infection outcomes.

Conclusions:

• Immune response duration to PRRSv is not solely dependent on cytokine levels but on the intricate interplay of specific immune mechanisms.
• Combining measurements of antiviral cytokines and IL10 can elucidate the adaptive immune response orientation and infection dynamics.
• The mathematical modeling framework offers a valuable tool for understanding PRRSv pathogenesis and for guiding the development of more effective PRRSv vaccines, addressing the limitations of current vaccines.