The effects of host heterogeneity on pathogen population structure

Area of Science:

• Immunology
• Evolutionary Biology
• Mathematical Modeling

Background:

• Pathogen populations can self-organize into strains with non-overlapping antigenic variants under strong immune selection.
• Previous models assumed uniform host immune responses to pathogen antigens.
• Host immune responses can be influenced by individual genotype, leading to varied responses.

Purpose of the Study:

• To investigate the impact of diverse host immune responses on pathogen strain structure.
• To explore how host genetic restriction affects pathogen evolution under immune pressure.
• To determine if discrete strain structure (DSS) is maintained with heterogeneous host immunity.

Main Methods:

• Development of a mathematical model simulating pathogen evolution.
• Inclusion of host populations with differential responses to variable and conserved antigens.
• Analysis of pathogen population dynamics under varying immune selection pressures.

Main Results:

• Discrete strain structure (DSS) is maintained even with a high frequency of hosts lacking variant-specific responses.
• The presence of hosts with cross-reactive immunity broadens the range of immune selection pressure under which DSS prevails.
• Cyclical or chaotic behavior in pathogen replacement is reduced with the inclusion of cross-reactive hosts.

Conclusions:

• Host immune repertoire diversity plays a crucial role in maintaining pathogen discrete strain structure (DSS).
• Cross-reactive immune responses in a portion of the host population enhance the stability of DSS.
• Understanding host-pathogen interactions with diverse immune responses is key to predicting pathogen evolution and disease dynamics.