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Evolutionary trade-offs between functional and immune selection shape multigene families in pathogens
Qi Zhan1, Mercedes Pascual2,3, Qixin He4
1Committee on Genetics, Genomics and Systems Biology, The University of Chicago, Chicago, IL, 60637, USA.
Biorxiv : the Preprint Server for Biology
|July 16, 2025
Summary
Pathogen evolution is shaped by competition for hosts. Strong immune selection favors novel antigens, altering gene proportions and reducing variance in virulence and infection duration.
Area of Science:
- Evolutionary biology
- Parasitology
- Computational modeling
Background:
- Infectious pathogens utilize multigene families for surface proteins, impacting host fitness.
- Pathogen gene evolution during host competition is understudied, despite links to coexistence theory.
- The Plasmodium falciparum parasite and its var gene family serve as a model system.
Purpose of the Study:
- To investigate how evolution shapes pathogen gene composition during host competition.
- To model the transmission dynamics of Plasmodium falciparum and the gene dynamics of the var multigene family.
- To understand the interplay between frequency-dependent and absolute fitness in pathogen evolution.
Main Methods:
- Development of a stochastic computational model.
- Simulation of Plasmodium falciparum transmission.
- Analysis of var gene family birth-death dynamics.
Main Results:
- Selection alone does not explain stable ratios of gene groups within parasite genomes.
- A trade-off between transmission and immune evasion influences gene selection.
- High R0 genes decrease with transmission intensity, becoming frequency-dependent.
- Immune selection enhances novel antigen invasion and niche differentiation.
Conclusions:
- Parasite gene group classifications may not accurately reflect transmission strategy or virulence.
- Immune selection shifts the balance towards antigenic diversification over absolute fitness traits.
- Transmission intensity gradients invert the proportion of high R0 genes.
- Strong immune selection reduces gene variance in transmissibility and virulence.
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