Reinfection with a Bacterial Pathogen Augments Heterogeneity in Host Disease Responses

Area of Science:

• Ecology and Evolutionary Biology
• Immunology
• Disease Dynamics

Background:

• Individual variation in disease response is crucial for pathogen transmission and evolution.
• Understanding how initial infections shape subsequent immune heterogeneity is vital for predicting disease spread.
• Previous studies showed priming increases susceptibility heterogeneity in house finches.

Purpose of the Study:

• To investigate if priming Mycoplasma gallisepticum exposure exacerbates heterogeneity in immune responses and transmission traits upon reinfection.
• To determine the effect of low vs. high dose priming on antibody responses, pathogen loads, and disease symptoms.
• To assess if antibody variability can predict susceptibility heterogeneity.

Main Methods:

• Wild-caught, pathogen-naïve house finches were experimentally primed with Mycoplasma gallisepticum (low or high dose).
• Birds were subsequently reinfected to measure antibody responses, pathogen loads, and disease symptoms.
• Population-level heterogeneity in these traits was analyzed in relation to prior exposure.

Main Results:

• Any prior exposure to Mycoplasma gallisepticum led to more heterogeneous antibody responses upon reinfection.
• Prior exposure also resulted in more variable pathogen loads during reinfection.
• Increased antibody variability correlated with previously observed heterogeneity in susceptibility.

Conclusions:

• Prior pathogen exposure amplifies heterogeneity in immune responses and pathogen loads within a host population.
• Antibody response variability serves as a potential proxy for susceptibility heterogeneity.
• This study highlights how initial infections shape downstream infection dynamics and disease spread.