Host Prior Exposure Augments Gene Expression Heterogeneity of Both Host and Pathogen During In Vivo Infection

Area of Science:

• * Infectious disease dynamics
• * Host-pathogen interactions
• * Gene expression analysis

Background:

• * Acquired immunity from infection or vaccination causes individual differences in disease susceptibility.
• * The impact of prior exposure on within-host gene expression heterogeneity for both host and pathogen is not well understood.

Purpose of the Study:

• * To investigate if prior pathogen exposure induces gene expression heterogeneity in the host and pathogen during infection.
• * To determine the consequences of this heterogeneity for reinfecting pathogens.

Main Methods:

• * Quantified gene expression in house finches (Haemorhous mexicanus) after a high-dose challenge with Mycoplasma gallisepticum.
• * Birds previously received controlled, varied exposures to the pathogen.
• * Collected transcriptomic data from host tissues (conjunctiva, spleen) and the pathogen (conjunctiva).

Main Results:

• * Prior exposure induced significant host gene expression heterogeneity in the conjunctiva, but not the spleen.
• * Hosts with lower prior exposure showed greater heterogeneity during re-challenge.
• * Pathogen gene expression also showed more heterogeneity in previously exposed hosts.
• * Immune response-related terms were over-represented in variable host genes.

Conclusions:

• * Prior exposure establishes a within-host environment promoting heterogeneous gene expression in both host and pathogen.
• * Gene expression variation is a crucial factor, alongside sequence variation, for understanding infectious disease coevolution.