Time-resolved post-translational histone modifications during BCG vaccine induced trained immunity in human monocytes

Trained immunity is the phenomenon whereby innate immune cells such as monocytes or macrophages undergo functional reprogramming after exposure to certain microbial components, altering their responses to future exposures. This study profiled the distribution of two active histone modifications (H3K27ac and H3K4me1) of human monocytes responding to two different BCG vaccine strains. Overall design: Time-course in vitro culture of human monocytes. Trained immunity was induced in culture through an initial exposure of primary human monocytes to BCG Denmark and BCG Bulgaria strains for 24 hours, followed by removal of stimulus and differentiation to macrophages for an additional 5 days. Cells were fixed for chromatin collection at baseline (day 0), 24 hours, and 6 days.