Epigenetic modifications and regulation in infection

Epigenetic modifications, such as DNA methylation and histone modification, alter gene expression without changing the nucleotide sequence. Epigenetic marks can be stably transmitted through cell divisions, allowing the cell to effect long-lasting changes in response to environmental cues including nutrient availability, metabolic changes, and infection, among many others. Many infectious pathogens employ epigenetic strategies to modulate the host cell to create a suitable microenvironment; conversely, the genomes of these pathogens can also be subjected to epigenetic modifications, which may limit replication but also contribute to the formation of viral latency. Furthermore, epigenetics is thought to underly the phenomenon of trained immunity, by which infection or vaccination primes innate immune cells in a nonspecific manner to respond more robustly to later infection by a broad range of pathogens. Epigenetic modifications that are linked to disease progression or enhancement of immune responses present an attractive target for therapeutics to mitigate infection and improve disease outcomes. This chapter offers a comprehensive review of current knowledge of epigenetic modifications and regulation in viral or bacterial infections, and sheds light on how epigenetic marks, in host or microbial genes, might be therapeutic targets.