Frontiers in Bioscience-Landmark (FBL) is published by IMR Press from Volume 26 Issue 5 (2021). Previous articles were published by another publisher on a subscription basis, and they are hosted by IMR Press on imrpress.com as a courtesy and upon agreement with Frontiers in Bioscience.
Academic Editor: Xiao-Feng Yang
Viral infections often lead to generalized immunosuppression characterized by the downregulation of virus-specific CD4+ and CD8+ T cell responses and/or non-specific inflammation. One of the mechanisms for the virus-induced immunosuppression is the induction of CD4+CD25+ regulatory T (Treg) cells that act to suppress effector T cell functions during infection. Depending on the situation, the CD4+CD25+ Treg cell-mediated suppression can be either beneficial or detrimental to the host. On one hand, they play a critical role in maintaining host homeostasis by controlling exaggerated and destructive inflammations paralleling strong antiviral immune responses and thus contribute to host protection. On the other hand, suppression of virus-specific T cell responses by the Treg cells depresses host antiviral immune responses and thus facilitates viral persistence and disease progression. Despite numerous reports on induction of CD4+CD25+ Treg cells in viral infections, it is still not fully clear how they are induced and how they act to suppress effector T cell functions in viral infections. This review discusses recent progress in our understanding of the role of virus-induced CD4+CD25+ Treg cells and the mechanisms by which they are induced and exert their function during infection.