Viral antigen and extensive division maintain virus-specific CD8 T cells during chronic infection

H Shin, SD Blackburn, JN Blattman… - The Journal of …, 2007 - rupress.org
H Shin, SD Blackburn, JN Blattman, EJ Wherry
The Journal of experimental medicine, 2007rupress.org
Efficient maintenance of memory CD8 T cells is central to long-term protective immunity. IL-7–
and IL-15–driven homeostatic proliferation is essential for long-term memory CD8 T cell
persistence after acute infections. During chronic infections, however, virus-specific CD8 T
cells respond poorly to these cytokines. Yet, virus-specific CD8 T cells often persist for long
periods of time during chronic infections. We have addressed this apparent paradox by
examining the mechanism for maintaining virus-specific CD8 T cells during chronic infection …
Efficient maintenance of memory CD8 T cells is central to long-term protective immunity. IL-7– and IL-15–driven homeostatic proliferation is essential for long-term memory CD8 T cell persistence after acute infections. During chronic infections, however, virus-specific CD8 T cells respond poorly to these cytokines. Yet, virus-specific CD8 T cells often persist for long periods of time during chronic infections. We have addressed this apparent paradox by examining the mechanism for maintaining virus-specific CD8 T cells during chronic infection. We find that homeostatic cytokines (e.g., IL-7/15), inflammatory signals, and priming of recent thymic emigrants are not sufficient to maintain virus-specific CD8 T cells over time during chronic infection. Rather, our results demonstrate that viral peptide is required for virus-specific CD8 T cell persistence during chronic infection. Moreover, this viral antigen-dependent maintenance results in a dramatically different type of T cell division than is normally observed during memory T cell homeostasis. Rather than undergoing slow, steady homeostatic turnover during chronic viral infection, CD8 T cells undergo extensive peptide-dependent division, yet cell numbers remain relatively stable. These results indicate that antigen-specific CD8 T cell responses during persisting infection are maintained by a mechanism distinct from that after acute infection.
rupress.org