Protective Immunity in Humans: A Glimpse Provided by the Analysis of Herpesvirus-Specific T Cells in Health and Disease

During the past years a wide array of immunologic tools has become available to study antigen-specific T cell immunity by flow cytometry. By means of these assays progress has been made in our understanding of virus-specific T cell immunity and the role of virus-specific CD4+ and CD8+ T-cell responses in protection against disease. In this review we describe advances made in understanding Epstein Barr-virus (EBV) and cytomegalovirus (CMV) specific T-cell immunity in healthy individuals and immunocompromised patients, such as HIV infected individuals and stem cell transplant (SCT) recipients, using flow cytometry based assays. EBV and CMV are both herpesviruses, which are characterised by a life-long persistence of the virus in the human body. It now becomes clear that the functional capacity, and more specifically poly-functionality, is the most important feature of virus-specific T-cells to protect against disease progression. However, responses directed to different proteins may have different effects, in relation to viral control and subsequent protection against disease. Improved knowledge on these factors may be translated to clinical applications.