T cell

HHV-6 reactivation reduces CD8+ T cell recovery with increased risk of infections and reduced survival

In All, Immunology, News, Transplant Complications by Kristin Loomis

In a French study of 366 adult allogenic hematopoietic stem cell transplantation (aHSCT) recipients, CD8+ T cell recovery was significantly reduced in patients with HHV-6 reactivation . HHV-6 infection was also associated with reduced survival and increased infections of CMV and BKV. HHV-6 can infect CD8+ and CD4+ T cells as well as natural killer cells, and is known to cause immunosuppression. Antiviral treatment resolved two thirds of the cases. In this study, CD4+ T cell count was not reduced. An earlier study also noted a reduced CD8+ lymphocyte count in HHV-6 infected patients (Chevallier 2010). The authors note that recent in vitro data has shown that HHV-6 infection can shift T cell differentiation toward HHV-6 specific regulatory T (Treg) cells known for potent immunosuppressive activity (Wang 2014).

This report confirms previous studies demonstrating higher non-relapse mortality in active HHV-6 infection after transplantation (Zerr 2012, Sakai 2011). Unlike previous reports, there was no difference in GVHD between HHV-6 infected and uninfected patients, perhaps due to differences in the timing of the HHV-6 testing. Several recent reports have found that early HHV-6 reactivation can predict acute GVHD (Aoki 2015, Verhoeven 2015, Inazawa 2015). For more information, see the full paper: Quintela 2015.