Virus specific cell-mediated immunity may play a role in controlling reactivated human herpesvirus 6B in patients under measles induced immunosuppression

For a better understanding of the cellular immune responses to reactivated HHV 6B the lymphoproliferative response to human herpesvirus 6B (HHV 6B) antigen was measured in three consecutive specimens obtained biweekly from 22 young children and infants suffering from acute measles, and in 19 influenza patients and nine healthy control subjects. HHV 6B DNA in peripheral blood mononuclear cells (PBMCs) was detected in 18 of 22 subjects with measles, but not in the influenza patients or the healthy population. A novel reactivation profile of HHV 6B was found in patients with measles in the milder form of immunosuppression than in patients with organ transplantation. HHV 6B specific lymphoproliferation activities increased correspondingly with reactivation of HHV 6B assessed by detecting HHV 6B DNA in PBMCs in patients with measles, but no significant change in either the antibody response to HHV 6B or DNAemia occurred in serial specimens obtained either from patients with influenza or healthy subjects. This novel form of HHV 6B reactivation without antibody response was observed in patients with measles. The dynamic fluctuations in lymphoproliferative responses in measles may represent the balance between HHV 6B reactivation and its suppression by the host immune system.