IN-VITRO ACTIVATION OF HUMAN HERPESVIRUS-6 AND HERPESVIRUS-7 FROM LATENCY

Human herpesviruses 6 and 7 (HHV-6 and HHV-7) are prevalent lymphotrop ic viruses that infect more than 80% of children at infancy or during early childhood. Infection ranges from asymptomatic to severe disease. HHV-6B causes exanthem subitum, The virus can be recovered from perip heral blood mononuclear cells during the acute phase of exanthem subit um, but the host remains latently infected throughout life. In immunoc ompromised patients undergoing kidney, liver, or bone marrow transplan tation latent HHV-6B is reactivated, at times causing severe or fatal disease. Here, we describe the establishment of an in vitro system for reactivation of HHV-6B and HHV-7 from latency. HHV-7 is reactivated f rom latently infected peripheral blood mononuclear cells by T-cell act ivation. HHV-6B could not be reactivated under similar conditions; how ever, the latent HHV-6B could be recovered after the cells were infect ed with HHV-7. Once reactivated, the HHV-6B genomes became prominent a nd the HHV-7 disappeared. We conclude that HHV-7 can provide a transac ting function(s) mediating HHV-6 reactivating from latency. Understand ing the activation process is critical for the development of treatmen ts to control the activation of latent viruses so as to avoid these so metimes life threatening infections in transplant recipients.