HUMAN HERPESVIRUS 6 INHIBITS THE PROLIFERATIVE RESPONSES OF HUMAN PERIPHERAL-BLOOD MONONUCLEAR-CELLS

Human herpesvirus 6 (HHV-6) was recently isolated from the blood of im munosuppressed individuals and children with exanthem subitum. In this study, the effect of HHV-6 on the proliferative response of human per ipheral blood lymphocytes was tested. T cell lines or human peripheral blood lymphocytes were infected with HHV-6 variant A, strain GS, or v ariant B, strain Z29. Infected and uninfected cell lysates were UV ina ctivated and sonicated; when lysates were added to peripheral blood mo nonuclear cells from HHV-6-seropositive adults, lymphoproliferative re sponses to antigens (tuberculin purified protein derivative or mumps) and mitogens (phytohemagglutinin or interleukin-2) were inhibited in a dose-dependent manner. This inhibition was reversed by a rabbit anti- HHV-6(GS) antiserum, and inhibition was not due to cell lysis induced by viral infection, since cell death was not observed. This in vitro s uppression of cellular immune responses by HHV-6 proteins may be relev ant to the in vivo pathogenesis of HHV-6 and its relationship to human diseases.