Presence and expression of human herpesvirus 6 in peripheral blood mononuclear cells of S100-positive, T cell chronic lymphoproliferative disease.

S100-positive, T cell chronic lymphoproliferative disease (S100-CLPD) is a rare and aggressive hematologic disorder in which the cytoplasmic protein S100 is expressed at high levels in abnormal lymphocytes. Using a DNA probe specific for human herpesvirus 6 (HHV-6), 2 cases of S100-CLPD were examined by DNA and RNA hybridization analysis. The results indicated that HHV-6 DNA was present in uncultured peripheral blood mononuclear cells (PBMC) and that a 1.3-kb viral transcript was expressed in both cases. Analysis of flow-sorted PBMC from 1 case demonstrated that HHV-6 DNA was present exclusively in the S100-positive fraction. Studies using other HHV-6 DNA probes suggested infection with HHV-6 variant B in both cases. Hybridization studies using DNA from PBMC of 27 cases of T cell chronic lymphoproliferative disease of other types showed no evidence of HHV-6. These studies suggest a possible specific association of HHV-6 with the unusual disorder S100-CLPD.