Quantification of human herpesvirus 8 by real-time PCR in blood fractions of AIDS patients with Kaposi's sarcoma and multicentric Castleman's disease.

Few studies have assessed human herpesvirus 8 (HHV8) viremia levels in different HHV8-related pathologies, using sensitive and reproducible molecular assays. Our objective was to compare the HHV8 DNA load in serial blood samples (collected every 3 months for 1 year) from acquired immunodeficiency syndrome (AIDS) patients with Kaposi's sarcoma (KS) and multicentric Castleman's disease (MCD). The HHV8 viral load was determined in both peripheral blood mononuclear cells (PBMC) and plasma fractions, using a competitive real-time polymerase chain reaction (PCR) assay developed in a LightCycler instrument (Roche Diagnostics). In six subjects with limited or extensive KS while on highly active antiretroviral therapy, the HHV8 DNA load was either undetectable (<50 copies/10(5) cells) or low (</=135 copies) in all PBMC samples. In contrast, the cellular HHV8 load was >1,000 copies in at least one of the samples from the two subjects with both KS and MCD. HHV8 DNA was detected in plasma only when the cellular viral load was >10,000 copies/10(5) cells. After chemotherapy, the HHV8 DNA load became undetectable in the MCD patients despite no changes in CD4 T-cell counts or highly active antiretroviral therapy (HAART) regimens. These results suggest that the pathogenesis of the two HHV8-associated diseases (i.e., KS and MCD) might be different, as only the latter was associated with important viremia in our patients.