Infection of circulating CD34(+) cells by HHV-8 in patients with Kaposi's sarcoma

Human herpesvirus type 8 (HHV-8) has been identified as the most likely can didate to be involved in the development of Kaposi's Sarcoma (KS). HHV-8 ha s been associated with all forms of KS, primary effusion lymphoma, and mult icentric Castleman's disease and detected in various non-neoplastic cells, Its presence in cells of the different hemopoietic lineages has not yet bee n investigated in a comprehensive and systematic manner. In this study we s earched for the presence of HHV-8 in different subpopulations of peripheral blood mononuclear cells (PBMC) from patients with classic and AIDS-associa ted KS, as well as from HIV-1 seropositive and sere-negative persons withou t KS. Thirty-four samples of PBMC were isolated from 30 patients. Subpopula tions were isolated with immunomagnetic beads. Polymerase chain reaction fo r HHV-8 DNA was performed on PBMC and subpopulations with a primer pair sel ected from ORF26 of the viral genome. Polymerase chain reaction products we re subsequently Southern blotted and hybridized. In patients with KS, HHV-8 DNA was detected in nine of 11 (81%) CD19(+) cells, four of 11 (36%) CD2() cells, three of 11 (27%) CD14(+) cells, and nine of 11 (81%) of the remai ning depleted cell populations (DP) that contain CD34 positive cells. In a subsequent set of experiments HHV-8 DNA was detected in 10 of 12 (83%) CD34 positive cell fractions. All cell subpopulations from the non-KS group wer e HHV-8 negative, with the exception of one positive B cell sample obtained from an HIV-infected patient. Our data demonstrate that in peripheral bloo d HHV-8 is detectable not only in CD19(+) cells, as previously reported, bu t also in other cells, including T cells, monocytes, and cells devoid of sp ecific lineage markers, We also show for the first time that CD34(+) cells in peripheral blood of KS patients are a predominant HHV-8-harboring popula tion, suggesting that they represent an additional important reservoir for this virus in vitro.