Abstract
Clonal disorders of large granular lymphocytes (LGL) result in leukemia due to the expansion of a discrete subset of either CD3+ T cells or natural killer (NK) cells. It has been hypothesized that a viral antigen acts as the initial stimulus causing the expansion of these cells. The possible involvement of human T cell lymphotropic virus types 1 and 2 (HTLV-1 and HTLV-2) in this disease has been studied but no conclusive evidence has linked either virus with LGL leukemia. In this study, we examined whether HTLV-3 or HTLV-4, two newly identified HTLV groups discovered in Central Africa in primate hunters, is involved in LGL leukemia. We developed two specific real-time PCR quantitative assays that are highly sensitive, capable of detecting 10 copies of HTLV-3 or HTLV-4 pol sequences in a background of 1 μg of DNA from human peripheral blood lymphocytes (PBL). We tested PBL DNA samples from 40 LGL leukemia patients in the United States and found that all samples were negative for HTLV-3 or HTLV-4 infection. These results suggest that HTLV-3 and HTLV-4 are not the causative agent of LGL leukemia.