Isolation of human T-cell leukemia virus type I from a transformed T- cell line derived spontaneously from lymphocytes of a seronegative Egyptian patient with mycosis fungoides

Mycosis fungoides (MF) is a rare form of cutaneous T-cell lymphoma that may be associated with human T-cell leukemia virus type I (HTLV-I) infection. Using the polymerase chain reaction, the HTLV-I pX region was constantly detected in the genomic DNA extracted from peripheral blood mononuclear cells (PBMCs) of an HTLV-I antibody-seronegative Egyptian MF patient enrolled in a study to isolate HTLV-I from North Africa. A CD4+ and interleukin-2 (IL-2) receptor-positive T-cell line was established when the phytohemagglutinin-stimulated PBMCs of that patient were maintained in IL-2-containing culture medium. The cell line (EMF) was initially IL-2 dependent and then became IL-2 independent after gradual withdrawal of the IL-2. The cells reacted positively with monoclonal antibodies specific for the HTLV-I Env or HTLV-I Gag proteins. Using the Southern blot analysis, HTLV-I provirus could be detected in the genomic DNA extracted from the EMF cells. Limited nucleotide sequence of the env region showed more than 95% homology between the EMF provirus and other known HTLV-I isolates. Western blot analysis of the cell lysates showed the expression of the HTLV-I structural proteins. These data imply that a transforming HTLV-I provirus may be present, at least in certain cases of MF, regardless of the presence or absence of the specific antibodies.