CLONAL EXPANSION OF HUMAN T-CELL LEUKEMIA-VIRUS TYPE I-INFECTED CELLSIN ASYMPTOMATIC AND SYMPTOMATIC CARRIERS WITHOUT MALIGNANCY

Human T-cell leukemia virus type I (HTLV-I) is associated with adult T -cell leukemia/lymphoma and tropical spastic paraparesis/HTLV-associat ed myelopathy. Both diseases are usually preceded by a long clinically asymptomatic period. PCR amplification of the HTLV-I proviral integra tion sites shows that clonal expansion of HTLV-I-bearing T cells, rath er than being an occasional phenomenon in nonmalignant disease, is the norm for both symptomatic and asymptomatic carriers. Sequencing of 10 0 molecular clones derived by PCR amplification of part of the envelop e gene from two asymptomatic carriers revealed almost no genetic varia tion. Viral amplification via clonal expansion, rather than by reverse transcription, would explain this remarkable genetic stability.