Retroviruses and cutaneous T-cell lymphoma

Since the discovery of the first human retrovirus, HTLV-I, and its etiologic role in ATL, the search for a retrovirus and its role in the development and progression of CTCL has been vigorously pursued and debated. Current studies in CTCL have evaluated serum antibodies to retroviral proteins, electron microscopy to identify viruslike particles, and Southern blot analysis and PCR amplification to detect proviral DNA sequences. There have been inconsistent findings within and between a variety of studies, emphasizing the need for critical evaluation of experimental methods and their potential shortcomings. Several interesting observations have included (1) serologic evidence of HTLV-I infection in a small subset of CTCL patients, (2) cloning of a deleted HTLV-I proviral genome from a B-cell line established from the peripheral blood of a CTCL patient, (3) detection of retrovirus in Langerhans cells and B cells, and (4) molecular evidence for the presence of an HTLV-I-like retrovirus. By viewing CTCL as a model of tumor progression, mechanisms by which retroviruses play a role in the development and progression of CTCL are facilitated. Future studies will need to correlate the detection of proviral sequences and the nature of a retroviral infection with specific cell types and stage of disease and determine if these findings demonstrate a causal role in CTCL or a secondary phenomenon due to CTCL-associated immunosuppression. It is likely that new data will be reported between the writing of this article and the time of publication; however, the currently available data reviewed in this article do not provide conclusive evidence that retroviruses play a primary etiologic role in CTCL.