Evidence for the cofactor role of human T-cell lymphotropic virus type 1 in mycosis fungoides and Sézary syndrome

The aetiology of mycosis fungoides (MF) and Sezary syndrome (SS) is unknown. A pathogenic role for the human T-cell lymphotropic virus type 1 (HTLV-1) has been suggested but remains controversial. We used an animal model to test the possibility that peripheral blood mononuclear cells (PBMC) obtained from MF patients harbour the HTLV-1 virus which may be infective. The polymerase chain reaction (PCR) was used to detect HTLV-1 proviral DNA sequences in PBMC of 27 MF patients and one SS patient of non-Iranian origin. Positive results were found in six of the patients. Twelve of the 28 patients tested by Western blot showed HTLV-1 antibodies. Twenty-eight immunosuppressed inbred Fisher F344 rats were inoculated intravenously with cultures of PBMC obtained from the 28 patients. Eight of these 28 rats showed antibodies to HTLV-1 while the proviral genome was demonstrated in the blood of only two of the rats. PBMC from two MF patients, in spite of showing negative results for the proviral genome by PCR, still induced HTLV-1 antibody formation in the F344 rat model. None of 10 control rats inoculated with normal donor PBMC showed antibodies to HTLV-1, nor the proviral genome. The present study suggests that HTLV-1 plays a cofactor role in MF/SS patients.