Objective: Human T lymphotropic virus type I (HTLV-I) may be associated with some connective tissue autoimmune diseases, including systemic lupus erythematosus (SLE). To determine the relationship between HTLV-I infection and SLE, we examined the clinical manifestations of SLE patients with HTLV-I infection.
Methods: Eighty-nine patients with SLE were screened for antibodies to HTLV-I by electrochemiluminescence immunoassay. The presence of HTLV-I proviral sequences in peripheral blood mononuclear cells (PBMC) was determined by real-time polymerase chain reaction (PCR) quantification and Southern blotting analysis. The differences in clinical manifestations between HTLV-I-seropositive and seronegative patients with SLE were analyzed statistically.
Results: Fourteen of 89 (15.7%) patients were HTLV-I seropositive. All PBMC samples from 11 patients tested by PCR and 3 samples from 10 patients tested by Southern blotting analysis were positive for HTLV-I-related sequences. The age of HTLV-I-seropositive patients with SLE was significantly higher than that of seronegative patients (median 60 vs 42 yrs; p < 0.0005). The age at onset of SLE in HTLV-I-seropositive patients was also significantly higher than that of seronegative patients (median 45.5 vs 30 yrs; p <0.0005). The lymphocyte count in HTLV-I-seropositive SLE patients was significantly higher than that of seronegative patients (median 1740 vs 1066/microl; p = 0.027). The maintenance dose of prednisolone in HTLV-I-seropositive patients with SLE was significantly lower than that in seronegative patients (median 5 vs 9 mg/day; p = 0.012).
Conclusion: This is the first report of the differences in clinical manifestations between SLE patients with and without HTLV-I infection. Our results suggest some involvement of HTLV-I in the pathogenesis of SLE.