IL-6 is involved in viral immunosurveillance. We studied the effect of tocilizumab (TCZ) on the evolution in viral load (VL) for the Epstein-Barr virus (EBV), cytomegalovirus (CMV) and varicella-zoster virus (VZV) in patients with rheumatoid arthritis (RA).
EBV, CMV and VZV loads were prospectively determined in whole blood of 22 RA patients at TCZ initiation and during treatment follow-up. A difference of 0.5 log10 or of threefold copies/mL between two VL was considered significant.
There were 20 (91%) women, (mean age of 57.8±11.2 years, mean disease duration 11.3±9.7 years) with 16 (73%) seropositive and 16 (73%) erosive patients. TCZ was administered alone for 8 patients (36.7%) or in combination with methotrexate for 11 patients (50%). At baseline, the EBV VL was positive in 8 patients with a mean VL value of 1777.2±3518.3 (3.5±0.4 log10) copies/mL. Only one patient had a positive CMV VL with 2337 copies/mL (3.4 log10). The VZV VL was negative in all patients. After 9.2±4.8 months, EBV VL became negative in 6 of 8 patients (P=0.01) and did not significantly vary in the remaining 2 patients. CMV VL became also negative. No VL (EBV, CMV, VZV) became positive. A positive EBV VL did not correlate with disease activity or with inflammatory biomarkers (ESR and CRP).
TCZ does not seem to increase the VL of EBV, CMV or VZV. Studies involving larger patient populations are necessary.