Paradoxical Expansion of Th1 and TH17 Cells in Peripheral Cultural Blood Cells of RA Patients following Infliximab Treatment : a Possible Correlation with Loss of Clinical Response and Adverse Events

Background: Immunogenicity of anti-TNF-α drugs may affect both safety and efficacy. Several authors have found antibodies reacting against biological agents in the sera of rheumatic patients who failed a biologic therapy. Infliximab (IFX), a chimeric monoclonal antibody which contains 25% mouse-derived proteins, induces the formation of antibodies up to rates of 60%. Some case reports and histological studies have demonstrated the involvement of the Th1 response following the immunization versus a TNF-α blocker. To our knowledge no study has still attempted to demonstrate that TNF-α blockers may induce Th17 responses. Objectives: To investigate whether the immunogenicity of a biologic agent may affect the Th1 and Th17 compartment, after performing a validation assay of the test. Methods: The whole blood samples was collected from a cohort of 10 healthy volunteers, 15 drug-free patients affected by rheumatoid arthritis (RA) according to EULAR/ACR 2010 criteria, 20 RA patients treated successfully with IFX and 20 RA patients who discontinued IFX due to a lack of efficacy or adverse events. Peripheral Blood Monunuclear Cells (PBMCs) were cultured in presence/absence of 50 μg/ml IFX. Th1 lymphocytes were identified as IFNγ, IL2- secreting, Tbet-expressing CD4+ T cells, and Th17 lymphocytes as IL17, IL21-secreting, RORγT-expressing CD4+ T cells. The variations in the percentage of Th1 and Th17 T cells following the treatments were analyzed by flow cytometric analysis. Data were analyzed with Student’s T Test. Unpaired T test “type 3” for unequal variances with a two tailed P value (Excel) was used. Significance was set at P <0.05. 10 healthy subjects and 10 RA drug-free patients were used for validation assay. Results: Twenty RA patients who had a loss of response to IFX or who developed an adverse event (females 16; mean age 61.3 ± 12.2 yrs, mean disease duration 13.4 ± 7.2 yrs) were compared with 20 matched RA controls (females 15, mean age 57.0 ± 12.2 yrs, mean disease duration 18.1 ± 9.5 yrs) successfully treated. Patients failing IFX developed Th1-Th17 responses following incubation with IFX 50mg/ml whereas responder patients did not. Indeed, IFX increased significantly the percentage of both Th1 and Th17 Tcell subpopulation (p <0.01and p <0.05, respectively) in patients failing IFX. In contrast, IFX incubation reduced significantly both Th1and Th17 T-cell percentage (p <0.05) in responder patients.