Immunogenicity of biopharmaceuticals in chronic inflammatory diseases
Sammanfattning: Multiple sclerosis (MS) and rheumatoid arthritis (RA) are chronic inflammatory diseases where genetic and environmental factors influence the pathogenesis. MS is a disease of the central nervous system, while RA primarily affects the joints. Biopharmaceuticals such as interferon beta (IFNβ) and tumor necrosis factor-alpha (TNF-α) inhibitors are widely used treatments to achieve a reduction in disease activity in people with MS and RA respectively. Over time, however, some of the treated patients develop anti-drug antibodies (ADA) or neutralizing ADA (NAb) that can reduce or abrogate the drug efficacy and subsequently lead to loss of clinical response. Five studies are included in this thesis, which assess endogenous immune processes affected and evaluates laboratory methods used for monitoring immunogenicity of IFNβ and TNF-α inhibitors. Collectively, the findings presented in this thesis aim to optimize methods for drug level and ADA screening to allow for easier treatment decisions. Additionally, the thesis highlights the skin site as a potential contributor to ADA development. In study I, we studied the immunomodulatory role of IFNβ and how it was affected by NAb. We found a 3-fold increase of serum IL-7 (genetically associated with MS) in IFNβ treated MS patients and this was related to the lowered IL-7Rα expression on cell surfaces. The presence of high NAb titers to IFNβ resulted in significantly lower serum IL-7 levels compared to NAb negative patients as measured with the myxovirus resistance protein A (MxA) gene expression assay (MGA). Since the MGA method is cumbersome we decided to evaluate a new method, iLite (in study II). We found that the NAb titers had a high degree of correlation between the two assays and that NAb titers of 150 TRU/mL were suggestive of significant neutralization of the drug. However, in the iLite assay (and MGA) NAb titers are calculated using the Kawade principle and this method has statistical limitations. In study III, we therefore continued to validate the iLite assay using a cut-point approach designed to be more sensitive and statistically accurate. By using the cut-point approach, we identified 12% more NAb positive samples compared to using the Kawade method, showing the increased sensitivity achieved with the cut-point design. In study IV, we evaluated different methods for ADA screening of the TNF-α inhibitor infliximab. We showed that ADA could be detected in the majority of samples with low drug levels using ELISA, but that samples with detectable drug levels also tested ADA positive using an acid and dissociation assay (PandA). Thus, the PandA proved useful as a complement to the routinely available ELISA to monitor immunogenicity. Lastly (in study V), to understand the mechanism of ADA induction, we investigated the primary immune response against repetitive injections with biologicals in skin cells. Using a human skin model, we found that the IFNβ injection enhanced dendritic cell maturation and elevated the expression of several inflammatory cytokines, which suggest that the administration triggers an immune response at the injection site.
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